Practice Questions - Week 11 - Foundations of Metabolism SAQ's Flashcards
What are the stages for extracting energy from food?
Answer:
There are three stages:
1) Large food molecules are broken down into smaller units, such as amino acids,
carbohydrates, and fatty acids.
2) The small units are further broken down to a subset of small molecules that are
critical to metabolism, such as acetyl CoA.
3) ATP is produced by oxidation of the acetyl units
If many compounds are common to both anabolic and catabolic paths, how can metabolism be controlled?
Answer:
The enzymes and their activities can be controlled by the energy charge in the cell. The
biosynthetic and catabolic paths are different from each other and may even be located in
different compartments in the cell. Thus, the two opposing processes can be controlled
independently.
Briefly describe the possible metabolic fates of pyruvate produced by glycolysis in humans, and explain the circumstances that favour each
Answer:
Under aerobic conditions, pyruvate is oxidized to acetyl-CoA and passes through the TCA
cycle. Under anaerobic conditions, pyruvate is reduced to lactate to recycle NADH to NAD +,
allowing the continuation of glycolysis.
Define “fermentation” and explain, by describing relevant reactions, how it differs from
glycolysis. Your explanation should include a discussion of the role of NADH in the
reaction(s).
Answer:
Fermentation is the operation of the glycolytic pathway under anaerobic conditions. Under aerobic conditions, the pyruvate produced by glycolysis is oxidized to acetyl-CoA, which passes through the TCA cycle. NADH produced in the oxidations passes electrons to O 2,
and is thus recycled to NAD + allowing the continuation of the glycolytic reactions. When no O2 is available to reoxidize the NADH produced by the glyceraldehyde 3-phosphate
dehydrogenase reaction, electrons from NADH must be passed to one of the products of glycolysis, such as pyruvate or acetaldehyde, forming lactate or ethanol
What are the regulatory implications for the cell with regard to ATP and AMP, given that the former are generally high, and the latter are low?
Answer:
Normally, [ATP] is 5-10 mM, while [AMP] is < 0.1 mM, thus AMP is a much more sensitive indicator of a cell’s energetic state. Small changes in ATP concentration are amplified into large changes in AMP concentration, hence many regulatory processes hinge on changes in the concentration of AMP.
Describe four major principles of metabolic regulation that have selectively evolved
throughout evolution.
Answer:
1. Maximize the efficiency of fuel utilization by preventing the simultaneous operation of opposing pathways (i.e., futile cycles).
2. Partition metabolites appropriately between alternative pathways.
3. Draw on the fuel best suited for the immediate needs of the organism.
4. Shut down biosynthetic pathways when their products accumulate
List four (4) activated carriers in metabolism, and give the vitamins that are the precursors of these carriers.
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) niacin
c) phototrophs
d) ATP
e) CO 2
f) coenzyme A
g) vitamins
h) amphibolic
i) ADP
j) NADPH
k) chemotrophs
l) FAD
i. ________ These organisms use energy from sunlight and convert it to chemical energy
c
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) niacin
c) phototrophs
d) ATP
e) CO 2
f) coenzyme A
g) vitamins
h) amphibolic
i) ADP
j) NADPH
k) chemotrophs
l) FAD
ii. ___________ These organisms obtain chemical energy from oxidation of foodstuff
k
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) niacin
c) phototrophs
d) ATP
e) CO 2
f) coenzyme A
g) vitamins
h) amphibolic
i) ADP
j) NADPH
k) chemotrophs
l) FAD
iii. ___________ Pathways that can be either anabolic or catabolic depending on the energy
conditions of the cell.
h
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) niacin
c) phototrophs
d) ATP
e) CO 2
f) coenzyme A
g) vitamins
h) amphibolic
i) ADP
j) NADPH
k) chemotrophs
l) FAD
iv. __________ In aerobic organisms, this is the ultimate acceptor of electrons.
a
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) niacin
c) phototrophs
d) ATP
e) CO 2
f) coenzyme A
g) vitamins
h) amphibolic
i) ADP
j) NADPH
k) chemotrophs
l) FAD
v. ________ In aerobic metabolism, this is the product of oxidation of carbon containing
fuels.
e
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) niacin
c) phototrophs
d) ATP
e) CO 2
f) coenzyme A
g) vitamins
h) amphibolic
i) ADP
j) NADPH
k) chemotrophs
l) FAD
vi. ________ This vitamin is required to manufacture the electron carrier, NADH
b
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) niacin
c) phototrophs
d) ATP
e) CO 2
f) coenzyme A
g) vitamins
h) amphibolic
i) ADP
j) NADPH
k) chemotrophs
l) FAD
vii. ________ This substance is the electron donor in most reductive biosyntheses.
j
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) niacin
c) phototrophs
d) ATP
e) CO 2
f) coenzyme A
g) vitamins
h) amphibolic
i) ADP
j) NADPH
k) chemotrophs
l) FAD
viii. _________ This compound serves as an acyl carrier in metabolism
f
