chapter 13

When food is plentiful, animals can store glucose as what? 1. glucose 6-phosphate 2. glycogen 3. starch 4. glycogen or starch 5. acetyl CoA

2. glycogen

How do enzymes maximize the energy harvested from the oxidation of food molecules? 1. They allow oxidation reactions to take place without an input of activation energy. 2. They allow the stepwise oxidation of food molecules, which releases energy in small amounts. 3. They guarantee that each reaction involved in the oxidation of food molecules proceeds in just one direction. 4. They allow a larger amount of energy to be released from food molecules such as glucose. 5. They allow what would otherwise be an energetically unfavorable oxidation reaction to occur.

2. they allow the stepwise oxidation of food molecules, which release energy in small amounts

In the electron transport chain, the oxygen atoms in O2 become part of which of the following molecules? 1. glucose (C6H12O6) 2. NADH 3. ATP 4. H2O 5. CO2

4. H2O

Although the citric acid cycle itself does not use O2, it requires a functioning electron transport chain (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle? 1. FADH 2. 2ATP 3. ADP 4. NAD+ 5. NADH

4. NAD+

The NADH generated during glycolysis and the citric acid cycle feeds its high-energy electrons to which of the following? 1. ADP 2. the citric acid cycle 3. FAD 4. the electron transport chain 5. H2O

4. the electron transport chain

Most of the energy released by oxidizing glucose is saved in the high-energy bonds of what molecules? 1. H2O and CO2 2. O2 3. ADP and other activated carriers 4. GDP and other activated carriers 5. ATP and other activated carriers

5. ATP and other activated carriers

What happens to the energy captured during glycolysis and the citric acid cycle by the activated carriers NADH and FADH2 1. It is passed to ADP to form ATP. 2. It is used to drive biosynthetic reactions. 3. It is passed to an electron transport chain that uses it to oxidize food molecules. 4. It is passed to an electron transport chain that uses it to produce oxygen. 5. It is passed to an electron transport chain that uses it to generate a proton gradient across the inner mitochondrial membrane.

5. it is passed to an electron transport chain that uses it to generate a proton gradient across the inner mitochondrial membrane

Your friends are on a low-fat, high-carbohydrate diet, which they claim will prevent fat accumulation within their bodies. They eat tons of pasta and bread without worrying about calorie count. What can you correctly say to your friends about their potential to accumulate lipids on their low-fat diet? A. They will accumulate fats because cells have no way of storing carbohydrates. B. They will accumulate fats because cells can convert glycolytic metabolites into lipids. C. They will not accumulate fats because carbohydrates have less energy per gram than fats. D. They will not accumulate fats because cells have no way of storing fats.

B.

The ethanol in wine and beer is produced from metabolic reactions carried out by the yeast Saccharomyces cerevisiae. Since it is of great commercial value, researchers have studied factors that influence ethanol production. To maximize ethanol yield, which environmental factor should be limiting? A. sunlight B. glucose C. oxygen D. carbon dioxide

C. oxygen

Which molecules are required for the citric acid cycle to fully oxidize the carbons donated by acetyl CoA? Choose one or more: GTP ATP O2 oxaloacetate NAD+ GDP

O2, oxaloacetate, NAD+, and GDP

The chemistry of many metabolic reactions was deciphered using molecules labeled with radioactive isotopes. If acetyl CoA labeled with radioactive 14C in both carbon positions were fed into the citric acid cycle, where would the radioactivity be after one turn of the cycle? a. in oxaloacetate b. in oxaloacetate and in CO2 c. in CO2 d. in acetyl CoA e. in citrate

a. in oxaloacetate

In cells that cannot carry out fermentation, which products derived from glycolysis will accumulate under anaerobic conditions? a. lactate and NAD+ b. glucose and NADH c. glucose 6-phosphate and NADH d. pyruvate and NADH e. pyruvate and NAD+

d. pyruvate and NADH Without oxygen, NADH would be unable to donate its electrons to the electron transport chain and the pyruvate produced by glycolysis would not be removed by fermentation.

If acetyl CoA labeled with radioactive 14C in both carbon positions were fed into the citric acid cycle, where would the radioactivity be after two turns of the cycle? a. in CO2 b. in oxaloacetate c. in malate d. in acetyl CoA e. in oxaloacetate and in CO2

e. in oxaloacetate and in CO2

You are packing for a hiking trip during which you'll be burning a lot of calories with physical activity. You want to pack as efficiently as possible since you need to carry a tent and all your food. You can get the most calories out of 5kg of food if it is in the form of

fat The oxidation of a gram of fat releases about twice as much energy (9 calories versus 4 calories) as the oxidation of a gram of glycogen. Fats contain mostly highly reduced C-H bonds, whereas carbohydrates are already partially oxidized.

Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ needed for glycolysis? 1. citric acid cycle 2. breakdown of amino acids 3. breakdown of fats 4. formation of acetyl CoA 5. fermentation

5. fermentation