2020 EXAM 03 F 2015 Dr Sperry NAME_________________

Multiple Choice Questions. Circle the BEST answer AND mark it on your scantron.

1) Which of the following statements regarding membranes is NOT TRUE? A) phospholipids rapidly diffuse within the plane of one monolayer in the bilayer. B) Membrane phospholipids rarely flip-flop between one monolayer and the other. C) The most stable form of a phospholipid bilayer in water is a flat sheet with exposed edges.

D) Phospholipid tails are hydrophobicE) diffusion of membrane proteins is may be limited by connections to the cytoskeleton

2) Cell membranes are NOT involved in:A) cell communication B) import and export of molecules C) harvesting energyD) cell growth and motility E) DNA Replication

3) TRUE or FALSE: A membrane containing phospholipids with tails 18 C long and having 2 double bonds would be more fluid than a membrane containing phospholipids with tails 20 C long and no double bonds.

A) TRUE B) FALSE

4) New membrane phospholipids are added on the _____________ face of the ______________ membrane. Flippases change the orientation of specific phospholipids to the __________ face.

A) luminal, Golgi, cytosolicB) cytosolic, plasma, lumenalC) extracellular, plasma, cytosolicD) cytosolic, endoplasmic reticulum, lumenalE) luminal, endoplasmic reticulum, cytosolic

5) The cholesterol in animal cell membranes is most important for which of the following functions? A) the ability of cells to recognize each other. B) maintaining normal membrane fluidity at low temperatures. C) reorienting phospholipids from the cytoplasmic to the luminal face, or vica versa D) establishing a proton gradient during cellular respiration. E) facilitated diffusion of molecules down their concentration gradients

6) Which of the following is NOT TRUE of membrane proteins? A) Transmembrane proteins contain at least 2 hydrophilic and one hydrophobic region B) A membrane protein function is to transport ions across membranes by active or by passive transport C) Channel proteins are peripheral proteins D) Membrane proteins may strengthen membranes via attachment to the cortex or extracellular matrix E) Transmembrane spanning α helices contain the hydrophobic R groups

7) Why do phospholipids spontaneously form bilayers in water? A) Phospholipids are amphipathic B) The hydrophilic head is attracted to water while the hydrophobic tails shun water. C) The bilayer conformation maximizes Hydrogen bond formation. D) All of the above are true E) None of the above are true

8) All of the following are examples of diffusion except: A) osmosis. B) passive transport. C) movement from high to low concentration

D) influx of Na+ thru voltage gated ion channels . E) active transport.

9) Which of the protein traces above most likely corresponds to the membrane protein indicated by the arrow on the left?

A) trace A, because it can diffuse freely throughout the membraneB) trace B, because it can flow freely, but only within the spectrin boundariesC) trace A, because it can flow freely, but only within the spectrin boundariesD) trace C, because it is anchored to the cell cortex and cannot diffuse freelyE) trace B, because it is anchored to the cell cortex and cannot diffuse freely

10) In the example of “rolling leukocytes” in blood vessels, the WBC’s (white blood cells) are stopped by the endothelial cells (blood vessel walls) when glycosylated proteins always present on the ___________ bind to ________ expressed by the endothelial cells in areas where infection is nearby.

A) Oligosaccharides, lectins B)Lectins, oligosaccharides C) WBC’s, oligosaccharidesD) Lectins, WBC’s E) WBC’s, lectins

11) Porin proteins—which form large, water-filled pores in mitochondrial and bacterial membranes—fold into β barrel structures. The amino acid R groups facing the outside of the barrel have what kind of side chains?A) Hydrophilic B) Hydrophobic C) unsaturated D) Porous E) Peptide

12) Which of the following statements is NOT TRUE regarding transport across membranes? A) A uniporter transports one type of solute one direction across the membrane B) Some solutes are moved across membranes against their concentration gradients, using energy from hydrolysis of ATP. C) Active transporters like rhodopsin couple the movement of solutes against their concentration gradient to a light driven conformational change. D) Channel proteins can be used to perform either active or passive transport E) Active transporters discriminate solutes with great specificity, similar to enzymes binding their substrate, and undergo a conformational change similar to a “revolving” rather than a swinging door.

13) Which of the following activities during an action potential repolarizes the cell to resting potential, but without restoring the resting ion gradients across the plasma membrane found in a resting cell?

A) The opening of voltage-gated Na+ channelsB) The opening of voltage-gated K+ channelsC) The leakage of K+ through K+ leak channels D) The pumping of ions by the Na+/K+ ATPaseE) The opening of voltage gated Ca++ channels

14) Which of the following molecules would move most rapidly across cell membranes?A) Glucose B) O2 C) Ca2+ D) H+ E) H2O

15) Which pump is commonly used by fungi, plants, and bacteria to drive the import of solutes against their gradient via secondary active transport? A) ATP pumps B) H+ pumps C) Ca2+ pumps D) K+ pumps E) sump pumps

16) Which of the following correctly describes the role of the Na+/K+ pump in cells?A) It maintains a high [Na+] outside the cell and high [K+] inside.B) It maintains a high [K+] outside the cell and high [Na+] inside.

C) Movement of Na+ out drives the movement of K+ in, by secondary active transport. D) It is responsible for depolarizing nerve cells to threshold potential.

E) It is a symporter

17) TRUE or FALSE The electrochemical gradient of K+ ions is made weaker by the fact that the ion has a positive charge.

A) TRUE B) FALSE

18) The release of neurotransmitters depends on the opening of Ca++ channels in the axon terminal. Which type of gating mechanism do these Ca++ channels use?

A) voltage-gated B) extracellular ligand-gated C) intracellular ligand-gatedD) stress-gated E) any of these can be used.

19) TRUE or FALSE: If a eukaryotic cell is in a hypertonic solution, the principle of osmosis predicts water will move into the cell, causing it to swell.

A) TRUE B) FALSE

20) Inhibitory neurotransmitters such as glycine and GABA make a postsynaptic cell harder to depolarize by:A) allowing an influx of Na+. B) allowing Na+ to escape. C) allowing an influx of Cl -.D) allowing an influx of K+. E) opening voltage gated Ca++ channels

21) In aerobic cellular respiration, a proton gradient is formed by:A) the splitting of water into protons, electrons and oxygenB) the breakdown of ATP into ADP and PiC) light energyD) the movement of electrons down an electron transport chainE) the formation of ATP

22) The ATP generated during glycolysis is produced by A) fermentationB) substrate-level phosphorylationC) photophosphorylationD) oxidative phosphorylationE) respiration

23) The oxidation of glucose by cellular respiration forms carbon dioxide during which steps?A) glycolysis B) the citric acid cycle C) oxidation of pyruvateD) glycolysis and the citric acid cycle E) The citric acid cycle and oxidation of pyruvate

24) Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ needed for glycolysis?

A) The citric acid cycle B) The formation of acetyl CoA C) FermentationD) The electron transport chain E) The Calvin cycle

25) ) The Calvin cycle _____. A) uses light energy to split water into protons, oxygen and electronsB) uses ATP and NADPH to fix atmospheric CO2 into organic moleculesC) occurs in the thylakoid membranes of the chloroplastD) occurs in the matrix of the mitochondriaE) oxidizes carbons of pyruvate to form CO2

26) Which of the following statements about NAD+ is FALSE? A) In the absence of NAD+, glycolysis cannot function. B) NAD + is reduced to NADH during glycolysis, pyruvate oxidation and the citric acid cycle. C) Dehydrogenase enzymes catalyze the reduction of NAD+. D) NAD+ is regenerated during oxidative phosphorylation.

E) NAD+ contains more chemical energy than NADH.

Use the diagram of steps 6 and 7 of glycolysis to answer the following questions (26 and 27): Step 6

Step 7

27) In Step 7, The energy needed to add a phosphate to ADP and form ATP comes from ________________.A) the hydrolysis of ATPB) the hydrolysis of a phosphate from 1,3 bisphosophoglycerate C) free phosphate in the cytoplasmD) free phosphate in the matrixE) None of the above

28) TRUE or FALSE: Cytochrome C oxidase (complex IV) transfers 4 electrons to oxygen to form water.A) TRUE B) FALSE

29) Which of the following statements is TRUE? A) Sugars are converted to Acetyl CoA in the mitochondria; fats are converted to Acetyl CoA in the cytosol. B) Fats are converted to Acetyl CoA in the mitochondria; sugars are converted to Acetyl CoA in the cytosol. C) Sugars and fats are both converted to Acetyl CoA in the mitochondria. D) Sugars are converted to Acetyl CoA but fats are not. E) None of the above are true. Fats cannot be converted to AcetylCoA

30) The Calvin cycle directly uses what source of energy to fix and reduce CO2 into sugars?A) A proton gradient across a membraneB) ATP and NADPH generated in the light reactionsC) ATP generated in cellular respirationD) NADP+ and ADP generated in the Calvin cycleE) CO2 and H2O produced in cellular respiration

31) Intermediates formed in glycolysis and the citric acid cycle can be used by the cell to synthesize:A) amino acids. B) glycerol. C) fatty acids. D) All of the above E) A and B, but not C

32) Pyruvate dehydrogenase is located in the mitochondrial membrane. Which of the following statements is FALSE? This enzyme _____.

A) is actually a large protein complex containing three enzymes B) produces Acetyl CoA and CO2 and NADH.C) produces one molecule of NADH per molecule of pyruvate.D) is inhibited when NADH levels in the cell are high.E) Actually, all of the above are true

33) Where are the enzymes of the citric acid cycle located? A) mitochondrial matrix B) mitochondrial inner membrane C) mitochondrial intermembrane space D) cytosol E) mitochondrial outer membrane

34) Why does a single molecule of NADH result in the production of more ATP molecules by oxidative phosphorylation than a single molecule of FADH2 does?

A) NADH donates more electrons to the chain than FADH2.B) FADH2 feeds its electrons into the electron transport chain further down the chain than NADH does.C) FADH2 is less likely than NADH to transfer electrons to the electron transport chain.D) FADH2 results in more H+’s being pumped than NADH doesE) NADH gets oxidized when it delivers electrons, whereas FADH2 gets reduced

35) Step 3 in glycolysis. phosphofructokinase converts fructose 6-phosphate into fructose 1,6-bisphosphate. Which of the following molecules is an allosteric inhibitor of this key enzyme?

A) Pi B) AMP C) ADP D) ATP E) all of the above36) TRUE or FALSE Combining CO2 and H2O to make a carbohydrate is an energetically favorable reaction.

A) TRUE B) FALSE

37) As electrons flow through the first electron transport chain of the light reactions of photosynthesis, protons become concentrated in the ______.A) stroma B) intermembrane space C) thylakoid membrane D) matrix E) thylakoid space

38) Which of the following statements is true about an electron transport chain? A) Electrons enter containing high energy and lose energy at each transfer step. B) Electrons enter containing low energy and gain energy at each transfer step. C) Electrons gain and release energy as they move from one complex to another in the chain. D) Electrons are pumped across a membrane as protons flow down the gradient E) Electrons are passed from molecules with high electron affinity to molecules with low electron affinity

39) Which of the following statements about the light reactions of photosynthesis is NOT TRUE?A) Protons are pumped into the thylakoid spaceB) Water is formed from electrons, protons and oxygenC) NADP+ is reduced to form NADPHD) Most chlorophyll molecules function as an antennae complex to absorb light energyE) A proton gradient across the thylakoid membrane is used to form ATP from ADP and Pi

40) Which of the following is NOT TRUE about oxygen?

A) It is the final electron acceptor in the mitochondrial electron transport chainB) It is produced by PSII during linear electron flowC) It is formed when C is removed from CO2 during the light reactionsD) It is necessary to regenerate NAD+ during aerobic cellular respirationE) It is not used when facultative anaerobes are in fermentation mode

Write the word in the space provided that is described by each of the following definitions. 1 pt each.

1 Enzyme responsible for changing the orientation of specific phospholipids from the cytosolic face to the luminal face

2 The final electron acceptor in the mitochondrial electron transport chain

3 The molecule formed by oxidation of sugars or of fatty acids, that feeds 2 carbon units into the citric acid cycle

4 A temporary reversal of the membrane voltage, propagated unidirectionally along an axon.

5 Word describing the chemical nature of molecules such as integral membrane proteins, cholesterol and phospholipids

6 The current explanation for the origin of mitochondria in eukaryotic cells

7 An amphipathic molecule with one fatty acid tail; often used to solubilize membranes

8 The diffusion of water across cell membranes

9 The final electron acceptor in the process of photophosphorylation

10 The formation of ATP using energy directly released by cleavage of phosphate from an organic substrate

11 Enzyme that oxidizes a substrate by removing a hydride ion

12 The combined force determining the direction of diffusion of an ion

13 The pigment responsible for absorbing light energy from the sun

14 A byproduct of fermentation in yeast cells

15 Word to describe a solution which is more concentrated than the cell

Short Answers: total 20 points Dr Sperry Name __________________Use correct terminology and sufficient detail to answer the questions. Use of diagrams is recommended.

1) (3 points) Use correct terminology to explain why membranes: a) spontaneously form in an aqueous environment

b) Form semipermeable barriers

c) Are deformable and self sealing

.

2) (1 pt) Describe why the electrochemical gradient of sodium is “steeper” than the potassium gradient across cell membranes.

3) (2 pts) Describe an experiment that demonstrates cell membranes are 2 dimensional fluids.

4) (3 pts) Epithelial cells can maintain different sets of proteins on their apical vs basolateral faces despite the fact that membranes are fluid due to the presence of tight junctions between these cells. On the drawing below a) indicate where the tight junctions are located b) Place a uniporter and a symporter in the correct membrane face of an epithelial cell such that glucose move from the gut lumen into the cell and then out to the interstitial fluids. Identify which transporter is active and which is passive. c) Describe how glucose movement into the body is dependant on the activity of the Na+/K+ pump. d) Which glucose transporter is an example of secondary active transport?

concentrationlow [glucose] in gut lumen

High [glucose] in cells

low [glucose] in interstitial fluids

5) (2 points) On the chart below draw in numbers showing steps 1-4 of an action potential. Describe what is happening at each of the numbered steps on the chart. (identify the channels or pumps involved in each phase and specify whether channels are voltage gated or ligand gated) . Also, label resting potential and threshold potential on the chart.

Direction of glucose

movement

6) (2 pt) How do neurons transduce the electrical action potential traveling down a neuron into a chemical signal which can cross the synapse?

7) (3 pts) Describe the flow of electrons from glucose to oxygen during aerobic respiration.

8) (2 pts) Compare and contrast the Citric Acid Cycle vs the Calvin cycle, stating at least 2 similarities and 2 differences between them.

9) (2 pts) Compare and contrast the formation and function of NADH and NADPH in cells.

Extra Credit: Test 3 Biol 2020 F14 Sperry Name ___________________________________

EC1) Which ATP molecule contains the most intrinsic bond energy? ATP made in lactic acid fermentation or ATP made via oxidative phosphorylation or ATP made during the light reactions of photosynthesis?

EC 2) Amino acids are taken up by animal cells using a symport in the plasma membrane. What is the most likely ion whose electrochemical gradient drives the import of amino acids? Is ATP consumed in the process? If so, how?

EC3) Explain why you breathe faster when you work hard?

EC 4) TRUE or FALSE (Consider the experiments used to determine how chemiosmosis works.) Artificial vesicles containing ATP Synthase, a H+ pump, and an uncoupling protein will produce no ATP in the presence of sunlight. Explain your answer.

A) TRUE B) FALSE

EC5) Circle the correct word for each choice in square brackets. “An electron bound to a molecule with low affinity for electrons is a [high/low]-energy electron. Transfer of an electron from a molecule with low affinity to one with higher affinity has a [positive/negative] ΔG° and is thus [favorable/unfavorable] under standard conditions. If the reduced form of a redox pair is a strong electron donor with a [high/low] affinity for electrons, it is easily oxidized; the oxidized member of such a redox pair is a [weak/strong] electron acceptor.”