CHAPTER 13 HOW CELLS OBTAIN ENERGY FROM FOOD 2009 Garland Science Publishing The Breakdown and Utilization of Sugars and Fats 13 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 phosphorylation 13 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 oxidized 13 4 The final metabolite produced by glycolysis is a acetyl CoA b pyruvate c 3 phosphoglycerate d glyceraldehyde 3 phosphate 13 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 NADH 13 6 Which of the following steps or processes in aerobic respiration include the production of carbon dioxide a breakdown of glycogen b glycolysis c conversion of pyruvate to acetyl CoA d oxidative phosphorylation 13 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 3phosphate Which enzyme catalyzes this reaction a aldolase b phosphoglucose isomerase c enolase d triose phosphate isomerase 13 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 diet 13 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 9 1 2 3 4 5 6 7 glycolysis citric acid cycle conversion of pyruvate to activated acetyl groups oxidation of fatty acids to acetyl CoA glycogen breakdown release of fatty acids from triacylglycerols oxidative phosphorylation 13 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 breakdown 13 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 phosphate 13 13 What purpose does the phosphorylation of glucose to glucose 6 phosphate by the enzyme hexokinase 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 B C How does the generation of ATP by oxidative phosphorylation differ from ATP generation by substrate level phosphorylation What catabolic process uses substrate level phosphorylation and how many ATP molecules are generated in this way in the reaction pathway 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 cells 13 16 In anaerobic conditions skeletal muscle produces a lactate and CO2 b ethanol and CO2 c lactate only d ethanol only 13 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 3bisphosphoglycerate with the accompanying conversion of NAD to NADH In a second energetically favorable reaction catalyzed by a second enzyme the 1 3bisphosphoglycerate 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 G for the oxidation of the aldehyde group on glyceraldehyde 3 phosphate to form a carboxylic acid is more negative than the G 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 Q13 19 a b c d It would oxidize the substrate and phosphorylate it without releasing it It would oxidize the substrate but not release it It would phosphorylate the substrate on the 2 position instead of the 1 position It would behave just like the normal enzyme 13 20 In the absence of