Biochemistry II (Chem 4420) Name______________________
Exam II May 14, 1999
- Uniformly labelled (every possible H was replaced with 3H) 3H-Palmitic acid (16:0) was
oxidized in liver mitochondria under aerobic conditions. The amount of radioactivity in the
isolated product (acetic acid, which was derived from acetyl CoA) contained only a small
percentage of the original radioactivity.
- (10 points) Give the reactions involved in fatty acid metabolism to yield acetyl-CoA.
- (5 points) Where did the rest of the radioactivity go? What molecule(s) would you
expect to be labelled?
- Dr. Science needed to make 14C labelled palmitate. Dr. Science used fully functional
acetylCoA carboxylase and fatty acid synthase; and then carefully added all of the cofactors,
NADPH, 14CO2 and unlabelled acetyl CoA. Unfortunately the product, palmitic acid, had no
- (10 points) Give all of the reactions that are involved in the synthesis of palmitate.
- (5 points) Explain the above results.
- (5 points) What combination of labelled and unlabelled substrates and enzymes should
be used in order to have the product (palmitic acid) labelled only on carbon-16.
(Recall that fatty acids are numbered starting from the carboxylic acid.)
- Elephant seals are sea mammals that obtain all of their water via metabolism. Their diets
consist mainly of squid, and delicious morsels have a very high fat content. In addition to
using stored fat for insulation, they also use fat stores as a source of water.
- ( 10 points) What are the specific reactions that produce water
- (10 points) How many moles of water are generated per mole of palmitate? (Your
reasoning is the important part of this answer. Please demonstrate how you determined
- (10 points) How many liters of water can be obtained from -oxidation of 5 lbs of
palmitic acid? (The density of water is 1 g/mL.)
Part II: take home and complete. Please bring your completed exam to class on Monday,
May 17th at 10:10. Using a word processor will brighten the day of your instructor!
- If there are no carbohydrates in the diet, mammals use fatty acids as a source of fuel. A
potentially severe side-effect of this type of diet is the accumulation of ketone bodies. (The
brain can not use fatty acids as a source of fuel, it must have glucose or ketone bodies as
- ( 5 points) Why is there an increase in the blood levels of ketone bodies? Why are high
levels of ketones dangerous?
- (5 points) Why can't the liver use ketone bodies for energy?
- (10 points) Explain (in detail) why fatty acids with an even number of carbons can not be
used to synthesize glucose. Also explain why fatty acids with an odd number of carbons can
be used to make glucose. Be sure to include relevant biochemical reactions to support your
- Fat metabolism (breakdown and synthesis) is carefully controlled so that the two opposing
processes do not operate simultaneously.
- (10 points) Discuss the control mechanisms of -oxidation and fatty acid synthesis that
are responsible for this regulation.
- ( 5 points) One of the enzymes in fat metabolism is regulated via phosphorylation of a
serine residue. If this serine residue is replaced with an alanine in a mutant protein,
what effect would this mutation have on fat metabolism?