BIO 250 Exam 2 V2 | BIO 250 Microbiology
| Actual Q&A with Rationale (BIO250 Exam
2) | StraighterLine
1. Which of the following describes the primary function of enzymes in microbial
metabolism?
A. To increase the activation energy of a chemical reaction.
B. To lower the activation energy required for a chemical reaction to occur.
C. To serve as a source of energy for endergonic reactions.
D. To permanently bind to substrates and become part of the product.
Answer: B
Rationale: Enzymes act as biological catalysts that significantly speed up the rate of
chemical reactions by lowering the activation energy barrier. They are typically composed
of proteins and are highly specific to their substrates due to the unique shape of their active
sites. Furthermore, enzymes are not consumed or permanently altered during the reactions
they catalyze, allowing them to be reused multiple times.
2. Which of the following elements are considered macronutrients required by all
microorganisms for growth and metabolism? (Select all that apply)
A. Carbon
B. Nitrogen
,C. Phosphorus
D. Zinc
E. Sulfur
F. Manganese
Answer: A, B, C, E
Rationale: Macronutrients are required by microorganisms in relatively large quantities
because they play essential roles in cell structure and metabolic processes. The key
macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur, often
remembered by the acronym CHONPS. Trace elements like zinc and manganese are
micronutrients that are needed only in very small amounts for enzyme function and
protein stability.
3. In the process of glycolysis, what is the net gain of ATP molecules produced per molecule of
glucose via substrate-level phosphorylation?
A. 2 ATP
B. 1 ATP
C. 4 ATP
D. 38 ATP
Answer: A
,Rationale: During glycolysis, a single molecule of glucose is broken down into two
molecules of pyruvate through a series of enzymatic steps. While four ATP molecules are
actually produced during the payoff phase, two ATP molecules are consumed during the
energy investment phase. Therefore, the net energy yield for the cell is two ATP molecules
and two NADH molecules per glucose.
4. Which of the following is the final electron acceptor in aerobic cellular respiration?
A. Nitrate
B. Pyruvate
C. Molecular Oxygen (O2)
D. Sulfate
Answer: C
Rationale: Aerobic respiration concludes at the electron transport chain where electrons
are transferred to a final inorganic electron acceptor. In aerobic organisms, this final
acceptor is molecular oxygen, which is subsequently reduced to form water. This process
allows for the maximum theoretical yield of ATP compared to anaerobic pathways or
fermentation.
5. In a bacterial growth curve, which phase is characterized by a period of maximum growth
rate and intense metabolic activity?
A. Lag phase
B. Log (Exponential) phase
, C. Stationary phase
D. Death phase
Answer: B
Rationale: The log phase, or exponential growth phase, is the interval during which cells
are dividing at their maximum rate under the given environmental conditions. During this
stage, the population doubles at regular intervals (generation time), and the cells are most
metabolically active. This phase is also when bacteria are most sensitive to adverse
conditions, such as the action of certain antibiotics like penicillin.
6. A molecule that loses an electron during a chemical reaction is said to be:
A. Oxidized
B. Reduced
C. Phosphorylated
D. Hydrogenated
Answer: A
Rationale: Oxidation-reduction (redox) reactions involve the transfer of electrons from
one reactant to another. Oxidation is defined as the loss of one or more electrons, while
reduction is the gain of electrons. These reactions are always coupled in biological systems
to manage energy transfer within metabolic pathways.
| Actual Q&A with Rationale (BIO250 Exam
2) | StraighterLine
1. Which of the following describes the primary function of enzymes in microbial
metabolism?
A. To increase the activation energy of a chemical reaction.
B. To lower the activation energy required for a chemical reaction to occur.
C. To serve as a source of energy for endergonic reactions.
D. To permanently bind to substrates and become part of the product.
Answer: B
Rationale: Enzymes act as biological catalysts that significantly speed up the rate of
chemical reactions by lowering the activation energy barrier. They are typically composed
of proteins and are highly specific to their substrates due to the unique shape of their active
sites. Furthermore, enzymes are not consumed or permanently altered during the reactions
they catalyze, allowing them to be reused multiple times.
2. Which of the following elements are considered macronutrients required by all
microorganisms for growth and metabolism? (Select all that apply)
A. Carbon
B. Nitrogen
,C. Phosphorus
D. Zinc
E. Sulfur
F. Manganese
Answer: A, B, C, E
Rationale: Macronutrients are required by microorganisms in relatively large quantities
because they play essential roles in cell structure and metabolic processes. The key
macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur, often
remembered by the acronym CHONPS. Trace elements like zinc and manganese are
micronutrients that are needed only in very small amounts for enzyme function and
protein stability.
3. In the process of glycolysis, what is the net gain of ATP molecules produced per molecule of
glucose via substrate-level phosphorylation?
A. 2 ATP
B. 1 ATP
C. 4 ATP
D. 38 ATP
Answer: A
,Rationale: During glycolysis, a single molecule of glucose is broken down into two
molecules of pyruvate through a series of enzymatic steps. While four ATP molecules are
actually produced during the payoff phase, two ATP molecules are consumed during the
energy investment phase. Therefore, the net energy yield for the cell is two ATP molecules
and two NADH molecules per glucose.
4. Which of the following is the final electron acceptor in aerobic cellular respiration?
A. Nitrate
B. Pyruvate
C. Molecular Oxygen (O2)
D. Sulfate
Answer: C
Rationale: Aerobic respiration concludes at the electron transport chain where electrons
are transferred to a final inorganic electron acceptor. In aerobic organisms, this final
acceptor is molecular oxygen, which is subsequently reduced to form water. This process
allows for the maximum theoretical yield of ATP compared to anaerobic pathways or
fermentation.
5. In a bacterial growth curve, which phase is characterized by a period of maximum growth
rate and intense metabolic activity?
A. Lag phase
B. Log (Exponential) phase
, C. Stationary phase
D. Death phase
Answer: B
Rationale: The log phase, or exponential growth phase, is the interval during which cells
are dividing at their maximum rate under the given environmental conditions. During this
stage, the population doubles at regular intervals (generation time), and the cells are most
metabolically active. This phase is also when bacteria are most sensitive to adverse
conditions, such as the action of certain antibiotics like penicillin.
6. A molecule that loses an electron during a chemical reaction is said to be:
A. Oxidized
B. Reduced
C. Phosphorylated
D. Hydrogenated
Answer: A
Rationale: Oxidation-reduction (redox) reactions involve the transfer of electrons from
one reactant to another. Oxidation is defined as the loss of one or more electrons, while
reduction is the gain of electrons. These reactions are always coupled in biological systems
to manage energy transfer within metabolic pathways.
