Free Enzymes MCQs with Answers

• A. Glyceraldehyde 3 phosphate dehydrogenase
• B. Lactate dehydrogenase
• C. Glucose 6-Phosphate dehydrogenase
• D. Beta hydroxy acyl CoA dehydrogenaseOrder DNA Kits

Explanation: Glucose 6-phosphate dehydrogenase uses NADP+ and produces NADPH in the pentose phosphate pathway.

• A. Pyruvate dehydrogenase
• B. Both A & B
• C. Succinate dehydrogenase
• D. Enolase
• E. Alpha ketoglutarate dehydrogenase

Explanation: Both pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase are multienzyme complexes containing several catalytic components and…

• A. Pyruvate carboxylase
• B. Lactate dehydrogenase
• C. Succinate thiokinase
• D. Phosphohexose isomerase

Explanation: Biotin is the covalently bound cofactor for carboxylases and carries activated carbon dioxide during carboxylation.

• A. Apoenzymes
• B. Coenzymes
• C. Proenzymes
• D. Holoenzymes

Explanation: Inactive enzyme precursors are called proenzymes or zymogens and become active after specific proteolytic cleavage.

• A. Zymogen
• B. Coenzyme
• C. Antienzyme
• D. Isozyme

Explanation: Lactate dehydrogenase exists as five molecular forms made from different combinations of H and M subunits, so it is an isozyme.

• A. Holoenzyme
• B. Coenzyme
• C. Apoenzyme
• D. Constitutive enzyme

Explanation: A holoenzyme is the complete, active enzyme formed when the apoenzyme combines with its required cofactor or coenzyme.

• A. Adenylate cyclase
• B. Polymerase
• C. ATP synthase
• D. Tyrosine kinase

Explanation: Adenylate cyclase is a membrane-bound enzyme that converts ATP into cyclic AMP, an important second messenger.

• A. Glutamine synthetase
• B. Cholinesterase
• C. Fumarase
• D. Amylase

Explanation: Fumarase is a lyase because it catalyses the reversible addition or removal of groups without hydrolysis or oxidation, converting fumarate…

• A. Pro enzyme
• B. HoloenzymeOrder DNA Kits
• C. Co-enzyme
• D. Iso enzyme

Explanation: Isoenzymes are different molecular forms of an enzyme that catalyse the same reaction but differ in properties such as structure…

• A. Lowering the activation energy
• B. Increasing the substrate concentration
• C. Decreasing the surface tension
• D. Increasing the activation energy

Explanation: Enzymes accelerate reactions by lowering the activation energy needed to reach the transition state.

• A. Transketolase
• B. Carboxylase
• C. Oxidase
• D. Dehydrogenase

Explanation: Biotin carries carbon dioxide in carboxylation reactions, so enzymes such as pyruvate carboxylase and acetyl-CoA carboxylase lose activity…

• A. Decrease of km and increase of Vmax
• B. increase of km and increase of Vmax
• C. Decrease of km and decrease of Vmax
• D. Increase of km and Unchanged of Vmax

Explanation: A competitive inhibitor competes at the active site, so a higher substrate concentration is needed to reach half-maximal velocity…

• A. Ferro protoporphyrin
• B. FAD
• C. NADP+
• D. FMN

Explanation: Dehydrogenases commonly use NAD+, NADP+, FAD, or FMN to transfer hydrogen or electrons.

• A. Cytochrome oxidase
• B. PeroxidaseOrder DNA Kits
• C. Hydrolase
• D. Dehydrogenase

Explanation: Peroxidase uses hydrogen peroxide to oxidize chromogenic substances such as benzidine, producing a characteristic positive colour…

• A. Carbomoyl Phosphate synthetase
• B. Malonyl CoA carboxylase
• C. Fatty acid synthetase
• D. Adenosine phospho ribosyl transferase

Explanation: Fatty acid synthetase is a multifunctional multienzyme complex containing several catalytic activities in one assembly.

• A. Follow Michaelis-Menton Kinetics
• B. They are multienzyme complex
• C. Presence of Modulator site
• D. Give sigmoid shaped curve

Explanation: Allosteric enzymes generally show cooperative, sigmoid kinetics rather than the hyperbolic Michaelis-Menten curve.

• A. Tocopherol
• B. Catalase
• C. Superoxide dismutase
• D. Urate

Explanation: Catalase is a preventive antioxidant because it removes hydrogen peroxide before it can generate more damaging reactive oxygen species.

• A. 5
• B. 3
• C. 11
• D. 2

Explanation: Lactate dehydrogenase has five isoenzymes, LDH-1 through LDH-5, formed from different combinations of H and M subunits.

• A. Cyclic AMP
• B. Adenosine tri phosphate
• C. Citrate
• D. Fructose 2,6 bis phosphate

Explanation: Fructose 2,6-bisphosphate is the strongest activator of phosphofructokinase-1 and promotes glycolysis.

• A. Phosphatase
• B. ATPase
• C. Dismutase
• D. Aldolase

Explanation: Magnesium commonly stabilises ATP and is required for the activity of many ATPases and phosphate-transfer enzymes.