Enzymes MCQs for MDCAT

Correct answer: A. RER

Lysosomal enzymes are synthesized on the rough endoplasmic reticulum (RER) before being packaged by the Golgi apparatus.

Correct answer: C. Non-competitive and reversible inhibition

Non-competitive, reversible inhibitors have no structural resemblance to the substrate and bind the enzyme at a site other than the active site.

Correct answer: A. Glucose

Glucose is the most commonly used respiratory substrate, providing the primary source of energy for cellular respiration.

Correct answer: D. Tertiary Structure

An enzyme's tertiary structure (its overall 3D folding) is essential for forming a functional active site and catalytic activity.

Correct answer: A. Induced fit

The induced fit model holds that an enzyme's active site is modified in shape as it interacts with and binds the substrate.

Correct answer: B. Taq Polymerase

Taq polymerase, isolated from the thermophilic bacterium Thermus aquaticus, is heat-stable and remains active at the high temperatures used in PCR.

Correct answer: B. Restriction Endonucleases

Restriction enzymes, also called restriction endonucleases, recognize a specific sequence of nucleotides in double stranded DNA and cut the DNA at a specific location. They are indispensable to the isolation of genes and the construction of cloned DNA molecules.

Correct answer: B. An activator

The zinc ion serves as an activator in the case of carboxypeptidase. Carboxypeptidase is a metalloenzyme, which means it requires a metal ion cofactor for its catalytic activity. In the case of carboxypeptidase, the zinc ion is essential for the enzyme's function.

Correct answer: A. Penetration of the sperm into the Ovum

The process of fusion of a sperm with the ovum is called fertilization. Before fusion of a spermatozoan with the egg, the spermatozoan has to penetrate a few barriers, the egg membranes, which cover the egg. The secretions of the acrosome help the sperm to enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane. All the chemicals are contained in the acrosome located at the tip of the sperm head and are collectively called sperm lysins. [e.g., CPE, Zonalysin, Hyaluronidase]. The function of hyaluronidase is to puncture the vitelline membrane of an egg.

Correct answer: C. Light intensity

Light intensity does not directly affect enzyme activity because enzymes are not influenced by light. They are affected by factors like temperature, pH and concentrations of enzyme and substrate.

Correct answer: D. Uncompetitive inhibition

The correct answer is Uncompetitive inhibition. This type of inhibition specifically involves the inhibitor binding to the enzyme-substrate complex, preventing the formation of products. In contrast, Reversible inhibition is a broader category that includes various forms of inhibition not limited to the enzyme-substrate complex. Competitive inhibition is characterized by the inhibitor directly competing with the substrate for the active site, while Non-Competitive inhibition refers to the inhibitor binding to a different site on the enzyme, not the enzyme-substrate complex. Therefore, uncompetitive inhibition is the only option that directly addresses the relationship between the inhibitor and the enzyme-substrate complex.

Correct answer: A. 1959

Koshlan proposed the "Induced Fit Model" of enzyme action in the year 1959.