Enzymes Questions in English

(A) $Statement-I$ is correct because isomerases catalyze the interconversion of isomers, which involves the intramolecular rearrangement of atoms.
$Statement-II$ is incorrect because oxidation and reduction reactions are catalyzed by oxidoreductases (or dehydrogenases), not by transferases.
Transferases catalyze the transfer of a functional group from one molecule to another.

(C) The correct matching is as follows:
$a$. Transferase: These enzymes catalyze the transfer of a group between substrates. Glucokinase is a transferase that transfers a phosphate group from $ATP$ to glucose.
$b$. Hydrolase: These enzymes catalyze the hydrolysis of bonds like ester,ether,peptide,etc. Sucrase is a hydrolase that breaks down sucrose into glucose and fructose.
$c$. Lyase: These enzymes catalyze the removal of groups from substrates by mechanisms other than hydrolysis,leaving double bonds. Aldolase is a classic example of a lyase.
$d$. Oxidoreductase: These enzymes catalyze oxidoreduction between two substrates. Alcohol dehydrogenase catalyzes the oxidation of alcohols to aldehydes or ketones by transferring electrons to $NAD^+$.
Therefore,the correct match is $a-iv, b-iii, c-i, d-ii$.

(D) An enzyme is a biological catalyst that speeds up chemical reactions in living organisms.
In any enzyme-catalyzed reaction,the specific molecule that the enzyme binds to and acts upon is called the $substrate$.
The enzyme binds to the $substrate$ at its active site to form an enzyme-$substrate$ complex,which eventually converts the $substrate$ into the product.
Therefore,the correct term for the substance upon which an enzyme acts is the $substrate$.

(C) The $Induced \ Fit$ model,proposed by $Daniel \ Koshland$,suggests that the active site of an enzyme is not a rigid structure.
Instead,it is flexible and undergoes conformational changes upon binding with the substrate.
This interaction ensures a precise fit between the enzyme and the substrate,facilitating the catalytic process.
In contrast,the $Lock \ and \ key$ model suggests a rigid active site that does not change shape.

(D) Enzymes are proteins,and proteins are composed of amino acids.
Amino acids contain both an amino group ($-NH_2$,which is basic) and a carboxyl group ($-COOH$,which is acidic).
Because of the presence of these functional groups,enzymes can act as both acids and bases,a property known as being $Amphoteric$.
Therefore,enzymes can react with both acidic and basic substances.

(C) The graph represents the potential energy changes during a chemical reaction.
$M$ represents the activation energy required for the reaction to proceed in the absence of an enzyme,which is higher.
$N$ represents the activation energy required for the reaction to proceed in the presence of an enzyme,which is lower because enzymes lower the activation energy barrier.
Therefore,$M$ is the activation energy without an enzyme and $N$ is the activation energy with an enzyme.
The correct option is $C$.

(B) The correct answer is $(B)$.
In the Michaelis-Menten enzyme kinetics graph,the $X$-axis represents the substrate concentration $[S]$,and the $Y$-axis represents the velocity of the reaction $(V)$.
As the substrate concentration increases,the velocity of the reaction increases until it reaches a maximum velocity,denoted as $V_{max}$.

(D) Lyases are enzymes that catalyze the removal of groups from substrates by mechanisms other than hydrolysis,leaving double bonds.
The reaction shown represents the formation of a double bond by the elimination of a group $(X-Y)$,which is a characteristic feature of the Lyases enzyme class.
Therefore,the correct enzyme class is Lyases.