C483 Summer 2015
Exam 4
Name ______________________________________________
1. 20 pts Fill in the blanks (2 points each)
A. _____________________ carry dietary fats and cholesterol from the liver to the tissues and
_____________________ carry then back from tissue to the liver.
B. Fatty acids are activated for breakdown by attachment to _________________ at the expense of ___
ATP equivalents.
C. Odd-carbon fatty acids produce acetyl CoA and _____________ in their final cleavage. This
compound must be converted to the four carbon citric acid cycle intermediate ______________
for full oxidation.
D. _____________ can be transported across the mitochondrial membrane to “carry” acetyl-CoA
into the cytosol to enter synthesis of fatty acids.
E. ____________ can be transaminated to make oxaloacetate.
F. __________________ is the metabolite formed in the catabolism of glutamate.
G. Phe is a/an _______________ amino acid because it cannot be biosynthesized in humans.
H. The urea cycle incorporates a nitrogen atom from carbamoyl phosphate and a nitrogen atom
from the amino acid _______________ into urea.
I. In the fed state, the liver catabolizes excess _______________ and _______________ to make acetyl
CoA to be stored as fats.
J. _______________ tissue responds to both epinephrine and glucagon to release stored carbohydrates,
but ______________ tissue only responds to epinephrine.
2. 10 points True or false (1 point each)
A. ______________ The carnitine transporter is the major regulation point of fatty acid synthesis.
B. ______________ Fatty acid synthesis and fatty acid degradation are different in their cellular location
and in redox cofactors used.
C. ______________The amount of ATP obtained from degradation of a 16-carbon fatty acid is
approximately equal to the amount of ATP required to synthesize a 16-carbon fatty acid from acetyl CoA.
D. ______________ In humans, the role of glutamine synthase is primarily as a transamination enzyme.
E. ______________ Succinate is used to make the backbone of arginine and histidine.
F. ______________ Ketogenic amino acids are broken down into acetyl-CoA and oxaloacetate.
G. ______________ One pathway for glycine degradation involves donation of the carbon atom to biotin,
which serves as a one-carbon transfer cofactor.
H. ______________ The Cori cycle allows lactate built up in muscles during anaerobic conditions to be
remade into alanine in the liver, for export back to the muscles.
I. ______________ Through signal transduction, insulin activates phosphatases, which activate glycogen
synthase and deactivate glycogen phosphorylase to control glycogen metabolism.
J. ______________ AMPK activates catabolic pathways in response to a low [AMP]/[ATP] ratio.
3. (20pts) Short answer (5 points each)
A. Draw the intermediates and final product of the degradation of this four carbon fatty acid:
B. How many ATP are consumed in the production of carbamoyl phosphate from carbonate?
Outline the intermediates necessary to produce carbamoyl phosphate.
C. Draw a rough outline of the alanine/glucose cycle, including tissues involved and compounds
transported though the blood in the correct direction. What is the purpose of the alanine/glucose
cycle?
D. How many molecules of ATP can be NET generated from complete oxidation via the -oxidation
pathway of an 18-carbon saturated fatty acid? Give a full accounting of how you got this number.
(Remember the activation of the fatty acid.)
Problems (10pts each)
4. Provide an enzyme-mediated mechanism for this transamination. You do not need to write every step
of Schiff base formation. (Which cofactor do you need?)
5. Fill in the boxes with a name OR structure of the appropriate compounds in lipid biosynthesis
6. All of the nonessential amino acids, with the exception of tyrosine, can be synthesized from four
metabolites: pyruvate, oxaloacetate, -ketoglutarate, and 3-phosphoglycerate. Fill in the box with the
FULL NAME of each amino acidto match the precursor metabolite. (HINT: Choices are A, C, D, E, G,
N, P, Q, R, S)
pyruvate
oxaloacetate
-ketoglutarate
3-phosphoglycerate
7. Degradation of isoleucine involves a series of six steps. The first step is common to all amino acid
degradation. The second step is analogous to pyruvate dehydrogenase. The last four steps are analogous
to -oxidation. Draw all intermediates and the final products of isoleucine degradation.
Based on the products you drew, is isoleucine glucogenic, ketogenic, or both? Explain.
8. Hexokinase exhibits normal Michaelis-Menton kinetics, but its isozyme, glucokinase does not. Why
does the sigmoidal behavior of glucokinase, the liver isozyme of hexokinase, help the liver adjust its
metabolic activities to the amount of available glucose? Draw a [S] vs. velocity diagram for glucokinase
and hexokinase to help in your answer.
Why might a small molecule allosteric activator of glucokinase be effective in treating diabetes?
9. (10pts Case study) An infant seemed normal at birth but was diagnosed at the age of three months with
a pyruvate carboxylase deficiency. She suffered from lactic acidosis and ketosis. She had poor muscle
tone and was experiencing seizures.
A. Which metabolites would be elevated in this patient? Which metabolites would be deficient?
B. Why does the patient suffer from ketosis?
C. The poor muscle tone results from a lack of the neurotransmitter GABA. Why is there a decreased
level of GABA?
pKa values for amino acids:
carboxy terminus: 3.5
amino terminus: 9.0
Sidechains:
Asp 3.9
Glu 4.1
Cys 8.4
Tyr 10.5
Arg 12.5
His 6.0
Lys 10.5
[𝑋]𝑓𝑖𝑛𝑎𝑙
G = RT ln[𝑋]𝑖𝑛𝑖𝑡𝑖𝑎𝑙 + ZF
R = 8.314 J/ mol . K
G = -nFEo’
F = 96,485 J/V . mol
pH = pKa + log [A-]/[HA]
v = (Vmax[S])/KM + [S]