7.6: Exercises

Review Questions for Chapter 7

Multiple Choice

1) Which of the following is an organism that obtains its energy from the transfer of electrons originating from chemical compounds and its carbon from an inorganic source?

1. chemoautotroph
2. chemoheterotroph
3. photoheterotroph
4. photoautotroph

2) Which of the following molecules is reduced?

1. NAD⁺
2. FAD
3. O₂
4. NADPH

3) Enzymes work by which of the following?

1. increasing the activation energy
2. reducing the activation energy
3. making exergonic reactions endergonic
4. making endergonic reactions exergonic

4) To which of the following does a competitive inhibitor most structurally resemble?

1. the active site
2. the allosteric site
3. the substrate
4. a coenzyme

5) Which of the following are organic molecules that help enzymes work correctly?

1. cofactors
2. coenzymes
3. holoenzymes
4. apoenzymes

6) During which of the following is ATP not made by substrate-level phosphorylation?

1. Embden-Meyerhof pathway
2. Transition reaction
3. Krebs cycle
4. Entner-Doudoroff pathway

7) Which of the following products is made during Embden-Meyerhof glycolysis?

1. NAD+
2. pyruvate
3. CO₂
4. two-carbon acetyl

8) During the catabolism of glucose, which of the following is produced only in the Krebs cycle?

1. ATP
2. NADH
3. NADPH
4. FADH₂

9) Which of the following is not a name for the cycle resulting in the conversion of a two-carbon acetyl to one ATP, two CO₂, one FADH₂, and three NADH molecules?

1. Krebs cycle
2. tricarboxylic acid cycle
3. Calvin cycle
4. citric acid cycle

10) Which is the location of electron transports systems in prokaryotes?

1. the outer mitochondrial membrane
2. the cytoplasm
3. the inner mitochondrial membrane
4. the cytoplasmic membrane

11) Which is the source of the energy used to make ATP by oxidative phosphorylation?

1. oxygen
2. high-energy phosphate bonds
3. the proton motive force
4. P_i

12) A cell might perform anaerobic respiration for which of the following reasons?

1. It lacks glucose for degradation.
2. It lacks the transition reaction to convert pyruvate to acetyl-CoA.
3. It lacks Krebs cycle enzymes for processing acetyl-CoA to CO₂.
4. It lacks a cytochrome oxidase for passing electrons to oxygen.

13) In prokaryotes, which of the following is true?

1. As electrons are transferred through an ETS, H⁺ is pumped out of the cell.
2. As electrons are transferred through an ETS, H⁺ is pumped into the cell.
3. As protons are transferred through an ETS, electrons are pumped out of the cell.
4. As protons are transferred through an ETS, electrons are pumped into the cell.

14) Which of the following is not an electron carrier within an electron transport system?

1. flavoprotein
2. ATP synthase
3. ubiquinone
4. cytochrome oxidase

15) Which of the following is the purpose of fermentation?

1. to make ATP
2. to make carbon molecule intermediates for anabolism
3. to make NADH
4. to make NAD⁺

16) Which molecule typically serves as the final electron acceptor during fermentation?

1. oxygen
2. NAD⁺
3. pyruvate
4. CO₂

17) Which fermentation product is important for making bread rise?

1. ethanol
2. CO₂
3. lactic acid
4. hydrogen gas

18) Which of the following is not a commercially important fermentation product?

1. ethanol
2. pyruvate
3. butanol
4. penicillin

19) Which of the following molecules is not produced during the breakdown of phospholipids?

1. glucose
2. glycerol
3. acetyl groups
4. fatty acids

20) Caseinase is which type of enzyme?

1. phospholipase
2. lipase
3. extracellular protease
4. intracellular protease

21) Which of the following is the first step in triglyceride degradation?

1. removal of fatty acids
2. β-oxidation
3. breakage of fused rings
4. formation of smaller peptides

22) During the light-dependent reactions, which molecule loses an electron?

1. a light-harvesting pigment molecule
2. a reaction center pigment molecule
3. NADPH
4. 3-phosphoglycerate

23) In prokaryotes, in which direction are hydrogen ions pumped by the electron transport system of photosynthetic membranes?

1. to the outside of the plasma membrane
2. to the inside (cytoplasm) of the cell
3. to the stroma
4. to the intermembrane space of the chloroplast

24) Which of the following does not occur during cyclic photophosphorylation in cyanobacteria?

1. electron transport through an ETS
2. photosystem I use
3. ATP synthesis
4. NADPH formation

25) Which of the following are two products of the light-dependent reactions?

1. glucose and NADPH
2. NADPH and ATP
3. glyceraldehyde 3-phosphate and CO₂
4. glucose and oxygen

26) Which of the following is the group of archaea that can use CO₂ as their final electron acceptor during anaerobic respiration, producing CH₄?

1. methylotrophs
2. methanotrophs
3. methanogens
4. anoxygenic photosynthesizers

27) Which of the following processes is not involved in the conversion of organic nitrogen to nitrogen gas?

1. nitrogen fixation
2. ammonification
3. nitrification
4. denitrification

28) Which of the following processes produces hydrogen sulfide?

1. anoxygenic photosynthesis
2. oxygenic photosynthesis
3. anaerobic respiration
4. chemoautrophy

29) The biogeochemical cycle of which of the following elements is based on changes in solubility rather than redox chemistry?

1. carbon
2. sulfur
3. nitrogen
4. phosphorus

Fill-in-the-Blanks

30) Processes in which cellular energy is used to make complex molecules from simpler ones are described as ________.

31) The loss of an electron from a molecule is called ________.

32) The part of an enzyme to which a substrate binds is called the ________.

33) Per turn of the Krebs cycle, one acetyl is oxidized, forming ____ CO₂, ____ ATP, ____ NADH, and ____ FADH₂ molecules.

34) Most commonly, glycolysis occurs by the ________ pathway.

35) The final ETS complex used in aerobic respiration that transfers energy-depleted electrons to oxygen to form H₂O is called ________.

36) The passage of hydrogen ions through ________ down their electrochemical gradient harnesses the energy needed for ATP synthesis by oxidative phosphorylation.

37) The microbe responsible for ethanol fermentation for the purpose of producing alcoholic beverages is ________.

38) ________ results in the production of a mixture of fermentation products, including lactic acid, ethanol and/or acetic acid, and CO₂.

39) Fermenting organisms make ATP through the process of ________.

40) The process by which two-carbon units are sequentially removed from fatty acids, producing acetyl-CoA, FADH₂, and NADH is called ________.

41) The NADH and FADH₂ produced during β-oxidation are used to make ________.

42) ________ is a type of medium used to detect the production of an extracellular protease called caseinase.

43) The enzyme responsible for CO₂ fixation during the Calvin cycle is called ________.

44) The types of pigment molecules found in plants, algae, and cyanobacteria are ________ and ________.

45) The molecule central to the carbon cycle that is exchanged within and between ecosystems, being produced by heterotrophs and used by autotrophs, is ________.

46) The use of microbes to remove pollutants from a contaminated system is called ________.

Short Answers

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47) In cells, can an oxidation reaction happen in the absence of a reduction reaction? Explain.

48) What is the function of molecules like NAD⁺/NADH and FAD/FADH₂ in cells?

49) What is substrate-level phosphorylation? When does it occur during the breakdown of glucose to CO₂?

50) Why is the Krebs cycle important in both catabolism and anabolism?

51) What is the relationship between chemiosmosis and the proton motive force?

52) How does oxidative phosphorylation differ from substrate-level phosphorylation?

53) How does the location of ATP synthase differ between prokaryotes and eukaryotes? Where do protons accumulate as a result of the ETS in each cell type?

54) Why are some microbes, including Streptococcus spp., unable to perform aerobic respiration, even in the presence of oxygen?

55) How can fermentation be used to differentiate various types of microbes?

56) How are the products of lipid and protein degradation connected to glucose metabolism pathways?

57) What is the general strategy used by microbes for the degradation of macromolecules?

58) Why would an organism perform cyclic phosphorylation instead of noncyclic phosphorylation?

59) What is the function of photosynthetic pigments in the light-harvesting complex?

60) Why must autotrophic organisms also respire or ferment in addition to fixing CO₂?

61) How can human activity lead to eutrophication?

Critical Thinking

62) What would be the consequences to a cell of having a mutation that knocks out coenzyme A synthesis?

63) The bacterium E. coli is capable of performing aerobic respiration, anaerobic respiration, and fermentation. When would it perform each process and why? How is ATP made in each case?

64) Do you think that β-oxidation can occur in an organism incapable of cellular respiration? Why or why not?

65) Is life dependent on the carbon fixation that occurs during the light-independent reactions of photosynthesis? Explain.

66) In considering the symbiotic relationship between Rhizobium species and their plant hosts, what metabolic activity does each organism perform that benefits the other member of the pair?