Chapter 3
1. What are the end products of glycolysis under aerobic and
anaerobic conditions?
2. What are the major substrates entering the Krebs cycle, and
what are the products formed?
3. Why does the Krebs cycle operate only under aerobic
conditions even though it doesn’t use molecular oxygen in any
of its reactions?
4. Identify the molecules that enter the oxidative phosphorylation
pathway and the products that form.
5. Where are the enzymes for the Krebs cycle located? The
enzymes for oxidative phosphorylation? The enzymes for
6. How many molecules of ATP can form from the breakdown
of one molecule of glucose under aerobic conditions? Under
anaerobic conditions?
7. Describe the origin and effects of reactive oxygen molecules.
8. What molecules can be used to synthesize glucose?
9. Why can’t fatty acids be used to synthesize glucose?
10. Describe the pathways used to catabolize fatty acids to carbon
11. Why is it more effi cient to store fuel as fat than as glycogen?
12. Describe the pathway by which glucose is converted into fat.
13. Describe the two processes by which amino groups are
removed from amino acids.
14. What can keto acids be converted into?
15. What is the source of the nitrogen atoms in urea, and in what
organ is urea synthesized?
16. Why is water considered an essential nutrient whereas glucose
is not?
17. What is the consequence of ingesting large quantities of water-
soluble vitamins? Fat-soluble vitamins?
Chapter 3 Test Questions
(Answers appear in Appendix A.)
1. Which cell structure contains the enzymes required for
oxidative phosphorylation?
a. mitochondria
b. smooth endoplasmic reticulum
c. rough endoplasmic reticulum
d. endosomes
e. peroxisomes
2. Which sequence regarding protein synthesis is correct?
a. translation
mRNA synthesis
b. transcription
splicing of primary RNA transcript
translocation of mRNA
c. splicing of introns
mRNA synthesis
d. transcription
mRNA production
e. tRNA enters nucleus
transcription begins
moves to cytoplasm
protein synthesis begins
3. Which is
regarding ligand:protein binding reactions?
a. Allosteric modulation of the protein’s binding site occurs
directly at the binding site itself.
b. Allosteric modulation can alter the affi nity of the protein for
the ligand.
c. Phosphorylation of the protein is an example of covalent
d. If two ligands can bind to the binding site of the protein,
competition for binding will occur.
e. Binding reactions are either electrical or hydrophobic in
4. According to the law of mass action, in the following reaction:
+ H
a. Increasing the concentration of carbon dioxide will slow
down the forward (left-to-right) reaction.
b. Increasing the concentration of carbonic acid will accelerate
the rate of the reverse (right-to-left) reaction.
c. Increasing the concentration of carbon dioxide will speed up
the reverse reaction.
d. Decreasing the concentration of carbonic acid will slow
down the forward reaction.
e. No enzyme is required for either the forward or reverse
5. Which of the following can be converted to glucose by
gluconeogenesis in the liver?
a. fatty acid
d. ATP
b. triglyceride
e. glycogen
c. glycerol
6. Which of the following is true?
a. Triglycerides have the least energy content per gram of the
three major fuel sources in the body.
b. Fat catabolism generates new triglycerides for storage in
adipose tissue.
c. By mass, the total body content of carbohydrates exceeds
that of total triglycerides.
d. Catabolism of fatty acids occurs in two-carbon steps.
e. Triglycerides are the major lipids found in plasma
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