UMSL Cell Biology Exam 1

In Eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are
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In Eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are
microtubules
Many cell organelles, most notably the nucleus, are anchored by _______, which are assembled from a diverse class of proteins.
intermediate filaments
Centrosomes are sites where protein dimers assemble into
microtubules
The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of _______.
microfilaments
The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the _______.
intemediate filaments
During muscle contractions, myosin motor proteins move across tracks of
microfilaments
What helps stabalize the structure of plasma membrane?
Cholesterol
What can be recognized by the presence of a head and two tails?
Phospholipids
What is composed of both a carbohydrate and a protein
glycoproteins
If you were shown an electron micrograph of a section of a cell and were asked to identify the cell as plant or animal, one thing you might do is to
look for plastids or a large vacuole
Part complete A slice of raw apple placed in a concentrated sugar solution will ______.become flaccid as water is drawn out of its cellsA cellular structure that is visible with an electron microscope but not with a light microscope is _a ribosomeSeveral environments in which you are more likely to find archaea than bacteria are ______.saltwater, hot springs, acidic environments, and sulfur containing environmentsOne reason that it might be difficult to separate lysosomes from peroxisomes by centrifugation techniques is that ________.lysosomes and peroxisomes are similar in sizeThe nucleic acid of a virus is composed ofeither DNA or RNA but not bothA phospholipid has a "head" made up of a glycerol molecule attached to a single _______________, which is attached to another small molecule.phosphate group2. Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a ------------- attached to phosphate.Choline group3. Because the phosphate group and its attachments are either charged or polar, the phospholipid head is ____________________ which means it has an affinity for water.hydrophilic4. A phospholipid also has two "tails" made up of two __________________molecules, which consist of a carboxyl group with a long hydrocarbon chain attached.fatty acidBecause the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are _________________, which means they are excluded from water.hydrophobicIn a plasma membrane is the extracellular fluid hydrophilic or hydrophobic?hydrophilicIn a plasma membrane is the membrane protein facing the extracellular fluid hydrophilic or hydrophobic?hydrophilicIs the membrane protein in the plasma membrane hydrophilic or hydrophobic?hydrophobicIn a plasma membrane is the membrane protein facing the cytoplasm hydrophilic or hydrophobic?hydrophilicIn a plasma membrane is the cytoplasm hydrophilic or hydrophobic?hydrophilicAre nonpolar molecules hydrophilic or hydrophobic?hydrophobicAre polar molecules hydrophilic or hydrophobic?hydrophilicAre ions hydrophilic or hydrophobic?hydrophilicAre nonpolar molecules able to cross the lipid bilayer?can cross easilyAre polar molecules able to cross the lipid bilayer?they have difficulty crossing the hydrophobic partCan ions able to cross the lipid bilayer?have difficulty crossing the hydrophobic partIs a transport protein required for nonpolar molecules?NOIs a transport protein required for polar molecules?transport protein is required to cross efficientlyAre transport proteins needed for ions?transport protein is needed to cross efficientlyFor each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C∘C is transferred to a culture room maintained at 25∘C∘C based on the stated reasoning. initial decrease in membrane fluidityThis is likely because membrane fluidity decreases as the temperature is lowered.For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C∘C is transferred to a culture room maintained at 25∘C∘C based on the stated reasoning. gradual replacement of shorter-chain fatty acids by longer-chain fatty acids in the membrane phospholipidsThis is unlikely because longer-chain fatty acids decrease membrane fluidity.For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C∘C is transferred to a culture room maintained at 25∘C∘C based on the stated reasoning. gradual replacement of stearate by oleate in the membrane phospholipidsThis is likely because unsaturated fatty acids (oleate) will increase membrane fluidity.For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C∘C is transferred to a culture room maintained at 25∘C∘C based on the stated reasoning. enhanced rate of synthesis of unsaturated fatty acidsThis is likely because unsaturated fatty acids will increase membrane fluidity.For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C∘C is transferred to a culture room maintained at 25∘C∘C based on the stated reasoning. incorporation of more cholesterol into the membraneThis is unlikely because bacteria do not contain cholesterol under any conditions.Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply. water lipids carbon dioxide oxygen ions proteins sucrosewater, lipids, CO2, and oxygenWhat is true only for channels?* they provide a continous path across the membrane * allow water molecules and small ions to flow quickly across the membraneWhat is true for only carrier?* undergo a change in shape to transport solutes across the membrane * transport primarily small polar organic moleculesWhat is true for both channels and carriers?* they provide a hydrophilic path across the membrane * transport solutes down a concentration or electrochemical gradient * are integral membrane proteinsAquaporin-1 exists in the cell membrane as a tetramer. Each monomer is a water channel that can hold 4 molecules of water at a time. How many water molecules would be present in a complete aquaporin complex in the membrane of a red blood cell at one time?16What do the numerous aromatic rings on the surface of the channel suggest about the chemical properties of the channel?The channel will have significant hydrophobic propertiesConserved histidine, asparagine (blue), and cysteine (yellow) residues are present on the surface of the water channel. Which of the following is LEAST likely to hydrogen-bond with a water molecule?The R group (side chain) of the cysteineWhat prevents glycerol from passing through the water channel?the narrow diameter(-2.8 A) of the selectivity channelAquaporins allow water to pass through the channel but prevent other solutes and ions from also crossing the membrane. Protons can move with water using the same hydrogen bonding facillitated movement. What PREVENTS protons from passing through the water channel?the chemical properties of the sulfur within the R group of the conserved cysteine in the channelConsider ammonia as a simple example of such compounds. What is the charged form of ammonia called?ammonium ionchemical formula for ammoniumNH4+Will ammonium or ammonia predominate in a solution with a highly acidic pH?Under acidic conditions ammonium (NH4+) will predominateFor which of these two forms (ammonium or ammonia) will the uptake across the plasma membrane of a cell be affected by the concentration gradient of that form on the inside versus the outside of the cell?The inward movement of both ammonia and ammonium ion will be affected by their respective concentration gradients across the membrane.For which of these two forms will uptake be affected by the membrane potential of the plasma membrane? (ammonium or ammonia)The membrane potential will affect the movement of ammonium ion only.What does it mean to say a cell has a negative membrane potential?That the inner surface of the plasma membrane has a more negative charge than the other surface.A positively charge solute such as NH4+ will be drawn were?inward by the membrane potential?The uptake of NH4+ across the plasma membrane will require what than the uptake of NH3- assuming the same concentration gradient for the two solutes?will require more energyInstead of ammonia, consider the uptake of acetic acid, CH3COOHCH3COOH, an important intermediate in several biological pathways. What is the charged form in this case?CH3COO-For which of the two forms will the uptake across the plasma membrane of a cell be affected by the concentration gradient of that form on the inside versus the outside of the cell? (CH3COOH or CH3COO-)Uptake of both forms will be affected by their respective concentration gradients across the plasma membrane.For which of these two forms will uptake be affected by the membrane potential of the plasma membrane? (acetate or acetic acid)Only the uptake of acetate ion will be affected by the membrane potential.For a cell that must take up acetic acid from its environment, will uptake of the charged form require more or less energy than uptake of the uncharged form, assuming that the cell has a negative membrane potential?Uptake of the acetate ion will require more energy than the uptake of acetic acid because in this case the ion is negatively charged, which means that its uptake will be against the negative membrane potential.Which of the following statements correctly describe(s) the driving forces for diffusion of Na+ and K+ ions through their respective channels? Select all that apply. The diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the plasma membrane. The diffusion of Na+ ions into the cell is impeded by the electrical gradient across the plasma membrane. The diffusion of K+ ions out of the cell is impeded by the K+ concentration gradient across the plasma membrane. The diffusion of K+ ions out of the cell is impeded by the electrical gradient across the plasma membrane. The electrochemical gradient is larger for Na+ than for K+.* The diffusion of Na+ ions into the cell is facilitated by the Na+ conc. gradiaent across the plasma membrane * The diffusion of K+ ions out of the cell is impeded by the K+ conc. gradient across the plasma membrane * The elctrochemical gradient is larger for Na+ than for K+A semipermeable membrane is placed between the following solutions. Which solution will decrease in volume? Solution A: 1.4% (m/v) starch Solution B: 7.62% (m/v) starchThe water molecules actually move in both directions, but they move to a greater extent toward Solution B because it has a higher solute concentration than Solution A. The net movement of water molecules causes Solution A to decrease in volume and Solution B to increase in volume.A semipermeable membrane is placed between the following solutions. Which solution will increase in volume? Solution C: 9% (m/v) NaCl Solution D: 12.4% (m/v) NaClThe water molecules actually move in both directions, but they move to a greater extent toward Solution D because it has a higher solute concentration than Solution C. This net movement of water molecules causes Solution D to increase in volume and Solution C to decrease in volume.The reaction A --> B + C + heat is released in a(n) _____ reaction.exergonicA(n) _____ reaction occurs spontaneously.exergonicWhich of these reactions requires a net input of energy from its surroundings?endergonicIn cells, what is usually the immediate source of energy for an endergonic reaction?ATPThe reaction ADP + P --> ATP is a(n) _____ reaction.endergonicThe energy for an endergonic reaction comes from a(n) _____ reaction.exergonicWhat is the fate of the phosphate group that is removed when ATP is converted to ADP?It is acquired by a reactant in an endergonic reactionSelect the INCORRECT association. exergonic ... uphill exergonic ... spontaneous enzyme ... protein kinetic energy ... motion potential energy ... positional energyexergonic.....uphillWhat is energy coupling?the use of energy released from an exergonic reaction to drive an endergonic reactionWhich term describes the degree to which an element attracts electrons?ElectronegativityWhich terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?Anion and cationWhich of the following statements is true of the bonds in a water molecule?Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?IonicGaseous hydrogen burns in the presence of oxygen to form water:2H2 + O2 → 2H2 O + energyWhich molecule is oxidized and what kind of bond is formed?hydrogen, polarHow many NADH are produced by glycolysis?2 NADHIn glycolysis, ATP molecules are produced by _____.substrate-level phosphorylationIn glycolysis, what starts the process of glucose oxidation?ATPIn glycolysis there is a net gain of _____ ATP.2When a compound donates (loses) electrons, that compound becomes __________________. Such a compound is often referred to as an electron donor.OxidizedWhen a compound accepts (gains) electrons, that compound becomes ____________________. Such a compound is often referred to as an electron acceptor.Reducedn glycolysis, the carbon-containing compound that functions as the electron donor isglucoseOnce the electron donor in glycolysis gives up its electrons, it is oxidized to a compound calledpyruvate_____is the compound that functions as the electron acceptor in glycolysisNAD+The reduced form of the electron acceptor in glycolysis isNADHAmong the products of glycolysis, which compounds contain energy that can be used by other biological reactions?pyruvate, ATP, and NADHWhat are some things that describe substrate-level phosphorylation in glycolysis* An enzyme is required in order for the reaction to occur * A bond must be broken between an organic molecule and phosphate between ATP can form * One of the substrates is a molecule derived from the breakdown of glucoseIn muscle cells, fermentation produces _____.lactate and NAD+In fermentation _____ is reduced and _____ is oxidized.pyruvate; NADHReword the following statement to make it true: Energy is stored in special high-energy bonds in molecules such as ATPATP and is released when these bonds are broken.Energy is always required to break a covalent bond. ATPATP is a high-energy compound because its hydrolysis is exergonic, which means that more energy is released as the bonds between the -H and -OH groups of water are formed than is required to break the phosphoanhydride bond of ATPATP.Reword the following statement to make it true: The terminal phosphate of ATPATP is a high-energy phosphate that takes its high energy with it when it is hydrolyzed.The phosphate group doesn't possess any intrinsic energy of its own. The term "high-energy" applies only to the phosphoanhydride bond that links the phosphate group to the rest of the ATPATP molecule.Reword the following statement to make it true: Phosphoester bonds are low-energy bonds because they require less energy to break than the high-energy bonds of phosphoanhydrides.Phosphoester bonds are low-energy bonds and they require more energy to break than the high-energy bonds of phosphoanhydrides.Ethanol catabolism in the body begins with its _______________ with NAD+ as the electron _____________.Oxidation; acceptorThe more ethanol is consumed, the greater the demand is for NAD+ and the more serious the __________ in NAD+ concentration.reductionThe supply of NAD+ may be inadequate for ____________- respiration of glucoseaerobicMost of the unpleasant effects of hangovers result from an accumulation of acetaldehyde and its metabolites. Where does the acetaldehyde come from?Acetaldehyde is the immediate product of ethanol oxidation. Ethanol+NAD+→acetaldehyde+NADH+H+The medical treatment for methanol poisoning usually involves administration of large doses of ethanol. Why is this treatment effective?Methanol and ethanol are both substrates of the enzyme alcohol dehydrogenase.The body is flooded with a large amount of ethanol to provide an effective competitor of methanol, thereby minimizing the production of formaldehyde.Keto-enol tautomerization is an important mechanism in glycolysis. What does this involve?movement of the double-bonded oxygen of a keto group to a neighboring hydroxyl groupHow many molecules of ATP are used in glycolysis, and how many are directly made?Two are used to phosphorylate the glucose, and four are directly made from 1,3-bisphosphoglycerate and phosphoenolpyruvate.In the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate (Gly-6), NADH is made and phosphate is attached. What drives this reaction?that 1,3-bisphosphoglycerate is much lower in energy (G°′) than glyceraldehyde-3-phosphateWhich of the following is true of Gly-10 (pyruvate kinase), which converts phosphoenol pyruvate to pyruvate?It is an example of substrate-level phosphorylation, producing ATP.The fourth reaction involving Gly-4 ( aldolase) is an especially important reaction in glycolysis. Why is this?It results in a splitting of a 6-carbon molecule into two 3-carbon molecules.Some scientists claim that there is another reason, an enthalpic reason, that the hydrolysis of ATP is exergonic, besides those listed in the textbook. Which of the following is a possible enthalpic reason that ATP hydrolysis is exergonic?The phosphoanhydride bond interacts poorly with the aqueous environment compared to the products of hydrolysis.Consider the following list of phosphorylated compounds with their free energies of phosphate hydrolysis:Glucose-1-phosphate: -5.0 kcal/molPEP: -14.8 kcal/moleATP: -7.3 kcal/molWhich of these molecules could phosphorylate an unknown compound whose free energy of phosphate hydrolysis is -10.3 kcal/mol?PEP onlyOxidation reactions in biological systems generally involveloss of electrons and hydrogen ionsEach of the following can be the final electron acceptor in bacterial aerobic or anaerobic respiration except sulfur. hydrogen ions. pyruvate. Fe3+. oxygen.pyruvateWhich part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?Terminal phosphateWhere is lactate produced?fermentation in human muscleWhere is ethanol produceedfermentation in yeast and bacteriaWhere is acetyl CoA produced?aerobic oxidation