NEET Biology: Enzymes properties and action Practice Questions

Correct answer: A — The coenzyme is necessary for the enzyme to perform its catalytic function

Coenzymes are auxiliary molecules that bind to the enzyme (often forming a holoenzyme) and participate directly in the chemical transformation, acting as necessary helpers for the enzyme's activity.

Correct answer: A — Facilitate the chemical reaction

Cofactors are non-protein chemical entities (often metal ions) that are required for the enzyme to achieve its functional three-dimensional structure and catalyze the reaction.

Correct answer: A — Holoenzyme

The holoenzyme is the complete, functional enzyme, which consists of the apoenzyme (the protein part) and the non-protein cofactor (if required) necessary for catalytic activity.

Correct answer: A — Active site

The active site is the specific region on the enzyme where the substrate binds, leading to the formation of the enzyme-substrate complex and the subsequent catalytic action.

Correct answer: A — It acts as a catalyst to control the reaction rate

Enzymes act as biological catalysts, meaning they speed up the rate at which biochemical reactions occur without being consumed in the reaction, thereby controlling the flow and rate of metabolic pathways.

Correct answer: C — Activation energy

Enzymes accelerate reactions by providing an alternative pathway with a much lower activation energy, making the reaction happen much faster.

Correct answer: B — The enzyme's binding site

Competitive inhibition occurs when the inhibitor binds directly to the active site of the enzyme, preventing the substrate from binding.

Correct answer: D — Cofactor

Cofactors (non-protein helper molecules, often metal ions or vitamins) are often essential for the enzyme to achieve its proper three-dimensional structure and facilitate the binding of the substrate, making them critical for catalytic activity.

Correct answer: B — The overall protein structure

Denaturation is the disruption of the enzyme's tertiary or quaternary structure, which consequently alters the shape of the active site, thereby destroying its ability to bind the substrate and catalyze the reaction.

Correct answer: D — The enzyme's ability to bind the substrate is altered, leading to reduced activity

Enzymes are sensitive to pH changes. Altering the pH changes the ionization state of amino acid residues in the active site, which disrupts the binding of the substrate and thus reduces the enzyme's catalytic activity.

Correct answer: B — Decrease the activation energy of the reaction

Enzymes function by providing an alternative reaction pathway with a significantly lower activation energy, thereby speeding up the rate of the biochemical reaction.

Correct answer: C — They bind only to one specific substrate

Enzyme specificity arises from the unique three-dimensional structure of the enzyme's active site, which is complementary only to its specific substrate (often described by the lock-and-key or induced fit model).

Correct answer: A — The overall shape and chemical properties of the active site

Enzyme specificity arises because the three-dimensional structure of the active site is complementary to the shape and chemical structure of the specific substrate it acts upon.

Correct answer: C — Active site

The active site is the specific region on the enzyme where the substrate binds and the chemical reaction occurs.

Correct answer: C — Active site

The specificity of an enzyme is due to the unique three-dimensional structure of its active site, which is perfectly shaped to bind only to its specific substrate (Lock and Key model).