Download Sample exam 1

Chemistry 256
Sample mid-quarter exam 1 (Lipids, amino acid metabolism, membrane
transport)
1. The enzyme that acts on ketone bodies to convert them into a form that can be broken
down into acetyl CoA is present in brain, but not in liver. What type of reaction is
catalyzed by this enzyme?
a. Oxidation.
b. Dehydration.
c. Transfer of CoA.
d. Hydroxylation.
e. Decarboxylation.
2. Erucic acid is 22:1, Δ13. Which one of the following choices correctly names the
position(s) of the double bond(s) using the ω numbering system?
a. ω-6
b. ω-9
c. ω-12
d. ω-6,9
e. ω-6,9,12
3. Which one of the following choices is not used to produce acetyl CoA in humans?
a. a 15:0 fatty acid.
b. Palmitate.
c. Acetoacetate.
d. Cholesterol.
e. Actually, all of the choices can be used to produce acetyl CoA in humans.
4. The pyrrole rings of heme each contain nitrogen atoms. What molecule provides that
nitrogen during the synthesis of heme in liver cells?
a. Carbamoyl phosphate.
b. Cobalamin.
c. Glycine.
d. Succinyl CoA.
e. Valine.
Essay questions: Answer these in paragraph form or drawings, as requested.
5. How many ATP molecules will the following fatty acids make? Give a reasonably
detailed accounting to justify your answers.
a. 16:0
b. 20:4
6. Gastric juice has a pH of 1.5 and is produced by pumping HCl from blood plasma (pH
7.4) into the stomach.
a. Calculate the free energy required to concentrate the H+ in 1 L of gastric juice at 37°C.
For this problem, you can ignore the effects of the transmembrane electrical potential
difference.
b. At these physiological conditions, ATP hydrolysis has a free energy change of – 58
kJ/mol. How many moles of ATP must be hydrolyzed to generate the gastric juice in
part a?
7. Even though acetate units, such as those obtained from fatty acid oxidation, cannot be
used for net synthesis of carbohydrates in animals, radioactive carbon from 14C-labeled
acetate can be found in newly synthesized glucose (for example, in liver glycogen) in
animal tracer studies. Explain which carbons of glucose you would expect to be the first
to be labeled by the 14C-labeled acetate, and what pathway those carbons took to end up
on glucose.
8. Adrenal androgens accumulate in someone with a 21α-hydroxylase deficiency.
Adrenal androgens are made in the adrenal cortex, the outer layer of the adrenal gland.
The cortex will grow as it is asked to produce more hormones. Given the mechanism of
cholesterol modification below and the definition of androgens (which includes all of the
“-ones” in the diagram except estrone and aldosterone), assess the following statements
as “true” or “false” and justify each answer.
a. Synthesis of androgens does NOT require 21α-hydroxylase.
b. Synthesis of cortisol DOES require 21α-hydroxylase.
c. The adrenal cortex can become enlarged when there is a deficiency of 21-hydroxylase.