METABOLISM REVIEW QUESTIONS
ADS 520
REVIEW OF NUTRIENT METABOLISM
The following questions are intended to help students review
and study their lecture notes on nutrient metabolism. It is
assumed that digestion and absorption already have occurred.
Assume that the question refers to nonruminants unless
ruminants are specified. There will be some duplication of
questions; this will help students tie together ideas and
concepts that might otherwise seem unrelated because they were
presented in different lectures.
Information for these questions is in class notes and the
overviews of Chapters 2, 3, 24, 31, 33, 37, 38, and 39 in
Basic Medical Biochemistry by Marks, Marks, and Smith.
1. Following a meal the carbohydrates, protein, and
triglycerides are digested and the end-products absorbed
into the blood. The following questions are "overview"
in nature and do not require discussion of pathways.
a. For what main purposes is the absorbed glucose used?
(i.e., what is the fate of the absorbed glucose?)
List the primary organs/tissues involved for each
fate.
b. What is the fate of the absorbed amino acids?
(Including what happens to amino acids not used for
their primary purpose?)
c. What does the body do with absorbed fatty acids?
2. Can absorbed or mobilized fatty acids be converted to
glucose? Explain how this happens or why it cannot.
3. What is the primary site (organ/tissue) of triglyceride
synthesis in the
a. Human
b. Pig
c. Ruminant
When fat is synthesized in the liver, how is it transported
to the adipose tissue?
4. What are the two primary storage sites for glycogen?
5. Fat stored in adipose cells originates from two general
sources. What are they?
6. Which tissues are most dependent on glucose for their
energy?
One of these can convert and use an alternative fuel.
Which tissue? What fuel? Under what conditions?
The other tissue is fully dependent on glucose for a
fuel. Why?
7. Which hormone has the primary role in stimulating the
utilization of glucose following a meal? What does this
hormone do to stimulate the utilization of glucose?
Which tissues do not require this hormone to utilize
glucose? (See also Chap. 24 in Basic Medical Biochemistry.)
8. (a) Illustrate with abbreviated pathways how glucose is
converted into triglycerides.
(b) How does acetyl-CoA, the building block of fatty acids,
get from its site of synthesis to the site of fatty acid
synthesis. Illustrate your answer with abbreviated pathways.
9. Referring to the previous question. Compare fatty acid
synthesis in nonruminants and ruminants. Which
tissues/organs are involved? What is the primary source
of carbons for fatty acid synthesis? (i.e., What is in
the blood, and where did it come from, that the tissues
can use to synthesize fatty acids?) What is the cellular
location of acetyl-CoA synthesis?
10. It has been two hours since a meal was consumed. What
changes are occurring in the two hormones primarily
responsible for regulating blood glucose? What effects
does the hormone that is now increasing have to maintain
blood glucose concentrations? (See also Chap 24 overview
in Basic Medical Biochemistry.)
11. What other hormones (non-pancreatic) are involved in the
regulation of blood glucose concentrations? What are
their overall effects on metabolism?
12. In the postabsorptive state, in what two ways does the
liver produce glucose to be released into the blood?
13. What are the major sources of carbon for gluconeogenesis
in nonruminants? Which source is quantitatively the most
important?
What are the major sources of carbon for gluconeogenesis
in ruminants? Which source is quantitatively the most
important?
14. Can muscle glycogen become a source of blood glucose?
Explain why.
15. Compare the oxidation of fatty acids by the liver to that
of muscle and kidney during starvation.
16. Name the ketone bodies.
17. What metabolic adaptations occur during PROLONGED fasting
that help conserve muscle protein?
18. Explain how the body "handles" nitrogen from amino acids
utilized for gluconeogenesis or oxidized for energy.
19. Protein, such as muscle protein, is "dynamic." What does
this mean?
20. Why is the urea cycle physiologically important? What
would happen if we did not have a urea cycle? In which
organ/tissues is the urea cycle located?
21. Before amino acids can be metabolized, the amino group
must be removed. Name and illustrate two ways the amino
group can be removed from an amino acid.
22. (a) In which tissus/organs can transamination occur?
(b) In which tissus/organs can deamination occur?
23. Illustrate the glucose-alanine cycle and explain its role
in the metabolism of amino acids during starvation.
24. Which two amino acids are primarily involved in the
"transport" of amino groups to the liver and kidney?
What happens to each of these amino acids at its primary
site of metabolism during starvation?