Enzyme Practice Questions

Which of the following is a common method for regulating enzyme activity in

cells?

o A) Changing the enzyme’s color

o B) Altering the enzyme’s genetic code

o C) Phosphorylation and dephosphorylation

o D) Increasing the cell’s temperature

C) Phosphorylation and dephosphorylation

What happens to an enzyme when it is denatured?

o A) It becomes more active

o B) It loses its shape and function

o C) It binds more tightly to substrates

o D) It speeds up the reaction

B) It loses its shape and function

Which of the following is true about enzyme specificity?

o A) One enzyme can catalyze multiple types of reactions

o B) Each enzyme can only catalyze one specific reaction

o C) Enzymes are not specific and can catalyze any reaction

o D) Enzyme specificity is determined by the enzyme’s color

B) Each enzyme can only catalyze one specific reaction

What is the term for the molecule upon which an enzyme acts?

o A) Product

o B) Substrate

o C) Inhibitor

o D) Coenzyme

B) Substrate

What is the effect of a competitive inhibitor on enzyme activity?

o A) It binds to the active site and decreases enzyme activity

o B) It binds to a different site and increases enzyme activity

o C) It binds to the active site and increases enzyme activity

o D) It binds to a different site and decreases enzyme activity

A) It binds to the active site and decreases enzyme activity

Which of the following statements about enzymes is true?

o A) Enzymes are consumed in the reactions they catalyze

o B) Enzymes are specific to their substrates

o C) Enzymes can function at any temperature

o D) Enzymes are made up of nucleic acids

B) Enzymes are specific to their substrates

Which of the following is an example of an enzyme?

o A) Hemoglobin

o B) Insulin

o C) Amylase

o D) Collagen

C) Amylase

What is a coenzyme?

o A) A protein that speeds up chemical reactions

o B) A non-protein molecule that assists enzyme function

o C) A molecule that inhibits enzyme activity

o D) A molecule that stores genetic information

B) A non-protein molecule that assists enzyme function

Which of the following factors does NOT affect enzyme activity?

o A) Temperature

o B) pH

o C) Substrate concentration

o D) Color of the enzyme

D) Color of the enzyme

What is the primary function of enzymes in biological systems?

o A) To provide structural support

o B) To store genetic information

o C) To catalyze biochemical reactions

o D) To transport molecules across cell membranes

C) To catalyze biochemical reactions

What does a low KM value indicate about an enzyme’s affinity for its substrate?

o A) Low binding affinity

o B) High binding affinity

o C) No binding affinity

o D) Variable binding affinity

B) High binding affinity

What happens to most human enzymes at temperatures higher than 37℃?

o A) They become more active

o B) They denature and lose their secondary and tertiary structure

o C) They bind more tightly to substrates

o D) They speed up the reaction

B) They denature and lose their secondary and tertiary structure

Which type of inhibition is characterized by a rapid dissociation of the enzyme-

inhibitor complex?

o A) Irreversible inhibition

o B) Reversible inhibition

B) Reversible inhibition

What is the effect of a non-competitive inhibitor on enzyme activity?

o A) It binds to the active site and decreases enzyme activity

o B) It binds to a different site and decreases enzyme activity

o C) It binds to the active site and increases enzyme activity

o D) It binds to a different site and increases enzyme activity

B) It binds to a different site and decreases enzyme activity

Which of the following is an example of a competitive inhibitor?

o A) Penicillin

o B) Aspirin

o C) Methotrexate

o D) Lactase

C) Methotrexate

What is the role of positive allosteric modulation in enzyme activity?

o A) It decreases the enzyme’s affinity for the substrate

o B) It enhances the attraction between substrate molecules and other

binding sites

o C) It inhibits the enzyme’s activity

o D) It changes the enzyme’s genetic code

B) It enhances the attraction between substrate molecules and other

binding sites

What is the function of phosphorylation in protein regulation?

o A) It turns off the enzyme’s activity

o B) It turns on the enzyme’s activity

o C) It degrades the enzyme

o D) It stores the enzyme for future use

B) It turns on the enzyme’s activity

What is the role of the ubiquitin-proteasome system (UPS) in protein

degradation?

o A) It degrades long-lived proteins and insoluble protein aggregates

o B) It eliminates short-lived proteins and soluble misfolded proteins

o C) It stores proteins for future use

o D) It transports proteins across cell membranes

B) It eliminates short-lived proteins and soluble misfolded proteins

What is the function of chaperone-mediated autophagy?

o A) It degrades long-lived proteins

o B) It facilitates the degradation of unfolded proteins

o C) It degrades damaged organelles

o D) It degrades intracellular pathogens

B) It facilitates the degradation of unfolded proteins

What is the Michaelis constant (KM)?

o A) The maximum velocity of an enzyme-catalyzed reaction

o B) The substrate concentration at which the reaction velocity is 50% of the

Vmax

o C) The rate of enzyme reaction at high substrate concentrations

o D) The energy required to start a reaction

B) The substrate concentration at which the reaction velocity is 50% of the

Vmax

Which of the following statements about enzyme inhibition is true?

o A) Irreversible inhibitors dissociate quickly from the enzyme

o B) Competitive inhibitors bind to a site other than the active site

o C) Non-competitive inhibitors compete with the substrate for the active

site

o D) Competitive inhibitors can be reversed by adding more substrate

D) Competitive inhibitors can be reversed by adding more substrate

What is the effect of a competitive inhibitor on enzyme activity?

o A) It binds to the active site and decreases enzyme activity

o B) It binds to a different site and increases enzyme activity

o C) It binds to the active site and increases enzyme activity

o D) It binds to a different site and decreases enzyme activity

A) It binds to the active site and decreases enzyme activity

Which of the following is an example of an irreversible inhibitor?

o A) Methotrexate

o B) Penicillin

o C) Lactase

o D) Amylase

B) Penicillin

What is the role of cofactors in enzyme activity?

o A) They provide structural support to the enzyme

o B) They assist in catalysis by being non-protein components

o C) They inhibit enzyme activity

o D) They store genetic information

B) They assist in catalysis by being non-protein components

What happens to an enzyme when it is denatured?

o A) It becomes more active

o B) It loses its shape and function

o C) It binds more tightly to substrates

o D) It speeds up the reaction

B) It loses its shape and function

Which of the following statements about allosteric regulation is true?

o A) Allosteric activators bind to the catalytic site

o B) Allosteric inhibitors increase the enzyme’s activity

o C) Allosteric activators change the conformation of the catalytic site to

increase substrate affinity

o D) Allosteric regulation involves the enzyme’s genetic code

C) Allosteric activators change the conformation of the catalytic site to

increase substrate affinity

Which of the following statements about GTP and GDP is true?

• A) GTP is the inactive form, and GDP is the active form

• B) GDP is the inactive form, and GTP is the active form

• C) Both GTP and GDP are active forms

• D) Both GTP and GDP are inactive form

B) GDP is the inactive form, and GTP is the active form

What happens to a target protein when it is bound to GTP?

o A) It becomes inactive

o B) It becomes active

o C) It is degraded

o D) It is transported out of the cell

B) It becomes active

What is the significance of the polyubiquitin tail in the UPS?

o A) It provides energy for protein degradation

o B) It marks proteins for degradation by the proteasome

o C) It transports proteins to the lysosome

o D) It synthesizes new proteins

B) It marks proteins for degradation by the proteasome

Which of the following processes is NOT associated with the ubiquitin-

proteasome system?

o A) Protein synthesis

o B) Protein degradation

o C) Regulation of protein levels

o D) Removal of misfolded proteins

A) Protein synthesis

Which of the following statements about the proteasome is true?

o A) It synthesizes new proteins

o B) It degrades ubiquitin-tagged proteins

o C) It transports proteins across cell membranes

o D) It stores genetic information

B) It degrades ubiquitin-tagged proteins

Which enzyme is responsible for attaching ubiquitin to target proteins?

o A) Protease

o B) Ubiquitin ligase (E3)

o C) Kinase

o D) Phosphatase

B) Ubiquitin ligase (E3)

Which of the following components is NOT involved in the ubiquitin-proteasome

system?

o A) Ubiquitin

o B) Proteasome

o C) Ribosome

o D) Ubiquitin ligases

C) Ribosome

All of the following statements about enzymes are false except

A. They are reusable

B. They increase the activation energy of a reaction

C. They decrease the rate of a reaction

D. They do not catalyze metabolic pathways.

A. They are reusable

True or False? Michaelis-Menten constant (Km) is a measure of substrate binding. If the rates of binding and reaction velocity are fast, Km will be high

False

Which term describes the model of enzyme activity where the enzyme changes

shape to fit the substrate?

o A) Lock and key model

o B) Induced fit model

o C) Fluid mosaic model

o D) Double helix model

B) Induced fit model

Which of the following statements about enzymes is true?

o A) Enzymes are consumed in the reactions they catalyze

o B) Enzymes are specific to their substrates

o C) Enzymes can function at any temperature

o D) Enzymes are made up of nucleic acids

B) Enzymes are specific to their substrates

How do enzymes affect the activation energy of a reaction?

o A) They increase the activation energy

o B) They decrease the activation energy

o C) They do not affect the activation energy

o D) They eliminate the need for activation energy

B) They decrease the activation energy

What is the function of chaperone-mediated autophagy?

o A) It degrades long-lived proteins

o B) It facilitates the degradation of unfolded proteins

o C) It degrades damaged organelles

o D) It degrades intracellular pathogens

B) It facilitates the degradation of unfolded proteins

What is the primary function of lysosomes in the cell?

o A) To store genetic information

o B) To degrade long-lived proteins, insoluble protein aggregates, and

damaged organelles

o C) To transport molecules across cell membranes

o D) To provide structural support to cells

B) To degrade long-lived proteins, insoluble protein aggregates, and

damaged organelles

What is the role of autophagosomes in lysosome-mediated degradation?

o A) They synthesize new proteins

o B) They transport proteins to the nucleus

o C) They encircle damaged organelles and fuse with lysosomes

o D) They store proteins for future use

C) They encircle damaged organelles and fuse with lysosomes

Which form of autophagy involves the direct engulfment of small cytoplasmic

solutes by lysosomes?

o A) Macroautophagy

o B) Microautophagy

o C) Chaperone-mediated autophagy

o D) Endocytosis

B) Microautophagy

What effect does the binding of one oxygen molecule have on the affinity of

hemoglobin for additional oxygen molecules?

o A) It decreases the affinity for additional oxygen molecules

o B) It increases the affinity for additional oxygen molecules

o C) It has no effect on the affinity for additional oxygen molecules

o D) It denatures hemoglobin

B) It increases the affinity for additional oxygen molecules

What is the primary difference between the T state and R state of hemoglobin?

o A) The T state has a higher affinity for oxygen than the R state

o B) The R state has a higher affinity for oxygen than the T state

o C) The T state is denatured, while the R state is not

o D) The R state is denatured, while the T state is not

B) The R state has a higher affinity for oxygen than the T state

True or False? Competitive inhibitors pushes km of enzymes towards higher side

True