A&P CH 3 CELLS

List three ways that substances can move across the plasma membrane.

**Passive Transport Mechanisms:diffusion/osmosis/facilitated diffusion **Active Transport Mechanisms:Active Trans/Secondary A.T **Vesicular Transport:Endocytosis/Exocytosis depending on the chemical characteristics of the molecules and ions and the structure and function of the cell. Molecules that are soluble in lipids, such as oxygen, carbon dioxide, and steroids, pass through the plasma membrane readily by dissolving in the lipid bilayer. Large, non-lipid-soluble molecules and ions that cannot diffuse across the phospholipid bilayer may move across the plasma membrane with the help of transport proteins. Large, non-lipid-soluble molecules and ions that cannot diffuse across the phospholipid bilayer may move across the plasma membrane with the help of transport proteins.

Give an example of the action of a plasma membrane enzyme.

Some membrane proteins function as enzymes, which can catalyze chemical reactions on either the inner or the outer surface of the plasma membrane- example epinephrine/ adrenaline

Compare and contrast how carrier proteins and ATP-powered pumps move ions or molecules across the plasma membrane.

*Carrier proteins, or transporters, are integral membrane proteins that move ions or molecules from one side of the plasma membrane to the other. Specific ions or molecules attach to binding sites within the carrier protein. The binding of the specific ion or molecule causes the carrier proteins to change shape and release the bound ion or molecule to the other side of the plasma membrane. The carrier protein then resumes its original shape and is available to transport more ions or molecules. *ATP-powered pumps are transport proteins that require cellular energy to move specific ions or molecules from one side of the plasma membrane to the other. The activity of ATP-powered pumps is fueled by the breakdown of adenosine triphosphate (ATP). The breakdown of ATP to adenosine diphosphate (ADP) releases energy, changing the shape of the protein, which moves the ion or molecule across the membrane

Describe specificity, competiton, and saturation as characteristics of transport proteins.

*Specificity means that each transport protein binds to and transports only a certain type of molecule or ion. The chemical structure of the binding site determines the specificity of the transport protein because only substances that are the right shape can bind to the protein. *Competition is the result of molecules with simlilar shape binding to the transport protein. Although the binding sites of transport proteins exhibit specificity, closely related substances that have the same shape may bind to the same binding site. The substance in the greater concentration or the substance that binds to the binding site more readily is moved across the plasma membrane at the greater rate. *Saturation means that the rate of movement of molecules across the membrane is limited by the number of available transport proteins. once the concentration of the substance is increased so that all the binding sites are occupied, the rate of movement remains constant, even though the concentration of the substance increases further.

What parts are common to most cells?

*The plasma membrane, or cell membrane, forms the outer boundary of the cell, through which the cell interacts with its external environment. *The nucleus is usually located centrally; it directs cell activities, most of which take place in the *cytoplasm , located between the plasma membrane and the nucleus. Within cells, specialized structures called *organelles perform specific functions.

Explain the four characteristic functions of the cell.

1. Cell metabolism and energy use, it involves all chemical reactions that occur within a cell. These metabolic reactions often involve energy transfers, meaning the energy released by one reaction is then used in another reaction. ex heat relaeased by MR helps maintain body temperature. 2. Synthesis of molecules. The different cells of the body synthesize, or produce, various types of molecules, including proteins, nucleic acids, and lipids. The structural and functional characteristics of cells are determined by the types of molecules they produce. 3. Communication. Cells communicate with each other by using chemical and electrical signals. For example, nerve cells produce chemical signals by which they communicate with muscle cells. Then, muscle cells respond to the chemical signals by contracting or relaxing. 4. Reproduction and inheritance. Most cells contain a complete copy of all the genetic information of the individual. This genetic information ultimately determines the structural and functional characteristics of the cell. As a person grows, cells divide to produce new cells, each containing the same genetic information. Specialized cells called gametes are responsible for transmitting genetic information to the next generation.

What are the three types of channel proteins, and what signal causes each to open or close?

1. Leak ion channels, or nongated ion channels, are always open and are responsible for the plasma membrane's permeability to ions when the plasma membrane is at rest. 2. Gated ion channels open and close depending on certain conditions of the cell. Some gated ion channels open or close in response to chemical signals binding to the ion channel. 3.Ligand is a generic term for any chemical signal molecule used by cells to communicate with each other, and ion channels that respond to these signals are called ligand-gated ion channels. Other gated ion channels open or close when there is a change in the membrane potential. These are called voltage-gated ion channels.

What are the three classes of transport proteins?

1. channel proteins, (2) carrier proteins, and (3) ATP-powered pumps.

Explain five functions of the plasma membrane.

1.It functions as a boundary separating the intracellular substances from the extracellular substances. 2. Encloses and Supports the cell contents and attaches to other cells. 3. recognize and communicate with each other 4.determines what moves into and out of cells. 5.

List three ways in which activated α subunits can stimulate a cell response.

2nd messengers

How is a start codon different from a promoter?

A DNA nucleotide sequence called a promoter signals the beginning of the gene and is the site for initial RNA polymerase binding...The attachment of RNA polymerase to the promoter causes a portion of the DNA molecule to unwind, exposing the DNA nucleotide sequence for that region of the template strand. Complementary RNA nucleotides then align with the DNA nucleotides of the template strand.

What is the function of the nucleolus?

A nucleolus is a dense region within the nucleus. A nucleolus lacks a surrounding membrane . Usually, one nucleolus exists per nucleus, but several nucleoli may be seen in the nuclei of rapidly dividing cells. The subunits for ribosomes are manufactured in the nucleolus, so the portions of chromosomes that contain DNA from which rRNA is produced are located in the nucleolus.

What is the role of alternative splicing in variation?

Alternative splicing allows a single gene to produce more than one specific protein; however, the various proteins usually have similar functions in different tissues. In humans, nearly all mRNAs undergo alternative RNA splicing.

What is the membrane potential?

An electrical charge difference across the plasma membrane called the membrane potential is a result of the cell's regulation of ion movement into and out of the cell. There are more positively charged ions immediately on the outside of the plasma membrane and more negatively charged ions and proteins inside. Positive on the outside and negative on the inside.

In what molecules are codons and anticodons found?

Another part of the tRNA, called the anticodon, consists of three nucleotides and is complementary to a particular codon of mRNA. On the basis of the pairing relationships between nucleotides, the anticodon can combine only with its matched codon. For example, the tRNA that has the anticodon CUA combines with the codon GAU of mRNA. The codon GAU codes for aspartic acid, so the matching tRNA will have aspartic acid attached to it.

What occurs during endocytosis?

Another way in which the cell can take in material from the extracellular envrionment. The cell membrane INVAGINATES and ENGULFS the material into the cell.

Distinguish between chromatin and a chromosome. What molecule is found in chromatin?

DNA wrapped around special proteins, histones, we connect histones and make a coiled structure called chromatin. combining 8 histones forms a structure called the nucleosome. Nucleosomes, can be wrapped into coils of PROTEIN/DNA/RNA called chromatin.

Explain diffusion

Diffusion is the movement of solutes from an area of higher solute concentration to an area of lower solute concentration

By increased temperature of a solution? By increased viscosity of the solvent?

As the temperature of a solution increases, the speed at which all molecules move increases, resulting in a greater diffusion rate. SSmall molecules diffuse through a solution more readily than do large ones, so smaller molecules diffuse faster than larger molecules. Viscosity is a measure of a fluid's resistance to flow. A fluid with a low viscosity flows more easily, and a fluid with a high viscosity flows less easily. Thick solutions, such as syrup, are more viscous than water. Diffusion occurs more slowly in viscous solvents than in thin, watery solvents.

Solution concentrations are defined by what? (solvent or solute?)

Because solution concentrations are defined in terms of solute concentrations, not in terms of water content (see chapter 2), water diffuses from the less concentrated solution (fewer solutes, more water) into the more concentrated solution (more solutes, less water).

As the concentration of a solution increases, what happens to its osmotic pressure and to the tendency for water to move into the solution?

Because water moves from less concentrated solutions (fewer solutes, more water) into more concentrated solutions (more solutes, less water), the greater the concentration of a solution (the less water it has), the greater the tendency for water to move into the solution, and the greater the osmotic pressure to prevent that movement.

Explain the relationship among centrosomes, spindle fibers, and chromosomes during cell division.

Before cell division, the two centrioles double in number; the centrosome divides into two; and one centrosome, containing two centrioles, moves to each end of the cell. Microtubules called spindle fibers extend out in all directions from the centrosome. These microtubules grow and shrink even more rapidly than those of nondividing cells. If the extended end of a spindle fiber comes in contact with a chromosome, the spindle fiber attaches to the chromosome and stops growing or shrinking. Eventually, spindle fibers from each centrosome bind to all the chromosomes. During cell division, the spindle microtubules facilitate the movement of chromosomes toward the two centrosomes

What is secondary active transport? Describe how it functions.

Coupling an ion's movement WITH its gradient to power another ion's movement AGAINST its gradient. Secondary active transport involves the active transport of an ion, such as sodium, out of a cell, establishing a concentration gradient, with a higher concentration of the ions outside the cell.

What are spindle fibers?

Before cell division, the two centrioles double in number; the centrosome divides into two; and one centrosome, containing two centrioles, moves to each end of the cell. Microtubules called spindle fibers extend out in all directions from the centrosome. These microtubules grow and shrink even more rapidly than those of nondividing cells. If the extended end of a spindle fiber comes in contact with a chromosome, the spindle fiber attaches to the chromosome and stops growing or shrinking. Eventually, spindle fibers from each centrosome bind to all the chromosomes. During cell division, the spindle microtubules facilitate the movement of chromosomes toward the two centrosomes

Differentiate between the cytoplasm and the cytosol.

Cytoplasm, the cellular material outside the nucleus but inside the plasma membrane, is about half cytosol and half organelles. The fluid portion of the cytoplasm is cytosol. The cytosol is a colloid, a viscous solution containing dissolved ions and molecules as well as suspended molecules, especially proteins.

How do phagocytosis and pinocytosis differ from each other?

Cell eating vs cell drinking.

How can the number of mitochondria in a cell increase?

Cells with a greater energy requirement have more mitochondria with more cristae than do cells with lower energy requirements. Increases in the number of mitochondria result from the division of preexisting mitochondria. When muscles enlarge as a result of exercise, the number of mitochondria within the muscle cells increases to provide the additional ATP required for muscle contraction.

What is the function of cholesterol in plasma membranes?

Cholesterol limits the movement of phospholipids, providing stability to the plasma membrane. The hydrophilic hydroxyl (-OH) group of cholesterol extends between the phospholipid heads to the hydrophilic surface of the membrane,

Describe the structure of the nucleus and the nuclear envelope.

Contains the genetic info. COntains ita own phospholipid bilayer, the nuclear membrane. The nucleolus is the region where we synthesize incomeplete ribosomes, found inside the cytosol. The outer membrane is connected to the rough ER, when we synthesize our Rrna , we need a quick way to transport this material. Nucleoplasm is the fluid in the nucleus. Intermediate fillaments makeup the nuclear lamina, which stabalize its structure and involved in gene expression.

How can DNA control the structural and functional characteristics of the cell without leaving the nucleus?

DNA determines the structural and functional characteristics of the cell by specifying the structure of proteins. Proteins form many of a cell's structural components, as well as all the enzymes that regulate most of the chemical reactions in the cell. DNA establishes the structure of proteins by specifying the sequence of their amino acids. DNA is a large molecule that does not leave the nucleus but functions by means of an intermediate, ribonucleic acid (RNA), which can leave the nucleus through nuclear pores.

Describe the process of DNA replication.

DNA replication is the process in which the two strands of a DNA molecule each serve as the template for making complementary new strands of nucleotides. The two old strands combine with their respective complementary new strand, thereby producing two molecules of DNA

Describe the cell's activities during the G1 , S, and G2 phases of interphase.

During G1, the cell carries out routine metabolic activities. During the S phase, DNA is replicated. During the G2 phase, the cell prepares for division. (a) Following mitosis, two cells are formed by the process of cytokinesis. Each new cell begins a new cell cycle. (b) Many cells exit the cell cycle and enter the G0 phase, where they remain until stimulated to divide, at which point they reenter the cell cycle.

Contrast facilitated diffusion and active transport in relation to energy expenditure and direction of movement with respect to the concentration gradient.

Facilitated diffusion is a mediated transport process that moves substances into or out of cells from a higher to a lower concentration. Facilitated diffusion does not require metabolic energy to transport substances across the plasma membrane. The rate at which molecules or ions are transported is directly proportional to their concentration gradient up to the point of saturation, when all the carrier proteins or channels are occupied. Then the rate of transport remains constant at its maximum rate. Active transport is a mediated transport process that requires energy provided by ATP. The maximum rate at which active transport proceeds depends on the number of ATP-powered pumps in the plasma membrane and the availability of adequate ATP. Active transport is important because it can move substances against their concentration gradients—that is, from lower concentrations to higher concentrations.

Contrast the structure and function of cilia with those of flagella.

Flagella have a structure similar to that of cilia, but they are longer (45 μm). Sperm cells are the only human cells that possess flagella, and usually only one flagellum exists per cell. Furthermore, whereas cilia move small particles across the cell surface, flagella move the entire cell. For example, each sperm cell is propelled by a single flagellum. In contrast to cilia, which have a power stroke and a recovery stroke, flagella move in a wavelike fashion.Cilia are cylindrical in shape, measuring about 10 μm in length and 0.2 μm in diameter. The shaft of each cilium is enclosed by the plasma membrane. Each cilium contains two centrally located microtubules and nine peripheral pairs of fused microtubules (the so-called 9 + 2 arrangement) Cilia are numerous on surface cells that line the respiratory tract and the female reproductive tract. In these regions, cilia move in a coordinated fashion, with a power stroke in one direction and a recovery stroke in the opposite direction . Their motion moves materials over the surface of the cells. For example, cilia in the trachea move mucus containing trapped dust particles upward and away from the lungs, thus helping keep the lungs clear of debris.

Compare the functions of free ribosomes and ribosomes attached to the endoplasmic reticulum.

Free ribosomes primarily synthesize proteins used inside the cell, whereas ribosomes attached to the endoplasmic reticulum produce integral membrane proteins and proteins that are secreted from the cell.

Explain what G-Protein Coupled Receptors do.

GPCRs are a large diverse family of cell surface receptors that respond to many different external signals binding of our signaling molecule or are likened to our GPC our results in g-protein activation which then triggers the production of other second messengers using the sequence of events GPCRs can regulate an incredible range of bodily functions from sensation to growth to even hormone response.

What is gene expression, and what two processes result in gene expression?

Genes are the functional units of heredity. Heredity is the transmission of genetic traits from parent to offspring. Each gene is a segment of a DNA molecule that specifies the structure of an RNA molecule. This RNA can be functional on its own, or it can produce a protein. The production of RNA and/or proteins from the information stored in DNA is called gene expression

Hyperosmotic

If one solution has a greater concentration of solute particles, and therefore a greater osmotic pressure than another solution, the first solution is said to be hyperosmotic

What are the general functions of the cytoskeleton?

Just as our skeleton supports many of the structures of our bodies, the cytoskeleton supports the cell and holds the nucleus and other organelles in place. In addition, some components of the cytoskeleton are responsible for changes in cell shape and the movement of cell organelles

Which cell features can be seen with a light microscope? With electron microscopes?

Light microscopes allow us to visualize the general features of cells, such as the nucleus. A scanning electron microscope (SEM) can reveal features of the cell surface and the surfaces of internal structures. A transmission electron microscope (TEM) allows us to see "through" parts of the cell and thus to discover detailed aspects of cell structure.

What is autophagy?

Lysosomes also digest the organelles of the cell that are no longer functional, a process called autophagy

Describe the process by which lysosomal enzymes digest phagocytized materials.

Lysosomes are membrane-bound vesicles that form at the Golgi apparatus . They contain a variety of hydrolytic enzymes that function as intracellular digestive systems. Vesicles taken into the cell fuse with the lysosomes to form one vesicle and to expose the endocytized materials to hydrolytic enzymes . Various enzymes within lysosomes digest nucleic acids, proteins, polysaccharides, and lipids. Certain white blood cells have large numbers of lysosomes that contain enzymes to digest phagocytized bacteria.

What is the centrosome? Relate the structure of centrioles.

MTOC- Microtuble organizing center of eukaryotic animal cells. The centrosome, a specialized zone of cytoplasm close to the nucleus, is the center of microtubule formation in the cell. Microtubules appear to influence the distribution of actin and intermediate filaments. Through its control of microtubule formation, the centrosome is closely involved in determining cell shape and movement. The microtubules extending from the centrosomes are very dynamic—constantly growing and shrinking. and the two centrioles are normally oriented perpendicular to each other within the centrosome . The wall of the centriole is composed of nine evenly spaced, longitudinally oriented, parallel units, or triplets. Each unit consists of three parallel microtubules joined together

What is receptor-mediated endocytosis?

Macromolecules such as sugars and hormones bind to protein receptors on the cell wall and are then signals INVAGINATION.

What occurs in posttranslational processing? How does it relate to proproteins and proenzymes?

Many proteins are modified through posttranslational processing before they are functional in the cell. An example of posttranslational processing is the addition of side chains, such as polysaccharides, following translation. -Many proteins are longer when they are first made than in their final, functional state. These proteins are called proproteins, and the extra piece of the molecule is cleaved off by enzymes to make the proprotein into a functional protein. -If many proenzymes were made within cells as functional enzymes, they could digest the cell that made them. Instead, they are made as proenzymes and are not converted to active enzymes until they reach a protected region of the body, such as inside the small intestine, where they are functional.

What are the five roles that proteins can play as part of the plasma membrane?

Membrane proteins can function as 1. marker molecules, 2. attachment proteins, 3. transport proteins, 4.receptor proteins, or 5.enzymes. The ability of membrane proteins to function depends on their three-dimensional shapes and their chemical characteristics.

How does its nickname, the cell's power plant, relate to its function?

Mitochondria are the major sites for the production of ATP, which is the primary energy source for most energy-requiring chemical reactions within the cell

Describe the structure of a mitochondrion.

Mitochondria are the organelles that provide the majority of the energy for the cell. Each mitochondrion has an inner and an outer membrane, separated by an intermembrane space. The outer membrane has a smooth contour, but the inner membrane has numerous infoldings called cristae that project like shelves into the interior of the mitochondrion. The material located inside the inner membrane is called the matrix.

Define organelles. Are all organelles found in all cells?

Organelles are structures within cells that are specialized for particular functions

Define osmosis, and describe how osmotic pressure is created.

Osmosis is the diffusion of water (solvent) across a selectively permeable membrane, such as a plasma membrane. Water diffuses from a solution with proportionately more water, across a selectively permeable membrane, and into a solution with proportionately less water. Osmotic pressure is the force required to prevent water from moving by osmosis across a selectively permeable membrane.

How does catalase protect cells?

Peroxisomes also contain the enzyme catalase, which breaks down hydrogen peroxide to water and oxygen thereby eliminating the toxic substance.

What are the structure and function of proteosomes?

Proteasomes are large protein complexes containing enzymes that break down and recycle other proteins within the cell. Proteasomes are not surrounded by membranes but instead page 84are a collection of specific proteins forming barrel-like structures. The inner surfaces of the barrel have enzymatic regions that break down the proteins. Other proteins at the ends of the barrel regulate which proteins are taken in for breakdown and recycling.

Name three ways in which proteins are distributed from the Golgi apparatus.

Proteins produced at the ribosomes attached to the rough endoplasmic reticulum move into the endoplasmic reticulum. These proteins are later packaged into transport vesicles that then move to the Golgi apparatus. These transport vesicles fuse with the Golgi apparatus membrane and release the proteins into the Golgi apparatus cisterna. The Golgi apparatus concentrates and, in some cases, chemically modifies the proteins by synthesizing and attaching carbohydrate molecules to the proteins to form glycoproteins or by attaching lipids to the proteins to form lipoproteins. The proteins are then packaged into vesicles that pinch off from the margins of the Golgi apparatus and are distributed to various locations. Some vesicles carry proteins to the plasma membrane, where the proteins are secreted from the cell by exocytosis; other vesicles contain proteins that become part of the page plasma membrane; and still other vesicles contain enzymes that are used within the cell.

To what part of a receptor molecule does a chemical signal attach?

Receptor proteins are membrane proteins or glycoproteins that have an exposed receptor site on the outer cell surface.

What are exons and introns? How do they relate to pre-mRNA and posttranscriptional processing?

Regions of the mRNA that do code for proteins are called exons, whereas the regions that do not code for a protein are called introns. mRNA that contains introns is called a pre-mRNA. The introns are removed from the pre-mRNA, and the exons are spliced together. After intron removal and splicing, the functional mRNA will then consist only of exons.

State two ways the cell controls what part of DNA is transcribed.

Regulatory molecules that interact with nuclear proteins can either increase or decrease the transcription rate of specific DNA segments. For example, triiodothyronine (T3), a hormone released by cells of the thyroid gland, enters cells, such as skeletal muscle cells; interacts with specific nuclear proteins; and increases transcription of mRNAs from specific genes.

What molecules combine to form ribosomes? Where are ribosomal subunits formed? And assembled?

Ribosomes are the sites of protein synthesis. Each ribosome is composed of a large subunit and a small subunit. The ribosomal subunits consist of ribosomal RNA (rRNA) produced in the nucleolus of the nucleus and proteins produced in the cytoplasm.

Explain the functions of the smooth endoplasmic reticulum.

Smooth endoplasmic reticulum, manufactures lipids, such as phospholipids, cholesterol, and steroid hormones, as well as carbohydrates. Enzymes required for lipid synthesis are associated with the membranes of the smooth endoplasmic reticulum, and cells that synthesize large amounts of lipids contain dense accumulations of smooth endoplasmic reticulum. It also participates in detoxification, the processes by which enzymes act on chemicals and drugs to change their structure and reduce their toxicity.

Do solutes diffuse with (down) or against their concentration gradient?

Solutes diffuse down their concentration gradients (from a higher to a lower solute concentration) until an equilibrium is achieved.

Compare isosmotic, hyperosmotic, and hyposmotic solutions with isotonic, hypertonic, and hypotonic solutions.

Solutions with the same concentration of solute particles have the same osmotic pressure and are referred to as isosmotic. The solutions are isosmotic even if the types of solute particles in the two solutions differ from each other. An isotonic solution may be isosmotic to the cytoplasm. Because isosmotic solutions have the same concentration of solutes and water as the cytoplasm of the cell, no net movement of water occurs, and the cell neither swells nor shrinks. Hypertonic solutions can be hyperosmotic and have a greater concentration of solute molecules and a lower concentration of water than the cytoplasm of the cell. Therefore, water moves by osmosis from the cell into the hypertonic solution, causing the cell to shrink, a process called crenation with red blood cells. Solutions injected into the bloodstream or the tissues must be isotonic because shrinkage or swelling of cells disrupts their normal function and can lead to cell death.

Explain how a chemical signal can bind to a receptor on a channel protein and cause a change in membrane permeability.

Specific substances, such as chemical signals, can attach to the receptor site. Many receptors and the chemical signals they bind are part of an intercellular communication system that coordinates cell activities. One cell can release a chemical signal that diffuses to another cell and binds to its receptor. The binding acts as a signal that triggers a response. ex: aceytlcholine released from nerve cells trigger Na+ channels to open up and be released into muscle cells to contract.

Describe how receptors alter the activity of G protein complexes.

The G protein complex acts as an intermediary between a receptor and other cellular proteins. The G protein complex interacts with a receptor protein when a chemical signal is bound to it. When the G protein complex is not interacting with a receptor protein, the α subunit of the G protein complex has guanosine diphosphate (GDP) attached to it, When a chemical signal binds to the receptor The α subunit releases the GDP and attaches to guanosine triphosphate. At this point the α subunit is considered activated. The activated α subunit can stimulate a cell response in at least three ways: (1) by means of intracellular chemical signals, (2) by the opening of ion channels in the plasma membrane, and (3) by the activation of enzymes associated with the plasma membrane.

Relate the structure and function of the Golgi apparatus.

The Golgi apparatus is composed of flattened, membranous sacs, containing cisternae, stacked on each other like dinner plates . The Golgi apparatus can be thought of as a packaging and distribution center because it modifies, packages, and distributes proteins and lipids manufactured by the rough and smooth endoplasmic reticula

Where do the events of transcription occur?

The Nucleus

Describe how the amount of solute in a solvent creates a concentration gradient.

The concentration difference between two points, divided by the distance between the two points, is called the concentration gradient. Solutes diffuse down their concentration gradients (from a higher to a lower solute concentration) until an equilibrium is achieved. The greater the concentration gradient, the greater the rate of diffusion of a solute down that gradient.

List and describe the functions of microtubules, actin filaments, and intermediate filaments.

The cytoskeleton consists of three groups of proteins: microtubules, actin filaments, and intermediate filaments 1. Microtubules are hollow tubes composed primarily of protein units called tubulin. They help provide support and structure to the cytoplasm of the cell. Microtubules are involved in cell division and in the transport of intracellular materials. form essential components of certain cell organelles, such as centrioles, spindle fibers, cilia, and flagella. 2. Microfilaments: 6-7 nm: composed mainly of ACTIN; ex: used in contraction of muscle cells. Myosin grabs the actin, walks on it, and creates the contraction: Actin can grow and push against a structure in the cell, cell membrane, giving the cell TENSILE strength. Stabalizing the stregnth and structure of the cell. 3. INTERMEDIATE filaments: 10 nm, fibers composed of several types of proteins. Also give cell TENSILE strength, giving strenght and structure. Also found in the nucleus of the cell. lamina.

What are cytoplasmic inclusions? Give several examples.

The cytosol also contains cytoplasmic inclusions, which are aggregates of chemicals either produced or taken in by the cell. EX: lipid droplets or glycogen granules store energy-rich molecules; hemoglobin in red blood cells transports oxygen; the pigment melanin colors the skin, hair, and eyes. Dust, minerals, and dyes can also accumulate in the cytoplasm.

What enzymes are found on the cristae? In the matrix?

The enzymes of the citric acid (Krebs) cycle are in the matrix. The enzymes of the electron-transport chain are embedded within the inner membrane.

Summarize the characteristics of the fluid-mosaic model of membrane structure.

The fluid-mosaic model of the plasma membrane describes the plasma membrane as being neither rigid nor static in structure. Instead, the plasma membrane is highly flexible and can change its shape and composition through time.

What is the glycocalyx composed of?

The glycocalyx is the collection of glycolipids, glycoproteins, and carbohydrates on the outer surface of the plasma membrane.

What are the two stages of the cell life cycle? Which stage is the longest?

The life cycle of a cell has two stages: interphase and cell division. Cell division includes mitosis, the division of the nucleus, and cytokinesis, the division of the cytoplasm. Interphase is the longest

How are secretory vesicles formed?

When proteins accumulate in the golgi apparatus and the sacs swell until the swollen ends pinch off.

What is a codon? What are start and stop codons?

The mRNA is organized into codons, three nucleotide sequences, each of which specifies an amino acid during translation. AUG, which specifies methionine, also acts as a start codon, which signals the beginning of translation. UAA, UGA, and UAG act as stop codons, which signal the end of translation. Unlike the start codon, stop codons do not specify amino acids.

Why do ion channels exhibit specificity, competition and saturation?

The number of ions moving into a channel protein can exceed the capacity of the channel, thus saturating the channel. Therefore, channel proteins exhibit specificity, competition, and saturation.

Describe the structure and location of the endoplasmic reticula.

The outer membrane of the nuclear envelope is continuous with a series of membranes distributed throughout the cytoplasm of the cel. The endoplasmic reticulum consists of broad, flattened, interconnecting sacs and tubules . The interior spaces of those sacs and tubules are called cisternae and are isolated from the rest of the cytoplasm.

What are the main chemical components of the plasma membrane?

The plasma membrane consists primarily of lipids and proteins, with a very small amount of carbohydrates. Lipids account for 45-50% of the plasma membrane volume, and proteins make up 45-50% of the plasma membrane. A small percentage of the plasma membrane (4-8%) is carbohydrates, which are found only on the outer surface of the plasma membrane. The carbohydrates combine with lipids to form glycolipids and with proteins to form glycoproteins.

How do the hydrophilic heads and hydrophobic tails of phospholipid molecules result in a plasma membrane?

The predominant lipids of the plasma membrane are phospholipids and cholesterol. Phospholipids readily assemble to form a lipid bilayer, a double layer of phospholipid molecules, because they have a polar (charged) head and a nonpolar (uncharged) tail. The polar heads are attracted to water molecules, so they are also called hydrophilic (water-loving) heads. The polar, hydrophilic heads are exposed to the aqueous extracellular and intracellular fluids of the cell.

What are the functions of DNA polymerase and DNA ligase?

The production of the new nucleotide strands is catalyzed by DNA polymerase, an enzyme that adds new nucleotides to the 3′ end of the growing strands. Because of the antiparallel orientation of the two DNA strands, the strands form differently.One strand, called the leading strand, forms as a continuous strand, whereas the other strand, called the lagging strand, forms in short segments called Okazaki fragments. The Okazaki fragments are then spliced by DNA ligase. DNA replication results in two identical DNA molecules. Each of the two new DNA molecules has one strand of nucleotides derived from the original DNA molecule and one newly synthesized strand

How is the rate of diffusion affected by an increased concentration gradient?

The rate of diffusion increases as the concentration gradient increases. The greater the concentration gradient, the greater the number of solute particles moving from a higher to a lower solute concentration.

What is a polyribosome/polysome?

The resulting cluster of ribosomes attached to the same mRNA is called a polyribosome. Each ribosome in a polyribosome produces an identical protein, and polyribosomes are an efficient way to produce many copies of the same protein using a single mRNA molecule.

What are the functions of the rough endoplasmic reticulum?

The rough endoplasmic reticulum is called "rough" because ribosomes are attached to it. The ribosomes of the rough endoplasmic reticulum are sites where proteins are produced and modified for use as integral membrane proteins and for secretion into the extracellular space.

Differentiate between intracellular and extracellular.

Things inside and outside of the cells.

What is the function of the nuclear pores?

To allow passage of particles into and out of the nucleus. They are protein complexes that helps transport Rna , ribosomal units and polymerase, betweem cytosol and nucleoplasm. Polymerase is important for replication translation and transcription.

What type of molecule results from transcription?

Transcription is the synthesis of mRNA, tRNA, and rRNA molecules based on the nucleotide sequence in DNA

Place the steps of translation in sequence.

Translation is the synthesis of a protein at the ribosome based on the sequence of the codons of mRN - Ribosomes align the codons of the mRNA with the anticodons of tRNA and then enzymatically join the amino acids of adjacent tRNA molecules. The mRNA moves through the ribosome one codon at a time. With each move, a new tRNA enters the ribosome and the amino acid is linked to the growing chain, forming a polypeptide -After a ribosome uses the initial part of mRNA, another ribosome can attach to the mRNA and begin to make a protein. The resulting cluster of ribosomes attached to the same mRNA is called a polyribosome

Define uniport, symport, and antiport.

Uniport is the movement of one specific ion or molecule across the membrane. Symport (cotransport) is the movement of two different ions or molecules in the same direction across the plasma membrane, whereas antiport (countertransport) is the movement of two different ions or molecules in opposite directions across the plasma membrane.

What types of particles move through the plasma membrane by mediated transport?

amino acids and glucose- large, water-soluble molecules or electrically charged molecules or ions.

What is the genetic code?

collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis- The genetic code is the information contained in mRNA and it relates the nucleotide sequence of mRNA to the amino acid sequence of a protein.

hyposmotic

compared with the more dilute solution. The more dilute solution, with the lower osmotic pressure, is compared with the more concentrated solution.

isotonic, hypertonic, and hypotonic solutions

isotonic- concentrations of the solutes are the same inside and outside the cell. Solutions injected into the bloodstream or the tissues must be isotonic because shrinkage or swelling of cells disrupts their normal function and can lead to cell death. hypertonic- the solution has a higher solute concentration outside the cell than inside hypotonic- the solution has a lower solute concentration outside than inside the cell

Explain why the plasma membrane is selectively permeable.

it allows only certain substances to pass through it. Enzymes, other proteins, glycogen, and potassium ions are present in higher concentrations intracellularly; sodium, calcium, and chloride ions exist in higher concentrations extracellularly. membrane's permeability and its ability to transport molecules selectively, the cell is able to maintain homeostasis.

List the types of RNA.

mRNA (messenger), tRNA (transfer), rRNA (ribosomal)

Describe the structure and function of microvilli. How are microvilli different from cilia?

many confuse microvilli with cilia, but microvilli are only one-tenth to one-twentieth the size of cilia. Individual microvilli can usually be seen only with an electron microscope, whereas cilia can be seen with a light microscope. Microvilli do not move, and they are supported with actin filaments, not microtubules. Microvilli are found on the cells of the intestine, kidney, and other areas where absorption is an important function. In certain locations of the body, microvilli are highly modified to function as sensory receptors. For example, elongated microvilli in hair cells of the inner ear respond to sound.

Describe the difference between integral and peripheral proteins in the plasma membrane.

many of the plasma membranes other functions are determined by its proteins. Based on their location among or attached to the phospholipid molecules, membrane proteins can be classified as integral or peripheral. Integral membrane proteins penetrate deeply into the lipid bilayer, in many cases extending from one surface to the other. Peripheral membrane proteins are attached to either the inner or the outer surfaces of the lipid bilayer. Integral membrane proteins consist of regions made up of amino acids with hydrophobic R groups and other regions of amino acids with hydrophilic R groups

What is mediated transport?

mediated transport, a membrane transport process by which membrane transport proteins mediate, or assist, the movement of large, water-soluble molecules or electrically charged molecules or ions across the plasma membrane. Because of their chemical structure or size, many essential molecules, such as amino acids and glucose, cannot enter or exit the cell by diffusing directly through the plasma membrane.

What is the function of peroxisomes?

membrane-bound vesicles that are smaller than lysosomes. Peroxisomes contain enzymes that break down fatty acids and amino acids. The breakdown of these molecules can produce hydrogen peroxide (H2O2) as a toxic by-product. Peroxisomes also contain the enzyme catalase, which breaks down hydrogen peroxide to water and oxygen thereby eliminating the toxic substance. Cells that are active in detoxification, such as liver and kidney cells, have many peroxisomes.

What are histones?

proteins that DNA wraps around

Describe and give examples of exocytosis.

some cells release material through a vesicular transport mechanism. The secretion of digestive enzymes by the pancreas and the secretion of mucus by the salivary glands are examples of exocytosis.

Place the events of transcription in sequence.

through transcription, the cell makes a copy of the gene (the recipe) necessary to makea particular protein (the cake). The copy, which is called mRNA, travels from the nucleus to ribosomes (the kitchen) in the cytoplasm, where the information in the copy is used to construct a protein (i.e., translation). Of course, to turn a recipe into a cake, ingredients are needed. The ingredients necessary to synthesize a protein are amino acids. Specialized transport molecules, called transfer RNA (tRNA), carry the amino acids to the ribosomes -Transcription occurs when a section of a DNA molecule unwinds and its complementary strands separate. One of the DNA strands serves as the template strand for the process of transcription. Nucleotides that form RNA align with the DNA nucleotides in the template strand by complementary base pairing