Module 1: Cell Function

How might the process of proteins carrying amino acids (building blocks e.g. muscles and tissues) affect a cell?

- This will affect the cell as it will not be able to develop proteins essential for the building of different cells in the body such as muscle cells. The cell would therefore not be able to regulate properly and would shut down and die

1.5- STAGES IN AEROBIC RESPIRATION THE FIRST STAGE:

1.5 The process of Respiration The general equation for aerobic (with oxygen) respiration is a summary of a chain of biochemical reactions. It occurs in 2 stages. 1. The splitting of the 6 carbon sugar to two 3 carbon sugars. 2. The combining with oxygen to produce carbon dioxide. Most of the energy that is produced is produced in stage 2. The energy is produced in a chemical form as the substance ATP. The rest of the energy is lost as heat. Respiration occurs in 2 stages. THE FIRST STAGE: • Occurs in the CYTOPLASM of the cell • It involves splitting a 6-carbon sugar molecule (glucose) into two 3-carbon molecule (Pyruvate). It is therefore often called GLYCOLYSIS. • Two molecules of ATP are also formed during gycolysis. Glucose pyruvate + 2 energy molecules C6 2C3 (2 ATP)

heterotroph and autotroph

A heterotroph is an organism that: An organism that cannot manufacture its own food and energy by taking in organic substances, usually plant or animal matter. Includes: animals, protozoan, fungi and most bacteria A Autotroph is an organism that: Capable of synthesising it's own food from inorganic substances, using light or chemical energy. Green plants, algae and certain bacteria DNA contains chemical information that controls the cell activities and the production of proteins. RNA assists in the manufacture of the proteins Autotrophs and heterotrophs require gases and nutrients to maintain efficient and effective metabolic function. Both heterotrophs amd autotrophs require inorganic and organic substances, water and oxygen gas. Autotrophs also require carbon dioxide gas. Heterotrophs need to take in all of their nutrients. Autotrophs produce their own organic nutrients using the energy from the sun, but need to obtain water, mineral ions and the gases carbon dioxide and oxygen Autotrophs manufacture their own glucose and other organic substances from inorganic nutrients Heterotrophs must obtain all of their organic nutrients by consuming autotrophs or other heterotrophs

Active Transport

Active transport mechanisms require the use of the cell's energy, usually in the form of adenosine triphosphate (ATP). If a substance must move into the cell against its concentration gradient—that is, if the concentration of the substance inside the cell is greater than its concentration in the extracellular fluid (and vice versa)—the cell must use energy to move the substance. Some active transport mechanisms move small-molecular weight materials, such as ions, through the membrane. Other mechanisms transport much larger molecules. Low to high concentration - Carrier proteins facilitate movement

Aerobic vs an anaerobic respiration

Aerobic vs an anaerobic respiration Aerobic respiration Anaerobic respiration O2 = Uses O2 / Does not require O2 ATP = Provides 36 ATP / Provides 2 ATP Efficiency = High / Low Products = CO2, H2O, ATP / Lactic acid & ATP in animal tissue Location = Mitochondria/ In the cytoplasm

Surface Area to Volume Ratio

An object's Surface Area to Volume Ratio is like a way of describing how close every internal part of it is to its surface. It is worked out by dividing an object's surface area by its volume: S.A.:Vol Ratio = Surface Area/Volume A high S.A.:Vol Ratio shows that every part of an object is quite close to the edge. This means heat energy can get in and out quickly, as there is only a short distance from the edge to the middle. A low SA:Vol Ratio means that there are parts of the object that are a long way from the edge. This means that matter (nutrients and wastes) and heat energy takes longer to get in or out, as there is a longer distance from the edge to the middle. Note: To calculate the ratio, the ratio must be simplified so that the volume is 1. This is why SA is divided by ratio in these examples HIGH S.A.:Vol Ratio: Diffusion occurs readily Also Heats/cools QUICKLY LOW S.A.:Vol Ratio Diffusion occurs slowy Also Heats/cools SLOWLY

Respiration and Photosynthesis

Autotrophs are self feeders because they are able to photosynthesize. This is because they contain glucose in their cells. All organisms need a constant input of energy. For plants this input of energy is initially in the form of light. Through the process of __synthesising___________ the energy is stored in mitochondria which can be used to make more complex carbohydrates such as starch & cellulose. The word equation for photosynthesis is: Reaction in the presence of light = Light/chlorophyll CO2 + water __________________> glucose + oxygen______________ Autotrophs and Heterotrophs both use respiration as a means of releasing stored energy and turning it into useable _____energy (ATP)______ for growth_________, metabolic functions__________, repair, remove wastes__________ and other cellular processes. Much of this energy is then given off as heat. The word equation for respiration is: glucose + _oxygen_________________> CO2 + water + energy (ATP) Some of the requirement of cells can be seen from these two equations. The REACTANTS are the needs and the PRODUCTS are the wastes. The word equations indicate that energy is needed (light or from stored or consumed matter) and energy is also produced (heat or bound in complex molecules) and both inorganic and organic matter is needed and also produced. Some of the products are used by the cell, others are waste that will need to be removed from the cell.

ATP and ADP

Because respiration in a series of steps it can be controlled to permit the slow release of energy needed for various cell activities. We do not want to release all the energy from glucose all at once because it would be like trying to operate a car by exploding all of the petrol instead of using the fuel slowly. Releasing all the energy in one step would be far more inefficient. At some steps, energy is released and stored in another molecule called an energy intermediate. These energy intermediates are the immediate source of energy for organisms. The most common energy intermediate is called adenosine triphosphate or ATP. Only 39% of the available energy of glucose is captured and stored as ATP. The conversion of ATP into energy requires the presence of another compound called adenosine diphosphate or ADP. ADP combines with phosphate (P) to form ATP. ADP + P ATP By oxidizing glucose, respiration takes the energy out of storage and makes it available for ATP production. When each glucose molecule is oxidised in air 38 ATP molecules are formed each storing energy. To release the energy, ATP is then hydrolysed (reacted with water). ATP + H2O ADP + P + energy Processes in the cell that need energy such as making proteins, transporting nutrients or generating electricity are often able to use ATP as their energy source. Thus respiration harvests the energy stored in organic molecules to generate ATP, which powers most cellular work. Animals and fungi, which make ATP only by respiration, are called heterotrophs. Plants are autotrophs and they make ATP by respiration and photosynthesis. • Glucose + 3 water ----> 6 carbon dioxide + 6 water + 36/38 ATP ATP and ADP Because respiration in a series of steps it can be controlled to permit the slow release of energy needed for various cell activities. We do not want to release all the energy from glucose all at once because it would be like trying to operate a car by exploding all of the petrol instead of using the fuel slowly. Releasing all the energy in one step would be far more inefficient. At some steps, energy is released and stored in another molecule called an energy intermediate. These energy intermediates are the immediate source of energy for organisms. The most common energy intermediate is called adenosine triphosphate or ATP. Only 39% of the available energy of glucose is captured and stored as ATP. The conversion of ATP into energy requires the presence of another compound called adenosine diphosphate or ADP. ADP combines with phosphate (P) to form ATP. ADP + P ATP By oxidizing glucose, respiration takes the energy out of storage and makes it available for ATP production. When each glucose molecule is oxidised in air 38 ATP molecules are formed each storing energy. To release the energy, ATP is then hydrolysed (reacted with water). ATP + H2O ADP + P + energy Processes in the cell that need energy such as making proteins, transporting nutrients or generating electricity are often able to use ATP as their energy source. Thus respiration harvests the energy stored in organic molecules to generate ATP, which powers most cellular work. DRAW ATP AND ADP CYCLE Animals and fungi, which make ATP only by respiration, are called heterotrophs. Plants are autotrophs and they make ATP by respiration and photosynthesis. • Glucose + 3 water ----> 6 carbon dioxide + 6 water + 36/38 ATP

What is Cellular respiration

Cellular respiration is a series of metabolic reactions essential to all living cells. Respiration releases energy from sugars and stores it in the form of adenine triphosphate (ATP). ATP is the basic energy currency for cell processes. Respiration can take place in the presence or absence of oxygen (aerobic vs. anaerobic conditions). For yeast, anaerobic respiration is known as fermentation, and produces carbon dioxide along with ethanol or lactate as the primary waste products, while aerobic respiration produces carbon dioxide and water as the primary waste products (Campbell and Reece, 2008). In this lesson, students will use the scientific method in one instructor-guided experiment and one student- designed experiment to explore cellular respiration in yeast. When yeast is mixed with a sugar source and water, foam forms, and may be measured as a proxy for carbon dioxide production. By comparing respiration rates between different water temperature and sugar sources, students can determine optimal conditions for yeast respiration. An environment that is too cold, too hot, or lacking in food will result in lowered rates of respiration or death.

Aerobic cellular respiration

Cellular respiration is the process by which an organism releases the energy from stored food. This process occurs within the cells of an organism, hence the name. Aerobic respiration is oxygen dependent whereas anaerobic respiration occurs without oxygen). Most cells use aerobic respiration. The overall reaction of respiration is the oxidation (loss of electrons) of an organic compound, often a carbohydrate such as glucose, to produce carbon dioxide and water. Energy is released in the process. Fats can also be used for respiration. Glucose + oxygen carbon dioxide + water + energy C6H12O6 + 6O2 6CO2 + 6H2O + energy This energy is not released suddenly or all at once but gradually in about 50 intermediate reactions or steps. Each step is catalysed by a different enzyme. (An enzyme is a substance that makes a reaction go faster without being used up itself in the reaction. This type of substance is also called a catalyst).

Diffusion

Diffusion is a passive process of transport. A single substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across a space. You are familiar with diffusion of substances through the air. For example, think about someone opening a bottle of ammonia in a room filled with people. The ammonia gas is at its highest concentration in the bottle; its lowest concentration is at the edges of the room. The ammonia vapor will diffuse, or spread away, from the bottle, and gradually, more and more people will smell the ammonia as it spreads. Materials move within the cell's cytosol by diffusion, and certain materials move through the plasma membrane by diffusion. Diffusion expends no energy. On the contrary, concentration gradients are a form of potential energy, dissipated as the gradient is eliminated.

Summary of Movements

Diffusion: - Any small molecules - Moves more generally from a high to low concentration until equilibrium is reached Osmosis: - The movement of water only from low to high concentration - Moves across a partially permeable membrane until equilibrium is reached Similarities: - Movement of molecules from areas of high to low concentration - Movement of small molcules/particlesboth in plants and animal cells to move substances in and out no energy required Passive moves molecules from high to low concentration using no metabolic energy. Active moves molecules from low to high concentration using energy in the form of ATP Endocytosis and exocyctosis can occur in the same cell as cells have multiple functions at the same time. It allows for the growth of the cell without building up of one or the other. They balance each process out with one exiting and the other entering. Active transport:low to high - Pumps molecules through the cell membrane against the concentration gradient - Utilises cellular energy as ATP - Endocytosis, exocytosis, secretion of substances into bloodstream active - Allows molecules to pass the cell membrane distrupting equilibrium - Ions, large proteins, complex sugars are transported - Reuired for the entrance of large molecule - Against diffusion Passive: high to low - Allows molecules to pass the cell membrane through a concentration gradient - Does not reuire energy - Diffusion, facilitated diffusion and osmosis - Nutrients, gases and wastes are maintained between cytosol and extracellular environment - Water soluble molecules like oxygen and water are transported - Maintaenance of homeostatis steady interval conditions between the cytosol and extracellular fluid - With diffusion Similarities: - Movement of molecules - Pass through cell membrane - Ways of cells regulating what enters and leaves can use channels of proteins

Endocytosis

Endocytosis is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane. The membrane folds over the substance and it becomes completely enclosed by the membrane. At this point a membrane-bound sac, or vesicle, pinches off and moves the substance into the cytosol. It is a form of active transport. Endocytosis is a type of active transport that moves particles, such as large molecules, parts of cells, and even whole cells, into a cell. There are two main kinds of endocytosis: • Phagocytosis, or cellular eating, occurs when the dissolved materials enter the cell. The plasma membrane engulfs the solid material, forming a phagocytic vesicle. • Pinocytosis, or cellular drinking, occurs when the plasma membrane folds inward to form a channel allowing dissolved substances to enter the cell, as shown in Figure below. When the channel is closed, the liquid is encircled within a pinocytic vesicle.

Factors that influence the direction of water movement Write table of transport

Factors that influence the direction of water movement in: - animals: type of environment - Plants: pressure exerted by cell wall environment How animal cells differ from plant cells with respect to the effects of net water movements: too much net water movement in cell membrane will burst and cell will die. Plants allow cell wal to expand with water (turgid) Preferably tonicity of the replacement drinks: hypotonic as the tonicity which describes tone to the cell and more pressure - high amounts of water from sweating Cell wall pressure in generating cell turgor in plants: when there is a alrge net movement of water into plant cells. This applies pressure to wall causing it to expand. This does not burst because f pressure in the wall. Role of turgor to plants: provides structure and support allowing it to remain upright and rigid. (without flaccid)

Tonicity in Living Systems plasmolysis

In a hypotonic environment, water enters a cell, and the cell swells. In an isotonic condition, the relative concentrations of solute and solvent are equal on both sides of the membrane. There is no net water movement; therefore, there is no change in the size of the cell. In a hypertonic solution, water leaves a cell and the cell shrinks. If either the hypo- or hyper- condition goes to excess, the cell's functions become compromised, and the cell may be destroyed.

Facilitated Transport

In facilitated transport, also called facilitated diffusion, materials diffuse across the plasma membrane with the help of membrane proteins. A concentration gradient exists that would allow these materials to diffuse into the cell without expending cellular energy. However, these materials are ions or polar molecules that are repelled by the hydrophobic parts of the cell membrane. Facilitated transport proteins shield these materials from the repulsive force of the membrane, allowing them to diffuse into the cell. The material being transported is first attached to protein or glycoprotein receptors on the exterior surface of the plasma membrane. This allows the material that is needed by the cell to be removed from the extracellular fluid. - Channels = moves substances down their concentration gradients. They may cross the plasma membrane with the aid of channel proteins. Channels are specific for the substance that is being transported. Channel proteins have hydrophilic domains exposed to the intracellular and extracellular fluids; they additionally have a hydrophilic channel through their core that provides a hydrated opening through the membrane layers. - Carrier Proteins = Another type of protein embedded in the plasma membrane is a carrier protein. This aptly named protein binds a substance and, in doing so, triggers a change of its own shape, moving the bound molecule from the outside of the cell to its interior; depending on the gradient, the material may move in the opposite direction. Carrier proteins are typically specific for a single substance. This selectivity adds to the overall selectivity of the plasma membrane. Channel and carrier proteins transport material at different rates. Channel proteins transport much more quickly than do carrier proteins. Channel proteins facilitate diffusion at a rate of tens of millions of molecules per second, whereas carrier proteins work at a rate of a thousand to a million molecules per second.

Factors That Affect Diffusion

Molecules move constantly in a random manner, at a rate that depends on their mass, their environment, and the amount of thermal energy they possess, which in turn is a function of temperature. While diffusion will go forward in the presence of a concentration gradient of a substance, several factors affect the rate of diffusion. • Extent of the concentration gradient: The greater the difference in concentration, the more rapid the diffusion. The closer the distribution of the material gets to equilibrium, the slower the rate of diffusion becomes. • Mass of the molecules diffusing: Heavier molecules move more slowly; therefore, they diffuse more slowly. The reverse is true for lighter molecules. • Temperature: Higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion. Lower temperatures decrease the energy of the molecules, thus decreasing the rate of diffusion. • Solvent density: As the density of a solvent increases, the rate of diffusion decreases. The molecules slow down because they have a more difficult time getting through the denser medium. If the medium is less dense, diffusion increases. Because cells primarily use diffusion to move materials within the cytoplasm, any increase in the cytoplasm's density will inhibit the movement of the materials. An example of this is a person experiencing dehydration. As the body's cells lose water, the rate of diffusion decreases in the cytoplasm, and the cells' functions deteriorate. Neurons tend to be very sensitive to this effect. Dehydration frequently leads to unconsciousness and possibly coma because of the decrease in diffusion rate within the cells. • Solubility: As discussed earlier, nonpolar or lipid-soluble materials pass through plasma membranes more easily than polar materials, allowing a faster rate of diffusion. • Surface area and thickness of the plasma membrane: Increased surface area increases the rate of diffusion, whereas a thicker membrane reduces it. • Distance travelled: The greater the distance that a substance must travel, the slower the rate of diffusion. This places an upper limitation on cell size. A large, spherical cell will die because nutrients or waste cannot reach or leave the center of the cell, respectively. Therefore, cells must either be small in size, as in the case of many prokaryotes, or be flattened, as with many single-celled eukaryotes.

Organic and inorganic molecules

Organic molecules are molecules of life that are built around chains of carbon atoms for building cells (four types: carbohydrates, proteins, lipids and nucleic acids). Inorganic molecules are simple and not generally in living things. E.g. water 2. Identify the following as either INORGANIC or ORGANIC i. Glucose organic ii. Water ______inorganic__________ iii. Carbon dioxide ___inorganic_____________ iv. Oxygen ___organic_____________ 3. It can be seen that the process of photosynthesis takes ______inorganic______molecules (water and Carbon dioxide) and makes an ___organic__________ molecule (Glucose) Recall that the plasma membrane allows the movement of inorganic and organic molecules into and out of the cell in an attempt to maintain a constant internal environment. Substances required for cell functioning (gases, nutrients, minerals and water) must pass through the cell membrane from the external environments whilst wastes (urea, uric acid, and excess carbon dioxide) and essential cellular products (hormones and enzymes) must pass out of the cell into the external environment.

Osmosis

Osmosis is the movement of water through a semipermeable membrane according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes. While diffusion transports material across membranes and within cells, osmosis transports only water across a membrane and the membrane limits the diffusion of solutes in the water.

Diffusion and osmosis experiment

PURPOSE: The purpose of the experiment was to test the permeability of dialysis tubing to glucose, starch and iodine. Living cells need to obtain nutrients from their environment and get rid of waste materials to their surroundings. This exchange of materials between the cell and its surroundings is crucial to its existence. Cells have membranes composed of a phospholipid bilayer embedded with proteins. This selectively-permeable-membrane cell membrane can distinguish between different substances, slowing or hindering the movement of other substances and allowing others to pass through readily. This property of the cell is known as selective permeability. Selective permeability is a property of a cell membrane that allows it to control which molecules can pass (moving into and out of the cell) through the pores of the membrane. Selective permeable membranes only allows small molecules such as glucose, amino acids to readily pass through, and inhibits larger molecules like protein, starch, from passing through it. The dialysis tubing is a semi-permeable membrane tubing used in separation techniques and demonstration of diffusion, osmosis, and movement of molecules across a restrictive membrane. It separates dissolved substances of different molecular sizes in a solution, and some of the substances may readily pass through the pores of the membrane while others are excluded. The dialysis tubing is made up of cellulose fibers. This is shaped in a flat tube. It was concluded that the dialysis tubing doesn't allow all kinds of substances to pass readily through the pores of its membrane. This means that it is selective in its permeability to substances. The dialysis tubing was permeable to glucose and iodine but not to starch. Starch was excluded because it has a larger molecular size than glucose and iodine.

Light phase and independent phase DRAW CYCLE

Photosynthesis is not a single reaction as the chemical equation shows but occurs as a chain of biological reactions with an overall outcome as shown in the chemical equation. Photosynthesis occurs in two phases: • light phase • dark phase (does not need light or independent of light) Light phase - in grana • Light is captured by chlorophyll in the grana and the energy is used to split water molecule into hydrogen and oxygen atoms. Oxygen is released via the stomata in the leaf, hydrogen moves into the stroma. Light-independent phase (no light required) - in stroma • Hydrogen atoms combine with CO2 (through a series of enzyme controlled reactions called the Calvin cycle) to form a sugar molecule, glucose or C6H12O6 • Glucose not used immediately is converted to starch for storage and stored in stroma.

Explain how substances are directly transported across a membrane

Plasma membranes are selectively permeable; if they were to lose this selectivity, the cell would no longer be able to sustain itself. In passive transport, substances simply move from an area of higher concentration to an area of lower concentration, which does not require the input of energy. Concentration gradient, size of the particles that are diffusing, and temperature of the system affect the rate of diffusion. Some materials diffuse readily through the membrane, but others require specialized proteins, such as channels and transporters, to carry them into or out of the cell. Substances diffuse according to their concentration gradient; within a system, different substances in the medium will each diffuse at different rates according to their individual gradients. After a substance has diffused completely through a space, removing its concentration gradient, molecules will still move around in the space, but there will be no net movement of the number of molecules from one area to another, a state known as dynamic equilibrium. Several factors affect the rate of diffusion of a solute including the mass of the solute, the temperature of the environment, the solvent density, and the distance traveled. Osmosis occurs according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes. Osmosis occurs until the concentration gradient of water goes to zero or until the hydrostatic pressure of the water balances the osmotic pressure. Osmosis occurs when there is a concentration gradient of a solute within a solution, but the membrane does not allow diffusion of the solute. Endocytosis consists of phagocytosis, pinocytosis, and receptor -mediated endocytosis. Endocytosis takes particles into the cell that are too large to passively cross the cell membrane. Phagocytosis is the taking in of large food particles, while pinocytosis takes in liquid particles. Receptor-mediated endocytosis uses special receptor proteins to help carry large particles across the cell membrane.

OBTAINING NUTRIENTS - REQUIRMENTS FOR PHOTOSYNTHESIS REFER TO FLOW CHART

REQUIREMENT OBTAINED FROM THROUGH (part of plant) Water soil Roots oxygen with water going up and stalk fibre phloem Carbon dioxide air Leaves stomates in leaf Chlorophyll Green pigment in plants Stalk and leaves Light sun Leaves (food makers)

The role of respiration in ecosystems

Respiration is the process by which cells obtain energy. In this process organic molecules, particularly sugars, are broken down to produce carbon dioxide and water and energy is released. When animals consume plants they obtain nutrients that are used in respiration in their body cells so that they too can obtain energy. This energy (released during respiration) drives all the metabolic processes in an organism and ultimately drives ecosystems. Photosynthesis, at a glance appears to be the reverse of respiration. This, however, is not the case. On an individual level the sequence of reactions that occurs in each process is very different. Transformation of energy in ecosystems In an ecosystem there is no reuse of energy. It is either used by a living thing or lost as heat. Because of this, a continual input of energy is needed to keep living systems functioning. About half of the products of photosynthesis in a plant are broken down and used as fuel in cellular respiration. The rest is used as building blocks to make organic molecules needed for growth maintenance and repair of body tissues. Chemical energy in glucose --> Heat energy + other forms of energy needed by organism --> Organic molecules need for growth, maintenance and repair. The waste products of respiration, carbon dioxide and water, are the very substances that chloroplasts use as raw materials for photosynthesis. Thus, the chemical elements essential to life are recycled. But energy is not: It flows into an ecosystem as sunlight and leaves it as heat.

Surface area and volume

Surface area refers to the outside area of an object, e.g. it is the area around the outside of a cell. Unit = cm2 . Volume refers to the amount of space inside of the object, e.g. it is the space inside the cell. Unit = cm3 . As the cube size increases or the cell gets bigger , then the surface area to volume ratio - SA:V ratio decreases.

THE SECOND STAGE:

THE SECOND STAGE: • Occurs in the MITOCHONDRIA • The pyruvate molecules are further broken down into carbon dioxide. • Oxygen is required in this stage. It combines with hydrogen to form water. • A lot of energy (ATP) is released gradually during the breakdown of the pyruvate molecules and 36 molecules of ATP are released. • Most of the energy (60%) during this process is lost as heat along the way. pyruvate carbon + water 2C3 dioxide energy (36 ATP) • In total there are 38 ATP molecules produced during aerobic respiration. i.e/ 2 ATP from stage one and 36 ATP from stage two.

Light Reaction

The first reaction requires light-hence "the light reaction" from light ---> Water hydrogen + Oxygen • In this reaction _______light_______ from the sun (absorbed by the chlorophyll) is converted to ___energy____________. • Some of this energy is used to ___split water________________ into _____hydrogen___ and ___oxygen_____________. • This reaction occurs on the internal membranes of the chloroplasts in the plant cells. These membranes are called ___thylakoids___________.. • Manganese is an important micronutrient in this process, as it is needed for the release of oxygen.

Energy flow and chemical recycling in ecosystems

The mitochondria of eukaryotes (including plants) use the organic products of photosynthesis as fuel for cellular respiration, which also consumes the oxygen produced by photosynthesis. Respiration harvests the energy stored in organic molecules to generate ATP, which powers most cellular work. The waste products of respiration, carbon dioxide and water, are the very substances that chloroplasts use as raw materials for photosynthesis. Thus, the chemical elements essential to life are recycled. But energy is not: It flows into an ecosystem as sunlight and leaves it as heat. ATP is a nucleotide containing adenosine attached to a sugar, which is bound to three phosphates. It is a renewable energy source. When a cell requires energy, the high-energy chemical bonds attaching the last phosphate group to ATP are broken releasing energy. The remaining molecule is ADP and has two remaining phosphates. Energy from a cell reaction can be used to add a phosphate group to ADP to convert it to ATP. 4

• Describe the roles of Photosynthesis and Respiration in Ecosystems

The products of one is the reactants of the other The Role of Respiration in ecosystems Aerobic Cellular Respiration is the process whereby cells obtain energy, by breaking down organic molecules (eg: sugars) to produce: • Carbon Dioxide • Water • Chemical Energy (as well as heat energy) This process is related to photosynthesis, but is NOT the reverse process: Solar Radiation Producers Photosynthesis (Energy) (Trap solar energy) (Converts to chemical energy) Cellular Respiration Glucose (+ Oxygen) Drives (keeps plant alive by Metabolic Using energy) Processes Consumers Cellular Respiration (obtain nutrients from producers) (Energy use) Energy Loss (Heat) The role of respiration is therefore to enable organisms within an ecosystem to utilise the energy input from the sun to drive cellular metabolic processes such as: • Synthesis of complex biomolecules (eg proteins) • Growth (division, elongation and differentiation of cells) • Repair and maintenance of cells • Active transport of materials from one cell to another • Normal cell functioning

Exocytosis

The reverse process of moving material into a cell is the process of exocytosis. Exocytosis is the opposite of the processes discussed in the last section in that its purpose is to expel material from the cell into the extracellular fluid. Waste material is enveloped in a membrane and fuses with the interior of the plasma membrane. This fusion opens the membranous envelope on the exterior of the cell, and the waste material is expelled into the extracellular space. Other examples of cells releasing molecules via exocytosis include the secretion of proteins of the extracellular matrix and secretion of neurotransmitters into the synaptic cleft by synaptic vesicles. In exocytosis, vesicles containing substances fuse with the plasma membrane. The contents are then released to the exterior of the cell.

Light independent

The second reaction uses carbon dioxide and is light independent. This stage is also referred to as the __carbon-fixing stage_____. Hydrogen + Carbon dioxide sugars • In this reaction ___hydrogen from the first reaction combines with carbon dioxide to form sugars_______________________________ • This reaction is a ___building up reaction and requires energy_. The energy comes from the light absorbed in the first reaction. • This reaction __occurs in the chloroplasts____ also but in the __stroma______or fluid matrix of the chloroplast. The __sugars made are used in cell respiration____. During the day when light is available for photosynthesis, there are _more sugars made than are _used in respiration_. These sugars are then _stored as starche______________. At night, the __starch is converted back into sugars___ and used for: repiration, built into proteins or lipids or starch

Tonicity

Tonicity describes how an extracellular solution can change the volume of a cell by affecting osmosis. A solution's tonicity often directly correlates with the osmolarity of the solution. Osmolarity describes the total solute concentration of the solution. Three terms—hypotonic, isotonic, and hypertonic—are used to relate the osmolarity of a cell to the osmolarity of the extracellular fluid that contains the cells. In a hypotonic situation, the extracellular fluid has lower osmolarity than the fluid inside the cell, and water enters the cell. (In living systems, the point of reference is always the cytoplasm, so the prefix hypo- means that the extracellular fluid has a lower concentration of solutes, or a lower osmolarity, than the cell cytoplasm.) It also means that the extracellular fluid has a higher concentration of water in the solution than does the cell. In this situation, water will follow its concentration gradient and enter the cell. As for a hypertonic solution, the prefix hyper- refers to the extracellular fluid having a higher osmolarity than the cell's cytoplasm; therefore, the fluid contains less water than the cell does. Because the cell has a relatively higher concentration of water, water will leave the cell. In an isotonic solution, the extracellular fluid has the same osmolarity as the cell. If the osmolarity of the cell matches that of the extracellular fluid, there will be no net movement of water into or out of the cell, although water will still move in and out. Blood cells and plant cells (Figure 7) in hypertonic, isotonic, and hypotonic solutions take on characteristic appearances.

Variegated geranium plants

Variegated geranium plants are those with green sections containing chlorophyll and the yellowish-white sections fo not conain chlorophyll

What does a cell "eat"? DRAW LABELLED DIAGRAM

Vesicle Transport Some molecules or particles are just too large to pass through the plasma membrane or to move through a transport protein. So cells use two other active transport processes to move these macromolecules (large molecules) into or out of the cell. Vesicles or other bodies in the cytoplasm move macromolecules or large particles across the plasma membrane. There are two types of vesicle transport, endocytosis and exocytosis. Both processes are active transport processes, requiring energy.

Size and Volume and Surface Area Why its important

When an object/cell is very small, it has a large surface area to volume ratio, while a large object/ cell has a small surface area to volume ratio. When a cell grows, its volume increases at a greater rate than its surface area, therefore it's SA: V ratio decreases. Cells may increase their SA:V ratio by having: • Long thin shape / elongated shape. e.g. nerve cells • Folding the surface of the object/ cell membrane. e.g. villi of the lining in the small intestines • Plant cells are much larger than animal cells and they have a large vacuole which pushes the organelles to the edge of the cell where they get regular access to resources. Why is SA:V ratio important: Cells need to be small because they rely on diffusion for getting substances into and out of their cells. When a cell grows, there is comparatively less membrane for the substances to diffuse through resulting in the centre of the cell not receiving the substances that it needs. Diffusion is less efficient, cell processes slow down and the cell stops growing. The cell then needs to divide into two smaller cells, which each have a larger SA: V ratio and can diffuse materials more efficiently again. In class you may have done an experiment where you placed special agar into a solution of NaOH. All three cubes soaked in the solution for the same amount of time but the bigger cubes did not change colour on the inside as the NaOH hadn't diffused in yet. This shows that large cell takes long/is less efficient at diffusing materials into the centre of the cell. SA:V ratio in unicellular organisms. Their small size means that they have a large SA:V ratio and it is adequate for the many materials to move into and out of the cell by diffusion and active transport. But it does limit the organism's size. Once they get too big, they must divide. SA:V ratio in multicellular organisms. By being multicellular, plants and animals have overcome the problems of small cell sizes. Each cell has a large SA:V ratio but they have evolved features such as gas exchange organs (lungs) and circulatory system (blood) to speed up and aid the movement of materials into and out of the organism. The advantage to cells diving to remain small? - The processes can allow for diffusion more efficiently Why shape is advantageous to plant? - More efficient for the cell to have a large surface area as it allows for diffusion to occur more effectively and quickly gases, nutrients and wastes exchange of substances The red cells are discshaped with a concave centre. This is important to the functioning of the red blood cell in order to allow for the red blood cel

PHOTOSYNTHESIS

Word equations are very useful to describe a range of reactions. Earlier in the topic we used word equations to describe the process of photosynthesis and the complex reactions involved in respiration. General word equation for photosynthesis: Carbon dioxide + Water --> light/chlorophyll Oxygen + Glucose • Photosynthesis involves a chain of _____chemical reactions__. These reactions can be generalised into two reactions (although it is actually continuous): The ____light phase___________ and the ____dark phase_______________ reaction PHOTOSYNTHESIS: A series of complex biochemical reactions

Anaerobic and aerobic

• All organisms breakdown glucose as a source of energy to drive metabolism. • Two types: Anaerobic - occurs in organisms that live in environments without oxygen (some bacteria and organisms from the archaea) so requires biochemical pathways using molecules other than oxygen eg alcohol fermentation. Aerobic - occurs in organisms that use oxygen (will concentrate on this one). Respiration Respiration as with photosynthesis, is a chain of many biological reactions that occur in the cell. It is summarised as follows. There are at least 20 separate reactions, each catalysed by specific enzymes to make the overall pathway. • Adenosine triphosphate molecule (ATP) is considered by biologists to be the energy currency of life. It is the high-energy molecule it has a lot of energy stored in the bond between the second and third phosphate groups that can be used to fuel chemical reactions. When a cell needs energy, it breaks this bond to form adenosine diphosphate (ADP) and a free phosphate molecule.

Anaerobic respiration

• Anaerobic respiration takes place without oxygen and produces less energy than aerobic respiration. E.g. running instead lactic acid in muscle cell • Anaerobic respiration breaks down glucose to form either lactic acid or ethanol (a tope of alcohol- this is called fermentation) • The general equation for anaerobic respiration is: Glucose carbon + alcohol + energy dioxide (2 ATP)

PLANTS- REQUIREMENTS FOR GROWTH

• Plants need proteins (C, H, O, N) for growth and repair • Plants need materials for the supply of energy, through the process of photosynthesis, for plant growth. INPUTS Water (H20) Nitrates (NO3-) Various inorganic minerals (eg. iron, zinc) Carbon dioxide (CO2) Oxygen (O2) Sunlight OUTPUTS Water Oxygen Energy (in the forms of carbohydrates in the plant body eg. Starch)

RESPIRATION

• Respiration occurs in all the cells of every living thing mitochondria. • It can occur in the presence of oxygen (aerobic) or without oxygen (anaerobic). • Respiration involves a series of reactions. • Enzymes are needed for the reactions to occur. • Respiration involves the breakdown of glucose (a sugar molecule) and the release of energy in the form of ATP (Adenosine triphosphate) • The general word equation for aerobic respiration is: Glucose + oxygen carbon+ water + energy dioxide (38 ATP)

Major biological processes REFER TO DIAGRAMS

• The two major biological processes are photosynthesis (in plants) and cellular respiration in all cells. Note: photosynthesis and respiration occur in plants cells. Photosynthesis is the most important biological process as all the energy required by living things comes from the sun. The energy is transformed in the chloroplasts of plants to chemical energy in the bonds of glucose molecules. Glucose moves out of the chloroplast to the mitochondria where the glucose molecule is converted into energy (cellular respiration) that is essential for cell functions.