Biol Exam 2 Answers

Allostery, i.e., the use of an activator or inhibitor molecule that can bind to the protein. Phosphorylation and it's complement, dephosphorylation. G-proteins are activated by binding GTP and turn off when they hydrolyze GTP to GDP and Pi.

(3 pts) Give examples of 2 different ways that proteins can be "switched on or off". In other words, what are 2 ways cells can reversibly change the structure of a protein.

__ligand_.

(4 pts) For each of the following sentences, fill in the blanks with the correct word or phrase selected from the list below. Use each word or phrase only once. transition state; activation energy; high-energy; low-energy; product; ligand; L-isomer; D-isomer; active site; allostery. Any substance that will bind to a protein is known as its ?

active site

(4 pts) For each of the following sentences, fill in the blanks with the correct word or phrase selected from the list below. Use each word or phrase only once. transition state; activation energy; high-energy; low-energy; product; ligand; L-isomer; D-isomer; active site; allostery. Enzymes bind their substrates at the ___

allostery

(4 pts) For each of the following sentences, fill in the blanks with the correct word or phrase selected from the list below. Use each word or phrase only once. transition state; activation energy; high-energy; low-energy; product; ligand; L-isomer; D-isomer; active site; allostery. Enzymes can change conformation when an activator or inhibitor binds, an example of

transition state

(4 pts) For each of the following sentences, fill in the blanks with the correct word or phrase selected from the list below. Use each word or phrase only once. transition state; activation energy; high-energy; low-energy; product; ligand; L-isomer; D-isomer; active site; allostery. Enzymes catalyze a chemical reaction by stabilizing the formation of the

2 ATP, 2 NADH and 2 pyruvate

) Glycolysis and oxidative phosphorylation a. If we start with one glucose, what are the net products of glycolysis?

ATP

1. The molecule at right is: a. DNA b. ATP c. NADH d. Glucose. e. A phospholipid

b. lipid bilayers held together by noncovalent, hydrophobic interactions

10. Cellular membranes are composed of a. lipid bilayers held together by covalent bonds between phospholipids b. lipid bilayers held together by noncovalent, hydrophobic interactions c. micelles held together by covalent bonds between phospholipids d. micelles held together by noncovalent, hydrophobic interactions

a. Amphipathic / hydrophobic / hydrophilic

11. Membrane lipids are ________ molecules because one end of the molecule is _________ while the other end is ____________ a. Amphipathic / hydrophobic / hydrophilic b. Amphibolic / large /small c. Water soluble / hydrophilic / hydrophilic d. Water soluble / hydrophobic / hydrophobic

a. Anabolism

12. The process of building new cellular macromolecules is called a. Anabolism b. Catabolism

d. All of the above.

13. Cells can use ATP to a. Drive conformation change, for example, in motor proteins b. Drive thermodynamically unfavorable reactions. c. Phosphorylate proteins to inactivate them. d. All of the above.

c. ATP / NADPH

14. In order to do the useful work of making new macromolecules cells generate large amounts of _______, used to do chemical work, and _________ which provides high energy electrons used for reduction reactions. a. ADP / NAD+ b. NADPH / ATP c. ATP / NADPH d. AMP / GTP

d. Both a and c.

15. You have identified a mutation in a G protein that causes the G protein to remain "active" much longer than normal. You recall that G proteins switch On when binding GTP and turn OFF when they hydrolyze the GTP to GDP and phosphate. Which of the following might be the explanation for your mutant? a. The mutant G protein hydrolyzes GTP much more slowly than the normal G protein. b. The mutant G protein can no longer interact with another protein that stimulates the binding of GTP c. The mutant G protein can no longer interact with another protein that stimulates its hydrolysis of GTP d. Both a and c.

a. Amphibolic

16. Eukaryotic plant cells run the glycolytic pathway in opposite directions in the cytosol and chloroplasts, hence the pathway is: a. Amphibolic b. Anabolic c. Catabolic

a. Lactic acid; pyruvate; NADH; NAD+

17. In skeletal muscle the glycolytic pathway is capable of producing ATP much more rapidly than the muscle mitochondria that are limited by oxygen availability. You are familiar with this as the "burn" associated with strenuous exercise. The "burning" is the result of decreased pH in your muscles due to the production of _________ from __________ as ________ is converted to ____________ a. Lactic acid; pyruvate; NADH; NAD+ b. NADH; NAD+; lactate; ethanol c. pyruvate; lactate; NAD+; NADH d. Lactic acid; pyruvate; NADP+; NADPH

b. Cytosol/Mitochondria

18. Glycolysis occurs in the ___________, oxidative phosphorylation occurs in the _______. a. Mitochondria/Chloroplast b. Cytosol/Mitochondria c. Mitochondria/Cytosol d. Cytosol/Chloroplast

e. All of the above

19. What are the functions of mitochondria? a. The oxidation of pyruvate b. The generation of ATP via oxidative phosphorylation c. The generation of NADH via the reactions of the TCA cycle d. Both b and c e. All of the above

D. All of the above

2. Reactions with positive standard free energy changes (ΔGo' > 0) can be made to occur in cells by: a. Coupling them with exergonic reactions via a common intermediate. b. Manipulating the concentrations of products and reactants such that ΔG < 0. c. Coupling them to the hydrolysis of ATP. d. All of the above

a. Substrate-level phosphorylation

20. Production of ATP in glycolysis is referred to as: a. Substrate-level phosphorylation b. Oxidative Phosphorylation

b. Oxidative Phosphorylation

21. Production of ATP in mitochondria is referred to as a. Substrate-level Phosphorylation b. Oxidative Phosphorylation

d. All of the above

22. There are many dehydrogenase enzymes used in glycolysis and in mitochondria. What do these enzymes do? a. They catalyze oxidation/reduction reactions b. They facilitate the transfer electrons and protons between molecules c. They oxidize one molecule and reduce a different molecule d. All of the above

a. The thylakoid membrane is permeable to protons.

23. Which of the following statements about chloroplasts is FALSE? a. The thylakoid membrane is permeable to protons. b. The thylakoid membrane contains the photosynthetic electron transport components. c. Protons are pumped from the stroma into the thylakoid space. d. ATP is synthesized in the stroma.

b. Anabolic

24. The dark reactions of photosynthesis (also known as the Calvin cycle) are a. Catabolic b. Anabolic

a. 12, 4

25. The F0 base of ATP synthase (the rotor) contains a ring of 12 subunits that each carry a single proton while the F1 head has three-fold symmetry that explains the three conformations required to a) bind ADP and Pi, b) bind ATP, and c) release ATP. In one revolution ____ protons move across the membrane powering each of the 3 subunits to make one ATP. In other words it takes _____ protons to make one ATP a. 12, 4 b. 12, 2 c. 4, 4 d. 6, 2

b. The redox reactions of the electron transport chain

26. What is the source of free energy (G) for moving protons out of the mitochondrial matrix against their concentration and electrical gradients? a. ATP b. The redox reactions of the electron transport chain c. Glycolysis d. Creatine phosphate

e. All of the above

27. Which of the following is/are correct a. NADH is oxidized to NAD+ b. H2O is oxidized to O2 c. NADP+ is reduced to NADPH d. Both a and c e. All of the above

true

28. The most important contribution of the citric acid cycle to energy metabolism is the extraction of high-energy electrons during the oxidation of acetyl CoA to CO2. a. True b. False

True

29. Each respiratory enzyme complex in the electron-transport chain has a greater affinity for electrons than its predecessors, so that electrons pass sequentially from one complex to another until they are finally transferred to oxygen, which has the greatest electron affinity. a. True b. False

e. Both b and c.

3. Which of the following statements about enzymes are correct? a. Enzymes enable energetically unfavorable reactions (ΔG > 0) to occur. b. An enzyme lowers the activation energy of the reaction. c. An enzyme typically catalyzes reactions with regard to stereochemistry (ie, they will make only a right OR a left-handed molecule, not both). d. An enzyme can bind to many structurally unrelated substrates. e. Both b and c.

d. All of the above

30. Certain poisons, like cyanide and carbon monoxide, are potent inhibitors of our respiratory electron transport chains (ETC). What would you expect to happen when mitochondria cannot transfer electrons through the ETC? a. There would be no proton pumping across the inner membrane b. There would be no synthesis of ATP c. The TCA cycle would stop due to a buildup of NADH d. All of the above

c. water, NADP+

31. The function of the light reactions of photosynthesis is to oxidize ___________ and reduce __________. a. water, NADH b. water. NAD+ c. water, NADP+ d. oxygen, NADP+

d. ATP and NADPH

32. The products of the light reactions of photosynthesis include oxygen and: a. Glucose b. Sucrose c. ATP and NADP+ d. ATP and NADPH

e. All of the above

33. The enzyme ribulose bis-phosphate carboxylase (RUBISCO): a. Is responsible for carbon fixation when CO2 is added to ribulose bis-phosphate b. Is found in the stroma of the chloroplast c. Is the most abundant protein on earth d. Both b and c e. All of the above

d. Fixation of CO2, Reduction, Regeneration of Ribulose-P2

34. Put the sequence of the reactions of the Calvin Cycle in the correct order a. Reduction, Regeneration of Ribulose-P2, Fixation of CO2 b. Regeneration of Ribulose-P2, Reduction, Fixation of CO2 c. Fixation of CO2, Regeneration of Ribulose-P2, Reduction d. Fixation of CO2, Reduction, Regeneration of Ribulose-P2

e. Both a and d

35. What is photorespiration? a. This is when RUBISCO incorporates O2 instead of CO2 b. This is when chloroplasts use oxidative phosphorylation to make ATP c. This is when plants close their stromata so they can't perspire d. This is an energy wasteful side reaction in chloroplasts that is a particular problem in hot climates e. Both a and d

c. They pump up the concentration of CO2 in the chloroplast

36. Some plants (those adapted to hotter climates) use a trick to reduce photorespiration. What modification do they use? a. They do only do the light reactions of photosynthesis at night b. They actively pump O2 out of mitochondria c. They pump up the concentration of CO2 in the chloroplast d. They turn off photosynthesis completely

eukaryotic animal cell.

39. (5 pts) Identify the following cell: a. Is this cell prokaryotic, or a eukaryotic plant, or a eukaryotic animal cell. b. Identify the following: rough ER, Golgi, nucleus, one mitochondria.

a. ΔG = 0. (Delta G)

4. Any reaction A <-----> B is at equilibrium when: a. ΔG = 0. b. ΔG°' = 0. c. [A] = [B]. d. ΔG = ΔG°'.

d. coupling of ATP hydrolysis to the reaction.

5. A common means of providing energy to an energetically unfavorable reaction in a cell is by: a. generation of a higher temperature by the cell. b. transfer of a phosphate group from the substrate to ADP. c. enzyme catalysis of the reaction. d. coupling of ATP hydrolysis to the reaction. e. coupling of the synthesis of ATP to the reaction

c. Creatine phosphate and enzyme A

6. You are studying a biochemical pathway that requires ATP as an energy source. To your dismay, the reactions soon stop, partly because the ATP is rapidly used up and partly because an excess of ADP builds up and inhibits the enzymes involved. You are about to give up when the following table from a biochemistry textbook catches your eye and you see an easy way to regenerate ATP from ADP to allow your reaction pathway to continue Which of the following reagents are most likely to revitalize your reaction? a. A vast excess of ATP. b. Phosphate and enzyme B. c. Creatine phosphate and enzyme A d. Pyrophosphate and enzyme D.

a. C

7. In the biosynthetic pathway shown schematically to the right . After showing that E inhibits Enzyme 6, and H inhibits Enzyme 3 you predict that Enzyme 1 will be most efficiently controlled via feedback inhibition by molecule: a. C b. E c. H d. E and H

d. Both A and B

8. The sodium/potassium pump is responsible for maintaining the membrane potential in our cells. What exactly does this pump do? a. It uses ATP to power the active transport of sodium and potassium ions across the membrane b. It pumps 3 sodium ions out of the cell and 2 potassium ions into the cell c. It pumps 2 sodium into the cell and 3 potassium out of the cell d. Both A and B e. Both A and C

True

9. Osmosis is the diffusion of water across a membrane down its concentration gradient a. True b. False

Hydrogen 1 Oxygen 2 Nitrogen 3 Carbon 4

What are the valences (or number of covalent bonds) of the following atoms: Hydrogen Oxygen Nitrogen Carbon

Generate a proton gradient across the membrane

a. The ETC of mitochondria and chloroplasts both use the power of the ETC to do exactly the same thing. What is this?

2 ATP and 2 lactic acid OR 2 ATP, 2 carbon dioxide and 2 ethanol

b. If we start with one glucose and do not have oxygen, what are the net products of fermentation (you may report this for animals or yeast)?

Mitochondria use NADH to power the ETC and reduce oxygen to water. Chloroplasts use light energy to oxidize water to oxygen while generating NADPH

b. The ETC of mitochondria and chloroplasts do something else in exactly opposite ways. What is this?

They are oxidized to carbon dioxide

c. What happens to the carbon atoms of pyruvate when it is catabolized by mitochondria?

They power the Electron Transport Chain (ETC) to pump protons (H+) across the membrane

d. The TCA (aka Krebs) cycle generates high energy electrons extracted from the oxidation of acetyl-CoA. To what immediate use are these high energy electrons put?

The proton gradient powers ATP synthase

e. What is the direct source of power that makes ATP in mitochondria and chloroplasts?