CH 5/6 Practice-Test

1. CH 5/6 Practice-Test The questions are in no particular order!

2. Atoms and electrons can be recycled indefinitely; energy ________. • - since it can be neither created nor destroyed - recycles as well • can be reorganized when plants reclaim the CO2 and water produced in respiration • must be continuously replaced because every use of energy degrades its ability to perform useful work • can be created when needed through cellular mechanisms • none of the choices

3. Patients with mitochondrial disorders share many symptoms, such as muscle weakness, because mitochondria ________. • organize the construction of muscle protein • generate the ATP that is necessary for muscle contraction • store and then release the oxygen used during muscle contraction • facilitate the transport of glucose across the muscle cell membrane

4. Which process below is correctly matched with its cellular location? • glycolysis - mitochondrion • Krebs cycle - cytoplasm • lactic acid fermentation - cytoplasm • electron transfer phosphorylation - Golgi • electron transfer phosphorylation – cytoplasm

5. Potential energy can be visualized as the energy ________. • of motion • of position and organization • of a falling object • of heat or thermal energy • that drives muscle contraction

6. In contrast to linear metabolic pathways, in cyclic pathways, ________. • the last step regenerates the same molecule as was used in the first step of the sequence • the product molecules are arranged in closed-loop configurations like the monosaccharides • reactants or intermediates are channeled into two or more reaction sequences • the enzymes are positioned sequentially along a membrane • only degradative reactions occur

7. Exergonic reactions produce both products and free energy; the free energy may be either ________. • heat or light • oxidation or reduction • kinetic or potential energy • heat or muscle contraction • mechanical or chemical energy

8. Enzymes lower activation energy by ________. • helping substrates get together • orienting substrates into positions that favor a reaction • shutting out water molecules • inducing a fit between the enzyme and the substrate • all of the choices

9. Less than 50% of the energy in glucose is converted to ATP bond energy; the remaining energy ________. • becomes activation energy for the enzymes • is stored in fat and metabolized later as needed • is carried off by CO2 and water • is used to move muscle and drive active processes • is converted to heat

10. Regardless of the source of energy, virtually all living organisms convert their energy source into ________ before using it. • glucose • carbon dioxide • ATP • light and heat

11. Where in the mitochondrion are the electron transfer chains located? • in the inner compartment • embedded in the inner membrane • in the outer compartment • embedded in the outer membrane • in the mitochondrial matrix

12. How many ATP molecules are formed during the Krebs cycle for each acetyl-CoA that enters? • 0 • 1* • 2 • 4 • 6 * We learned this as 2 ATP are formed during the Krebs cycle for 2 acetyl-CoA.

13. What statement best characterizes glycolysis? • glycogen, a large carbohydrate molecule, is broken down to monosaccharides • a molecule of glucose is converted into two molecules of pyruvate • overall, there is a net energy cost to the cell during glycolysis • the carbon atoms in glucose are oxidized to form carbon dioxide and water

14. What cofactor accepts electrons in both glycolysis and the Krebs cycle? • ATP • NADP • FAD • NAD+ • CoA

15. Substrate-level phosphorylation, in contrast to electron transfer phosphorylation, can occur ________. • both in the cytoplasm and the mitochondrion • under anaerobic conditions • without the aid of the enzyme ATP synthase • all of the choices are correct

16. After two turns of the Krebs cycle, the original glucose is completely disassembled but the cell has gained only four ATP. What happened to the bulk of the energy? • it has been converted to heat and is no longer capable of producing work • glucose is a small molecule; four ATP was all the cell could hope to recover • it was used to reduce NAD+ and FAD but will be recovered during electron transfer phosphorylation • it is still contained within the carbon-oxygen bonds of carbon dioxide

17. Prior to entering the Krebs cycle, pyruvate loses ________ and is converted to ________. • a water, acetyl-CoA • a carbon dioxide, oxaloacetate • a carbon dioxide, acetyl-CoA • a water, oxaloacetate • electrons, lactate

18. What is the role of the molecular oxygen (O2) in aerobic respiration? • it donates H's and electrons • oxygen combines with carbon from glucose to form CO2 • it transfers H's from the Krebs cycle by temporarily forming water • oxygen accepts electrons from the electron transfer chain and hydrogen ion to form water • oxygen is needed to synthesize ATP

19. The energy released during electron transfer reactions is initially used to push ________ into the outer compartment. • electrons • NADH • hydrogen ions • oxygen • ATP

20. A mitochondrion has a double membrane with the outer compartment between them. Within the outer compartment, ________. • hydrogen ions accumulate to form the proton gradient that drives ATP synthase • carbon dioxide accumulates and is stored until it can be transported to the lung • the matrix containing Krebs cycle enzymes is located • the soluble electron transport enzymes are found

21. For glycolysis to continue in eukaryotes, NAD+ must be regenerated. In anaerobic environments, this is accomplished by ________, which produces ________ as the end product(s). • fermentation, ethanol or lactic acid • phosphorylation, ATP • an exchange reaction, FADH2 and NAD+ • hydrogenation, NADPH2

22. Substrate-level phosphorylation occurs in only the ________stage(s) of aerobic respiration. • glycolysis and electron transfer • Krebs cycle • glycolysis • glycolysis and Krebs cycle • Krebs cycle and electron transfer

23. Careful measurement reveals that the cofactors coenzyme A, NAD+, and FAD are present in cells in relatively low concentrations. This is not surprising because ________. • each becomes toxic at higher concentrations and would damage cell metabolism • like enzymes, each can be used over and over • they are costly molecules to synthesize and cells make them only as needed • each is degraded immediately after being used, preventing any buildup from occurring • their roles in aerobic respiration are extremely minor

24. Chemical reactions that end with a net release of energy are classified as ________. • endodermal • endothermal • endergonic • exergonic

25. Activation energy describes the minimum amount of energy required ________. • for the reactants to reach the transition state and react • before water and carbon dioxide will combine to form glucose • to raise the temperature of a cell to within its homeostatic range • before nutrients can cycle between producers and consumers

26. How does the release of a phosphate group from ATP provide energy for other reactions? • the associated heat provides the activation energy to start the reaction • the phosphate collides with one or more of the reacting molecules • the phosphate is transferred to another molecule, energizing it • phosphate must be added to the substrate before it will enter an active site

27. Which of the following is an example of an exergonic reaction? • 6 CO2 + 6 H2O - > C6H12O6 + 6 O2 • ATP - > ADP + Pi • ADP + Pi - > ATP • glycerol + 3 fatty acids - > triglyceride + H2O

28. Enzymes are considered catalysts because ________. • they make reactions occur much faster than they would on their own • like a bullet that can be fired once, the enzyme is destroyed after each use • they are energy carriers, providing the activation energy needed to start a reaction • all of the choices accurately describe a catalyst

29. Enzymes speed up reactions by lowering the ________ energy. • activation • kinetic • mechanical • potential

30. That portion of the enzyme that binds the substrate is called the ________. • allosteric activator site • transitional site • active site • substrate site

31. A molecule becomes reduced when it ________. • gains an electron • is degraded into smaller products • gives up an electron • releases hydrogen ion

32. Pickling preserves foods by first soaking them in strong salt solutions; how might this delay spoilage? • bacteria probably don't like the taste of pickled foods • pickling oxidizes the foods, making them unsuitable to bacteria • the high salt concentration denatures bacterial enzymes • salt is an antioxidant

33. In feedback inhibition, ________ usually inhibits the first enzyme in a metabolic pathway. • the first reactant • the first intermediate • the end-product • none of the choices

34. In the absence of oxygen, ________. • energy metabolism completely ceases and the organism dies • a small amount of ATP can be produced using glycolysis • eukaryotic cells can use alternative electron acceptors such as sulfur or iron • carbon dioxide molecules can't be constructed and the Krebs cycle stops

35. How many ATPs are required for the early stages of glucose breakdown in glycolysis? • 0 • 1 • 2 • 4

36. What is the typical yield of ATP from the complete aerobic respiration of glucose? • 30 (most cells) • 32 (liver, heart and kidney cells) • 12 • 6 • 4

37. What is the final carbon-containing end product of the complete aerobic respiration of glucose? • carbon dioxide • pyruvate • starch • water

38. When muscle cells are deprived of oxygen, they can continue to form ATP through ________. • lactate fermentation • alcoholic fermentation • anaerobic electron transfer • sulfur reduction • both alcoholic and lactate fermentation