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| What seperates internal metabolic events from the external environment and controls the movement of materials in and out of the cell? | plasma membrane |
| What has a double phospholipid membrane (lipid bilayer) with the polar hdrophilic heads forming the two outer faces and the nonpolar hydrophobic tails pointing toward the inside of the membrane? | plasma membrane |
| What proteins are attached loosely to the inner or outer surface of the membrane? | peripheral proteins |
| What proteins extend into the membrane? | integral proteins |
| Proteins that span across the membrane appearing at both surfaces are called? | transmembrane proteins or integral proteins. |
| Are integral proteins amphipathic? Hint: amphipathic means that it has both hydrophilic and hydrophobic regions. | Yes, like phospholips they have a hydrophobic region embedded in the membrane and the hydrophilic region exposed to the aqueous solutions bordering the membrane.Integral proteins consist of one or more stretches of nonpolar amino acid usually coiled into alpha helices. |
| The cell membrane is referred to as fluid mosaic why? | A membrane is a mosaic or collage of many different proteins bobbing and embedded in the fluid bilayer of phopholipids. |
| What determines most of the membranes specific functions? | proteins |
| How many different kinds of protein have been found to date in the plasma membrane of red blood cells? | 50 |
| What molecules can pass freely across the phopholipid membrane?lip membrane. | 1. selectONLY SMALL, UNCHARGED, POLAR moleucles (such as water and carbon dioxide) and HYDROPHOBIC MOLECULES (nonpolar molecules like oxygen and lipid soluble molecules such as hydrocarbons) freely pass across the membrane. |
| What molecules cannot pass through the phospholipid membrane? | LARGE MOLECULES such as GLUCOSE and all IONS. ( Remember ions are charged particles). |
| What molecule found in the membrane reduces membrane fluidity by reducing phospholipid movemtn at moderat temperatues and keeps your membranes from solidifying (close packing of phospholipids) at low temperatures? | cholesterol |
| What class of macromolecules does cholesterol belong to? | lipids, it is a steroid |
| What is glycocalyx? | a carbohydrate coat covering the outer face of the plasma membrane. It is made of oligosaccharides that are attached to membrane phospholipids (glycolipids) and proteins (glycoproteins). The glycocalyx provides markers for cell to cell recognition. |
| What is cell to cell recognition? | The cells ability to tell one type of neighboring cell from another. This is critical to the functioning of an organism. It is involved in the sorting of cells into tissues and organs in an animal embryo. It is the basis for the rejection of foreign cells including those of transplanted organs by the immune systme. It is an important line of defense in vertebrate animals. |
| How do cells recognize other cells? | They key on surface molecules like carbohydrates on the plasma membrane. |
| What is an oligosaccharide? | oligo= few saccharide =sugar oligosaccharide = short polysaccharide with fewer than 15 sugar units. |
| What are two types of oligosaccharides that are involved in cell to cell recognition? | glycoprotein and glycolipids |
| What is a glycoprotein? | They are carbohydrates covalently bonded to proteins glyco= carbohydrate |
| I am a oligosaccharide involved in cell to cell recognition and I have oligosaccharides covalently bonded to lipids forming a molecule called? | glycolipids |
| What is meant by amphiphathic ? | This means it has both hydrophobic and hydrophilic regions. |
| What did freeze fracture and electron microscopy show? | It showed that proteins are embedded in the phospholipid bilayer of the membrane, rather than being spread on the surface. It splits the membrane into outer and inner faces, so you can view the proteins clearly penetrating the hydrophobic regions. |
| A membrane is primarily held together by what interactions? | hydrophobic which are weaker than covalent bonds |
| Explain the movement inside the cell membrane showing the fluidity of the membrane. | Phospholipis move along the plane of the membrane rapidly, about 2 micrometers per second (length of a bacterial cell). Proteins are larger than lipids and move more slowly. |
| Many membrane proteins are held immobile and do not move because they are attached to the cytoskeleton. Some membrane proteins seem to move in a very directed waY. What is thought to drive them along? | Cytoskeletal fibers by motor proteins connected to the membrane proteins cytoplasmic ends. |
| The temperature at which a membrane solidifies depends on its lipid composition. What lipid composition is found in membranes that remain fluid at lower temperatures? | The membrane would be rich in phospholipids with unsaturated hydrocarbon tails. This is where ther are double bonds between the carbons in the fatty acid tails. This causes kinks where the double bonds are found and the unsaturated hydrocarbons dont pack as close as satuarated hydrocarbons. Remember unsaturated fat is liquid at room temperature. |
| What does the steroid (lipid) cholesterol do to the cell membrane? | stabilizes the membrane. At warm temperatures body temperature of humans cholesterol makes the membrane less fluid by restraining the movement of phospholipids. Because it stops the packing of phopholipids it lowers the temperature necessary for membranes to solidify. |
| Membranes must be fluid to work correctly. They are as fluid as salad oil. What happens if a membrane solidifies? | Its permeability changes and the enzymatic proteins in it may become inactive. |
| On the cytoplasmic side of the plasma membrane some membrane proteins are held in place by attachment to the? | cytoskeleton |
| On the exterior side of the plasma membrane certain membrane proteins are attached to the? | extracellular matrix |
| Name the six kinds of function exhibied by proteins of the plasma membrane. | CASEIT- Cell to cell recognition, Attachment to the cytoskeleton and extracellular matrix, Signal transduction, Intercellular joining, Enzmatic activity, Transport. |
| What is the job of a transport protein in the membrane? | A protein that spans the membrane and provides a hydrophilic channel across the membrane that is selective for a particular solute. Substances such as polar and uncharged molecules can move through the membrane this way.2. Some hydrolyze (using water to break) ATP as an energy source to pump substances like sodium and potassium across the membrane. Some bind to their passengers and physically move them across the membrane.In all cases the protein is very specific for the substances it moves. |
| Explain how enzymatic activity occurs in the membrane and is one of jobs of protein in the membrane? | Enzymatic activity can be seen when a protein that is built into the membrane is an enzyme that has its active site exposed to substances in the solution. They may be involved in several steps of a metabolic pathway. |
| Explain how Signal transduction works in the membrane. | A membrane protein may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone. The external messenger (signal) may cause a conformational change in the protein that relays the message to the inside of the cell. |
| Explain how intercellular joining protein works in the membrane. | This is when membrane proteins of adjacent cells may be hooked together in various kinds of junctions. Examples: Tight junctions, desmosomes (anchoring junctions) and Gap junctions(communicating junctions). |
| Explain how cell to cell recognition proteins work in the membrane. | These are oligosaccharides or some glycoproteins that serve as ID tags that are recognized by other cells. Remember the golgi apparatus has golgi enzymes that change the oligosaccharide portion of glycoproteins. The Golgi removes some sugar monomers and substitutes other making different oligosaccharides. |
| Explain adhesion proteins or attachment to the cytoskeleton and ECM. | Microfilaments or other elements of the cytoskeleton may be bonded to membrane proteins, a function that helps maintain cell shape and fixes the location of certain membrane proteins. Proteins that adhere to the ECM can coordinate extracellular and intracellular changes. |
| Glucose carried in the blood to the human liver enters liver cells rapidly through ______ proteins in the plasma membrane?This protein is so selective it rejects fructose a structural isomer of glucose. | transport proteins |
| Molecules that have intrinsic kinetic energy are called? | thermal motion or heat |
| One result of thermal motion is called? | diffusion |
| What is diffusion? | The tendency for molecules to move from an area of high concentration to an area of low concentration. |
| If I say substances move down their concentration gradient what does this mean? | Substances will move from high to low concentration (diffusion) without the use of energy. |
| Diffusion is a spontaneous process because it increases or decreases free energy? | decreases |
| Does diffusion of a solute decrease or increase entropy (randonmess or disorder)? | Increases entropy because diffusion of a solute in water produces a more random mixture than exists when there are localized concentrations of the solute. |
| In cellular respiration oxygen diffuses into the cell because ......? | Dissolved Oxygen is diffusing from a high concentration to a low concentration by coming into the cell and diffusing into the cell across the plasma membrane. |
| What is passive transport? | the diffusion of a substance across a biological membrane without requiring energy due moving down the concentration gradient. |
| What is osmosis | passive transport of water. The diffusion of water through a SELECTIVELY PERMEABLE MEMBRANE. |
| What is hypertonic? | hyper=more MORE SOLUTE. Solutions with more solute concentration. |
| What is hypotonic? | hyo=less LESS SOLUTE. Solutions with less solute concentration. |
| What is isotonic? | iso= same solutions of equal solute concentration |
| What is osmoregulation? | the control of water balance |
| A Protist called a paramecium lives in pond water that is hypotonic to the cell. What occurs and how does the paramecium exhibit osmoregulation? | Water will continually come into the paramecium moving to the hypertonic state. Osmoregulation is the control of water balance and is maintained in the paramecium by a contractile vacuole which is continually squeezing excessive water out as fast as it enters by osmosis. |
| Explain turgidity in plants. | This is when a plant cell swells as water enters it by osmosis. The elastic wall will expand only so much before it exerts back pressure on the cell that opposes further water uptake. When the plant cell gets to this point it is considered turgid or very firm. This is a healthy state for most plants. |
| Explain why plants become flacid or wilt. | Plants that are non-woody like your house plants depend on mechanical support on cells kept turgid by a surrounding being hypotonic solutions. If a plant cells surroundings are isotonic there will be not tendency for water to enter and the cells will become flacid or wilt. |
| What is facillitated diffusion? | The passage of molecules and ions bound to specific carrier transport proteins across a biological membrane down a concentration gradient. The diffusion of solutes through channel proteins in the plasma membrane. Note water can pass through the membrane without the aid of specialized protein. |
| Compare a transport protein and an enzyme. | Like an enzyme is specific for its substrate,a transport protein is specialized for the solute it transports and may have a specific binding site like the active site of an enzyme.Like enzymes there are so many molecules of each type of transport protein built into the plasma membrane, ane when these molecules are moving passengers as fast as they can transport is occuring at a high rate. Also they can be inhibited by molecules that resemble the normal substrate. Like when an imposter comptetes with the normally transported solute by binding to the transport protein. They are made of amino acids. |
| Contrast enzymes and transport proteins. | Transport proteins do NOT catalyze chemical reactions. |
| Explain how proteins function as gated channels. | Where a transport protein provides a selective corridor allowing a specific solute to cross the membrane. A gated channel has a stimulus either electrical or chemical which opens or closes the channel. |
| Stimulation of a nerve cell by neurotransmitter molecules open ___________ channels to allow sodium ions into the cell. | gated channels |
| Explain active transport. | Transport proteins move solutes against their concentration gradient across the plasma membrane from the side where they are less concentrated to the side that they are more concentrated. This is an uphill movement and requeites metabolic energy. |
| Explain how the sodium potassium pump illustrates active transport. | 1. Sodium binds to the transport protein and stimulates phophorylation of ATP. 2. Phophorylation causes the protein to change its conformational shape. 3. The conformational change will expel sodium to the outside and the potassium molecules from the outside (extracellular K+) will bind to the protein. 4. The potassium binding triggers the release of a phosphate group. 5. Loss of a phophate restores the original conformational shape. 6. Potassium is released and sodium sites are receptive again; the cycle repeats over and over. 3 sodiums are pumped out and 2 potassium in. They move against their concentration gradient requiring ATP energy. |
| Explain membrane potential. | The voltage across a membrane. This ranges from about -50 millivolts to -200 millivolts. The minus sign showns that the inside of the cell is negative compared to the outside. The membrane potential acts like a battery, an energy source that affects the traffic of all charged substances across the membrane. |
| Because the inside of the cell (cytoplasm) is negative compared to the outside of the cell (extracellular fluid) the membrane potential favors the passive transport of cations/or anions into the cell and cations/or anions out of the cell. | cations into the cell and anions out of the cell. Remember High concentration to low concentration. The inside is high in anions and outside is high in cations. |
| What two forces drive diffusion across a membrane? | chemical force (the ions concentration gradient) 2. electrical force ( the effect of the mmebrane potential on the ions movement. |
| What is the electrochemical gradient? | Combination of forces acting on an ion. The forces are the two forces that drive diffusion; chemical and electrical. |
| What is the electrogenic pump?Give an example. | a transport protein that generates voltage across a membrane. By generating voltage across membranes electrogenci pumps store energy that can be tapped for cellular work, including a type of membrane traffic called cotransport.. Sodium potassium pump in animal cells. Proton pump in plants, bacteria and fungi. |
| What is a proton pump? | found in plants bacteria and fungi and it is an electrogenic pump that actively transports hydrogen ions (protons) out of the cell. This transfers hydrogens or positive charges from the cytoplasm to the extracellular solution. |
| What is cotransport? | An ATP driven pump stores energy by concentrating a substance like Hydrogen on one side of the membrane. As the substance leaks back across the membrane through specific transport proteins it escorts other substances into the cell like sucrose. This indirectly drives sucrose build up by a plant cell, with the help of a protein that cotransports the two solutes. |
| What is exocytosis? | Cell secretes macromolecules by the fusion of vesibles with the plasma membrane. A transport vesicle budded from the trans side of the Golgi apparatus is moved by the cytoskeleton to the plasma membrane. When the vesicle membrane and the plasma membrane come together the lipid molecules of the 2 bilayers rearrange themselves so that the 2 membranes fuse. The contents of the vesicle will then spill to the OUTSIDE of the cell. EXO- released CYTO= cell |
| What is endocytosis? | ENDO = in Cyto = cell When the cell takes in macro molecules and particulater matter by forming new vesicles from the plasma membrane. The small area of the plasma membrane sinks inward to form a pocket. As the pocket deepens, it pinches in forming a vesicle containing material that had been outside the cell. |
| What are the 3 types of endocytosis? | 1. pinocytosis- cell drinking 2. phagocytosis 3. receptor mediated endocytosis |
| Explain how phagocytosis works. | phagocytosis- cell eating a cell engulfs a particle by wrapping pseudopodia around it packaging it within a membrane enclosed sac large enough to be classified a vacuole. The particle is digested after the vacuole fuses with a lysosome containing hydrolytic enzymes. |
| Explain how pinocytosis works. | the cell gulps droplets of extracellular fluid in tiny vesicles. Because any and all solutes dissolved in the droplet are taken into the cell pinocytosis is not specific in which substances it transports. |
| Explain how Receptor mediated endocytosis works. | This is very specific in which substances they transport. They have specific receptor sites exposed to the extracellular fluid. The extracellular substances that bind to the receptors are called ligands which are any molecule that binds specifically to a receptor site of another molecule. |
| What is a ligand? | which are any molecule that binds specifically to a receptor site of another molecule. |
| Explain hypercholesterolemia and how it is related to receptor mediated endocytosis. | Hypercholesterolemia is an inherited disease which is characterized by a very high level of cholesterol in the blood. The LDL receptor proteins are defective and the LDL particles that contain cholesterol cannot enter the cell and accumulate in the blood where it contributes to early atherosclerosis. The build up of fat deposits on blood vessel linings. |
| How does cholesterol travel in the body? | it travels in the blood in particles called low density lipoproteins (LDLs), which are complexes of lipids and proteins. These particles bind to LDL receptors on membranes and then enter the cell by endocytosis. Cholesterol is then used in the human cell to make membranes and is the precursor for making other steroids. |
| What do vesicle do in the cell? | They transport substances between the cell and its surroundings, they also provide a mechanism for rejuvenating or remodeling the plasma membrane. |
| Active Transport is powered by what? | ATP |
| Compare and contrast chemical and kinetic energy. | compare: both are forms of energy Contrast : Chemical is potential energy and kinetic is energy that is doing work. |
| What is stored energy? | Potential energy |
| What is the energy that is associated with the movement of molecules in a body of matter? | heat |
| Heat and light energy are examples of potential or kinetic energy? | kinetic |
| State the first law of thermodynamics, also known as the law of energy of conservation.. | Energy can be transferred and transformed, but it cannot be created or destroyed. |
| State the second law of thermodynamics. | Energy changes such as the conversion of chemical energy to kinetic energy, and this is accompanied by an increase in disorder or randomness called entropy. |
| What is entropy? | The amount of disorder in a system. |
| What is one form of entropy? | Heat which is random molecular motion, disorder. |
| What means energy going in and yields products rich in potential energy, like the building of macromolecules? | Endergonic reactions |
| Contrast exergonic and endergonic reactions. | Exergonic release energy Endergonic absorb energy, Exergonic break bonds and are catabolic reactions and Endergonic are anabolic and form bonds. |
| The transfer of a phosphate group to a molecule or a compound is called? | phosphorylation |
| What is ATP? | Adenosine tri phosphate, it is a high energy molecule, it has potential energy, it is like a tight spring ready to launch due to the 3 phosphates which are negatively charged, causing the ATP molecule to become unstable. |
| When an enzyme catalyzes a reaction it will? | lower the activation energy |
| What is the region in which the substrate and the enzyme form Van der Waals interactions and attach to each other? | active site |
| Temperature inactivates enzymes by ? | breaking hydrogen bonds |
| Name four things that can affect the rate of an enzyme catalyzed reaction. | 1. temperature 2. pH 3. competitive inhibitors 4. noncompetitive inhibitors |
| What is negative feedback? | It inhibits the metabolic reaction by blocking its products. |
| Can ATP act as a noncompetitive inhibitor? | Yes, when a cells supply of ATP is to much ATP will act as a noncompetitive inhibitor and interfere with enzymes that drive ATP synthesis |
| Some pesticides and antibiotics work by inhibiting _______? | inhibiting enzymes. Penicillin works by inhibiting the enzyme that bacteria us in making cell walls |
| What is a major function of glycoproteins and glycolipids in the cell membrane? | To allow the cells of an embryo to identify and sort out into tissues. |
| A plant cell in a hypotonic solution becomes? | Turgid |
| An animal cell in a hypotonic solution will? | lyse or break open |
| Why do animals cells lyse in hypotonic solutions but a plant will not? | Because the cell wall provided inelasticity and strength to the plant cell. |
| A cell that neither gains or loses water when it is immersed in a solution is? | isotonic to its environment |
| List some characteristics of the cell membrane. | Amphipathic, glycerol-phosphate head that is hydrophilic, and two fatty acid tails which are hydrophobic, fluid, mosaic, kinks are found in the unsaturated fatty acid tails to help prevent solidifying and control fluidity, intrinsic and extrinsic proteins are found throughout, has cholesterol. |
| What molecules are responsible for membrane transport? | protein |
| Because Paramecia live in hypotonic environments they have an organelle that contracts to eliminate excess water from the cell. Name that organelle | contractile vacuole |
