BIO 250 Exam 2 V1 | BIO 250 Microbiology | Actual
Q&A with Rationale (BIO250 Exam 2) |
StraighterLine
1. Which of the following factors are known to influence the rate of enzymatic reactions in a
microbial cell? (Select all that apply)
A. Temperature
B. pH levels
C. Atmospheric nitrogen concentration
D. Substrate concentration
E. Presence of inhibitors
F. The color of the growth medium
Correct Answer: A, B, D, E
Explanation: Enzymatic activity is highly sensitive to physical and chemical environments.
Temperature and pH can denature the protein structure, while substrate concentration
determines how often active sites are occupied. Inhibitors specifically block or alter the
active site to prevent catalysis from occurring.
2. During DNA replication, which enzyme is responsible for unwinding the DNA double helix
at the replication fork?
A. DNA Polymerase III
,B. DNA Helicase
C. DNA Ligase
D. Primase
Correct Answer: B
Explanation: DNA Helicase breaks the hydrogen bonds between the complementary
nitrogenous bases to separate the strands. This separation creates the replication fork
necessary for other enzymes to access the template strands. Without helicase, the double
helix would remain closed and replication could not proceed.
3. Which of the following best describes the ‘Log Phase’ of a bacterial growth curve?
A. Cells are adjusting to the new environment and synthesizing enzymes.
B. Cells are dividing at a maximal and constant rate.
C. The rate of cell death equals the rate of new cell formation.
D. Nutrients are exhausted and toxic waste products have accumulated.
Correct Answer: B
Explanation: The log phase, or exponential phase, is characterized by a constant
generation time where the population doubles at regular intervals. This is the stage where
bacteria are most metabolically active and susceptible to antibiotics like penicillin. It
follows the lag phase and precedes the stationary phase.
, 4. What is the primary purpose of fermentation in anaerobic microbes?
A. To produce large amounts of ATP via oxidative phosphorylation.
B. To generate oxygen for the cell.
C. To regenerate NAD+ from NADH so glycolysis can continue.
D. To synthesize complex carbohydrates from carbon dioxide.
Correct Answer: C
Explanation: Fermentation does not produce additional ATP beyond what is made in
glycolysis. Its essential role is to oxidize NADH back into NAD+ by using an organic
molecule as the final electron acceptor. This ensures a steady supply of NAD+ is available
for the glyceraldehyde-3-phosphate dehydrogenase reaction in glycolysis.
5. A mutation that results in the substitution of one amino acid for another in a protein is
called a:
A. Silent mutation
B. Missense mutation
C. Nonsense mutation
D. Frameshift mutation
Correct Answer: B
Explanation: A missense mutation occurs when a single nucleotide change results in a
codon that codes for a different amino acid. This can lead to a range of effects, from neutral
Q&A with Rationale (BIO250 Exam 2) |
StraighterLine
1. Which of the following factors are known to influence the rate of enzymatic reactions in a
microbial cell? (Select all that apply)
A. Temperature
B. pH levels
C. Atmospheric nitrogen concentration
D. Substrate concentration
E. Presence of inhibitors
F. The color of the growth medium
Correct Answer: A, B, D, E
Explanation: Enzymatic activity is highly sensitive to physical and chemical environments.
Temperature and pH can denature the protein structure, while substrate concentration
determines how often active sites are occupied. Inhibitors specifically block or alter the
active site to prevent catalysis from occurring.
2. During DNA replication, which enzyme is responsible for unwinding the DNA double helix
at the replication fork?
A. DNA Polymerase III
,B. DNA Helicase
C. DNA Ligase
D. Primase
Correct Answer: B
Explanation: DNA Helicase breaks the hydrogen bonds between the complementary
nitrogenous bases to separate the strands. This separation creates the replication fork
necessary for other enzymes to access the template strands. Without helicase, the double
helix would remain closed and replication could not proceed.
3. Which of the following best describes the ‘Log Phase’ of a bacterial growth curve?
A. Cells are adjusting to the new environment and synthesizing enzymes.
B. Cells are dividing at a maximal and constant rate.
C. The rate of cell death equals the rate of new cell formation.
D. Nutrients are exhausted and toxic waste products have accumulated.
Correct Answer: B
Explanation: The log phase, or exponential phase, is characterized by a constant
generation time where the population doubles at regular intervals. This is the stage where
bacteria are most metabolically active and susceptible to antibiotics like penicillin. It
follows the lag phase and precedes the stationary phase.
, 4. What is the primary purpose of fermentation in anaerobic microbes?
A. To produce large amounts of ATP via oxidative phosphorylation.
B. To generate oxygen for the cell.
C. To regenerate NAD+ from NADH so glycolysis can continue.
D. To synthesize complex carbohydrates from carbon dioxide.
Correct Answer: C
Explanation: Fermentation does not produce additional ATP beyond what is made in
glycolysis. Its essential role is to oxidize NADH back into NAD+ by using an organic
molecule as the final electron acceptor. This ensures a steady supply of NAD+ is available
for the glyceraldehyde-3-phosphate dehydrogenase reaction in glycolysis.
5. A mutation that results in the substitution of one amino acid for another in a protein is
called a:
A. Silent mutation
B. Missense mutation
C. Nonsense mutation
D. Frameshift mutation
Correct Answer: B
Explanation: A missense mutation occurs when a single nucleotide change results in a
codon that codes for a different amino acid. This can lead to a range of effects, from neutral
