Chapter 5

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Which of the following is not true about photoautotrophs?

(a) They require CO2 and light.

(b) They synthesize organic molecules from inorganic molecules.

(c) They are a subdivision of heterotrophs.

(d) They are a subdivision of autotrophs.

(e) All of the above are true.



Metabolic pathways rely on many enzymes to synthesize or catabolize substrates to an end product. Within a given metabolic pathway, a product can become another enzyme's substrate.

(a) True

(b) False



Which of the following statements about enzyme characteristics is true?

(a) Enzymes generally exhibit a high degree of specificity for one particular substrate.

(b) Enzyme-substrate complexes occur when a substrate molecule collides with the allosteric site of an enzyme.

(c) Chemical bonds within a substrate are strengthened when this substrate forms an enzyme-substrate complex.

(d) a and d.



Enzyme cofactors are usually inorganic ions that enhance enzymatic activity improving the "fit" between an enzyme and its substrate.

(a) True

(b) True



All of the following statements about competitive and non-competitive inhibitors are true EXCEPT:

(a) Competitive inhibitors are structurally similar to an enzyme's substrate and bind to the enzyme's allosteric site.

(b) Competitive inhibitors work by competing with a substrate for binding to an enzyme's active site.

(c) Noncompetitive inhibitors can bind at sites other than the active site of an enzyme, distorting the tertiary protein structure, which alters the shape of the active site, rendering it ineffective for substrate binding.

(d) Some noncompetitive inhibitors bind reversibly while some bind irreversibly to their enzyme.

(e) b and d



Which of the following would influence the rate of an enzyme reaction?

(a) Temperature

(b) pH

(c) Concentration of substrate molecules

(d) Concentration of product molecules

(e) All of these



What is feedback inhibition?

(a) When the end product competitively inhibits the enzyme that produced it.

(b) When the first enzyme in line shuts down because of a buildup in its substrate.

(c) When an end product accumulates, it often binds to and inactivates the first enzyme that catalyzes the first reaction in the pathway.

(d) It is a reversible noncompetitive inhibition that regulates the rate of many metabolic pathways.

(e) c and d.



Which of the following is true regarding the relationship between photosynthesis and respiration?

(a) Respiration is the exact reversal of the biochemical pathway of photosynthesis.

(b) Photosynthesis energy in glucose and respiration releases energy from glucose.

(c) Photosynthesis occurs only in plants and respiration only occurs only in animals.

(d) ATP molecules are produced in photosynthesis whereas respiration depletes ATP.

(e) All of the above are true.



Which of the following statements about glycolysis is not true?

(a) Glycolysis, like fermentation, is an aerobic metabolic pathway that reduces glucose, transferring the electrons to the coenzyme ATP, which in turn passes these electrons to the final electron acceptor, an organic molecule.

(b) Glycolysis can occur under aerobic or anaerobic conditions and is a metabolic pathway by which glucose is oxidized to pyruvic acid.

(c) Glycolysis depends on the expenditure of the two ATPs in substrate level phosphorylations of the glucose molecule to initiate the metabolic pathway.

(d) Energy from glycolysis is captured in the form of ATP at the substrate level when released energy from substrate molecules (late in the process) is used to form high-energy bonds between ADP and Pi.

(e) Glycolysis is a metabolic process that splits glucose ( a six-carbon molecule) into three-carbon molecules of pyruvic acid that captures a relatively small amount of energy in the form of ATP compared to electron transport and oxidative phosphorylation.



Which of the following is a characteristic of fermentation?

(a) Produces acids, gases, and alcohol

(b) Occurs in the absence of oxygen

(c) Starts with the breakdown of pyruvic acid

(d) Occurs following glycolysis and produces NAD

(e) All of the above



During aerobic cell respiration most of the energy is produced during:

(a) Krebs cycle

(b) Glycolysis

(c) Fermentation

(d) ATP --> ADP

(e) Electron transport chain reactions



The typical end products of complete aerobic cell respiration are carbon dioxide, water and:

(a) ATP

(b) Glucose

(c) Citric acid

(d) Lactic acid

(e) Pyruvate



The end products of photosynthesis in cyanobacteria and plant cells are:

(a) Water and oxygen

(b) Glucose and water

(c) Glucose and oxygen

(d) Water and carbon dioxide

(e) Glucose and carbon dioxide



Which of the following final electron acceptors is used during anaerobic respiration?

(a) Lactic acid

(b) Pyruvic acid

(c) Nitrate

(d) Glucose

(e) Water