BIOC 385 - Practice Exam 3 questions
n answers rated A+
What makes the ribonucleotide reductase reaction mechanism so unusual compared to other
enzyme-mediated mechanisms? - correct answer ✔✔Answer:
It is dependent on the formation of a free radical.
The twenty amino acids needed for protein synthesis can be categorized in animals as essential
or nonessential with regard to dietary sources. Answer the three questions below.
a) What is a characteristic of the biosynthetic pathways needed to generate essential amino
acids?
b) Why is arginine an essential amino acid even though it is generated by arginase in the urea
cycle?
c) Why is tyrosine a nonessential amino acid in animals since they don't have the shikimate
pathway? - correct answer ✔✔Answer:
a) metabolic pathways to synthesize essential amino acids require many enzymes; b) arginase
does not generate enough arginine in the urea cycle to support protein synthesis; c) tyrosine is
generated from phenylalanine, which is an essential amino acid in animals
Explain how regulatory cross-talk mechanisms within purine biosynthetic pathways ensure that
pools of ATP and GTP are balanced - correct answer ✔✔Answer:
ATP is required for the GMP synthetase reaction leading to GMP production, and GTP is
required for the adenylosuccinate synthetase reaction leading to AMP production.
What enzyme is present in genetically-modified organism (GMO) crops called Round-Up-Ready?
- correct answer ✔✔Answer:
CP4 EPSP synthase
, Ribose sugar in ribonucleosides and deoxyribonucleosides is derived from which pathway? -
correct answer ✔✔Answer:
Pentose Phosphate
Which statement below describes the structural basis for allosteric control of the catalytic
activity of the regulatory enzyme AMP-activated protein kinase (AMPK) by the metabolites AMP
and ATP? - correct answer ✔✔Answer:
AMP binding to AMPK facilitates formation of a salt bridge between R299-g and E364-a, which
stimulates AMPK catalytic activity in the alpha subunit; ATP binding does not form this salt
bridge.
What THREE biochemical mechanisms determine glucose-6P flux through metabolic pathways?
1. Ratio of NADPH to NAD+ in the cell under conditions of oxidative stress
2. Configuration of C-C bonds in glucose-6P (cis or trans)
3. Levels of acetyl-CoA in liver cells before breakfast
4. Bioavailability of glucose-6P (concentration) when used as a substrate
5. Activity level of enzymes (allosteric control) for which glucose-6P is a substrate
6. Bioavailability of enzymes (cell localization) for which glucose-6P is a substrate
7. Level of DNA and RNA synthesis under low atmospheric pressure - correct answer
✔✔Answer: 4, 5, 6
4. Bioavailability of glucose-6P (concentration) when used as a substrate
5. Activity level of enzymes (allosteric control) for which glucose-6P is a substrate
6. Bioavailability of enzymes (cell localization) for which glucose-6P is a substrate
What biochemical marker differentiates insulin-sensitive and insulin-resistant muscle cells? -
correct answer ✔✔Answer:
n answers rated A+
What makes the ribonucleotide reductase reaction mechanism so unusual compared to other
enzyme-mediated mechanisms? - correct answer ✔✔Answer:
It is dependent on the formation of a free radical.
The twenty amino acids needed for protein synthesis can be categorized in animals as essential
or nonessential with regard to dietary sources. Answer the three questions below.
a) What is a characteristic of the biosynthetic pathways needed to generate essential amino
acids?
b) Why is arginine an essential amino acid even though it is generated by arginase in the urea
cycle?
c) Why is tyrosine a nonessential amino acid in animals since they don't have the shikimate
pathway? - correct answer ✔✔Answer:
a) metabolic pathways to synthesize essential amino acids require many enzymes; b) arginase
does not generate enough arginine in the urea cycle to support protein synthesis; c) tyrosine is
generated from phenylalanine, which is an essential amino acid in animals
Explain how regulatory cross-talk mechanisms within purine biosynthetic pathways ensure that
pools of ATP and GTP are balanced - correct answer ✔✔Answer:
ATP is required for the GMP synthetase reaction leading to GMP production, and GTP is
required for the adenylosuccinate synthetase reaction leading to AMP production.
What enzyme is present in genetically-modified organism (GMO) crops called Round-Up-Ready?
- correct answer ✔✔Answer:
CP4 EPSP synthase
, Ribose sugar in ribonucleosides and deoxyribonucleosides is derived from which pathway? -
correct answer ✔✔Answer:
Pentose Phosphate
Which statement below describes the structural basis for allosteric control of the catalytic
activity of the regulatory enzyme AMP-activated protein kinase (AMPK) by the metabolites AMP
and ATP? - correct answer ✔✔Answer:
AMP binding to AMPK facilitates formation of a salt bridge between R299-g and E364-a, which
stimulates AMPK catalytic activity in the alpha subunit; ATP binding does not form this salt
bridge.
What THREE biochemical mechanisms determine glucose-6P flux through metabolic pathways?
1. Ratio of NADPH to NAD+ in the cell under conditions of oxidative stress
2. Configuration of C-C bonds in glucose-6P (cis or trans)
3. Levels of acetyl-CoA in liver cells before breakfast
4. Bioavailability of glucose-6P (concentration) when used as a substrate
5. Activity level of enzymes (allosteric control) for which glucose-6P is a substrate
6. Bioavailability of enzymes (cell localization) for which glucose-6P is a substrate
7. Level of DNA and RNA synthesis under low atmospheric pressure - correct answer
✔✔Answer: 4, 5, 6
4. Bioavailability of glucose-6P (concentration) when used as a substrate
5. Activity level of enzymes (allosteric control) for which glucose-6P is a substrate
6. Bioavailability of enzymes (cell localization) for which glucose-6P is a substrate
What biochemical marker differentiates insulin-sensitive and insulin-resistant muscle cells? -
correct answer ✔✔Answer:
