HOW CELLS OBTAIN ENERGY FROM FOODThe Breakdown and Utilization of Sugars and FatsCHAPTER 13HOW CELLS OBTAIN ENERGY FROM FOOD 2009 Garland Science PublishingThe Breakdown and Utilization of Sugars and Fats13-1 Glycolysis is an anaerobic process used to catabolize glucose. What does it mean for this process to be anaerobic?(a) No oxygen is required.(b) No oxidation occurs.(c) It takes place in the lysosome.(d) Glucose is broken down by the addition of electrons.13-2 Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP?(a) the digestion of starch to glucose(b) glycolysis(c) the citric acid cycle(d) oxidative phosphorylation13-3 The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is that ________________.(a) more free energy is released for a given amount of glucose oxidized(b) no energy is lost as heat(c) energy can be extracted in usable amounts(d) more CO2 is produced for a given amount of glucose oxidized13-4 The final metabolite produced by glycolysis is ___________.(a) acetyl CoA(b) pyruvate(c) 3-phosphoglycerate(d) glyceraldehyde 3-phosphate13-5 Glycolysis generates more stored energy than it expends. What is the net number of activated carrier molecules produced in this process (number and type of molecules produced minus the number of those molecules used as input)?(a) 6 ATP, 2 NADH(b) 4 ATP, 4 NADH(c) 2 ATP, 2 NADH(d) 4 ATP, 2 NADH13-6 Which of the following steps or processes in aerobic respiration include the production ofcarbon dioxide?(a) breakdown of glycogen(b) glycolysis(c) conversion of pyruvate to acetyl CoA(d) oxidative phosphorylation13-7 In step 4 of glycolysis, a six-carbon sugar (fructose 1,6-bisphosphate) is cleaved to produce two three-carbon molecules (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate). Which enzyme catalyzes this reaction?(a) aldolase(b) phosphoglucose isomerase(c) enolase(d) triose phosphate isomerase13-8 On a diet consisting of nothing but protein, which of the following is the most likely outcome?(a) loss of weight because amino acids cannot be used for the synthesis of fat(b) muscle gain because the amino acids will go directly into building muscle(c) tiredness because amino acids cannot be used to generate energy(d) excretion of more nitrogenous (ammonia-derived) wastes than with a more balanced diet13-9 Figure Q13-9 represents a cell lining the gut. Draw numbered labeled lines to indicate exactly where inside a cell the following processes take place.Figure Q13-91. glycolysis2. citric acid cycle3. conversion of pyruvate to activated acetyl groups4. oxidation of fatty acids to acetyl CoA5. glycogen breakdown6. release of fatty acids from triacylglycerols7. oxidative phosphorylation13-10 Fill in the spaces in the table below. For steps 1, 4, 5, and 8, name the correct substrates, enzyme, or products. For all the other steps, name the enzyme and draw the missing structure.13-11 Which of the following processes do not take place in the mitochondria?(a) citric acid cycle(b) conversion of pyruvate to activated acetyl groups(c) oxidation of fatty acids to acetyl CoA(d) glycogen breakdown13-12 Which reaction does the enzyme phosphoglucose isomerase catalyze?(a) glucose → glucose 6-phosphate(b) fructose 6-phosphate → fructose 1,6-bisphosphate(c) glucose 6-phosphate → fructose 6-phosphate(d) glucose → glucose 1-phosphate13-13 What purpose does the phosphorylation of glucose to glucose 6-phosphate by the enzymehexokinase serve as the first step in glycolysis?(a) It helps drive the uptake of glucose from outside the cell.(b) It generates a high-energy phosphate bond.(c) It converts ATP to a more useful form.(d) It enables the glucose 6-phosphate to be recognized by phosphofructokinase, the next enzyme in the glycolytic pathway.13-14 A. How does the generation of ATP by oxidative phosphorylation differ from ATP generation by substrate-level phosphorylation?B. What catabolic process uses substrate-level phosphorylation, and how many ATP molecules are generated in this way in the reaction pathway?C. Where does oxidative phosphorylation take place, and what other processes are required for this to occur?13-15 Which of the following cells rely exclusively on glycolysis to supply them with ATP?(a) anaerobically growing yeast(b) aerobic bacteria(c) skeletal muscle cells(d) plant cells13-16 In anaerobic conditions, skeletal muscle produces _____________.(a) lactate and CO2(b) ethanol and CO2(c) lactate only(d) ethanol only13-17 Anaerobically growing yeast further metabolizes the pyruvate produced by glycolysis to CO2 and ethanol as part of a series of fermentation reactions.A. What other important reaction occurs during this fermentation step?B. Why is this reaction (i.e., the answer to part A) essential for the anaerobically growing cell?13-18 The first energy-generating steps in glycolysis begin when glyceraldehyde 3-phosphate undergoes an energetically favorable reaction in which it is simultaneously oxidized and phosphorylated by the enzyme glyceraldehyde 3-phosphate dehydrogenase to form 1,3-bisphosphoglycerate, with the accompanying conversion of NAD+ to NADH. In a second energetically favorable reaction catalyzed by a second enzyme, the 1,3-bisphosphoglycerate is then converted to 3-phosphoglycerate, with the accompanying conversion of ADP to ATP. Which of the following statements is true?(a) The reaction glyceraldehyde 3-phosphate → 1,3-bisphosphoglycerate should be inhibited when levels of NADH fall.(b) The δG° for the oxidation of the aldehyde group on glyceraldehyde 3-phosphate to form a carboxylic acid is more negative than the δG° for ATP hydrolysis.(c) The high-energy bond to the phosphate group in glyceraldehyde 3-phosphate contributes to driving the reaction forward.(d) The cysteine side chain on the enzyme is oxidized by NAD+.13-19 The simultaneous oxidation and phosphorylation of glyceraldehyde 3-phosphate forms a highly reactive covalent thioester bond between a cysteine side chain (reactive group –SH) on the enzyme (glyceraldehyde 3-phosphate dehydrogenase) and the oxidized intermediate (see arrow in Figure Q13-19A). If the enzyme had a serine (reactive group –OH) instead of a cysteine at this position, which could form only a much lower-energy bond to the oxidized substrate (see arrow in Figure Q13-19B), how might this new enzyme act?Figure