BIOL 271 Microbiology w/ Lab | Module 2: Microbial Metabolism and
Enzymatic Reactions
200 Questions — Review Set
Question 1
What is microbial metabolism?
✓ Answer: The sum of all chemical reactions that occur within a microbial cell to
maintain life.
Feedback: Metabolism includes both catabolic (breakdown) and anabolic (synthesis) reactions that occur
simultaneously in the cell.
Question 2
What is the difference between catabolism and anabolism?
✓ Answer: Catabolism breaks down complex molecules into simpler ones, releasing
energy, while anabolism uses energy to synthesize complex molecules from simpler
ones.
Feedback: Catabolic reactions are exergonic (release energy), while anabolic reactions are endergonic
(require energy input).
Question 3
What is an enzyme?
✓ Answer: A biological catalyst, typically a protein, that accelerates the rate of a
chemical reaction without being consumed in the process.
Feedback: Enzymes lower the activation energy required for a reaction to proceed, making metabolic
reactions occur at biologically relevant rates.
Question 4
What is the active site of an enzyme?
✓ Answer: The specific region on an enzyme where the substrate binds and the
catalytic reaction takes place.
Feedback: The active site has a unique three-dimensional shape that is complementary to the substrate,
allowing for specific binding and catalysis.
Question 5
What is a substrate?
, ✓ Answer: The specific molecule that an enzyme acts upon to catalyze a chemical
reaction.
Feedback: Substrates bind to the enzyme's active site and are converted into products through the catalytic
process.
Question 6
What is the induced fit model of enzyme action?
✓ Answer: A model describing how the enzyme's active site undergoes
conformational changes upon substrate binding to achieve optimal catalysis.
Feedback: Unlike the lock-and-key model, the induced fit model explains enzyme flexibility and the dynamic
nature of enzyme-substrate interactions.
Question 7
What factors affect enzyme activity?
✓ Answer: Temperature, pH, substrate concentration, enzyme concentration, and the
presence of inhibitors or activators.
Feedback: Each enzyme has optimal conditions for activity, and deviations from these conditions can reduce
or eliminate catalytic function.
Question 8
What is the optimal temperature for most microbial enzymes?
✓ Answer: Generally between 20°C and 40°C for mesophilic organisms, though
thermophiles have enzymes that function optimally at higher temperatures.
Feedback: Enzymes from psychrophiles function optimally at cold temperatures, while thermophile enzymes
are adapted to high temperatures.
Question 9
What happens to enzymes at extreme temperatures?
✓ Answer: High temperatures can denature enzymes by disrupting non-covalent
bonds, while low temperatures slow molecular motion and reduce reaction rates.
Feedback: Denaturation results in the loss of the enzyme's three-dimensional structure and catalytic activity,
often irreversibly.
Question 10
What is the optimal pH for most microbial enzymes?
✓ Answer: Near neutral pH (6.5-7.5) for many enzymes, though some enzymes
function optimally at acidic or alkaline pH.
,Feedback: pH affects enzyme activity by altering the ionization state of amino acid residues at the active site.
Question 11
What is enzyme specificity?
✓ Answer: The ability of an enzyme to selectively bind to one substrate or a group of
closely related substrates.
Feedback: Enzyme specificity is determined by the shape and chemical properties of the active site.
Question 12
What is a competitive inhibitor?
✓ Answer: A molecule that resembles the substrate and competes for binding to the
enzyme's active site.
Feedback: Competitive inhibitors can be overcome by increasing substrate concentration, as they bind
reversibly to the active site.
Question 13
What is a non-competitive inhibitor?
✓ Answer: A molecule that binds to a site other than the active site (allosteric site),
changing the enzyme's shape and reducing activity.
Feedback: Non-competitive inhibitors cannot be overcome by increasing substrate concentration.
Question 14
What is an allosteric enzyme?
✓ Answer: An enzyme that has a regulatory site separate from the active site where
molecules can bind to modulate activity.
Feedback: Allosteric regulation allows for fine-tuning of metabolic pathways in response to cellular
conditions.
Question 15
What is feedback inhibition?
✓ Answer: A regulatory mechanism where the end product of a metabolic pathway
inhibits an enzyme involved in its synthesis.
Feedback: Feedback inhibition prevents the overproduction of metabolites and maintains cellular
homeostasis.
Question 16
, What is an apoenzyme?
✓ Answer: The protein portion of an enzyme that requires a cofactor to become
catalytically active.
Feedback: Without its cofactor, an apoenzyme is inactive and is referred to as an inactive enzyme.
Question 17
What is a cofactor?
✓ Answer: A non-protein molecule required for enzyme activity, which can be
inorganic (metal ions) or organic (coenzymes).
Feedback: Cofactors help stabilize the enzyme structure or participate directly in the catalytic reaction.
Question 18
What is a coenzyme?
✓ Answer: An organic cofactor that often serves as a carrier of chemical groups or
electrons in enzymatic reactions.
Feedback: Coenzymes are derived from vitamins and are essential for many metabolic reactions.
Question 19
What is a holoenzyme?
✓ Answer: The complete, catalytically active enzyme consisting of the apoenzyme and
its cofactor.
Feedback: Holoenzymes are fully functional and capable of carrying out their catalytic function.
Question 20
What is the function of NAD+ in metabolism?
✓ Answer: NAD+ (nicotinamide adenine dinucleotide) serves as an electron carrier,
accepting electrons to become NADH in redox reactions.
Feedback: NAD+ is a coenzyme involved in many oxidation-reduction reactions, particularly in catabolic
pathways.
Question 21
What is the function of NADP+ in metabolism?
✓ Answer: NADP+ (nicotinamide adenine dinucleotide phosphate) serves as an
electron carrier, primarily involved in anabolic reactions and biosynthesis.
Feedback: NADPH, the reduced form of NADP+, is a key reducing agent in biosynthetic pathways and
antioxidant defense.
Enzymatic Reactions
200 Questions — Review Set
Question 1
What is microbial metabolism?
✓ Answer: The sum of all chemical reactions that occur within a microbial cell to
maintain life.
Feedback: Metabolism includes both catabolic (breakdown) and anabolic (synthesis) reactions that occur
simultaneously in the cell.
Question 2
What is the difference between catabolism and anabolism?
✓ Answer: Catabolism breaks down complex molecules into simpler ones, releasing
energy, while anabolism uses energy to synthesize complex molecules from simpler
ones.
Feedback: Catabolic reactions are exergonic (release energy), while anabolic reactions are endergonic
(require energy input).
Question 3
What is an enzyme?
✓ Answer: A biological catalyst, typically a protein, that accelerates the rate of a
chemical reaction without being consumed in the process.
Feedback: Enzymes lower the activation energy required for a reaction to proceed, making metabolic
reactions occur at biologically relevant rates.
Question 4
What is the active site of an enzyme?
✓ Answer: The specific region on an enzyme where the substrate binds and the
catalytic reaction takes place.
Feedback: The active site has a unique three-dimensional shape that is complementary to the substrate,
allowing for specific binding and catalysis.
Question 5
What is a substrate?
, ✓ Answer: The specific molecule that an enzyme acts upon to catalyze a chemical
reaction.
Feedback: Substrates bind to the enzyme's active site and are converted into products through the catalytic
process.
Question 6
What is the induced fit model of enzyme action?
✓ Answer: A model describing how the enzyme's active site undergoes
conformational changes upon substrate binding to achieve optimal catalysis.
Feedback: Unlike the lock-and-key model, the induced fit model explains enzyme flexibility and the dynamic
nature of enzyme-substrate interactions.
Question 7
What factors affect enzyme activity?
✓ Answer: Temperature, pH, substrate concentration, enzyme concentration, and the
presence of inhibitors or activators.
Feedback: Each enzyme has optimal conditions for activity, and deviations from these conditions can reduce
or eliminate catalytic function.
Question 8
What is the optimal temperature for most microbial enzymes?
✓ Answer: Generally between 20°C and 40°C for mesophilic organisms, though
thermophiles have enzymes that function optimally at higher temperatures.
Feedback: Enzymes from psychrophiles function optimally at cold temperatures, while thermophile enzymes
are adapted to high temperatures.
Question 9
What happens to enzymes at extreme temperatures?
✓ Answer: High temperatures can denature enzymes by disrupting non-covalent
bonds, while low temperatures slow molecular motion and reduce reaction rates.
Feedback: Denaturation results in the loss of the enzyme's three-dimensional structure and catalytic activity,
often irreversibly.
Question 10
What is the optimal pH for most microbial enzymes?
✓ Answer: Near neutral pH (6.5-7.5) for many enzymes, though some enzymes
function optimally at acidic or alkaline pH.
,Feedback: pH affects enzyme activity by altering the ionization state of amino acid residues at the active site.
Question 11
What is enzyme specificity?
✓ Answer: The ability of an enzyme to selectively bind to one substrate or a group of
closely related substrates.
Feedback: Enzyme specificity is determined by the shape and chemical properties of the active site.
Question 12
What is a competitive inhibitor?
✓ Answer: A molecule that resembles the substrate and competes for binding to the
enzyme's active site.
Feedback: Competitive inhibitors can be overcome by increasing substrate concentration, as they bind
reversibly to the active site.
Question 13
What is a non-competitive inhibitor?
✓ Answer: A molecule that binds to a site other than the active site (allosteric site),
changing the enzyme's shape and reducing activity.
Feedback: Non-competitive inhibitors cannot be overcome by increasing substrate concentration.
Question 14
What is an allosteric enzyme?
✓ Answer: An enzyme that has a regulatory site separate from the active site where
molecules can bind to modulate activity.
Feedback: Allosteric regulation allows for fine-tuning of metabolic pathways in response to cellular
conditions.
Question 15
What is feedback inhibition?
✓ Answer: A regulatory mechanism where the end product of a metabolic pathway
inhibits an enzyme involved in its synthesis.
Feedback: Feedback inhibition prevents the overproduction of metabolites and maintains cellular
homeostasis.
Question 16
, What is an apoenzyme?
✓ Answer: The protein portion of an enzyme that requires a cofactor to become
catalytically active.
Feedback: Without its cofactor, an apoenzyme is inactive and is referred to as an inactive enzyme.
Question 17
What is a cofactor?
✓ Answer: A non-protein molecule required for enzyme activity, which can be
inorganic (metal ions) or organic (coenzymes).
Feedback: Cofactors help stabilize the enzyme structure or participate directly in the catalytic reaction.
Question 18
What is a coenzyme?
✓ Answer: An organic cofactor that often serves as a carrier of chemical groups or
electrons in enzymatic reactions.
Feedback: Coenzymes are derived from vitamins and are essential for many metabolic reactions.
Question 19
What is a holoenzyme?
✓ Answer: The complete, catalytically active enzyme consisting of the apoenzyme and
its cofactor.
Feedback: Holoenzymes are fully functional and capable of carrying out their catalytic function.
Question 20
What is the function of NAD+ in metabolism?
✓ Answer: NAD+ (nicotinamide adenine dinucleotide) serves as an electron carrier,
accepting electrons to become NADH in redox reactions.
Feedback: NAD+ is a coenzyme involved in many oxidation-reduction reactions, particularly in catabolic
pathways.
Question 21
What is the function of NADP+ in metabolism?
✓ Answer: NADP+ (nicotinamide adenine dinucleotide phosphate) serves as an
electron carrier, primarily involved in anabolic reactions and biosynthesis.
Feedback: NADPH, the reduced form of NADP+, is a key reducing agent in biosynthetic pathways and
antioxidant defense.
