Download Question 2 (20 points)

Bio302 Biochemistry II
Final Examination June 4, 2004
Question 1. (10 points)
Compare ATP, NADH and NADPH with respect to their functions in metabolism.
Question 2. (20 points)
A (10 points) Name the seven-transmembrane helix proteins that you know. Can you
make any suggestions for relations between these proteins? What are the common
features for this group?
B (10 points). Some oncogenes are variants of G-proteins (like v-ras). Describe what
could make a regulatory G-protein an oncogene.
Question 3. (5 points)
Fill in the blanks:
Phosphofructokinase is the most important control enzyme in glycolytic pathway of
mammals. It is stimulated by ............................................which .........................its
affinity for fructose 6-phosphate. One other regulator of phosphofructokinase is
................................................ . Increasing concentration of
......................................................... inhibits phosphofructokinase.
Question 4. (5 points)
You are interested in studying citric acid cycle enzymes. You are given a calf liver as
the starting tissue. Which subcellular fractions would you separate to purify your
enzymes?
a) cell membrane
b) nucleus
c) endoplasmic reticulum
d) mitochondria
e) cytoplasma
Question 5. (10 points).
Under anaerobic conditions gluconeogenesis is unlikely to occur. Why? Discuss
briefly.
Question 6. (10 points)
A. (5 points)What are the two metabolic products formed from pyruvate in yeast
which turns grape juice into champagne?
B. (5 points) Name the two enzymes involved in this reaction.
Question 7. (10 points)
What is the purpose of hexokinase variants in different cells?
Liver has a variant of hexokinase, known also as glucokinase (or hexokinase IV),
which shows sigmoidal kinetics in contrast to other hexokinases which obey
Michaelis-Menten kinetics. Explain the purpose of this variation.
In fact, glucokinase is a monomeric protein which shows cooperative behaviour.
Suggest how this cooperativity can be achieved.
Question 8 (10 points).
Why is the pentose phosphate pathway more active in cells that are dividing than in
cells that are not?
Question 9 (10 points)
What is phosphorolysis? Explain briefly why it would be the preferred reaction in
glycogen breakdown?
Question 10 (10 points)
Outline the effects of insulin on glycogen synthase . How does this effect achived?