Plant Biology Test 1

Phagocytosis

("cell eating") involves the ingestion of relatively large, solid particles, such as bacteria or cellular debris, via large vesicles derived from the plasma membrane

mycology

(the study of fungi)

What is the history of opioid use by people?

- 3000 - 2000 BC: Babylonians and Egyptians show use of opioids - Early Western Medicine to Middle Age Use (Hippocrates, Diosorides, Galen) - Power and wealth related to opium poppy

Distinguish between a substance moving down a concentration gradient and a substance moving against a concentration gradient.

- A substance is said to have moved down a concentration gradient when it has travelled from an area of its higher concentration to an area of its lower concentration. This process does not require ATP but happens through simple diffusion. On the other hand, a substance is said to have moved against its concentration gradient when it has moved from an area of its lower concentration to an area of its higher concentration. This process requires energy in the form of ATP to transport the substance against the concentration gradient.

What is ATP

- ATP is the cells major energy currency. The principal energy carrier for most processes in living organisms is the molecule adenosine triphosphate, or ATP.

CAM Plants Can Fix CO2 in the Dark

- Crassulacean acid metabolism (CAM) occurs in many succulent plants. In CAM plants, the fixation of CO2 to phosphoenolpyruvate (PEP) to form oxaloacetate occurs at night, when the stomata are open. The oxaloacetate is rapidly converted to malate, which is stored overnight in the vacuole as malic acid. During the daytime, when the stomata are closed, the malic acid is recovered from the vacuole and the fixed CO2 is transferred to ribulose 1,5-bisphosphate (RuBP) of the Calvin cycle. The C4 pathway and the Calvin cycle occur within the same cells in CAM plants; hence, these two pathways, which are spatially separated in C4 plants, are temporally separated in CAM plants.

What is the opioid crisis?

- Greater than 90 Americans die from overdose daily - Economic cost of $504 billion - 1 in 20 used pain meds when not prescribed - Opium poppy cultivation is ambiguous in United States - Legal for culinary or aesthetic reasons - Plant Product

What is water potential, and what value does the concept of water potential have for plant physiologists?

- In simple terms, the potential energy of water is known as the water potential. Water potential is stated as "potential energy of water per unit volume of water as compared to pure water." Since it implies the potential energy that the water possesses, thus it is a unit that shows that quantifies the tendency of water to move from one place to another. For plant physiologist water potential is an important term as it helps them to understand the possible movement of water in the plant under various conditions as temperature, pressure and more. Thus it is easier for them to understand how the water will move due to osmosis, capillary action, gravity and pressure in the plants

Fermentation Reactions Occur under Anaerobic Conditions

- In the absence or shortage of oxygen, pyruvate produced by glycolysis may be converted either to lactate (in many bacteria, fungi, protists, and animal cells) or to ethanol and carbon dioxide (in yeasts and most plant cells). These anaerobic processes— called fermentation—yield 2 ATP for each glucose molecule.

a. Explain the hierarchical nature of our classification system - KP(Div)COFGS

- Kingdom, Division, Class, Order, Family, Family, Genus, Species

Lignin, a cell wall constituent, is believed to have played a major role in the evolution of terrestrial plants. Explain in terms of all the presumed functions of lignin.

- Lignin adds strength and stiffness to the cell wall. Thus, during the evolution of terrestrial plants, lignin helped them to increase in height and girth and develop large photosynthetic surfaces in the form of leaves. Lignin acts as a waterproofing agent. Thus, it made it capable for the plants to transport water upwards to varied heights. Further, since lignin increases resistance of the cell walls to mechanical penetration, it thus helped the plants to protect themselves from invasion against fungi

Essential oils

- Many of the monoterpenoids and sesquiterpenoids are called essential oils because, being highly volatile, they con- tribute to the fragrance, or essence, of the plants that produce them

Explain why we should care about plant biology - Role in maintaining Earth's environment?

- Photosynthesis altered earth atmosphere which in turn influenced evolution of life providing earth oxygen and protection from ultraviolet rays - oxygen molecules in outer layer of atmosphere converted to ozone molecules

Describe the unique qualities of water and why it has them

- Polarity / Hydrogen Bonds - Cohesion - Ice Less Dense Than Liquid Water - Universal Solvent - High Specific Heat

What are the several levels of protein organization?

- There are four main levels of protein organization; primary structure, secondary structure, tertiary structure and quaternary structure.

The coagulation of egg white when an egg is cooked is a common example of protein denaturation. What happens when a protein is denatured?

- When a protein is denatured, then the bonds that hold the tertiary structure together are broken and the tertiary structure as a result is disrupted. The protein unfolds itself. Further when the secondary structure is denatured, then the alpha helices and beta pleated sheets are disrupted resulting in random coiling of the polypeptide chain.

Polysaccharides Definition

- a carbohydrate (ex. starch, cellulose, or glycogen) whose molecules consist of a number of sugar molecules bonded together.

Tannins

- denaturing proteins) - 5th step

9. In what sense do plants differ from animals with respect to the location of most cell division activity?

- in plants, most of the cell division activity occurs at the apical meristems. The apical meristems are located at the apex of the plant like the auxiliary buds, main root tip and at the apex of the main stem. These meristematic cells are thus located in places called meristems which are specialized cells that undergo continuous division for the growth and elongation of the plant - in animals, until the growth into a full adult, cell division usually takes place in al the cells. But in adults, the cell division and formation of new cells is primarily restricted to cells called stem cells. These stems cells are specialized as they have regenerative capabilities and undergo fast cell divisions. The stems cells are restricted to very few areas of the human body such as the bone marrow and umbilical cord

Capsaicin

- the molecule that causes the burning sensation when we eat the chili peppers, deters browsing mammals but is not detected by birds, which eat the fruit and distribute the seeds in their droppings.

Pit membranes are exceedingly important to the safety of water transport. Explain.

- the presence of two cell walls and the lamella between the pits Is called pit membrane, the pit is nothing but the cavity in the cell wall. Pit membranes are very important because they transport the water in safe manner by preventing the air bubbles while transport of water form one xylem to another

economic botany

- the study of past, present, and future uses of plants by people

ecology

-the study of the relationships between organisms and their environment

Secondary Metabolites - Alkaloids

Alkaloids are among the most important compounds in terms of their pharmacological or medicinal effects Ex. Morphine (opium poppy), cocaine, caffeine, nicotine, atropine

Channel proteins

Channel proteins form water-filled pores that extend across the membrane and, when open, allow specific solutes (usually inorganic ions such as Na+, K+, Ca2+, and Cl-) to pass through.

Cell wall

Consists of cellulose microfibrils embedded in a matrix of hemicelluloses, pectins, and glycoproteins. Lignin, cutin, suberin, and waxes may also be present. Strengthens the cell and determines cell size and shape.

This increase in oxygen level had two important consequences

First, some of the oxygen molecules in the outer layer of the atmosphere were converted to ozone (O3) molecules. When there is a sufficient quantity of ozone in the atmosphere, it absorbs the ultraviolet rays—rays highly destructive to living organisms.

the membrane potential

If a solute carries a net charge, however, both the concentration gradient and the total electrical gradient across the membrane (the membrane potential) influence its transport.

Lipids - water solubility

Lipids are fats and fatlike substances. They are generally hydrophobic ("water-fearing") and thus are insoluble in water.

Lipids

Lipids are fats and fatlike substances. They are generally hydrophobic ("water-fearing") and thus are insoluble in water. Typically, lipids serve as energy-storage molecules—usually in the form of fats or oils—and also for structural purposes, as in the case of phospholipids and waxes.

Monosaccharides

Monosaccharides can be described by the formula (CH2O)n, where n can be as small as 3, as in C3H6O3, or as large as 7, as in C7H14O7.

The most successful of the autotrophs were those in which a system evolved for making direct use of the sun's energy— that is, the process of photosynthesis. The earliest photosynthetic organisms, although simple in comparison with plants, were much more complex than the primitive heterotrophs. Use of the sun's energy required a complex pigment system to capture the light energy and, linked to this system, a way to store the energy in an organic molecule.

No doubt that heterotrophs evolved before autotrophs

nucleoplasm

Nuclear matrix

Ribosomes

Ribosomes are small particles, only about 17 to 23 nanometers in diameter, consisting of protein and RNA. Ribosomes actively involved in protein synthesis occur in clusters or aggregates called polysomes.

Ribosomes Are the Sites of Protein Synthesis

Ribosomes, which are found both free in the cytosol and attached to the endoplasmic reticulum and the outer surface of the nuclear envelope, are the sites where amino acids are linked together to form proteins. During protein synthesis, the ribosomes occur in clusters called polysome

Transpiration Adaptative?

The Cuticle Serves as an Effective Barrier to Water Loss, The Opening and Closing of Stomata Controls the Exchange of Gases across the Leaf Surfaces, Stomatal Movements Result from Changes in Turgor Pressure within the Guard Cells, Carbon Dioxide Concentration and Temperature Also Affect Stomatal Movement

Cuticle

The cuticle also tends to prevent the exchange of gases between the plant and the surrounding air that is necessary for both photosynthesis and respiration.

Nucleic Acids - Roles

The information dictating the structures of the enormous variety of proteins found in living organisms is encoded in and translated by molecules known as nucleic acids. Just as proteins consist of long chains of amino acids, nucleic acids consist of long chains of molecules known as nucleotides. A nucleotide, however, is a more complex molecule than an amino acid.

Distinguish between a centromere and a kinetochore.

The main differences between centromere and kinetochore are: - a centromere is a constricted region of highly specialized repetitive DNA sequences that is found on a chromosome. A kinetochore on the other hand is a protein complex that is associated with the centromere and assembles on it - centromere is the center to which the chromatids are attached, and kinetochore is the center to which the spindle fibers are attached - during cell division, the kinetochores are attached to the microtubules along which the chromosomes travel; the centromeres are not attached to these microtubules - centromere can be seen with the help of a light microscope clearly, while kinetochores can only be seen with the help of an electron microscope

How do ions move in plants - Osmosis

The movement of water molecules through such a membrane is known as osmosis. Osmosis involves a net flow of water from a solution that has higher water potential to a solution that has lower water potential

nuclear envelope

The nucleus is surrounded by a pair of membranes called the nuclear envelope. This structure contains a large number of pores. The pores provide a direct passageway through the nuclear envelope for the exchange of materials between the nucleus and the cytoplasm

Secondary Metabolites - Phenolics

The term phenolics encompasses a broad range of compounds, all of which have a hydroxyl group (—OH) attached to an aromatic ring (a ring of six carbons containing three double bonds). They are almost universally present in plants and are known to accumulate in all plant parts (roots, stems, leaves, flowers, and fruits).

Primary growth

The type of growth that originates from apical meristems is known as primary growth

Transpiration - Describe water movement in plants in terms of moving along energy gradient (water potential)

Water loss makes the water potential of the roots more negative and increases their capacity to extract water from the soil.

Describe carbohydrate structure

described by the formula (CH2O)n, where n can be as small as 3, as in C3H6O3, or as large as 7, as in C7H14O7.

tertiary structure

in this level, the protein folds itself and is held together by disulfide bridges and hydrogen bonds. This structure provided strength and stability to the protein structure

Protoplast:

refers to the contents of the cells (two parts - nucleus and cytoplasm)

Elements

substances that cannot be broken down into other substances by ordinary means.

Alkaloids

the most important ones in relation to pharmacology or medicinal value

Virology, bacteriology, phycology

the study of algae

M phase:

this is the mitotic phase. In this phase, the cell undergoes mitosis with the formation of spindle fibers and the two sets of chromosomes are separated, the nucleus divides into two and finally the cytoplasm divides into two completing the cell division

In Photosynthesis, Light Energy Is Converted to Chemical Energy and Carbon Is "Fixed" into Organic Compounds

- A complete, balanced equation for photosynthesis can be writ- ten as follows: Light 3CO2 + 6H2O ⎯→ C3H6O3 + 3O2 + 3H2O The first step in photosynthesis is the absorption of light energy by pigment molecules. The pigments involved in eukaryotic photosynthesis include the chlorophylls and the carotenoids, which are packed in the thylakoids of chloroplasts as photosynthetic units called photosystems. Light absorbed by pigment molecules boosts their electrons to a higher energy level. Because of the way the pigment molecules are arranged in the photosystems, they are able to transfer this energy to a pair of special chlorophyll a molecules at the reaction centers. There are two different kinds of photosystems, Photosystem I and Photosystem II, which generally work together simultaneously and continuously. Photosystem I can also carry out photosynthesis independently of Photosystem II, but when only Photosystem I is operating (a process called cyclic photophosphorylation) there is no external electron donor (water) and thus no production of NADPH. Cyclic phosphorylation only results in proton gradients that are used for ATP production. The many reactions that occur during photosynthesis are divided into two major processes: the light reactions and the carbon-fixation reactions.

How is ATP different from ADP, and why is ATP important to cells?

- ATP stand for adenosine triphosphate and ADP stands for adenosine monophosphate. In ATP, three phosphates are attached to the adenosine while in ADP two phosphates are attached to adenosine molecule. ATP is important to the cell because the cleavage of a phosphate group form ATP produces a large amount of energy that is used a number or energy intensive reaction. Energy obtained from the conversion of ADP to AMP is comparatively less. Thus, energy is stored in cells in the form of ATP

The Citric Acid Cycle Is the "Metabolic Hub" for the Breakdown and Synthesis of Many Different Types of Molecules

- Although glucose is regarded as the main substrate for respiration in most cells, fats and proteins can also be converted to molecules that can enter the respiratory sequence at several different steps. The various pathways by which organic molecules are broken down to yield energy are known collectively as catabolism. The biosynthetic processes of life are known collectively as anabolism.

Plants enter our lives in innumerable ways other than as sources of food. How many ways can you list? Have you thanked a green plant today?

- Apart from being the main source of food for us plants have other innumerable uses. Some of them are: a. plants like hemp, cotton palm are sources of fiber. These fibers can be used for the production of clothes, mats, hats, and shelter. b. plants also are the source of paper c. plants are also sources of cash crops like rubber, cashews and many more that provide economic growth to the country d. plants are most importantly a source of medicine. Different secondary metabolites in the plants are cures for a number of diseases e. plants are also a source of fuel in the form of wood or coal f. most importantly plants are the sole natural cleansers of the air that we breathe

What were some of the problems encountered by plants as they made the transition from the sea to the land, and what structures in terrestrial plants evolved to solve those problems?

- As plants transitioned from water to land all necessary factors for photosynthesis were available in abundance that the plants had to address when the transition from water to land occurred. The plants thus developed specialized structures to overcome the problem due to the transition. They were: a. roots developed further and branched out so that they can search for water and transport them to the other parts of the body b. the stems and the leaves were covered with a waxy cuticle that prevented loss of water due to transpiration. c. the stomata were developed as cuticles prevented the exchange of gases also. The stomata thus developed were sensitive to the environmental conditions and opened and closed in response to the environmental conditions. d. in plants with a very short life span, even the stem was photosynthetic e. the development of secondary growth resulted in thickening of stems and roots and prevented further loss of water f. also to reproduce effectively, plants developed spores that were drought resistant

What are biomes, and what are the principal roles of plants in an ecosystem?

- Biomes are large communities of plants and animals that are characterized by organisms that are climatically controlled and distinct from other biomes. The principal role of plants in an ecosystem is that they are the ones that are there at the base of productivity. They are the only ones along with certain photosynthetic bacteria and algae that can produce their own food and a prime source of amino acids, minerals and vitamins. Also, it is only by means of plants that the oxygen level in the atmosphere is maintained at a level that is sustainable for other living organisms.

Certain chemicals function as "uncoupling" agents when they are added to respiring mitochondria. The passage of electrons down the electron transport chain to oxygen continues, but no ATP is formed. One of these agents, the antibiotic valinomycin, is known to transport K+ ions through the inner membrane into the matrix. Another agent, 2,4-dinitrophenol, transports H+ ions through the membrane. How do these substances prevent the formation of ATP?

- Both these substances act at different levels of the electron transport chain thus affecting the formation of a proton gradient is necessary for the formation of ATP from ADP, thus these chemicals indirectly prevent the formation of ATP. In the case of the antibiotic valinomycin, it is known that it transports K+ ions from the inner membrane to the matrix. This thus affects the flow of H+, which is created by electron transport, in the other direction as protons in the form of K+ are already transported to the matrix. Thus there is no formation of proton gradient which hence results in no formation of ATP. In the case of 2,4- ditrophenol since already H+ ions get transported across the membrane to the matrix by the action of this chemical, there is no further transport of protons due to the electron transport. Hence it seems that the inner membrane becomes leaky to the proton, resulting in the absence of a proton gradient that is necessary for the formation of ATP

List the main products of the carbon-fixation reactions of photosynthesis. Carbon fixation reaction of photosynthesis can be mainly categorized into 3 types:

- C3 cycle: this is also known as the calvin Melvin cycle. The main products of this reaction are: 1 molecules of glyceraldehyde-3-phosphate; 9 ADP and 6NADP+. The ATP and NADP+ are used in the light reactions and the glyceraldehyde-3-phosphate is used to produce sugars - C4 cycle: this cycle is similar to the C3 cycle except for the fact that photorespiration by RuBISCO is prevented by these plants by separating the sites of carbon fixation and light reactions. The site where light reaction takes place that is the mesophyll cells contain phosphoenolpyruvate which fixes CO2 and forms oxaloacetic acid. This oxaloacetic acid or malate, is transferred to specialized bundle sheath cells where RuBISCO is located. Here in thses bundle sheath cells decarboxylation takes place and the normal C3 cycle is carried. As a result, the carbon fixation is increased, and photorespiration is decreased in high temperatures and humid conditions - CAM pathway: the only difference of this pathway from the C4 pathway is the fact that this pathway separates the processes of C3 and C4 cycle temporally. That is the C4 cycle takes place in the night and the C3 cycle takes place in the day. The products of the photosynthesis are the same as C4 plants

Of the 92 naturally occurring elements which ones comprise 99% of living tissue?

- Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorous, Sulfur

Who was the "Father of Taxonomy"

- Carolus Linnaeus

Hemicellulose and pectin

- Cellulose molecules form the fibrous part of the plant cell wall. The long, rigid cellulose molecules combine to form microfibrils, each consisting of hundreds of cellulose chains. In plant cell walls, the cellulose microfibrils are embedded in a matrix containing two other complex, branched polysaccharides, namely, hemicelluloses and pectin. Hemicelluloses stabilize the cell wall by hydrogen bonding to the cellulose microfibrils. Pectins make up most of the middle lamella, a layer of intercellular material that cements together the walls of adjacent plant cells. Pectins, which are especially plentiful in certain fruits, such as apples and cranberries, allow jams and jellies to thicken and gel.

What is the standard suffix for Order and Family (and Division and Class)?

- Division (-phyta) - Class (-ae) - Order (-ales) - Family (-aceae)

Explain the phenomenon of autumn leaf coloration.

- During summer, the rate of photosynthesis remains almost constant due to optimal environmental conditions for photosynthesis. Thus, chlorophyll pigments remain active and help in maintaining the green color of the leaf as they are numerous in numbers as compared to the other pigments. In late summer, as temperature decreases and the amount of sunlight available to the plant decreases, a layer of cork begins to form at the base of the leaves. As this layer of cork increases, it effects the flow of nutrients and water to the leaves. As a result, the rate of photosynthesis is affected and thus chlorophyll pigments reduce in number. Now the other pigments such as anthocyanins, Carotenoids and xanthophylls are able to exhibit their colors. Thus, the color of the leaf changes to the color of the most abundant pigment in the late summer or during autumn

How do energy-storage polysaccharides and structural polysaccharides differ from one another? What are some examples of each?

- Energy storage polysaccharides are those polysaccharides that when broken down to disaccharides or monosaccharide, release energy in the process. Thus, the energy is stored in their from in the cells. Structural polysaccharides are those polysaccharides whose main function is to provide structural stability to the cell. They are mainly found in such areas of the cell where structural stability and rigidness is needed. They form the exoskeleton of the cell. Examples of energy storage polysaccharides are starch, glycogen, carbohydrates. Examples of structural polysaccharides are cellulose and chitin.

What is an enzyme, and why are enzymes important to cells?

- Enzymes are large complex proteins that are globular in structure. Their man function is to act as a catalyst for various chemical reactions that occur in the cell. Enzymes are important to the cell as they accelerate the rate of a reaction even at low concentrations. They remain unchanged during the reaction and thus can be used over and over again by the cells.

Why do biologists believe that all living things on Earth today share a common ancestor?

- Evidence suggest that the life on Earth has evolved from a single common ancestor. The genetic material of living organisms is made up of an exact similar chemical building blocks, named nucleobases. These nucleobases are sufficient to evolve into separate life forms, in a due course of time. A comparison of DNA genetic sequence would reveal the connection between life forms. The organisms lying close to each other in the phylogenetic tree, reveals close resemblance in the DNA sequences. In addition, the usage of energy source as ATP is another evidence.

In the typical cell cycle, there are checkpoints. What are these checkpoints? What purpose do they serve?

- In a typical eukaryotic cell, there are certain control mechanisms that ensure that every process in the cell cycle has been completed accurately before a phase progresses to the next phase. These control mechanisms are called the checkpoints of the cell. There are two main checkpoints in a cell cycle. The first checkpoint is at the end of the G1 phase which either stops the cycle or initiates the S phase depending upon the accuracy of the G1 phase. The second checkpoint is at the end of the G2 phase that either arrests the cycle or triggers the initiation of mitosis, again depending on the accuracy of the earlier phases

Explain Cell Theory

- In its modern form, the cell theory states simply that (1) all living organisms are com- posed of one or more cells; (2) the chemical reactions of a living organism, including its energy-releasing processes and its bio- synthetic reactions, take place within cells; (3) cells arise from other cells; and (4) cells contain the hereditary information of the organisms of which they are a part, and this information is passed from parent cell to daughter cell

In the Calvin Cycle, CO2 Is Fixed via a Three-Carbon Pathway

- In the carbon-fixation reactions, which take place in the stroma of the chloroplast, the NADPH and ATP produced in the light reactions are used to reduce carbon dioxide to organic carbon. The Calvin cycle is responsible both for the initial fixation of CO2 and for the subsequent reduction of the newly fixed carbon. In the Calvin cycle, a molecule of CO2 combines with the starting compound, a five-carbon sugar called ribulose 1,5-bisphosphate (RuBP), to form two molecules of the three-carbon compound 3-phosphoglycerate (PGA). The PGA is then reduced to the three-carbon molecule glyceraldehyde 3-phosphate (PGAL), with electrons provided by NADPH and energy provided by ATP hydrolysis. At each turn of the Calvin cycle, one carbon atom enters the cycle. Three turns of the cycle produce one molecule of glyceraldehyde 3-phosphate. At each turn of the cycle, RuBP is regenerated. Most of the fixed carbon is converted to either sucrose or starch.

The Citric Acid Cycle Completes the Metabolic Breakdown of Glucose to Carbon Dioxide

- In the course of respiration, the three-carbon pyruvate molecules are oxidized in the mitochondrial matrix to two-carbon acetyl groups, which then enter the citric acid cycle as acetyl CoA. In the citric acid cycle, each acetyl group is oxidized in a series of reactions to yield two additional molecules of carbon dioxide, one molecule of ATP, and four molecules of reduced electron carriers (three NADH and one FADH2). With two turns of the cycle, the carbon atoms derived from the glucose molecule are completely oxidized and released as molecules of CO2.

In the Light Reactions, Electrons Flow from Water to Photosystem II, down an Electron Transport Chain to Photosystem I, and Finally to NADP+ to Photosystem II, down an Electron Transport Chain to Photosystem I, and Finally to NADP+

- In the currently accepted model of the light reactions, light energy enters Photosystem II, where it is trapped by pigment molecules and passed to the P680 chlorophyll molecules of the reaction center. Energized electrons are transferred from P680 to an electron acceptor. As the electrons are removed from P680, they are replaced by low-energy electrons from water molecules, and oxygen is produced (water photolysis). Pairs of electrons then pass downhill to Photosystem I along an electron transport chain. This passage generates a proton gradient that drives the synthesis of ATP from ADP and phosphate (photophosphorylation). Meanwhile, light energy absorbed in Photosystem I is passed to the P700 chlorophyll molecules of the Photosystem I reaction center. The energized electrons are ultimately accepted by the coenzyme molecule NADP+, and the electrons removed from P700 are replaced by the electrons from Photosystem II. The energy yield from the light-dependent reactions is stored in the molecules of NADPH and in the ATP formed by photophosphorylation. Photophosphorylation also occurs in cyclic electron flow, a process that does not require Photo- system II. The only product of cyclic electron flow is ATP. This extra ATP is required by the Calvin cycle, which uses ATP and NADPH in a 3:2 ratio.

What is vesicle-mediated transport, and how does endocytosis differ from exocytosis?

- In the process of vesicle mediated transport, the substance or molecule to be transported is bound within a vesicle that either gets pinched off from the cell to the outside/inside or the vesicle fuses with the membrane and gets released inside or outside of the cell. This type of transport is useful for larger molecules that can otherwise not enter through the plasma membrane. In the process of endocytosis, the molecule that needs to be transported into the cell, reaches the plasma membrane. The plasma membrane then forms a groove and surrounds the molecule forming a vesicle towards the inside of the cell. This vesicle then gets pinched off and fuses with the organelle to which the molecule needs to be transported. The process is of three types: pinocytosis, phagocytosis and receptor mediated endocytosis. In the process of phagocytosis, the molecule that needs to be transported out of the cell gets bound by a vesicle which is then transported to the plasma membrane. Here the vesicle fuses with the membrane and the molecule gets released outside the cell.

By what processes are all four types of organic molecules split into their subunits, and by what process can these subunits be joined together?

- In the synthesis of a disaccharide from two monosaccharide molecules, a molecule of water is removed, and a new bond is formed between the two monosaccharides. This type of chemical reaction, which occurs when sucrose is formed from glucose and fructose, is known as dehydration synthesis. When the reverse reaction occurs—for example, when a disaccharide is split into its monosaccharide subunits—a molecule of water is added. This splitting, which occurs when a disaccharide is used as an energy source is known as hydrolysis

What advantages do terrestrial plants have over their aquatic ancestors? Can you think of any disadvantages to being a terrestrial plant?

- It is a well-known fact that the basic elements that are needed for the process of photosynthesis and growth - oxygen, carbon dioxide and minerals - are available in abundance on land as compared to water. Thus, terrestrial plants have an advantage over aquatic plants in this aspect. But it is also fact that the availability of water on land is limited, thus terrestrial plants is at a greater risk of drying out due to scarcity of water and dehydration

In the Electron Transport Chain, Electron Flow Is Coupled to Proton Pumping and ATP Synthesis by a Chemiosmotic Mechanism

- Like oxidative phosphorylation in mitochondria, photophosphorylation in chloroplasts is a chemiosmotic process. As electrons flow down the electron transport chain from Photosystem II to Photosystem I, protons are pumped from the stroma into the thylakoid lumen, creating a gradient of potential energy. As protons flow down this gradient from the thylakoid lumen back into the stroma, they pass through an ATP synthase, generating ATP.

Microtubules

- Microtubules are cylindrical structures about 24 nanometers in diameter and of varying lengths. Each microtubule is built up of subunits of the protein called tubulin. Microtubules have many functions. In enlarging and differentiating cells, microtubules just inside the plasma membrane (cortical microtubules) are involved in the orderly growth of the cell wall, especially through their control of the alignment of cellulose microfibrils as they are added to the cell wall. Microtubules serve to direct secretory Golgi vesicles containing non cellulosic cell wall substances toward the developing wall. In addition, microtubules make up the spindle fibers that play a role in chromosome movement and in cell plate formation in dividing cells. Microtubules are also important components of flagella and cilia and are involved in the movement of these structures.

Most of the Water Transpired by a Vascular Plant Is Lost through the Stomata

- Most of the water taken up by plant roots is lost to the air as water vapor. This process, called transpiration, is inextricably linked to the uptake by the leaf of CO2, which is essential in photosynthesis. A pair of guard cells can change their shape to bring about the opening and closing of the stoma, or pore. Closing of stomata prevents the loss of water vapor from the leaf. Stomatal movements result from changes in turgor pressure within the guard cells and the radial micellation of the guard cell walls. The turgor changes are closely correlated with changes in the solute level in the guard cells. A stoma opens when its guard cells become turgid and closes when they become flaccid.

What are alkaloids?

- Naturally N-containing compounds that can be found in plants - Greater than 20 alkaloids found in poppy - "Secondary Metabolites" - Morphine = first alkaloid (ID'ed 1806)

Explain why we should care about plant biology -Importance in food webs/trophic relationships?

- Only a small amount of sugars in nature to provide the rest of the ecosystem with essential nutrient for life. The plants are the base of all life

What are opioids?

- Opioids are a drug that are found naturally in the plant opium poppy. Used to create heroin or synthetic opioids such as fentanyl or oxycodone.

What were the opium wars and how has modern conflicts in the "Golden Triangle" influenced opium production?

- Opium Wars (1839-1842 / 1856 - 1860) tobacco use in china addiction / increase opium - Trade war (tea, silk, porcelain-silver - opium) - Taliban banned poppy cultivation - 2015: Afghanistan produced 66% of world opium

What are the differences between phagocytosis and receptor- mediated endocytosis?

- Phagocytosis is the process of ingestion of solid and large molecules by the cell by bounding them within vesicles. This termed as "cell eating" Receptor mediated endocytosis on the other hand is a process as the name suggests in which the endocytosis occurs through a receptor protein. The molecule gets bound to the receptor protein and then endocytosis occurs. This process occurs for some specialized molecules that need receptors for their transport across the cell

The Carbon-Fixation Pathway in C4 Plants Is a Solution to the Problem of Photorespiration

- Plants in which the Calvin cycle is the only carbon-fixation pathway, and in which the first detectable product of CO2 fixation is the three-carbon compound 3-phosphoglycerate (PGA), are called C3 plants. In the so-called C4 plants, CO2 is initially fixed to phosphoenolpyruvate (PEP) to yield oxaloacetate, a four-carbon compound. This reaction occurs in the mesophyll cells of the leaf. The oxaloacetate is rapidly converted to malate (or to aspartate, depending on the species), which moves from the mesophyll cells to the bundle-sheath cells. There the malate is decarboxylated and the CO2 enters the Calvin cycle by reacting with ribulose 1,5-bisphosphate (RuBP) to form PGA. Thus, the C4 pathway takes place in the mesophyll cells, but the Calvin cycle occurs in bundle-sheath cells. C4 plants are more efficient utilizers of CO2 than C3 plants, in part because PEP carboxylase is not inhibited by O2. Thus, C4 plants can attain the same photosynthetic rate as C3 plants, but with smaller stomatal openings and, hence, with less water loss. In addition, C4 plants are more competitive than C3 plants at high temperatures.

Explain the structure of a plasmodesma.

- Plasmodesma are specialized cytoplasmic channels that are found only in plant cells. They are present as channels that are lined by plasma membrane. The channels are continuous with the endoplasmic reticulum forming a tubular strand of structure called a desmotubule. The desmotubule is continuous with the endoplasmic reticulum of the other cells. Thus, the plasmodesma is the main source of intercellular transport. The desmotubule is surrounded by cytoplasmic channels known as the cytoplasmic sleeve. The plasmodesma therefore is made up of desmotubules in the center that are surrounded by cytoplasmic sleeve which are in turn encircled outwardly by the plasma membrane.

Which 3 additional elements compose another 0.95%?

- Potassium, Calcium, Magnesium

What is the difference between primary and secondary metabolites?

- Primary metabolites are those substances or molecules that are necessary for the sustenance of life and are found in all plant cells. Secondary metabolites in contrast are limited in distribution and availability of both within the plant and among different species of plants. The secondary metabolites are produced in specific organs or tissues at specific or defined stages of the plant development. There are three major types of secondary metabolites in plants; alkaloids, terpenoids and phenolics.

Proteins

- Proteins are among the most abundant organic molecules. In the majority of living organisms, proteins make up 50 percent or more of the dry weight. Only plants, with their high cellulose content, are less than half protein in their dry weight. Proteins perform an incredible diversity of functions in living organisms. In their structure, however, proteins all follow the same simple blueprint: they are all polymers of nitrogen-containing molecules known as amino acids.

Explain, in general terms, what happens in each step—reception, transduction, and induction—of a signal-transduction pathway.

- Reception: in this step a chemical message in the form of a molecule is detected by the cell. This molecule is known as the ligand. When the ligand binds to the specific receptor a transmembrane protein then a signal is created. - transduction: this step includes a cascade of steps and different molecules for each step. Thus, when the ligand binds to the receptor, it produces conformational changes in the receptor. This change initiates a cascade of reactions in which different molecules called relay molecules change the next molecule in the pathway - induction: this is the last stage that initiates a response to the signal in the form of gene regulation, enzyme activation and so on

What are the 2 organ systems in vascular plants?

- Root system, Shoot system

Why is it an advantage for a plant to store food energy as fructans rather than as starch? As oils rather than as starch or fructans?

- Starch is a large molecule and need to be hydrolyzed to be used as a form of energy as compared to fructans. Thus, it is advantageous for the plant to store food energy in the form of fructans as it can be stored in higher concentrations and is a readily available form of energy. It is still more advantageous for the plant to store energy in the form of oils or fast as they produce more energy per gram on oxidation as compared to fructans or starch.

What are nodes and internodes?

- Stems are divided in nodes and internodes. The nods are the point at which branches are able to grow (leaves, flower, etc.) Internodes are the space in between nodes

Describe stomatal opening and closing

- Stomata open in the morning as light levels reaching the leaf surfaces increase, and close as light levels decrease. Stomatal opening occurs when solutes are actively accumulated in the guard cells. This accumulation of solutes (and resultant decrease in guard cell water potential) causes osmotic movement of water into the guard cells and a buildup of turgor pressure in excess of that in the surrounding epidermal cells. Stomatal closing is brought about by the reverse process: with a decline in guard cell solutes (and resultant increase in guard cell water potential), water moves out of the guard cells and the turgor pressure decreases.

What is the central role played by the citric acid cycle in the metabolism of the cell?

- The citric acid cycle is important in the metabolism of all cells as it is this cycle that results in the complete breakdown of sugars, proteins and fats. Also, a large amount of energy in the form of ATP to NADH is generated from this cycle. Another most important role of the citric acid cycle is that the electrons that are produced at the end of this cycle are the ones that pass through the electron transport which is a key source of energy to the cells in the form of ATP. Thus, the citric acid cycle is important for the generation of energy in the form of ATP that is needed for al biochemical processed of the cell.

What aspect of their structure do all amino acids have in common? What part of an amino acid determines its identity?

- The common aspect of all amino acids structurally is the presence of an amino group, a carboxyl group and a hydrogen atom that are bonded to a central carbon atom. The fourth side of the carbon atom is boned with an "R" group. The amino acids differ from one another by the structure of the "R" group. It is the one that maintains the identity of the amino acid.

What is the "cytoskeleton" of the cell, and with what cellular processes is it involved?

- The cytoskeleton of the cell is a three-dimensional network of different protein filaments that are present throughout the cytoplasm. The cytoskeleton proteins are mainly made up of two types of protein filaments: Microtubules that are made of the protein tubulin and microfilaments that are made up of the protein actin. The main functions of the cytoskeleton include, formation of spindle fibers in cell division, proper alignment of chromosomes on the spindle fibers, helps in growth of the cell, differentiation of various organelles and also the movement of organelles from one place to the other within a cell.

1. Describe plant tissues (= dermal, ground, vascular)

- The dermal tissue system makes up the outer, protective covering of the plant. The vascular tissue system comprises the conductive tissues—xylem and phloem—and is embedded in the ground tissue system

Taxol

- The diterpenoid taxol has attracted considerable attention because of its anti-cancer properties. It has been shown to shrink cancers of the ovary and the breast

Apart from the production of ATP during the process of respiration, chemiosmotic power has lots of other uses in living organisms.

- The flagella that act as locomotory organs in bacteria, is driven by the process of chemiosmotic coupling - the process of transfer of pyruvate across the mitochondrial membrane coupled with the transport of protons is also an example of chemiosmotic coupling - the process of photosynthesis, the process of splitting of water to form oxygen by light energy and simultaneous transfer of excited electron acceptors is also an example of chemiosmotic coupling

Rubber

- The largest known terpenoid compound is rubber, which consists of molecules containing 400 to more than 100,000 isoprene units. Rubber is obtained commercially from the milky fluid, called latex.

How do primary cell walls differ from secondary cell walls?

- The main points of difference between the primary cell wall and the secondary cell wall are: 1. The primary cell wall is composed of cellulose, hemicellulose, protein, water, enzymes and pectins. They may also contain lignin suberin or cutin. Secondary cell walls are primarily composed of cellulose and some hemicelluloses. Cells of wood that have secondary cell also contain lignin as one of the major components. Proteins, enzymes and pectins are absent in secondary cell walls. 2. The primary cell wall is deposited before the plant cell is formed and during the growth of the plant cell. The secondary cell wall is formed after the plant cell has stopped growing and usually the cell dies in sometime after the formation of the secondary cell wall. 3. The cells with primary cell walls are capable of division and forming new cells thus they are responsible in wound healing and regeneration of the plant. Cells with secondary cell wall are not capable of division and thus their main function is in strengthening the stems or other parts of the plant and in condition of water.

A number of insects, including the monarch butterfly, have adopted a strategy of utilizing certain secondary metabolites of plants for protection against predators. Explain.

- The members of the milkweed family produce a secondary metabolite called cardiac glycosides. These cardiac glycosides are bitter to taste and induce vomiting, Thus, they are effective defense for the plants against animals. The monarch butterfly preferentially teed on this milkweed plant and stores the cardiac glycosides in its body. Thus, when it is eaten by a bird, the secondary metabolites in the form of cardiac glycosides induce the bird to vomit. The birds start to avoid eating monarch butterflies.

In the Electron Transport Chain, the Flow of Electrons Is Coupled to the Pumping of Protons across the Inner Mitochondrial Membrane and the Synthesis of ATP by Oxidative Phosphorylation

- The next stage of respiration is the electron transport chain, which involves a series of electron carriers and enzymes embedded in the inner membrane of the mitochondrion. Along this series of electron carriers, the high-energy electrons carried by NADH and FADH2 move "downhill" energetically, ultimately reducing oxygen to water. The large quantity of free energy re- leased during the passage of electrons down the electron trans- port chain powers the pumping of protons (H+ ions) out of the mitochondrial matrix. This creates an electrochemical gradient of potential energy across the inner membrane of the mitochondrion. When protons pass through the ATP synthase complex as they flow down the gradient back into the matrix, the free energy released is used to form ATP from ADP and phosphate. This process, known as chemiosmotic coupling, is the mechanism by which oxidative phosphorylation is accomplished. In the course of the aerobic breakdown of a glucose molecule to CO2 and H2O, 36 molecules of ATP are generated, most of them in the mitochondrion in the final stage of respiration, oxidative phosphorylation.

What role did oxygen play in the evolution of life on Earth?

- The oxygen played two important roles when its concentration in the atmosphere increased. First, the oxygen molecules that reached the outer layers of the earth were converted to ozone. Thus, due to the formation of an ozone layer, the earth was shielded for the harmful ultraviolet rays of the sun. Thus, this enabled life to evolve and survive in the water and on the shores. And for the first-time life started emerging on the land. Second, the presences of oxygen, the energy rich carbon molecules formed by photosynthesis were utilized much more efficiently and broken down through oxidation by the process of respiration

Describe the important elements of cell membranes (selectively permeable, interaction with environment outside of the cell, transport)

- The permeability of a cell membrane is affected by the polarity, electric charge and molar mass of the molecules that diffuse through it. The phosolipid layers that make up the cell membrane also affect its permeability.

What is the preprophase band? What role does it play in plant cell division?

- The preprophase band is a band of microtubules that is formed just before the start of mitosis. It is formed as a band of microtubules and some actin filaments around the phragmosome and the place where the cell would be divided after the mitosis, just below the plasma membrane. The most important role of the preprophase band is that it marks the location where the new cell plate will be formed after the telophase of the mitosis. Also, since plant cells lack centrosomes, thus the microtubules form the preprophase band help in formation of spindle fibers and in the proper orientation of the spindle fibers in mitosis

What developmental and functional relationships exist between the endoplasmic reticulum and the Golgi bodies of the plant cell?

- The rough endoplasmic reticulum is the one that is developmentally and functionally related to the Golgi bodies. The rough endoplasmic reticulum send out secretory vesicles that fuse with the Golgi bodies. These secretory vesicles usually contain immature proteins in the form of amino acids that need to be further processed before they are sent outside the cell. Also, the secretory vesicles that bud off from the trans side of the Golgi bodies use with the plasma membrane thus releasing the proteins out of the cell. The fusion of these secretory vesicles to the plasma membrane thus contributes to the growth of the plasma membrane in growing cell. The trans Golgi network also produces vesicles that fuse with tonoplast thus forming vacuoles. Now since so much of secretory vesicles are pinched off from the Golgi bodies, they thus need to be renewed. This is done by the vesicles that are released by the endoplasmic reticulum, that fuse with the forming face of the Golgi bodies, thus helping in the development of new sacs of Golgi apparatus.

What are the main types of secondary metabolites?

- There are three major types of secondary metabolites in plants; alkaloids, terpenoids and phenolics.

What are transport proteins, and of what importance are they to plant cells?

- Transport proteins are proteins present in the membrane of the cells that help in the transportation of ions, molecules or other macromolecules in or out of the cell depending on the needs. There are several types of transport proteins depending on the type of molecules and the way in which they transport the material in or out of the cell. The transport proteins usually use energy for the process of transportation. As mentioned above, transport proteins act as channels for the passage of macromolecules or hydrophilic molecules inside or outside the cell. These molecules would otherwise not be able to move in or out of the cell due to its semi permeable nature. Further the transport proteins thus also help in the distribution of nutrients and other molecules throughout the organism, by helping them move out of the cell and making them available for other organelles also

Describe the role of turgor and the orientation of cellulose microfibrils in the guard cell walls in the opening and closing of stomata.

- Turgor pressure is the pressure induced by the cell vacuole, which makes the cell wall rigid by pushing the cell membrane towards the cell wall which stops the water loss form the plant. The phenomenon of increase effect of the turgor pressure happens by means of the increased solute concentration. The guard cells are the specialized cells present around the stomata makes the stomata rigid by the action of cellulose microfibrils which allows the cell to lengthen and makes the stomata by open position, the fibrils micellation creates the opening and closing of stomata by means of the turgor pressure, due to this charge balances the effect of transpiration so the pressure and the transpiration is regulated

Describe turgor pressure (movement of water in relationship to a hypertonic or hypotonic environment)

- Turgor pressure is the pressure that develops in a plant cell as a result of osmosis and/or imbibition. Plant cells tend to concentrate relatively strong solutions of salts within their vacuoles, and they can also accumulate sugars, organic acids, and amino acids. As a result, plant cells absorb water by osmosis and build up their internal hydrostatic pressure. This pressure against the cell wall keeps the cell turgid, or stiff.

What are vascular and non-vascular plants

- Vascular plants make up majority of plants on earth and are plants that have xylem and phloem to transport material. - Non-Vascular plants do not have well developed system for transport water and food (no true, roots, stems or leaves), they get nutrients direct from environment. Example: mosses, liverworts, hornworts

With some strains of yeast, fermentation stops before the sugar is exhausted, usually at an alcohol concentration in excess of 12 percent. What is a plausible explanation?

- We all are aware that the process of fermentation gives alcohol as a byproduct. Alcohol after a certain concentration becomes toxic to living cells. Thus, the process of fermentation by yeast will occur to the level that is not toxic to the yeast cells and then stop which is usually at 12% alcohol concentration

What criteria would you use to determine whether an entity is a form of life?

- We can determine whether an entity is a form of life by observing the below four criteria: a. cellular organization: we need to see if the entity has a properly defined cellular organization with a plasma membrane and nucleus b. growth: we also need to observe if the entity has the ability to grow and develop c. reproduction: if the entity is a life form it will also have the need to reproduce and multiply in some possible way - either asexually or sexually d. hereditary: the entity as a result of reproduction should also be able to pass on its characteristics to the next generation

A knowledge of botany—of plants, fungi, algae, and bacteria—is key to our understanding of how the world works. How is that knowledge important for dealing with today's and tomorrow's problems?

- With the increasing population size, it is easier for us to utilize the plants and algae as a source of food, if we have knowledge of botany. We are also facing changes in the environmental conditions in the form of ozone depletion and global warming. Knowledge of botany will thus help us to choose and develop plants and crops that can thrive under such conditions. Also, it will help us to understand the need of growing more trees and maintain green cover in the form of forests. Knowledge of botany will help us preserve those species that are important to us but are threatened with extinction.

Both plastids and mitochondria are said to be "semiautonomous" organelles. Explain.

- both plastids and mitochondria contain their own DNA and thus have the ability to replicate or divide themselves. They are semi-autonomous and not completely autonomous because though they can replicate independently for the other requirements to carry out the cell reactions they depend upon the nucleus. Thus, they are semiautonomous

What is cytokinesis, and what roles do the phragmosome, the phragmoplast, and the cell plate play during the process?

- cytokinesis is the division of cytoplasm that occurs at the end of mitosis. Phragmosplast is a barrel shaped structure made up of microtubules that forms during the early telophase. The phragmoplast also contain actin filaments and these along with the microtubules form two arrays on the opposite sides of the division plane. The cell plate is present as a suspended structure in the phragmoplast. The phragmoplast starts dividing along with the cell plate until it reaches the cell wall of the dividing cell. Once the cell plate is completely formed, the phragmoplast microtubules disappear. Cells that have large vacuoles have phragmosomes within which the cell plate and phragmoplast are formed

How do ions move in plants - Diffusion

- diffusion may be defined as the dispersion of sub- stances by a movement of their ions or molecules, which tends to equalize their concentrations throughout the system. A membrane that permits the passage of some substances while inhibiting the passage of others is said to be selectively permeable.

Describe plasmolysis

- if a turgid plant cell is placed in a solution (for example, a sugar or salt solution) with a relatively low water potential, water will leave the cell by osmosis. As a result, the vacuole and rest of the protoplast shrink, thus causing the plasma membrane to pull away from the cell wall. This phenomenon is known as plasmolysis.

How and why does the net energy yield under aerobic conditions differ from that obtained under anaerobic conditions?

- in aerobic conditions after glycolysis, pyruvate is formed. This pyruvate enters the citric acid cycle and then the electron transport chain leading to complete breakdown of glucose into water and carbon dioxide. But in anaerobic conditions, the pyruvate that is formed cannot undergo oxidation but undergoes fermentation to form ethanol or lactic acid. Thus, there is not complete breakdown of glucose Thus, in aerobic conditions the total energy yield comes to 30 ATPs whereas in anaerobic conditions the total energy yield is only 2 ATPs that accounts for the energy produced during glycolysis

1. Using the following terms, explain the process of cell wall growth and cellulose deposition in expanding cells: cellulose microfibrils, cellulose synthase complexes (rosettes), cortical microtubules, secretory vesicles, matrix substances, plasma membrane.

- in expanding cells, the process of cell wall growth and cellulose deposition takes place in the following ways. The plasma membrane of plants has certain cellulose synthase complexes called rosettes. These complexes are movable complexes and they synthesize the new cellulose microfibrils are added to the plasma membrane by the means of secretory vesicles that fuse with the membrane. As mentioned earlier, the rosettes are movable. The motility of these rosettes is due to the cortical microtubules that underlie the plasma membrane. The cytoplasm of the cell is increased by the secretory vesicles again, that carry matrix substances into the cell. Thus, the cellulose microfibrils and rosettes help in the development of a new cell wall.

What role is played by vesicle-mediated transport? Compare movement out of the cell with movement into the cell.

- in plants, large molecules such as glucose, glycogen and some amino acids that need to be transported in or out of the cell are done by the process of vesicle mediated transport. In this method, a fragment of the substance to be transported is surrounded by a portion of the membrane forming a vesicle. This vesicle moves in and out of the cell depending on where it needs to be transported. The process in which the vesicle moves into the cell is called endocytosis. In the process, the vesicle that carries the substance fusses with the cell membrane and the substance gets released in the cell. The process in which the vesicles moves out of the cell as the substance need to be transported to the outside is called exocytosis. In the process the substance that needs to be transported out of the cell goes and fuses with the membrane. As a result, a pit or groove is formed which buds off eternally, forming a vesicle containing the substance that need to be transported

Where in the cell does the citric acid cycle occur, and what are the products formed?

- in the cell, the citric acid cycle occurs in the matrix of the mitochondria. The products formed after one citric acid cycle is: 1 GTP, 3 NADH, 1 FADH2 and 2 CO2

tertiary structure

- in this level, the protein folds itself and is held together by disulfide bridges and hydrogen bonds. This structure provided strength and stability to the protein structure

secondary structure

- in this structure, the polypeptide chain coils into a helix or bends to form sheets. Thus, two types of structure: alpha helix or beta pleated sheet are formed by this level.

Explain why we should care about plant biology - Importance in symbioses?

- interaction between two different organisms living in close physical association, typically to the advantage of both.

Where are alkaloids stored?

- leaves and roots / plant tissue

Explain how matter is composed of atoms

- matter is made up of whatever atoms and molecules are made, which is protons, neutrons and electrons

Basic chemistry of life: photosynthesis & respiration

- photosynthesis: CO2 + 6H2O -> C6H12O6 + O2: Radiant energy from the sun is captured and used to form the sugars all life depends, and oxygen is also released as byproduct. Chlorophyll is essential to carry out photosynthesis. - respiration: Plants reproduce sexually through the fusion of male and female gametes in the flower. Asexual reproduction is through stems, roots and leaves

During the transition "to the air," plants also underwent further adaptations that made it possible for them to reproduce on land

- production of drought-resistant spores - evolution of complex, multicellular structures in which the gametes, or reproductive cells, were held and protected from drying out by a layer of sterile cells

How did prokaryotes and eukaryotes get their name?

- prokaryote means "before a nucleus," and eukaryote, "with a true nucleus."

Why do plants produce alkaloids?

- protection: preventing insects and animals from eating them

Anthocyanins

- range in color from red through purple to blue; plant pigments (signaling, antioxidants, sunscreen)

Explain why we should care about plant biology - Overall biodiversity - approximate number of species of flowering plants relative to age or origin?

- range of 250,000 to 400,000 species showing very diverse range of flowering plants compared to only 12,000 species of mosses

Describe the components of a species name

- species name: Papaver (genus) somniferum (specific epithet)

1. Distinguish between microtubules and actin filaments. With what functions are each of these protein filaments associated?

- the actin filaments structurally form a double helix and are smaller than microtubules in size. The microtubules on the other hand have helical lattice structure and are larger in size than the actin filaments - as the name suggests, the actin filaments are mainly made up of actin fibers that are contractile protein. The microtubules are mainly composed of a different protein called tubulin that is two types- alpha and beta proteins - structurally, the actin filaments are strong but flexile due to the presence of actin protein. Whereas microtubules are structurally stiff and resist bending force - the main function of actin filaments is cell or cytoplasmic movement while the main function of microtubules is in cell division like mitosis and another cell transport. The main function of the actin filaments in plants is in cytoplasmic movement. The main function of the microtubules in plants ins in chromosome separation during mitosis and maintaining cell shape apart from some cellular transport within the cell

What is the basic structure of cellular membranes?

- the basic structure of all cellular membranes consists of a phospholipid bilayer. The membrane is composed of a two layer of phospholipids in which the hydrophobic tails form the external periphery and the hydrophilic heads come together in the venter forming the core of the layer. This layer is interspersed with membrane proteins that help in the transfer of molecules across the membrane

What is the role of light in photosynthesis, and what are the properties of light that suggest it is both a wave and a particle?

- the light is one of the most important factors responsible for the process of photosynthesis. It is light energy that facilitates the photolysis of water, in the process of photosynthesis. Further, light is also needed for the activation of the pigment molecules of the photosystem, by which ATP and NADPH are generated for use by the other processes. The properties of reflection and refraction by light suggest that it is both a wave and a particle. Further, the fact that light energy can excite the electrons in the pigment molecules of photosystem suggests that it is a particle made up of various photons. But at the same time the fact that it is absorbed at various wavelengths by the pigment molecules also suggest that it is a wave. Thus, it proves that light is both a particle and a wave

Explain the role of light, potassium ions, and sucrose in stomatal movement.

- the light is the major source of photosynthesis. The blue light regulates the movement of the stromata, by means of activating the proton pumps in the guard cells. In general, the stomata is open during the day time (rich light source) and closes while the time of dark For the production of pressure in the guard cells (due to the pressure in guard cells gives the stomata closes), certain ion is taken to create the turgor pressure which is created by the efflux of the potassium ions. The sucrose will also play the same role as the potassium ions So, these are the roles of the light, potassium ions and the sucrose in stomatal movement

Secondary active transport is significant to the plant because it enables a cell to accumulate even neutral solutes at concentrations much higher than those outside the cell. Using the terms proton pump (H+-ATPase), proton gradient, proton- coupled cotransport, sucrose-proton cotransport, primary active transport, and secondary active transport, explain how this system works.

- the mentioned terms can be used together to explain the transport of sucrose into a cell. The enzyme H-ATPase is one of the enzymes, that drives the proton pump. The proton pump helps in the establishment of a proton gradient by the active transport of protons out of the cell. Once the proton gradient is established, the protons that have moved out of the cell flow back into the cell passively which generates ATP. This ATP is used as the energy that is required to transport sucrose into the cell against its concentration gradient. This process is a case of secondary active transport. It is called so as the transport of the substance is by the energy created by the active outflow and then passive inflow of the protons creating a proton gradient. Since in this process, the transport of sucrose is aided and coupled with the transport of protons into the cell, this is known as proton-coupled cotransport or sucrose proton cotransport

How does the flow of electrons in the electron transport chain result in the formation of ATP?

- the most abundant carriers of electrons in the electron transport chain are quinine molecules. These molecules are present on the inner mitochondrial membrane and are orientated in such a way that as they accept an electron from a preceding electron carrier, they also pick up a proton (H+) from the mitochondrial matrix. The proton is then released in the intermembrane space as the electron is passed to the next carrier. Thus,as this process of transfer of electron takes place, alongside the protons are transported from the matrix to the intermembrane space through the inner membrane. This thus creates a proton gradient across the inner membrane. The potential energy of this proton gradient is then used for the production of ATP from ADP

What is the cell cycle, and what key events occur in the G1, S, G2, and M phases of the cell cycle?

- the regular repeated set of events that take place during cell division leading to the formation of new cells is called a cell cycle. The cell cycle is commonly divided into two stages: the interphase and mitosis. The interphase is further divided into three stages: G1, S, and G2 phase G1 phase, S phase, G2 phase and M phase

What is the role of mitosis? What events occur during each of the four mitotic phases?

- the role of mitosis is to ensure that after cell division each cell has the same genetic material and information that the parent cell had. Thus, after mitosis the daughter cell contains a nucleus that has chromosomes complementary to the parent chromosome and also half of the cytoplasm so that cell growth and function can start immediately. Thus, mitosis is necessary to maintain cellular genetic identity and function There are four phases in mitosis- Prophase: Metaphase: Anaphase: Telophase:

paleobotany

- the study of the biology and evolution of fossil plants.

genomics

- the study of the content, organization, and function of genetic information in whole genomes

molecular biology

- the study of the structure and function of biological molecules

ethnobotany - the study of the uses of plants for medicinal and other purposes by indigenous peoples

- the study of the uses of plants for medicinal and other purposes by indigenous peoples

What are the roles of signal transduction and plasmodesmata in cell-to-cell communication?

- there are various ways by which cells communicate with one another. One of the ways is by sending signals and receiving them. The signals can be sent in two ways: - the first way is through a receptor on the membrane that includes the signal transduction pathway. In the signal transduction pathway, the signal in the form of a molecule gets attached to a receptor on the membrane. Only the cells that need to illicit a response have the required receptor proteins. Once the signal is bound to the receptor, the shape of the receptor changes. This illicit a response in the cell forming another signal. Thus, this process is continued until the signal reaches the organelle to which it needs to be transmitted. - the second is through plasmodesmata. Plasmodesmata are microscopic cytoplasmic tunnels or connections that connects the cells to one another. Some signals can pass directly through these plasmodesmata and trigger a response

What are phycobilins?

- these are water soluble pigments present only in cyanobacteria and rhodophyta. These pigments help in soaking up the light energy and thus storing further use

What are Carotenoids?

- these pigments are present along with chlorophyll a molecule in the antenna of photosystems of plants and photosynthetic bacteria

What is Chlorophyll a?

- this is the most abundant and important pigment for photosynthesis. It has an absorption wavelength of 430nm to 662 nm. It reflects green light. The light absorbing pigments in the reaction center of photosystems are a pair of chlorophyll a molecule. The antennas of photosystems also have chlorophyll a molecule along with other pigments

quaternary structure

- this level is formed by the coming together of two large or more polypeptide chains leading to a complex protein structure

What is Chlorophyll b?

- this pigment is present along with chlorophyll a but in less quantities comparatively. The chlorophyll b molecules are present along with chlorophyll a molecule in the antenna of the photosystems of vascular plants that help in absorbing light and transmitting them to the reaction centers

primary structure

- this structure is basically determined by the order in which the amino acids are placed with one another. The sequence is unique to each protein

Explain how each of the following factors affects the rate of transpiration: temperature, humidity, air currents.

- transpiration means the water loss from the plant some factors will affect the rate of transpiration. They are listed below: Temperature - the increase in temperature leads to the increase in the rate of transpiration because temperature raises the water vapor which reduces the water content of the plant, it leads the plant to scarcity of water Humidity - the increase in the humidity leads to the decrease in the rate of transpiration Air Currents - air currents also increase the rate of the transpiration, because the flow of the air current along the surface of the leaves, increases the vapor pressure in the leaf surface due to this the water loss will take place results the increased level of the transpiration

Lignin

- unlike other phenolic compounds, are deposited in the cell wall rather than in the vacuole. The major importance of lignin is the compressive strength and stiffness it adds to the cell wall.

plant physiology

- which is the study of how plants function, that is, how they capture and transform energy and how they grow and develop

Amino acids

1. Amino Acids Are the Building Blocks of Proteins: Each specific protein is made up of a precise arrangement of amino acids. All amino acids have the same basic structure consisting of an amino group (—NH2), a carboxyl group (—COOH), and a hydrogen atom, all bonded to a central carbon atom. The differences arise from the fact that every amino acid has an "R" group—an atom or a group of atoms—also bonded to the central carbon. It is the R group ("R" can be thought of as the "rest of the molecule") that determines the identity of each amino acid.

Adaptation Moving to Land "water" to "air"

1. Cuticle 2. Stomata 3. Vascular Systems 4. Roots --> Shoots 5. UV protection (Anthocyanins) 6. Seeds and seed coats 7. Sporopollenin

The increase in free oxygen opened the way to a much more efficient utilization of the energy-rich carbon- containing molecules formed by photosynthesis

1. It enabled organisms to break down those molecules by the oxygen-utilizing process known as respiration. Respiration yields far more energy than can be extracted by any anaerobic, or oxygen-less, process.

Roots

1The roots are continuously reaching new sources of water and minerals, and the photosynthetic regions are continuously extending toward the light.

Number of amino acids

20

When did the land plants evolve?

450 mya

heterotrophic organism

A heterotrophic organism is dependent on an outside source of organic molecules for its energy.

The average temperature will have increased between 1.5° and 4.5°C due to the greenhouse effect. This global-warming phenomenon—the trapping of heat radiating from the Earth's surface out into space—is intensified through the increased amounts of carbon dioxide, nitrogen oxides, CFCs, and methane in the atmosphere resulting from human activities.

A large portion of the total number of species of plants, animals, fungi, and micro- organisms is disappearing during our lifetime—the victims of human exploitation of the Earth—resulting in a loss of biodiversity.

A necessary preliminary step to respiration

A necessary preliminary step to respiration—the complete oxidation of sugars or other organic molecules to carbon dioxide and water—is the hydrolysis of these storage molecules to the monosaccharides glucose and fructose. Respiration itself is generally considered to begin with glucose, an end product of the hydrolysis of both sucrose and starch.

Osmosis Is the Movement of Water across a Selectively Permeable Membrane

A selectively permeable membrane is a membrane that permits the movement of water but inhibits the passage of solutes. In the absence of other forces, the movement of water by osmo- sis is from a region of lower solute concentration, and therefore of higher water potential, to a region of higher solute concentration, and so of lower water potential. The turgor (rigidity) of plant cells is a consequence of osmosis, as well as of a strong but somewhat elastic cell wall.

Cytoskeleton

All eukaryotic cells possess a cytoskeleton, a dynamic, three- dimensional network of protein filaments that extends through- out the cytosol and is intimately involved in many processes. These processes include cell division, growth, and differentiation, as well as the movement of organelles from one location to another within the cell. The cytoskeleton of plant cells consists of two types of protein filaments: microtubules and actin filaments.

The Cell Is the Fundamental Unit of Life

All living matter is composed of cells. Although extremely varied in structure and function, all cells are remarkably similar in their basic structure. All cells possess an outer membrane, known as the plasma membrane, that isolates the cell's contents from the external environment. Enclosed within this membrane are the cytoplasm and the hereditary information in the form of DNA.

chemically speaking, is composed of organic molecules

Almost all the rest of a living organism, chemically speaking, is composed of organic molecules—that is, of molecules that contain carbon.

Proteins Are Versatile Polymers of Amino Acids

Amino acids have an amino group, a carboxyl group, a hydro- gen, and a variable R group attached to the same carbon atom. Twenty different kinds of amino acids—differing in the size, charge, and polarity of the R group—are used to build proteins. By the process of dehydration synthesis, amino acids are joined by peptide bonds. A chain of amino acids is a polypeptide, and proteins consist of one or more long polypeptides. A protein's structure can be described in terms of levels of organization. The primary structure is the linear sequence of amino acids joined by peptide bonds. The secondary structure, most commonly an alpha helix or a beta pleated sheet, is formed as a result of hydrogen bonding between amino and carboxyl groups. The tertiary structure is the folding that results from interactions between R groups. The quaternary structure results from specific interactions between two or more polypeptide chains. Enzymes are globular proteins that catalyze chemical reactions in cells. Because of enzymes, cells are able to accelerate the rate of chemical reactions at moderate temperatures.

Ecosystem Connectivity

An ecosystem functions as an integrated unit, although many of the organisms in the system compete for resources. Virtually every living thing, even the smallest bacterial cell or fungal spore, provides a food source for some other living organism. - The energy captured by green plants is transferred in a highly regulated way through a number of different types of organisms before it is dissipated. - It is impossible to change a single component of an ecosystem without the risk of destroying the balance on which the stability of the ecosystem depends

By what mechanisms do apoplastic and symplastic phloem- loading plants move sugars into the sieve tube-companion cell complexes?

Apopplastic use sucrose -proton transport and Symplastics use polymer -trapping mechanism

Explain Cohesion-Tension Theory

As a result, water is with- drawn from the roots, pulled up the xylem, and distributed to the cells that are losing water vapor to the atmosphere. This water loss makes the water potential of the roots more negative and increases their capacity to extract water from the soil. Hence, the lowered water potential in the leaves, brought about by transpiration and/or by the use of water in the leaves, results in a gradient of water potential from the leaves to the soil solution at the surface of the roots. This water potential gradient provides the driving force for the movement of water

Ecosystems Are Relatively Stable, Integrated Units That Are Dependent on Photosynthetic Organisms

As plants have evolved, they have come to constitute biomes, great terrestrial assemblages of plants and animals. The interacting systems made up of biomes and their nonliving environments are called ecosystems. Human beings, which appeared about 2 million years ago, developed agriculture about 10,500 years ago and thus provided a basis for the huge increase in their population levels. Subsequently, they have become the dominant ecological force on Earth. Humans have used their knowledge of plants to foster their own development and will continue to do so with increasingly greater importance in the future.

Early in evolutionary history, the principal photosynthetic organisms were microscopic cells floating below the surface of the sunlit waters.

As the cellular colonies multiplied, they quickly depleted the mineral resources of the open ocean. (It is this shortage of essential minerals that is the limiting factor in any modern plans to harvest the seas)

primary active transport & secondary active transport

As we have already seen, the proton pump in plant and fungal cells is energized by ATP and mediated by an H+-ATPase located in the membrane. The enzyme generates a large electrical potential and a pH gradient— that is, a gradient of protons (hydrogen ions)—that provide the driving force for solute uptake by all the H+-coupled cotransport systems. By this process, even neutral solutes can be accumulated to concentrations much higher than those outside the cell, simply by being cotransporter with a charged molecule (for example, an H+). The energy-yielding first process (the pump) is referred to as primary active transport, and the second process (the cotransporter) as secondary active transport

What is astringency?

Astringency is a tactile taste felt as a dry, rough feeling in the mouth and contraction of the tongue tissue. It usually involves the formation of aggregated precipitates between tannins or polyphenols and proteins in the saliva.

Plastids and Mitochondria Share Certain Features with Prokaryotic Cells

Both plastids and mitochondria are semiautonomous organelles. Their DNA is found in nucleoids, and they possess small ribosomes similar to those of bacteria. Plastids and mitochondria originated as bacteria that were engulfed within larger heterotrophic cells. Plant cells contain three genomes: those of the nucleus, the plastids, and the mitochondria.

Facilitated Diffusion, or Active Transport

Both simple diffusion and facilitated diffusion (diffusion assisted by carrier or channel proteins) are passive transport processes. If transport requires the expenditure of energy by the cell, it is known as active transport. Active transport can move substances against their concentration gradient or electrochemical gradient. This process is mediated by transport proteins known as pumps. In plant and fungal cells, an important pump is a membrane-bound H+-ATPase enzyme.

Water Movement Takes Place by Bulk Flow and Diffusion

Bulk flow is the overall movement of water molecules, as when water flows downhill or moves in response to pressure. Sap moves by bulk flow from the leaves to other parts of the plant body. Diffusion involves the independent movement of molecules and results in net movement down a concentration gradient. Diffusion is most efficient when the distance is short and the gradient is steep. By their metabolic activities, cells maintain steep concentration gradients of many substances across the plasma membrane and between different compartments of the cytoplasm. The rate of movement of substances within cells is increased by cytoplasmic streaming. Carbon dioxide and oxygen are two important nonpolar molecules that move into and out of cells by diffusion across the plasma membrane.

Respiration, or the Complete Oxidation of Glucose, Is the Chief Source of Energy in Most Cells

C6H12O6 (Glucose) + 6O2 (Oxygen) → 6CO2 (Carbon Dioxide) + 6H2O (water) + Energy As glucose is oxidized in a series of sequential enzyme- catalyzed reactions, some of the energy released is packaged in the form of terminal phosphoanhydride bonds in ATP and the rest is lost as heat

During the photosynthetic process, radiant energy from the sun is captured and used to form the sugars on which all life, including our own, depends. Oxygen, also essential to our existence, is released as a by-product.

CO2 + 6H2O -> C6H12O6 + O2

Carbohydrates Are Sugars and Their Polymers

Carbohydrates serve as a primary source of chemical energy for living systems and as important structural elements in cells. The simplest carbohydrates are the monosaccharides, such as glucose and fructose. Monosaccharides can be combined to form disaccharides, such as sucrose, and polysaccharides, such as starch and cellulose. Starch molecules are storage polysaccharides made of polymers of alpha-glucose that form into coils, whereas cellulose is a structural polysaccharide that forms linear microfibrils impervious to the enzymes that break down starch. Carbohydrates can usually be broken apart by the addition of a water molecule at each linkage, that is, by hydrolysis.

Carbohydrates roles in plants?

Carbohydrates store energy in the form of starch which, depending on the type of carbohydrate, provide either simple or complex sugars

What are the four main types of organic molecules found in plant cells?

Carbohydrates, Lipids, Proteins, Nucleic Acids

Carriers

Carriers bind the specific solute being transported and undergo a conformational change to transport the solute across the membrane.

Under the pressure of this competition, cells that could make efficient use of the limited energy sources now available were more likely to survive than cells that could not.

Cells evolved that were able to make their own energy-rich molecules out of simple inorganic materials. Such organisms are called autotrophs, "self-feeders."

One might say that two distinct events take place in chemiosmotic coupling. What are those events? What are some uses of chemiosmotic power in living organisms?

Chemiosmotic coupling is a word that is derived from two separate words: Chemical and osmotic. The chemical word indicates the chemical process that occurs and the osmotic word indicates the transport that occurs across a semi permeable membrane. Thus, the two distinct processes that occur in chemiosmotic coupling are: - the creation of a proton gradient across the inner membrane of the mitochondria by the transfer of electron across a series of carriers and the transfer of protons to the matrix - the generation of ATP from ADP by the potential energy that is stored in the proton gradient due to movement of electrons

chromatin

Chromatin is made up of DNA, which carries the hereditary information of the cell, combined with histone proteins.

What evidence supports the cohesion-tension theory?

Cohesion tension theory, states that the uptake of water by the root hair, by the action of both sticking a creating the pressure due to the transpiration pull, in other words, the water is the polar molecule which able to cohesive with each other and creates the enormous pressure due to the action of the transpiration. The evidence will support the action of cohesion tension theory is easy to understand in tall trees, where the root pressure is increased due to the transpiration also for the essential function of the plants with water, the root uptakes the water and transported through the xylem and reaches the leaves

How does the cohesion-tension theory account for the movement of water to the top of tall trees?

Cohesion-tension; cohesion means the sticky effect and the tension means the stretching effect, both the effects plays in the movement of water in the plant through the specialized system called xylem is said to be the cohesion - tension theory. We know well water is the polar molecule which has the positively charged oxygen, the root pressure always induce the uptake of water from the soil and the water molecule are transported through the xylem to the leaves, also due to the environmental situation, the water loss will take place (this is known as transpiration). If one water molecule losses by the transpiration the other water molecule will replace the loss. This phenomenal effect is called as the cohesion-tension theory In tall plants, the roots are widespread also have the large cell arrangement due to the widespread of root system the root pressure is increased, the large number of xylem arrangement concentrates in the water movement from the root to the leaves and the effect of water movement from the root to the leaves, and the effect of water uptake is regulated continuously.

Dividing Eukaryotic Cells Pass through a Regular Sequence of Events Known as the Cell Cycle

Commonly, the cell cycle is divided into interphase and mitosis. Interphase consists of three phases (G1, S, and G2), which are the preparatory phases of the cycle. During the G1 phase, the cell doubles in size. This size increase is accompanied by an increase in numbers of cytoplasmic molecules and structures. DNA replication occurs only during the S phase, resulting in duplication of the chromosomes. The primary role of the G2 phase is to make sure that chromosome replication is complete and to allow for the repair of damaged DNA. Progression through the cycle is mainly controlled at two crucial check- points, one at the transition from G1 to S and the other at the transition from G2 to the initiation of mitosis. Mitosis and cytokinesis together are referred to as the M phase of the cell cycle.

Large Molecules and Particles Cross Membranes by Vesicle-Mediated Transport

Controlled movement of large molecules into and out of a cell occurs by endocytosis or exocytosis, processes in which substances are transported within vesicles. Three forms of endocytosis are known: phagocytosis, in which solid particles are taken into the cell; pinocytosis, in which liquids are taken in; and receptor-mediated endocytosis, in which molecules and ions to be transported into the cell are bound to specific receptors in the plasma membrane. During exocytosis and endocytosis, portions of membranes are recycled between the Golgi bodies and the plasma membrane.

Waxes

Cutin and suberin are unique lipids that are important structural components of many plant cell walls. The major function of these lipids is to form a matrix in which waxes - long chain lipid compounds - are embedded. The waxes, in combination with cutin or suberin, form barrier layers that help prevent the loss of water and other molecules from plant surfaces. Waxes are the most water repellent lipid.

Multicellular photosynthetic organisms were better able to maintain their position against the action of the waves, and, in meeting the challenge of the rocky coast, new forms developed.

Developed relatively strong cell walls for support, as well as specialized structures to anchor their bodies to the rocky surfaces

Cells Reproduce by Cell Division

During cell division, the cellular contents are apportioned be- tween two new daughter cells. The new cells are structurally and functionally similar both to the parent cell and to one another, because each new cell inherits an exact replica of the genetic information of the parent cell. In eukaryotes, cell division consists of two overlapping stages: mitosis (the division of the nucleus) and cytokinesis (the division of the cytoplasm).

nucleolus

Each nucleolus contains high concentrations of RNA (ribonucleic acid) and proteins, along with large loops of DNA emanating from several chromosomes. The loops of DNA, known as nucleolar organizer regions, are the sites of formation of ribosomal RNA. The nucleolus, in fact, is the site of formation of ribosomal subunits (large and small), which are then transferred, via the nuclear pores, to the cytosol, where they are assembled to form ribosomes.

Ionic Bond

Electron Donation (NaCl (salts) , Acids/Bases)

Covalent Bond

Electron Sharing (N2)

Explain what enzymes are (active sites, denaturing...)

Enzymes are large complex proteins that are globular in structure. Their man function is to act as a catalyst for various chemical reactions that occur in the cell. Enzymes are important to the cell as they accelerate the rate of a reaction even at low concentrations. They remain unchanged during the reaction and thus can be used over and over again by the cells.

The uptake of inorganic nutrients is an energy-requiring process. Explain.

Every process which takes place in the universe which needs the energy the uptake of the inorganic nutrients in plants is the energy required process. In plants and other life forms, the transport or uptake of nutrients by the cells through the principle called absorption here the nutrients for the uptake the chemical channels present in the surface of the cell wall and the cell membrane have to open the opening of those channels requires the protons and the imbalance in the chemical barrier between the inside and outside of the cells which is supported with the Adenosine Tri-phosphate (ATP) which is nothing but energy molecule So, the import of the inorganic substance requires the energy

Hydrogen Bond

Ex. Water (Loose positive and negative bonds)

Fats & oils - saturated/unsaturated?

Fats and oils have similar chemical structure. Each consists of three fatty acid molecules bonded to one glycerol molecule and each bond is formed by dehydration synthesis (removing h20). Fat and oil molecules are also known as triglycerides, containing no polar groups. Non-polar groups tend to clump together in water. A fatty acid that has no double bonds between carbon atoms is said to be saturated. Each carbon atom in the chain has formed covalent bonds to four other atoms, and bonding possibilities are therefore complete. By contrast, a fatty acid that contains carbon atoms joined by double bonds is said to be unsaturated. The double-bonded carbon atoms have the potential to form additional bonds with other atoms. The physical nature of a fat is determined by the length of the carbon chains in the fatty acids and by the extent to which the fatty acids are saturated or unsaturated. The terms fat and oil generally refer to the physical state of the triglyceride. Fats are triglycerides that are usually solid at room temperature, whereas oils are usually liquid

secondary cell wall

Found in cells with strengthening and/or water conducting functions. Is rigid and thus imparts added strength

Glucose

Glucose can be used as a source of energy under both aerobic (that is, in the presence of oxygen) and anaerobic (in the absence of oxygen) conditions. When energy is extracted from organic compounds without the involvement of oxygen, the process is called fermentation,

What is guttation?

Guttation - Dewlike droplets of water at the tips of grass and other leaves in the early morning demonstrate the effects of root pressure. These droplets are not dew—which is water that has condensed from the air—but come from within the leaf by a process known as guttation. The water of guttation is literally forced out of the leaves by root pressure.

Explain the relationship between root pressure and guttation.

Guttation is the phenomenon of water loss in guttation water loss is as like as water but not like a vapor (transpiration). Root pressure is the phenomenon of pressure to imply the uptake of water molecules and distribute the water to the leaves. The relationship between the guttation and the root pressure is the guttation of water from the leaves which takes place by the root pressure

Heterotrophic Organisms Evolved before Autotrophic Organisms, Prokaryotes before Eukaryotes, and Unicellular Organisms before Multicellular Organisms

Heterotrophs, organisms that feed on organic molecules or on other organisms, were the first life forms to appear on Earth. Autotrophic organisms, those that could produce their own food by photosynthesis, evolved no less than 3.4 billion years ago. Until about 2.1 billion years ago, the prokaryotes—archaea and bacteria—were the only organisms that existed. Eukaryotes, with larger, much more complex cells, evolved at that time. Multicellular eukaryotes began to evolve at least 650 million years ago, and they began to invade the land about 450 million years ago. With the advent of oxygen-producing photosynthesis, in which water molecules are split and oxygen is released, oxygen began to accumulate in the atmosphere. The presence of this free oxygen enabled organisms to break down the energy-rich products of photosynthesis by aerobic respiration.

concentration gradient

If a molecule is uncharged, the direction of its transport is determined only by the difference in the concentration of the molecule on the two sides of the membrane (the concentration gradient).

osmotic pressure.

If enough pressure is applied on the solution in the tube by a piston, it is possible to prevent the net movement of water into the tube. The pressure that would have to be applied to the solution to stop water movement is called the osmotic pressure.

endocytosis

In endocytosis, material to be taken into the cell induces the plasma membrane to bulge inward, producing a vesicle enclosing the substance. Three different forms of endo- cytosis are known: phagocytosis, pinocytosis, and receptor- mediated endocytosis.

Perennials

In longer- lived plants—perennials—the stem may become thickened and woody and covered with cork, which, like the cuticle-covered epidermis, retards water loss

Signal Transduction Is the Process by Which Cells Use Chemical Messengers to Communicate

In multicellular organisms, communication among cells is essential for coordination of the different activities of the cells in the various tissues and organs. Much of this communication is accomplished by chemical signals that either pass through the plasma membrane or interact with receptors on the membrane surface. Most receptors are transmembrane proteins that become activated when they bind a signal molecule and generate second messengers inside the cell. The second messengers, in turn, amplify the stimulus and trigger the cell's response. This process is known as signal transduction

What are the main events associated with each of the two photosystems in the light reactions, and what is the difference between antenna pigments and reaction center pigments?

In photosystem II, the main reaction or events that occur are: - Photolysis of water takes place that releases electron into the photosystem II, releasing oxygen by splitting of water - light energy is absorbed at 680nm wavelength that excites the electron in the chlorophyll a - the excited electrons flow down a series of electron acceptors downhill and through the cytochrome b complex that releases protons and creates a proton gradient - the proton gradient created helps in the generation of ATP that is used for light independent reactions - the electron further move downhill through plastocyanin and reached the photosystem I In photosystem I, the main reactions take place are: - light energy is absorbed at 700 nm that excited the electrons received from photosystem II - the excited electrons pass through a series of electron gradients again, the final electron acceptor being NADP+ - The NADP+ gets reduced to NADPH that gets used in the Calvin cycle The antennae pigments form the outer ring of the reaction center that funnel light energy of a particular wavelength to the reaction center. The antennae pigment thus form a light harvesting complex is made up of eight polypeptide molecules. Each polypeptide molecule binds itself to three chlorophyll molecules and a carotenoid molecule. All these together form a ring that surround the reaction center. The chlorophyll molecules contain primarily chlorophyll a molecule and few chlorophyll b molecules The reaction center pigments on the other hand are a pair of chlorophyll a molecule that absorb the funneled light energy of a particular wavelength

hemicelluloses and pectin.

In plant cell walls, the cellulose microfibrils are embedded in a matrix containing two other complex, branched polysaccharides, namely, hemicelluloses and pectin. Hemicelluloses stabilize the cell wall by hydrogen bonding to the cellulose microfibrils. Pectins make up most of the middle lamella, a layer of intercellular material that cements together the walls of adjacent plant cells. Pectins, which are especially plentiful in certain fruits, such as apples and cranberries, allow jams and jellies to thicken and gel.

Two types of nucleic acids are found in living organsims

In ribonucleic acid (RNA), the sugar subunit in the nucleotides is ribose. In deoxyribonucleic acid (DNA), it is a deoxyribose. DNA is the carrier of genetic information. RNA is involved with protein synthesis

Seed plants

In the seed plants, which include almost all familiar plants except the ferns, mosses, and liverworts, the young plant, or embryo, is enclosed within a specialized covering (seed coat) provided by the parent. There the embryo is protected from both drought and predators and is provided with a supply of stored food. The embryo, the supply of stored food, and the seed coat are the components of the seed.

dehydration synthesis

In the synthesis of a disaccharide from two monosaccharide molecules, a molecule of water is removed and a new bond is formed between the two monosaccharides. This type of chemical reaction, which occurs when sucrose is formed from glucose and fructose, is known as dehydration synthesis

Annuals

In younger plants and in annuals—plants with a life span of one year—the stem is also a photosynthetic organ.

Isoprene

Isoprene itself is a gas emitted in significant quantities by the leaves of many plant species and is largely responsible for the bluish haze that hovers over wooded hills and mountains in the summer.

In Well-Watered Plants, Light Is the Dominant Signal Controlling Stomatal Movements

It is blue light that regulates stomatal movements, through its activation of a proton-pumping ATPase in the guard cell plasma membrane. In the morning, potassium is the principal solute involved in stomatal opening. On potassium efflux, sucrose becomes the dominant osmoticum. Stomatal closing at the end of the day parallels a decrease in sucrose and a resultant loss of guard cell turgor.

Why is the evolution of photosynthesis thought to be such an important event in the evolution of life in general?

It is only due to the evolution of photosynthesis and photosynthetic organisms, that energy from the sun was able to be used to convert simple inorganic molecules from the soil into organic molecules from the soil into organic molecules such as sugar and other carbohydrates. Without the evolution of this, the life on earth would have come to a stop due to the competition for the available complex molecules and its scarcity due to usage by heterotrophs.

four different types make up most of the dry weight of living organisms

Just four different types make up most of the dry weight of living organisms. These four are carbohydrates (consisting of sugars and chains of sugars), lipids (most of which contain fatty acids), proteins (composed of amino acids), and nucleic acids (DNA and RNA, which are made up of complex molecules known as nucleotides).

Lipids Are Hydrophobic Molecules That Play a Variety of Roles in the Cell

Lipids are another source of energy and structural material for cells. Compounds in this group—fats, oils, phospholipids, cutin, suberin, waxes, and steroids—are generally insoluble in water. Fats and oils, also known as triglycerides, store energy. Phospholipids are modified triglycerides that are important components of cellular membranes. Cutin, suberin, and waxes are lipids that form barriers to water loss. The surface cells of stems and leaves are covered with a cuticle, composed of wax and cutin, that prevents water loss. Steroids are molecules having four interconnected hydrocarbon rings. Steroids are found in cellular membranes, and they may have other roles in the cell as well.

Living Matter Is Composed of Only a Few of the Naturally Occurring Elements

Living organisms are composed primarily of only six elements: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. The bulk of living matter is water. Most of the rest of living material is composed of organic (carbon-containing) molecules—carbohydrates, lipids, proteins, and nucleic acids. Polysaccharides, proteins, and nucleic acids are examples of macromolecules, which are made up of similar monomers joined together by dehydration synthesis (removing H2O) to form polymers. By the reverse process, called hydrolysis (adding H2O), polymers can be split apart to their constituent monomers.

Macromolecules

Macromolecules (large molecules), such as polysaccharides, that are made up of similar or identical small subunits are known as polymers ("many parts"). The individual subunits of polymers are called monomers ("single parts"); polymerization is the stepwise linking of monomers into polymers.

Apical meristems

Meristems located at the tips of all roots and shoots—the apical meristems—are involved with the extension of the plant body in both annuals and perennials

Inventory of a plant cell?

Mitochondria - Surrounded by a double-membrane envelope. The inner membrane is folded into cristae. Semiautonomous organelles, containing their own DNA and ribosomes. - Sites of cellular respiration. Peroxisomes - Surrounded by a single membrane. Sometimes contain crystalline protein bodies. Contain enzymes for a variety of processes such as photorespiration and conversion of fats to sucrose. Vacuoles - Surrounded by a single membrane (the tonoplast); may take up most of the cell volume. Some filled with cell sap, which is mostly water. Often contain anthocyanin pigments; store primary and secondary metabolites; break down and recycle macromolecules Ribosomes - Small, electron-dense particles, consisting of RNA and protein. Sites of protein synthesis. Oil bodies - Have an amorphous appearance. Sites of lipid storage, especially triglycerides. Endoplasmic reticulum - A continuous, three-dimensional membrane system that permeates the entire cytosol. Multiple functions, including protein synthesis (rough endoplasmic reticulum) and lipid synthesis (smooth. endoplasmic reticulum.) Channels materials throughout the cell. Golgi apparatus - Collective term for the cell's Golgi bodies, stacks of flattened, membranous sacs. processes and packages substances for secretion and for use within the cell. Endomembrane system - The continuous, interconnected system of cellular membranes, consisting of the endoplasmic reticulum, Golgi apparatus, trans-Golgi network, plasma membrane, nuclear envelope, tonoplast, and various vesicles. A dynamic network in which membranes and various substances are transported throughout the cell. See functions of various components. Cytoskeleton - Complex network of protein filaments, consisting of microtubules and actin filaments. Involved in cell division, growth, and differentiation. Microtubules - Dynamic, cylindrical structures composed of tubulin. Involved in many processes, such as cell plate formation, deposition of cellulose microfibrils, and directing the movement of Golgi vesicles and chromosomes. Actin filaments (microfilaments) - Dynamic, filamentous structures composed of actin. Involved in many processes, including cytoplasmic streaming and the movement of the nucleus and organelles.

Mitochondria

Mitochondria are the sites of respiration, a process involving the release of energy from organic molecules and its conversion to molecules of ATP (adenosine triphosphate), the chief immediate source of chemical energy for all eukaryotic cells. Most plant cells contain hundreds or thousands of mitochondria, the number of mitochondria per cell being related to the cell's demand for ATP. Mitochondria are involved in numerous other metabolic processes, among them the biosynthesis of amino acids, vitamin cofactors, and fatty acids, and they play a pivotal role in programmed cell death, the genetically determined process that leads to the death of the cell. Mitochondria are in constant motion, turning and twisting and moving from one part of the cell to another; they also fuse and divide. Mitochondria, like plastids, are semiautonomous organelles. The inner membrane of the mitochondrion encloses a matrix that contains proteins, RNA, DNA, small ribosomes similar to those of bacteria, and various solutes (dissolved substances).

Mitochondria Are the Sites of Respiration

Mitochondria, like plastids, are organelles surrounded by two membranes. The inner membrane is folded to form an extensive inner membrane system, increasing the surface area available to enzymes and the reactions associated with them. Mitochondria are the principal sites of respiration in eukaryotic cells.

The urgent efforts of botanists and agricultural scientists will be needed to feed the world's rapidly growing human population

Modern plants, algae, and bacteria offer the best hope of providing a renewable source of energy for human activities, just as extinct plants, algae, and bacteria have been responsible for the massive accumulations of gas, oil, and coal on which our modern industrial civilization depends.

transport proteins

Most substances required by cells, however, are polar and require transport proteins to transfer them across membranes. Each transport protein is highly selective; it may accept one type of ion (such as Ca2+ or K+) or molecule (such as a particular sugar or amino acid) and exclude a nearly identical one. These proteins provide the specific solutes they transport with a continuous pathway across the membrane, without the solutes coming into contact with the hydrophobic interior of the lipid bilayer. Transport proteins can be grouped into three broad classes: pumps, carriers, and channels. Pumps are driven by either chemical energy (ATP) or light energy, and in plant and fungal cells they typically are proton pumps H+-ATPase). Both carrier and channel proteins are driven by the energy of electrochemical gradients

active transport

Neither simple diffusion nor passive transport is capable of moving solutes against a concentration gradient or an electrochemical gradient. The capacity to move solutes against a concentration or electrochemical gradient requires energy. This process is called active transport and it is always mediated by carrier proteins

Monosaccharides Function as Building Blocks and Sources of Energy

Notice that each monosaccharide has a carbon chain (the carbon "skeleton") with a hydroxyl group (—OH) attached to every carbon atom except one. The remaining carbon atom is in the form of a carbonyl group (—C==O). Both these groups are hydrophilic ("water-loving"), and thus monosaccharides, as well as many other carbohydrates, readily dissolve in water. Monosaccharides are the building blocks—the monomers—from which living cells construct disaccharides, polysaccharides, and other essential carbohydrates

Nucleic Acids Are Polymers of Nucleotides

Nucleotides are complex molecules consisting of a phosphate group, a nitrogenous base, and a five-carbon sugar. They are the building blocks of the nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), which transmit and trans- late the genetic information. Some RNA molecules function as catalysts. Adenosine triphosphate (ATP) is the cell's major energy currency. ATP can be hydrolyzed, releasing adenosine diphosphate (ADP), phosphate, and considerable energy. This energy can be used to drive other reactions or physical processes in the cell. In the reverse reaction, ADP can be "recharged" to ATP with the addition of a phosphate group and an input of energy.

Once light energy is trapped in chemical form, it becomes available as an energy source to all other organisms, including human beings. We are totally dependent on photosynthesis, a process for which plants are exquisitely adapted.

Once light energy is trapped in chemical form, it becomes available as an energy source to all other organisms, including human beings. We are totally dependent on photosynthesis, a process for which plants are exquisitely adapted.

One example of passive transport is the simple diffusion

One example of passive transport is the simple diffusion of small polar molecules across a lipid bilayer. Most passive transport, however, requires carrier proteins to facilitate the passage of ions and polar molecules across the hydrophobic interior of the membrane.

Photosynthesis Is the Process by Which the Sun's Energy Is Captured to Form Organic Molecules

Only a few kinds of organisms—plants, algae, and some bacteria—have the capacity to capture energy from the sun and use it to form organic molecules by the process of photosynthesis. Almost all life on Earth depends, directly or indirectly, on the products of this process.

facilitated diffusion

Passive transport with the assistance of carrier proteins is called facilitated diffusion

Inorganic Nutrients Become Available to Plants in Soil Solution in the Form of Ions

Plants employ metabolic energy to concentrate the ions they require. Ion transport from the soil to the vessels of the xylem requires two active, or energy-dependent, events: uptake at the plasma membrane of epidermal cells and secretion into the vessels at the plasma membrane of parenchyma cells bordering the vessels. Inorganic ions follow a mostly symplastic pathway from the epidermis to the xylem. Substantial amounts of the inorganic ions imported into leaves through the xylem are exchanged with the phloem of the leaf veins and exported from the leaf in the assimilate stream. Nutrient uptake from the soil by most seed plants is greatly enhanced by mycorrhizal fungi

a. Essential amino acids - relationship with plants

Plants incorporate the nitrogen from ammonia, nitrites, and nitrates into carbon- hydrogen compounds to form amino acids. Animals are able to synthesize some of their own amino acids, using ammonia derived from their diet as a nitrogen source. The amino acids they cannot synthesize, the so-called essential amino acids, must be obtained in the diet, either from plants or from the meat of other animals that have eaten plants. For adult human beings, the essential amino acids are lysine, tryptophan, threonine, methionine, histidine, phenylalanine, leucine, valine, and isoleucine. To take full advantage of the protein-building capabilities of these amino acids, it is important to have a diet that supplies them in the right ratio.

We are utterly dependent on plants.

Plants provide us with fiber for clothing; wood for furniture, shelter, and fuel; paper for books (such as the page you are reading at this moment); spices for flavor; drugs for medicines; and the oxygen we breathe

Colonization of the Land Was Associated with the Evolution of Structures to Obtain Water and Minimize Water Loss

Plants, which are basically a terrestrial group, have achieved a number of specialized characteristics that suit them for life on land. These characteristics are best developed among the members of the dominant group known as the vascular plants. Among these features are a waxy cuticle, penetrated by specialized openings known as stomata through which gas exchange takes place, and an efficient conducting system. This system consists of xylem, in which water and minerals pass from the roots to the stems and leaves, and phloem, which transports the products of photosynthesis to all parts of the plant. Plants increase in length by primary growth and expand in girth by secondary growth through the activity of meristems, which are embryonic tissue regions capable of adding cells indefinitely to the plant body

Plasmodesmata Enable Cells to Communicate

Plasmodesmata are also important pathways in cell-to-cell communication. All of the protoplasts of interconnected cells, together with their plasmodesmata, constitute a continuum called the symplast. The cell wall continuum surrounding the symplast is called the apoplast. Once thought of as rather passive entities through which ions and small molecules move by simple diffusion or bulk flow, plasmodesmata are now known to be dynamic structures capable of controlling the intercellular movement of various-sized molecules.

There Are Three Main Types of Plastids: Chloroplasts, Chromoplasts, and Leucoplasts

Plastids are characteristic components of plant cells. Each plastid is surrounded by an envelope consisting of two membranes. Mature plastids are classified, in part, on the basis of the kinds of pigments they contain: chloroplasts contain chlorophyll and carotenoid pigments; chromoplasts contain carotenoid pigments; and leucoplasts are nonpigmented. Proplastids are the precursors of plastids.

cellulose

Polysaccharides are also important structural compounds. In plants, the principal component of the cell wall is the important polysaccharide known as cellulose Cellulose molecules form the fibrous part of the plant cell wall. The long, rigid cellulose molecules combine to form microfibrils, each consisting of hundreds of cellulose chains.

Polysaccharides Function as Storage Forms of Energy or as Structural Materials

Polysaccharides are polymers made up of monosaccharides linked together in long chains. Some polysaccharides function as storage forms of sugar and others serve a structural role

Metaphase, Anaphase, and Telophase Followed by Cytokinesis Result in Two Daughter Cells

Prophase ends with the breakdown of the nuclear envelope and the disappearance of the nucleolus. During metaphase, the chromatid pairs, maneuvered by kinetochore microtubules of the mitotic spindle, come to lie in the center of the cell, with their centromeres on the equatorial plane. During anaphase, the sister chromatids separate and, as daughter chromosomes, move to opposite poles of the spindle. During telophase, the separation of the two identical sets of chromosomes is made final as nuclear envelopes are formed around each set. Nucleoli also re- form at this time. Mitosis is generally followed by cytokinesis, the division of the cytoplasm. In plants and certain algae, the cytoplasm is divided by a cell plate that begins to form during mitotic telophase. The developing cell plate arises from fusing Golgi vesicles guided to the division plane by microtubules and actin filaments of the phragmoplast, an initially barrel-shaped system of microtubules that forms between the two daughter nuclei in early telophase

Assimilate Movement in the Phloem Is from Source to Sink

Research on movement of substances in the phloem has been greatly aided by the use of aphids and radioactive tracers. Sieve- tube sap contains sugar (mainly sucrose) and a complex mix of organic and inorganic materials, including amino acids, proteins, RNAs, hormones, and phloem-mobile ions. Rates of longitudinal movement of substances in the phloem greatly exceed the normal rate of diffusion of sucrose in water; the phloem rates typically range from 50 to 100 centimeters per hour. According to the pressure-flow hypothesis, assimilates move from sources to sinks along turgor pressure gradients developed osmotically. Sugars are loaded into the sieve tube- companion cell complexes at a source. This decreases the water potential in the sieve tube and causes water to move into the sieve tube by osmosis. Meanwhile, removal of sugar at the sink increases the water potential of the sieve tube there. With the movement of water into the sieve tube at the source and out of it at the sink, sugar molecules are carried passively by water along the concentration gradient from source to sink. Phloem loading can be apoplastic or symplastic. Apoplastic loading is an active process, involving sucrose-proton symport. Species that transport raffinose and stachyose are active symplastic loaders. They have specialized companion cells called intermediary cells and employ a polymer-trapping mechanism. In passive symplastic loaders, sugars produced at high levels in the mesophyll diffuse along concentration gradients to the sieve tubes of minor veins.

Respiration

Respiration involves glycolysis, the formation of acetyl CoA from pyruvate, the citric acid cycle, and the electron transport chain, which produces a gradient that drives oxidative phosphorylation. In glycolysis, the six-carbon glucose molecule is broken down to a pair of three-carbon molecules of pyruvate. The pyruvate molecules are then oxidized to two molecules of acetyl CoA. In the citric acid cycle, the acetyl CoA molecules are completely oxidized to carbon dioxide, and the resulting electrons are transferred to the electron transport chain. In oxidative phosphorylation, the free energy that is released as electrons are moved through the electron transport chain (ultimately reducing oxygen to water) is used to form ATP from ADP and phosphate.

What is root pressure

Root pressure - the water potential of the xylem becomes more negative, and water moves into the xylem by osmosis through the surrounding cells. In this manner, a positive pressure, called root pressure, is created, and it forces both water and dissolved ions up the xylem

Simplified purpose of roots and stems

Roots anchor the plant in the ground and collect the water required for maintenance of the plant body and for photosynthesis, while the stems provide support for the principal photosynthetic organs, the leaves.

What is the principal difference between a saturated and an unsaturated fat or oil?

Saturated fats have no double bonds while unsaturated fats have double bonds. Thus unsaturated fats can undergo hydrogenation to convert them into fats or waxes

Starch - amylose & amylopectin?

Starch, the primary storage polysaccharide in plants, consists of chains of glucose molecules. There are two forms of starch: amylose (unbranched molecule) and lopectin (branched molecules). Amylose and amylopectin are stored as starch grains within plant cells

Sterols

Steroids can be easily distinguished from the other classes of lipids by the presence of four interconnected hydrocarbon rings. When a hydroxyl group is attached at the carbon-3 position, the steroid is called a sterol. Sitosterol is the most abundant sterol found in green algae and plants, and ergosterol occurs frequently in fungi. In all organisms except prokaryotes, sterols are important components of membranes, where they stabilize the phospholipid tails. Steroids may also function as hormones.

The Disaccharide Sucrose Is a Transport Form of Sugar in Plants

Sucrose, a disaccharide composed of glucose and fructose, is the form in which sugar is transported in most plants from the photosynthetic cells (primarily in the leaves), where it is produced, to other parts of the plant body.

Secondary Metabolites - Terpenoids

Terpenoids, also called terpenes, occur in all plants and are by far the largest class of secondary metabolites, with over 22,000 terpenoid compounds described. The simplest of the terpenoids is the hydrocarbon isoprene (C5H8). All terpenoids can be classified according to their number of isoprene units. Categories of terpenoids are the monoterpenoids, which consist of two isoprene units; sesquiterpenoids (three isoprene units); and diterpenoids (four isoprene units).

The Golgi Apparatus Is a Highly Polarized Membrane System Involved in Secretion

The Golgi apparatus consists of Golgi bodies, which are com- posed of stacks of flattened, disk-shaped sacs, or cisternae. Most plant Golgi bodies are involved in the synthesis and secretion of complex noncellulosic cell wall polysaccharides, which are transported to the surface of the cell in secretory vesicles derived from the trans-Golgi network. All cellular membranes, with the exception of mitochondrial, plastid, and peroxisomal membranes, constitute a continuous, interconnected system, known as the endomembrane system.

Carbohydrates:

The basic structural subunit of carbohydrates is sugar that is made up of linked carbon atoms to which hydrogen and oxygen atoms are arranged in the ration of one carbon to two hydrogen to one oxygen atom. They are a source of ready energy to the cell. As cellulose they also are a component of the cell wall and provide structure and rigidity to the plant cell

Lipids:

The basic structural subunit of lipids consists of three fatty acid molecules bonded to a glycerol. The lipids are the only source of energy in seeds and fruits. They are also the form in which energy is stored in reserve in plants and animals. In the form of phospholipids, they are a major component of all cell membranes and provide protection to plants in the form of waxes and cutin.

Proteins:

The basic structural subunit of proteins are amino acids. They contain an amino group, a carboxyl group and a hydrogen atom boned to a central carbon atom. Another atom or group of atoms called the "R" molecule is also attached to the central carbon atom that is specific to every protein. These have various functions such as structural functions in the form of filaments and fibers, as enzymes in catalyzing reactions and in the development of muscles in animals.

Distinguish between the cell theory and organismal theory.

The cell theory and the organismal theory can be distinguished as follows: - the cell theory states that all living organisms are made up aggregation of cells that are individual and have specialized functions. The activities of the organism as a whole is the total activities carried out by the individual The organismal theory on the other hand states that, the plants or animals are not made up of single units of cells, but instead are made up of continuous mass of protoplasm that over the course of time have divided to form cells - the cell theory holds the cells more important than the entire organism as a whole. The organismal theory holds the entire organism of prime importance rather than the cells - the cell theory is applicable to both plants and animals in general to both plants and animals in general, but the organismal theory is particularly applicable to plants as they have plasmodesmata, which connect the cytoplasm of the cells. Thus, even divisions of cells in plants, the cells remain interconnected by means of plasmodesmata and thus are never completely separated

The Cell Wall Is the Major Distinguishing Feature of the Plant Cell

The cell wall determines the structure of the cell, the texture of plant tissues, and many important characteristics that distinguish plants as organisms. Cellulose is the principal component of plant cell walls. All plant cells have a primary wall. In addition, many also have a secondary wall, which is laid down on the inner surface of the primary wall. The region of union of the primary walls of adjacent cells is a pectin-rich layer called the middle lamella. The cellulose microfibrils of primary walls occur in a cross-linked matrix of non cellulosic molecules, including hemicelluloses, pectins, and glycoproteins. Because of the presence of pectins, primary walls are highly hydrated, making them more plastic. Actively dividing and elongating cells commonly have only primary walls. Secondary walls contain hemicelluloses but apparently lack pectins and glycoproteins. Lignin may also be present in primary walls but is especially characteristic of cells with secondary walls. Lignin adds compressive strength and rigidity to the wall. The protoplasts of adjacent cells are connected to one an- other by cytoplasmic strands called plasmodesmata, which traverse the cell walls. Plasmodesmata provide pathways for the transport of certain substances between cells. Callose, a widely distributed cell wall polysaccharide, is deposited rapidly in response to wounding, sealing the plasmodesmata.

Water Moves from the Roots to the Leaves through the Conduits—Vessels and Tracheids—of the Xylem

The current and widely accepted theory for the mechanism of water movement to the top of tall plants through the xylem is the cohesion-tension theory. According to this theory, water is pulled up through the plant body. This pull, or tension, is brought about by transpiration and/or by the use of water in the leaves, which results in a gradient of water potential from the leaves to the soil solution at the surface of the roots. It is the cohesiveness of water that permits it to withstand tension. Embolisms—the presence of air or water vapor—in xylem conduits are the bane of the cohesion-tension mechanism. Fortunately, the pit membranes of the bordered pit-pairs between adjacent tracheary elements usually prevent the passage of air from an embolized conduit into a functional one.

The Cytoskeleton Is Composed of Microtubules and Actin Filaments

The cytosol of eukaryotic cells is permeated by the cytoskeleton, a complex network of protein filaments, of which there are two well-characterized types in plant cells: microtubules and actin filaments. Microtubules are thin, cylindrical structures of variable length and are composed of subunits of the protein tubulin. They play a role in cell division, the growth of the cell wall, and the movement of flagella. Actin filaments are com- posed of the protein actin. These long filaments occur singly and in bundles, which play a role in cytoplasmic steaming.

The Endoplasmic Reticulum Is an Extensive Three- Dimensional System of Membranes with a Variety of Roles

The endoplasmic reticulum exists in two forms: rough endoplasmic reticulum, which is studded with ribosomes, and smooth endoplasmic reticulum, which lacks ribosomes. The rough form is involved with membrane and protein synthesis, and the smooth form with lipid synthesis. Some of the lipids produced occur as oil bodies in the cytosol.

In Glycolysis, Glucose Is Split into Pyruvate

The first phase in the oxidation of glucose is glycolysis, in which the six-carbon glucose molecule is split into two three- carbon molecules of pyruvate. This reaction occurs in the cytosol of eukaryotic cells and results in the formation of two molecules of ATP and two of NADH.

Describe the movement of water into roots - Mycorrhizal Fungi

The fungi colonize the root system of a host plant, providing increased water and nutrient absorption capabilities while the plant provides the fungus with carbohydrates formed from photosynthesis.

exocytosis

The hemicelluloses, pectins, and glycopro- teins that form the matrix of the cell wall are carried to developing cell walls in secretory vesicles that fuse with the plasma membrane, thus releasing their contents into the wall. This process is known as exocytosis

Explain the benefit of hydraulic redistribution to plants.

The hydraulic redistribution of the water from the plants to the soil, generally roots uptake the water for growth and the essential function of the plants. In some plants like vascular plants can redistribute the water to the soil after getting the sufficient amount of water uptake this process can happen because of the system which has both tap root as well as lateral roots where the condition of lateral surface water dried, the lateral roots become dry and die so the plants able to get the support of water transport from the tap roots, in the flood condition or abundance of water limit on the surface of the plant, means the water necessary uptake will take place and redistribute the water to the soil. The water redistribution is good benefit to the ecosystem where the mixture of plants will be able to get the water, because in area of long trees along with the small plants or herbs generally the herbs and the short plants of the lateral roots or fibrous roots, which couldn't be able to uptake water from the dense interior of the soil like tap root in case of the hydraulic redistribution, the short plants able to get water easily from the tall trees.

What was the likely source of the raw material incorporated into the first life forms?

The likely source of raw material for the earliest source of life forms could have been organic molecules that were formed by the action of lighting, rain and solar on gases.

primary structure

The linear sequence of amino acids, which is dictated by the information stored in the cell for that particular protein, is known as the primary structure of the protein

What is the principal difference between a heterotroph and an autotroph, and what role did each play on the early Earth?

The main difference between autotrophs and heterotrophs are that autotrophs can produce their own food, while heterotrophs depend on autotrophs or other living forms for their food. The autotrophs can produce their own food either by the process of photosynthesis or by the process of chemosynthesis. Earlier there were only heterotrophs that survived on the complex molecules and used them to produce energy, but as the complex molecules necessary for their sustenance began becoming scarce, competition increased and it slowly and gradually led to the development of organisms, which developed specialized cells to make their own energy rich molecules from simple inorganic materials available. Such organisms were called autotrophs. Without the evolution of autotrophs, the life on earth would have come to an end

How does the structure of a prokaryotic cell differ from that of a eukaryotic cell?

The main differences between structure of a prokaryotic cell and a eukaryotic cell are: - A prokaryotic cell is generally much smaller in size as compared to the eukaryotic cell. The general size of a prokaryotic cell varies from 1-10 micrometers. Eurkaryotic cells on the other hand are much bigger in size and vary between 5-100 micrometers. Some eukaryotic cells are even longer than 100 micrometers and are generally found in plants. - A prokaryotic cell does not have a nuclear envelop while a eukaryotic cell has a nucleus that is properly enclosed by a nuclear membrane - Further a prokaryotic cell lacks membrane bound organelles whereas a eukaryotic cell possesses number of specialized membranes bound organelles that have characteristic functions - Also, a prokaryotic cell structurally lacks the presence of a cytoskeleton while an eukaryotic cell has a cytoskeleton that is made of microtubules and actin filaments

What are the main events that occur during glycolysis?

The main events that occur in the glycolysis are: - glucose-6-phosphate is formed form glucose by the help of energy from ATP - Fructose-6-phospahte is formed from glucose-6-phosphate by the process of rearrangement - fructose 1,6-biphosphate is formed from Fructose-6-phospahte by the addition of a phosphate group - 2 molecules of glyceraldehyde-3-phosphate are formed from fructose 1,6-biphosphate by its cleavage - the oxidation of glyceraldehyde-3-phosphate to 1,3-biphosphoglycerate results in the formation of 2 ATPs from 2 ADPs - 3-phosphoglycerate is converted to 2-phosphoglycerate and then to phosphoenolpyruvate in two steps - the last step is the conservation of phosphoenolpyruvate to pyruvate that leads to the formation of 2 ATPs from 2 ADPs

Distinguish between diffusion and osmosis. What kinds of substances enter and leave cells by each process?

The main points of differences between diffusion and osmosis are: - Diffusion is the spontaneous movement of particles from an area of higher concentration to an area of lower concentration. Osmosis on the other hand is the movement of water, specifically from an area of its higher concentration to an area of its lower concentration through a selectively permeable membrane. - Diffusion does not need the presence of water to occur as it is possible even in gaseous molecules. In osmosis water is a must as it in relation to the movement of water - Diffusion occurs from a higher concentration gradient to a lower concentration gradient, while osmosis occurs from a region of higher to a region of lower water potential. By the process of diffusion, gases, water and other uncharged small polar molecules diffuse to and from the cells easily. The process of osmosis, mainly water and some other solutes move in and out of the cells. Since the membrane is selectively permeable, it does not allow the movement of other big particles in or out of the cell

List the main products of the light reactions of photosynthesis.

The main products of the light reaction of photosynthesis are: - NADPH: this is produced from NADPH+ when it absorbs the electron that have passed downhill from a series of electron acceptors - ATP: this is produced when the photons produced by photolysis of water, pass through the ATP synthase complex leading to a proton gradient. This proton gradient results in the formation of ATP. Where NADP+ is absent as an electron acceptor, then ATP is produced when the electron acceptors pass through a series of electron acceptors and finally fall into the reaction of PS 1 again - Oxygen: this is produced as a byproduct of photolysis of water

Distinguish between substrate-level phosphorylation and oxidative phosphorylation. Where do these processes occur in the cell in relation to respiration?

The major differences between oxidative phosphorylation and substrate level phosphorylation are: - substrate level phosphorylation refers to the direct formation of ATP from ADP without the involvement of ATP synthase. Oxidative phosphorylation refers to the indirect formation of ATP by chemiosmosis through the gradient created by the acceptance of electron by oxygen. It involves the action of ATP synthase - Substrate level phosphorylation takes place during glycolysis and citric acid cycle. Oxidative phosphorylation on the other hand takes place during electron transport chain (ETC) - In substrate level phosphorylation, NAD and FAD gets reduced and glucose gets broken down. On the other hand, in oxidative phosphorylation, NADH+ and FADH+ get oxidized - the net production of ATP in substrate level phosphorylation is 4 ATP. Oxidative phosphorylation produces much more ATP a net of 34 ATPs are produced Oxidative phosphorylation occurs in the mitochondrial membrane during the last stages of the cellular respiration in mitochondria. Substrate level phosphorylation on the other hand takes place both in the mitochondrial membrane and the matrix during krebs cycle of cellular respiration

How does the osmotically generated pressure-flow mechanism account for the movement of sugars from source to sink?

The movement of sugar to the sink from source is based on the pressure flow mechanism which carried out by osmosis, the principle of osmosis is solvent moves through the lower concentration and vice versa by mean of the semi permeable membrane, the principle of the osmosis is have to maintain the state of equilibrium In plants the sugar molecules are loaded in the sieve tubes which makes the movement of water into the cell because the flow of equilibrium have to maintain, so the water molecules have to uptake by the sieve tube, in meanwhile the removal sugar at the sink raises the water potential, so the sugar molecules are passively uptake along with the water from the source to the sink

The Nucleus Is Surrounded by a Nuclear Envelope and Contains Nucleoplasm, Chromatin, and One or More Nucleoli

The nucleus is the control center of the cell and contains most, though not all, of the cell's genetic information; that contained in the nucleus is referred to as the nuclear genome. The nuclear envelope, which consists of a pair of membranes, may be considered a specialized, locally differentiated portion of the endoplasmic reticulum. The chromatin (chromosomes) consists of DNA and histone proteins. The nucleoli are the sites of ribosomal subunit formation.

nucleus:

The nucleus performs two important functions: (1) it controls the ongoing activities of the cell by determining which protein molecules are produced by the cell and when they are produced, and (2) it stores the genetic information (DNA), passing it on to the daughter cells in the course of cell division.

Epidermis

The outermost layer of cells, the epidermis, of all the aboveground portions of the plant that are ultimately involved in photosynthesis is covered with a waxy cuticle, which retards water loss

What is the overall reaction, or equation, for respiration, and what is the principal function of this process?

The overall reaction for respiration is: C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy (30 ATP) The main function of respiration is to breakdown the organic molecules like sugar into ATP, that is the form of stored energy required for carrying out other biochemical processes

photosynthetic organisms makes it possible for life to exist on the land

The oxygen that is released into the atmosphere by photosynthetic organisms makes it possible for life to exist on the land and in the surface layers of the ocean. Oxygen is necessary for the energy-producing metabolic activities of the great majority of organisms, including photosynthetic organisms

The Chemical Building Blocks of Life Accumulated in the Early Oceans

The planet Earth is some 4.6 billion years old. The oldest known fossils date back 3.5 billion years and resemble today's filamentous bacteria. Although the process by which living organisms arose is a matter of speculation, there is general agreement that life as we know it probably emerged on Earth only once—that is, all living things share a common ancestor.

Membranes Consist of a Lipid Bilayer and Proteins

The plasma membrane and other cellular membranes are com- posed of lipid bilayers in which proteins are embedded. The lipid bilayer provides the basic structure and impermeable nature of the membrane. In plant cells, the major types of lipids are phospholipids (the more abundant) and sterols. Different membrane proteins perform different functions; some are enzymes, others are receptors, and still others are transport proteins. The two surfaces of a membrane differ considerably in chemical composition. The exterior surface of the plasma mem- brane is characterized by short carbohydrate chains that are believed to play important roles in the recognition of molecules that interact with the cell. Small Molecules Cross Membranes by Simple Diffusion,

aquaporins

The plasma membrane and tonoplast also contain water channel proteins called aquaporins, which facilitate the movement of water and/or small neutral solutes (urea, boric acid, silicic acid) or gases (ammonia, carbon dioxide) across the membranes.

Plastids

The principal types of plastids are chloroplasts, chromoplasts, and leucoplasts. Each plastid is surrounded by an envelope consisting of two membranes. Internally, the plastid is differentiated into a membrane system consisting of flattened sacs called thylakoids and a more or less homogeneous matrix, called the stroma. The number of thylakoids present varies among plastid types.

1Photosynthetic organisms are the route by which all other living things, including ourselves, obtain energy, oxygen, and the many other materials necessary for their continued existence.

The protective stratospheric ozone layer formed 450 million years ago has been seriously depleted by the use of chlorofluorocarbons (CFCs), and damaging ultraviolet rays penetrating the depleted layer have increased the incidence of skin cancer in people all over the world.

Cells Are of Two Fundamentally Different Types: Prokaryotic and Eukaryotic

The protoplast consists of the cytoplasm and a nucleus. The plasma membrane is the outer boundary of the protoplast, next to the cell wall. The cytosol, or cytoplasmic matrix, of individual plant cells is always in motion, a phenomenon known as cytoplasmic streaming.

Life began to develop more abundantly toward the shores, where the waters were rich in nitrates and minerals carried down from the mountains by rivers and streams and scraped from the coasts by the ceaseless waves.

The rocky coast presented a much more complicated environment than the open sea, and, in response to these evolutionary pressures, living organisms became increasingly complex in structure and more diversified.

Uptake of Water by Roots Takes Place Largely through the Root Hairs

The root hairs provide an enormous surface area for water uptake. In some plants, the uptake of water from the soil results in the buildup of positive pressure, or root pressure, when transpiration is very slow or absent. This osmotic uptake depends on transport of inorganic ions from the soil into the xylem by the living cells of the root, and it can result in guttation, a process in which liquid water is forced out through special structures (hydathodes) in the tips or margins of leaves. The pathway followed by water across the root may be apoplastic, symplastic, or transcellular; however, apoplastic movement is blocked at the endodermis by the Casparian strips. The water must pass through the plasma membranes and protoplasts of endodermal cells on its way to the xylem. Many plants redistribute soil water hydraulically. Hydraulic redistribution is a nighttime process by which the roots of plants transfer water from moist soil regions to dry soil regions. Water can be redistributed hydraulically upward, downward, or horizontally.

What are the similarities and differences between facilitated diffusion and active transport?

The similarities between facilitated diffusion and active transport are: - both of them transport the same kind of materials across the cell membrane - ions, macromolecules, water, oxygen and sugars. - both of the processes use transport proteins for the transport process. In this, the proteins change their structure by joining with the substance to be transported and help in their transportation across the cell - the main goal of both of the processes is the transportation of substances across the cells The differences between facilitated diffusion and active transport are: - as the name suggests, in facilitated diffusion, the process of diffusion is only aided by transport proteins. Thus, there is no energy that is used for the transport. On the other hand, in active transport, ATP is used for energy to transport the substances across the cells - facilitated diffusion happens from a region of higher concentration to a region of lower concentration. That is, it happens along with the concentration gradient. Active transport on the other hand, happens against a concentration gradient of the substance that is transported. Thus, it requires energy in the form of ATP

Carbohydrates are the most abundant organic molecules in nature and are the primary energy-storage molecules in most living organisms

The simplest carbohydrates are small molecules known as sugars; larger carbohydrates are composed of sugars joined together. There are three principal kinds of carbohydrates, classified according to the number of sugar subunits they contain. Monosaccharides ("single, or simple, sugars"), such as ribose, glucose, and fructose, consist of only one sugar molecule. Disaccharides ("two sugars") contain two sugar subunits linked covalently. Familiar examples are sucrose (table sugar), maltose (malt sugar), and lactose (milk sugar). Cellulose and starch are polysaccharides ("many sugars"), which contain many sugar subunits linked together.

Stomata

The solution to this dilemma is found in the stomata (singular: stoma), each consisting of a pair of specialized epidermal cells (the guard cells), with a small opening between them. The stomata open and close in response to environmental and physiological signals, thus helping the plant maintain a balance between its water losses and its oxygen and carbon dioxide requirements

Why must starch be hydrolyzed before it can be used as an energy source or transported?

The starch is structurally a very big molecule and hence cannon be transported across the cell without being broken down into smaller molecule. Also, the starch is a complex molecule and thus for it to be used as a source of energy it must first be reduced to simpler molecules like glucose that can undergo reaction to generate energy

Distinguish between rough endoplasmic reticulum and smooth endoplasmic reticulum, both structurally and functionally.

The structural differences between the rough endoplasmic reticulum and the smooth endoplasmic reticulum are: - the rough endoplasmic reticulum has ribosomes attached to it while the smooth endoplasmic reticulum does not have any ribosomes associated - the rough endoplasmic reticulum is present as flattened sacs in the cell while the smooth endoplasmic reticulum is present as a network of interconnected tubules - the rough endoplasmic reticulum is found in abundance near the nucleus and the Golgi apparatus while the smooth endoplasmic reticulum is found almost evenly distributed throughout the cell The functional differences between the two are: - the main function of the rough endoplasmic reticulum is protein synthesis in the ribosomes. The main function of the smooth endoplasmic reticulum is lipid synthesis - the rough endoplasmic reticulum is also involved in the quality check of manufactured proteins, transfer of protein to the Golgi apparatus and storage of minerals and calcium. The smooth endoplasmic reticulum also serves in the breakdown of glycogen to glucose, production of steroid hormones and as a detoxification unit

Golgi apparatus

The term Golgi apparatus, or Golgi complex, is used to refer collectively to all of the Golgi bodies of a cell. Golgi bodies consist of five to eight stacks of flattened, disk-shaped sacs, or cisternae, which often are branched into a complex series of tubules at their margins. Golgi bodies are involved in secretion. In plants, most of the Golgi bodies are involved in the synthesis and secretion of no cellulosic polysaccharides (hemicelluloses and pectins) destined for incorporation into the cell wall. Golgi bodies also process and secrete glycoproteins that are transferred to them from the rough endoplasmic reticulum, via transition vesicles. (part of the endomembrane system)

What three features of plant cells distinguish them from animal cells?

The three features of plant cells that distinguish them from animal cells are: 1. Plants cells have cell wall made up of cellulose as their outermost layer. Thus, the plant cells have fixed shaped and are mostly rectangular. Whereas animal cells have cell membrane as their outermost layer. Thus, the animal cells do not have a rigid structure and are mostly circular or oval 2. Plants cells have a single large vacuole that covers almost 90% of the cell space. Animal cells have two or more small vacuoles 3. Plant cells have chloroplasts that give the plants a green color and thus are capable of making their own food. Animal cells do not have chloroplasts and thus cannot make their own food

vesicle-mediated transport.

The transport proteins that ferry ions and small polar molecules across the plasma membrane cannot accommodate large molecules, such as proteins and polysaccharides, or large particles, such as microorganisms or bits of cellular debris. These large molecules and particles are transported by means of vesicles that bud off from or fuse with the plasma membrane, a process called vesicle-mediated transport.

secondary growth

The type of growth that results in a thickening of stems and roots—secondary growth— originates from two lateral meristems, the vascular cambium and the cork cambium.

What are the principal pigments involved in photosynthesis, and why are leaves green?

The various pigments that are important for photo synthesis are: Chlorophyll a, Chlorophyll b, Carotenoids and Phycobilins. The principle pigments present in chloroplasts in abundance are the chlorophyll a molecule. These molecules reflect back green light very strongly. Thus, the leaves appear green

Describe where the various stages in the complete breakdown of glucose take place in relation to mitochondrial structure. What molecules and ions cross the mitochondrial membranes during these processes?

The various stages of complete breakdown of glucose can be summarized as follows with respect to the mitochondrial structure: - the first stage of glucose breakdown is glycolysis. It is an anaerobic process and it occurs in the cytosol, closer to the mitochondria. The end product of this glycolysis is pyruvate. The pyruvate now enters the mitochondria into the citric acid cycle - the pyruvate is not used as such in the citric acid cycle. Thus when the pyruvate enters the mitochondrial matrix, it is converted to Acetyl CoA - the citric acid cycle primarily takes place in the mitochondrial matrix as the enzymes for this cycle are present in the matrix. The final product of this cycle is oxaloacetate which enters the cycle again - the last stage of the complete breakdown of glucose is the electron transport chain. In this the electrons that are produced from NADH and FADH2 are passed step by step leading to the formation of water. The electrons pass through various carriers that form a chain and these are located in the inner mitochondrial membrane. At the end, the electrons are accepted by oxygen and combine with protons to form water. ATP is also generated in the process due to oxidative phosphorylation - the first molecule that passes through the mitochondrial membrane into the matrix is the pryruvate - the second ion that pass from the matrix to the inner mitochondrial membrane are the energized electrons that pass from citric acid cycle to the electron transport chain - the third ions that pass from the mitochondrial membrane to the matix are the protons that result in the formation of a proton gradient across the inner mitochondrial membrane - the final ions that pass through the inner membrane to the matrix at the electrons that are accepted by oxygen and combine with protons to form water

What are the various types of plastids, and what role(s) does each play in the cell?

The various types of plastids that are found in a plant cell are: - Chloroplast - Chromoplasts - Leucoplasts The functions of the different types of plastids are: - Chloroplast: These are the principal plastids that are present in large numbers in a plant. Though these plastids contain both chlorophyll and carotenoid pigments but due to the presence of large number of chlorophyll pigments that are green in color, the other carotenoid pigments get masked. It is because of these plastids that the leaves get their green color. These chloroplasts are also the site of photosynthesis and thus are the sites where food and energy in the form of ATP is produced. These plastids are also involved in the synthesis of fatty acids, secondary metabolites and amino acids. - Chromoplasts: These are pigmented plastids like chloroplasts but lake the pigment chlorophyll. They synthesize and retain the carotenoids and thus are the pigments that are responsible for the various colors of flowers, fruits, ageing leaves and some roots. - Leucoplasts: these plastids lack pigments and are less differentiated than the rest of the plastids. A special kind of leucoplasts called amyloplasts is known to synthesize starch. Other functions of leucoplasts include generation of oils and proteins.

vascular plant

The vascular plant is characterized by a root system that serves to anchor the plant in the ground and to collect water and minerals from the soil; a stem that raises the photosynthetic parts of the plant body toward its energy source, the sun; and leaves, which are highly specialized photosynthetic organs. Roots, stems, and leaves are interconnected by a complicated and efficient vascular system for the transport of food and water. The reproductive cells of plants are enclosed within multicellular protective structures, and in seed plants the embryos are protected by resistant coverings

Of the 92 elements that occur naturally on Earth, only six were selected in the course of evolution to form the complex, highly organized material of living organisms.

These six elements—carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (CHNOPS)—make up 99 percent of the weight of all living matter.

Vesicles

These transition vesicles flow from the endoplasmic reticulum to the forming face of the Golgi body. The glycoproteins are transported stepwise across the stack to the maturing face by means of shuttle vesicles

chemical signals

This communication is accomplished in large part by means of chemical signals—that is, by substances that are synthesized within and transported out of one cell and then travel to another cell. In plants, the chemical signals are represented largely by hormones, chemical messengers typically produced by one cell type or tissue in order to regulate the function of cells or tissues elsewhere in the plant body

Secondary Metabolites Play a Variety of Roles Not Directly Related to the Basic Functioning of the Plant

Three main classes of secondary metabolites found in plants are alkaloids, terpenoids, and phenolics. Although the botanical functions of these substances are not clearly known, some are thought to deter predators and/or competitors. Examples of such compounds include caffeine and nicotine (alkaloids), as well as cardiac glycosides (terpenoids) and tannins (phenolics). Others, such as anthocyanins (phenolics) and essential oils (terpenoids), attract pollinators. Still others, such as phenolic lignins, are responsible for the compressive strength, stiffness, and waterproofing of the plant body. Some secondary metabolites, such as rubber (a terpenoid) and morphine and taxol (alkaloids), have important commercial or medicinal uses. Primary metabolites, in contrast to secondary metabolites, are found in all plant cells and are necessary for the plant to live.

passive transport.

Transport down a concentration gradient or an electrochemical gradient is called passive transport.

lipids - structure

Typically, lipids serve as energy-storage molecules—usually in the form of fats or oils—and also for structural purposes, as in the case of phospholipids and waxes. Phospholipids are important components of all biological membranes

Peroxisomes Are Surrounded by a Single Membrane

Unlike plastids and mitochondria, peroxisomes are organelles surrounded by a single membrane. Moreover, they possess neither DNA nor ribosomes. Some peroxisomes play an important role in photorespiration. Others are involved in the conversion of stored fats to sucrose during seed germination.

Vacuoles Perform a Variety of Functions

Vacuoles are organelles bounded by a single membrane called the tonoplast. Together with plastids and cell walls, they are characteristic components of plant cells. Many vacuoles are filled with cell sap, an aqueous solution containing a variety of salts, sugars, anthocyanin pigments, and other substances. Vacuoles play an important role in cell enlargement and the maintenance of tissue rigidity. Some vacuoles are important storage compartments for primary metabolites, whereas others sequester toxic secondary metabolites. In addition, many vacuoles are involved in the breakdown of macromolecules and the recycling of their components within the cell.

Water Moves down a Water Potential Gradient

Water is one of the principal substances passing into and out of cells. Water potential determines the direction in which the water moves; that is, the movement of water is from regions of higher water potential (lower solute concentration) to regions of lower water potential (higher solute concentration), provided that the pressure in the two regions is equal. The concept of water potential is useful because it enables plant physiologists to predict how water will move under various conditions

Water

Water, a molecule consisting of two hydrogens and one oxygen (H2O), makes up more than half of all living matter and more than 90 percent of the weight of most plant tissues.

During Prophase, the Duplicated Chromosomes Shorten and Thicken

When the cell is in interphase, the chromosomes are in an un- coiled state and are difficult to distinguish from the nucleoplasm. Mitosis in plant cells is preceded by migration of the nucleus to the center of the cell and the appearance of the pre- prophase band, a dense band of microtubules that marks the equatorial plane of the future mitotic spindle. As prophase of mitosis begins, the chromatin gradually condenses into well- defined chromosomes, each chromosome consisting of identical strands called sister chromatids, held together at the centromere. Simultaneously, the spindle begins to form.

hydrolysis

When the reverse reaction occurs—for example, when a disaccharide is split into its monosaccharide subunits—a molecule of water is added. This splitting, which occurs when a disaccharide is used as an energy source is known as hydrolysis

Genetic Engineering Allows Scientists to Transfer Genes between Entirely Different Species

With the advent of genetic engineering, it became possible for biologists to transfer genes from one species into an entirely different species. Genetic engineering has already resulted in the development of transgenic plants with desirable traits such as increased nutritive value and resistance to certain diseases and pest

All living things share a common ancestor

a DNA-based microbe that lived more that 3.5 billion years ago. Near the end of On the Origin of Species, Charles Darwin wrote: "Probably all the organic beings which have ever lived on this earth have descended from someone primordial form, into which life was first breathed."

Endoplasmic reticulum

a complex, three- dimensional membrane system that permeates the entire cytosol. The endoplasmic reticulum functions as a communication system within the cell and as a system for channeling materials— such as proteins and lipids—to different parts of the cell. In addition, the cortical endoplasmic reticulum of adjacent plant cells is interconnected by cytoplasmic strands, called plasmodesmata, that traverse their common walls and play a role in cell-to-cell communication. The endoplasmic reticulum is one of the main sites of lipid synthesis in plants, the other being the plastid. Part of the endomembrane system

Molecules

a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.

Compound

a thing that is composed of two or more separate elements

Explain some of the primary adaptations that plants have to the terrestrial environment

a. Cuticle - the stems and the leaves were covered with a waxy cuticle that prevented loss of water due to transpiration. b. Stomata - stomata were developed as cuticles prevented the exchange of gases also. The stomata thus developed were sensitive to the environmental conditions and opened and closed in response to the environmental conditions. c. Vascular System d. Root -> Shoots e. UV Protection (Anthocyanins) f. Seeds and Seed Coats g. Sporopollenin

Describe the movement of water into roots - endodermis

an inner layer of cells in the cortex of a root and of some stems, surrounding a vascular bundle.

Cellulose

an insoluble substance which is the main constituent of plant cell walls and of vegetable fibers such as cotton. It is a polysaccharide consisting of chains of glucose monomers.

Disaccharides Definition

any of a class of sugars whose molecules contain two monosaccharide (glucose and fructose = sucrose)

Monosaccharides Definition

any of the class of sugars (e.g., glucose) that cannot be hydrolyzed to give a simpler sugar.

Actin filaments

are polar structures with distinct plus and minus ends. Actin filaments are involved in a variety of activities in plant cells, including cell wall deposition, tip growth of pollen tubes, movement of the nucleus before and following cell division, organelle movement, vesicle-mediated secretion, organization of the endoplasmic reticulum, and cytoplasmic streaming

Terpenoids

are the most commonly occurring secondary metabolites and constitute the largest classes of secondary metabolites. They are basically made up of subunits of isoprene. Example: isoprene, taxol, and cardiac glycosides

Oil bodies

arise in the endoplasmic reticulum and then are released into the cytosol. Oil bodies are widely distributed throughout the cells of the plant body but are most abundant in fruits and seeds. In fact, approximately 45 percent of the weight of sun- flower, peanut, flax, and sesame seeds is composed of oil. The oil provides energy and a source of carbon to the developing seedling. Oil bodies often are described as organelles, but this is incorrect because they are not surrounded by a membrane.

Describe the movement of water into roots - Apoplastic

around the protoplast via the cell wall

Phenolics

as the names suggests have a hydroxyl group attached to an aromatic ring. The phenolics are known to occur in almost all parts of the plant. Examples: flavonoids, tannins, lignin and salicylic acid.

Telophase:

at the beginning of this phase, the spindle fibers completely disappear, and the daughter chromosomes are at the extreme ends of the cell. Cytoplasmic constriction begins to appear. As the phase progresses, the cytoplasm divides and the nuclear membrane begins to appear along with the nucleolus. The daughter chromosomes again elongate and become thread like structures and cell division is complete.

account for only about 1 percent of living matter

electrically charged ions, such as potassium (K+), magnesium (Mg2+), and calcium (Ca2+), important as they are, account for only about 1 percent

primary cell wall

first wall layer to form, contains primary pit fields. Found in actively dividing and actively metabolizing cells

Describe the movement of water into roots - Transmembrane

from cell to cell, across the plasmamembrane and tonoplast

Describe the movement of water into roots - Symplastic

from protoplast to protoplast via plasmadesmata

glycolysis

glycolysis (from glyco-, meaning "sugar," and lysis, meaning "splitting"), the six-carbon glucose molecule is split into two molecules of pyruvate. Glycolysis occurs in a series of 10 steps, each catalyzed by a specific enzyme Glucose + 2NAD+ + 2ADP + 2P → 2 Pyruvate + 2NADH + 2H+ +2ATP + 2H2O

What are the closest relatives to land plants?

green algae

Explain why we should care about plant biology - Current role in human's lives?

i. Medicine - plants are most importantly a source of medicine. Different secondary metabolites in the plants are cures for a number of diseases ii. Agriculture - provided a basis for the huge increase in their population levels iii. Building materials - plants like hemp, cotton palm are sources of fiber. These fibers can be used for the production of clothes, mats, hats, and shelter. Wood for building iv. Spice - culinary - aesthetic - flavor v. Connections with nature vi. Phytoremediation - Phytoremediation is a bioremediation process that uses various types of plants to remove, transfer, stabilize, and/or destroy contaminants in the soil and groundwater.

Vacuoles (surrounded by tonoplast)

important storage compartments for primary metabolites, such as sugars and organic acids and the reserve proteins in seeds. Vacuoles also remove toxic secondary metabolites, such as nicotine and tannin, from the rest of the cytoplasm. The vacuole is often a site of pigment deposition. Vacuoles are also involved in the breakdown of macromolecules and the recycling of their components within the cell.

Anaphase:

in this phase the centromeres of the sister chromatids separate thus separating the sister chromatids. As this phase progresses, the sister chromatids or daughter chromosomes move to the opposite sides of the spindle. The spindle fiber also begins to disappear slowly

G2 phase:

in this phase, the chromosomes begin to condense and get ready for mitosis and the other organelles like the cell wall begin to form making the cell ready for mitosis

Metaphase:

in this phase, the spindle fibers are distinctly formed, and the chromosomes are arranged at the equatorial plane of the spindle fiber

secondary structure

in this structure, the polypeptide chain coils into a helix or bends to form sheets. Thus, two types of structure: alpha helix or beta pleated sheet are formed by this level

Cytoplasm

includes distinct membrane bound entities (organelles such as plastids and mitochondria), systems of membranes (the endoplasmic reticulum and Golgi apparatus), and non-membranous entities (such as ribosomes, actin filaments, and microtubules and "cellular soup." The cytoplasm is surrounded by a single membrane, the plasma membrane.

plasmodesmata

interconnect protoplast of adjacent cells, providing a pathway for the transport of substances between cells

plant taxonomy and systematics

involving the naming and classifying of plants and the study of the relationships among them

Chromoplasts

lack chlorophyll but synthesize and retain carotenoid pigments, which are often responsible for the yellow, orange, or red colors of many flowers, aging leaves, some fruits, and some roots, such as carrots

Leucoplasts

lack pigments and an elaborate system of inner membranes. Some leucoplasts, known as amyloplasts, synthesize starch, whereas others are thought to be capable of forming a variety of substances, including oils and proteins.

Plant organs

leaves, stem, roots

The requirements of a photosynthetic organism are relatively simple:

light, water, carbon dioxide for photosynthesis, oxygen for respiration, and a few minerals.

Explain Transpiration

loss of water vapor from plants, known as transpiration, may involve any above- ground part of the plant body, but leaves are by far the most important organs of transpiration.

Nucleic Acids - Structure (3 Parts)

nucleotides consists of three components: a phosphate group, a five-carbon sugar, and a nitrogenous base—a molecule that has the properties of a base and contains nitrogen

The tendency of water to move across a membrane because of the effect of solutes on water potential is called the osmotic potential (also called solute potential), which is negative

osmotic potential

middle lamella

pectin rich layer between cells. Cements adjacent cells together

Phospholipids

phospholipids are composed of fatty acid molecules attached to a glycerol backbone. In the phospholipids, however, the third carbon of the glycerol molecule is linked not to a fatty acid but to a phosphate group to which another polar group is usually attached. Phosphate groups are negatively charged. As a result, the phosphate end of the molecule is hydrophilic and therefore soluble in water, whereas the fatty acid end is hydrophobic and insoluble. If phospholipids are added to water, they tend to form a film along its surface, with their hydrophilic "heads" under the water and their hydrophobic "tails" protruding above the surface

Describe the movement of water into roots - Root Hairs

provide greater surface area for absorption. From the root hairs, the water moves through the cortex, the outer layer or layers of which may be differentiated as an exodermis (a subepidermal layer of cells with Casparian strips). From there, the water progresses through the endodermis (the innermost layer of cortical cells) and into the vascular cylinder. Once in the conducting elements of the xylem, the water moves upward through the root and stem and into the leaves, from which most of it is lost to the atmosphere by transpiration.

simple diffusion

small nonpolar molecules, such as oxygen and carbon dioxide, and small uncharged polar molecules, such as water, can permeate cellular membranes freely by simple diffusion. The observation that hydrophobic molecules diffuse readily across plasma membranes provided the first evidence of the lipid nature of the membrane

Proplastids

small, colorless or pale green, undifferentiated plastids that occur in meristematic (dividing) cells of roots and shoots. Precursor of other plastids

Peroxisomes

spherical organelles that have a single bounding membrane. possess neither DNA nor ribosomes and must there- fore import the materials required for their replication. Some peroxisomes play an important role in photorespiration, a process that consumes oxygen and releases carbon dioxide, exactly the reverse of what happens during photosynthesis.

Pinocytosis

taking up liquids

Cytosol

the "cellular soup," or cytoplasmic matrix, in which the nucleus, various entities, and membrane systems are suspended—is called the cytosol. Organelles surrounded by two membranes:

Peptide bonds

the amino group of one amino acid links to the carboxyl group of the adjacent amino acid by the removal of a molecule of water. Again, this is an energy-requiring process. The covalent bond formed is known as a peptide bond, and the molecule that results from the linking of many amino acids is known as a polypeptide. Proteins are large polypeptides

Nucleic Acids:

the basic structural unit of nucleic acids is a nucleotide. A nucleotide consists of a phosphate group, a five-carbon sugar and a nitrogenous base. They serve the most important function of carrying the genetic material, transferring them to new cell and carrying protein synthesis

Once regarded as depositories for waste products in plant cells, vacuoles now are known to play many different roles. What are some of those roles?

the different roles played by vacuoles are: - the vacuoles serve as repositories of primary metabolites and proteins - they also are a store house of anthocyanins - apart from these functions, the macromolecules that enter the cell in the form of vesicles, sometimes get fused with the vacuoles and thus are released in them. Here these macromolecules undergo breakdown into simpler ones - Further the organelles or macromolecules that are not required by the cells are transported to the vacuoles where they undergo breakdown. Thus, the vacuoles help in the recycling of chemical elements

The increase of relatively abundant free oxygen was accompanied by...

the first appearance of eukaryotic cells—cells with nuclear envelopes, complex chromosomes, and organelles, such as mitochondria (sites of respiration) and chloroplasts (sites of photosynthesis), surrounded by membranes.

What is transpiration, and why is it dubbed an "unavoidable evil"?

the phenomenon of the water loss from the plants is said to be transpiration. This means that the water from the plants is evaporated due to the process of photosynthesis. Photosynthesis is the process of making the energy to the plants by themselves, with the requirement of sunlight, water and carbon dioxide. Sunlight is absorbed by the leaves and the carbon dioxide. Sunlight is absorbed by the leaves and the carbon dioxide is diffused through the pores present in the leaves. The water comes from the root, where these three requirements meet the photosynthesis, once the carbon dioxide is diffused it meets the moist cells of the plant and gives out the vapor. These water vapor evaporated results to the water losss in the plant. In the above said explanation regarding the water loss, considered in the case of the in sufficient water on the plant means the plants wont undergoes photosynthesis further, so there is no energy to continue the growth. So the phenomenon of transpiration is considered as the unavoidable evil.

Plasma membrane

the plasma membrane has several important functions: (1) it separates the protoplast from its external environment; (2) it mediates the transport of substances into and out of the protoplast. (3) it coordinates the synthesis and assembly of cell wall microfibrils (cellulose); and (4) it detects and facilitates responses to hormonal and environmental signals involved in the control of cell growth and differentiation

Starch

the primary storage polysaccharide in plants, consists of chains of glucose molecules. There are two forms of starch: amylose (unbranched molecule) and lopectin (branched molecules). Amylose and amylopectin are stored as starch grains within plant cells

Chloroplasts

the sites of photosynthesis contain chlorophylls and carotenoid pigments. The chlorophyll pigments are responsible for the green color of these plastids. The carotenoids are yellow and orange pigments that, in green leaves, are masked by the more numerous chlorophyll pigments

cytology

the study of cell structure, function, and life histories

genetics

the study of heredity and variation

plant morphology

the study of the form of plants; plant anatomy, the study of their internal structure

Prophase:

this is the first stage in mitosis and is further divided into early prophase, mid prophase and late prophase. In early prophase, the chromosomes appear as thread like structures that are scattered throughout the nucleus. In the mid prophase, the chromosomes condense and appear to be consisting of two chromatids that are attached by a centromere. In the late prophase, the chromatids further condense, and microtubules align themselves along the spindle axis. The nuclear envelop dissolves and the nucleolus disappears

G1 phase:

this is the preparatory phase of the cell for cell division. In this phase, the cell doubles in size and the various organelles of the cell along with the enzymes and other molecules multiply in number

S phase:

this is the synthesis phase of the cell. This is the most important phase where the DNA of the cell is duplicated and synthesized. Along with the DNA its associated proteins like histones are also synthesized

quaternary structure

this level is formed by the coming together of two large or more polypeptide chains leading to a complex protein structure