Enzymes Questions in English

(D) The mechanism of enzyme action involves the formation of an enzyme-substrate $(ES)$ complex.
$1$. The substrate binds to the active site of the enzyme to form the $ES$ complex.
$2$. The enzyme facilitates the conversion of the substrate into the product $(P)$.
$3$. Once the product is formed,the enzyme-product $(EP)$ complex is created.
$4$. Finally,the enzyme releases the product and returns to its original,unchanged form,ready to bind with another substrate molecule.
Therefore,the enzyme is released in its original form only at the end of the reaction.

(C) Enzymes that catalyze the transfer of a group,$G$ (other than hydrogen),between a pair of substrates $S$ and $S'$ are called Transferases. The reaction is represented as: $S-G + S' \rightarrow S + S'-G$. Therefore,the correct option is $C$.

(D) The enzymes that catalyze the hydrolysis of bonds (such as $C-O, C-N, C-C$,etc.) by adding a water molecule are known as Hydrolases.
These enzymes are responsible for breaking down complex molecules into simpler ones during metabolic processes.
Therefore,the correct option is $D$.

(B) The reaction shows the hydrolysis of the disaccharide Maltose into two molecules of Glucose.
This reaction is catalyzed by the enzyme Maltase.
Invertase catalyzes the hydrolysis of sucrose into glucose and fructose.
Lactase catalyzes the hydrolysis of lactose into glucose and galactose.
Amylase is involved in the breakdown of starch into smaller carbohydrate units.

(A) Enzymes are classified based on the type of reaction they catalyze.
$Dehydrogenases$ are enzymes that catalyze the removal of hydrogen atoms from a substrate,often involving the transfer of electrons to a coenzyme like $NAD^+$ or $FAD$.
$Oxidases$ catalyze oxidation reactions involving oxygen.
$Lyases$ catalyze the removal of groups from substrates by mechanisms other than hydrolysis,leaving double bonds.
$Transferases$ catalyze the transfer of a functional group from one molecule to another.
Therefore,the correct answer is $Dehydrogenase$.

(B) The enzymes that catalyze the removal of groups from substrates by mechanisms other than hydrolysis (leaving double bonds) are known as $Lyases$.
Unlike hydrolases,$Lyases$ do not involve the addition of water molecules to break down large molecules into smaller units.
$Dehydrogenases$ are involved in oxidation-reduction reactions.
$Oxidases$ catalyze oxidation reactions.
$Hexokinases$ are transferases that catalyze the phosphorylation of hexose sugars.

(B) Enzymes that catalyze the linking together of two compounds,for example,enzymes which catalyze the joining of $C-O, C-S, C-N, P-O$ etc. bonds,are called Ligases or Synthetases. These enzymes utilize energy derived from the hydrolysis of $ATP$ (specifically the pyrophosphate bond) to facilitate the formation of these chemical bonds.

(A) The reaction $\text{Acetic acid} + ATP + Co-A \to \text{Acetyl } Co.A + AMP + PPi$ is catalyzed by the enzyme $\text{Acetyl } Co.A \text{ synthetase}$.
This enzyme belongs to the class of ligases, which catalyze the joining of two molecules by forming a new chemical bond, coupled with the hydrolysis of $ATP$.

(A) The correct answer is $A$. Adenylate kinase is an enzyme,and enzymes are biological catalysts that are primarily proteinaceous in nature. $NAD$ (Nicotinamide Adenine Dinucleotide),$FAD$ (Flavin Adenine Dinucleotide),and $FMN$ (Flavin Mononucleotide) are coenzymes or prosthetic groups that function as non-protein components required for the activity of certain enzymes,but they are not proteins themselves.

(B) Enzymes are biological catalysts that speed up chemical reactions in living organisms. Almost all enzymes are proteins,which are composed of long chains of amino acids folded into specific three-dimensional shapes. These shapes are crucial for their catalytic activity. While some $RNA$ molecules (ribozymes) can also act as catalysts,the vast majority of enzymes are proteinaceous in nature.

(A) In the given enzymatic reaction equation $E + S \rightarrow E.S \text{ Complex} \rightarrow E + P$:
$E$ represents the Enzyme.
$S$ represents the Substrate.
$P$ represents the Product.
$E.S \text{ Complex}$ is the transient enzyme-substrate complex formed during the reaction.
The substance that binds to the active site of the enzyme and undergoes chemical transformation is called the substrate $(S)$. Therefore,the enzyme acts upon the substrate.

(D) Enzymes are biological catalysts that speed up chemical reactions in living organisms.
$NAD$ (Nicotinamide Adenine Dinucleotide),$FMN$ (Flavin Mononucleotide),and $NADP$ (Nicotinamide Adenine Dinucleotide Phosphate) are coenzymes or electron carriers,not enzymes themselves.
Ligase is a class of enzymes that catalyze the joining of two large molecules by forming a new chemical bond.

(D) Enzymes are primarily composed of amino acids linked together by peptide bonds to form polypeptide chains.
Each amino acid has a central carbon atom bonded to an amino group $(-NH_2)$,a carboxyl group $(-COOH)$,a hydrogen atom,and a variable $R$-group.
In a polypeptide chain,the amino acids are linked such that one end of the chain possesses a free amino group (the $N$-terminus) and the other end possesses a free carboxyl group (the $C$-terminus).
Therefore,the two ends of an enzyme's structure are characterized by the presence of $-NH_2$ and $-COOH$ groups.

(C) Enzymes are biocatalysts that speed up chemical reactions.
$1$. Enzymes are proteinaceous in nature and are amphoteric,meaning they can act as both acids and bases.
$2$. Enzymes are highly sensitive to temperature; they function optimally within a specific temperature range.
$3$. Enzymes are sensitive to $pH$; they show maximum activity at an optimum $pH$.
$4$. Regarding reversibility,while some enzymes can catalyze reactions in both directions,the majority of metabolic enzymes are highly specific and often catalyze reactions in a single direction under physiological conditions. Therefore,stating that the action of 'most' enzymes is reversible is incorrect as a general characteristic property.

(A) The 'Lock and Key' hypothesis,proposed by Emil Fischer,explains the specificity of enzyme action.
According to this model,the enzyme has a specific 'Active site' that is geometrically complementary to the shape of the 'Substrate' molecule.
Just as a specific key fits into a specific lock,the substrate fits into the active site of the enzyme to form an enzyme-substrate complex.
Therefore,the active site and the substrate are the units that are complementary to each other.

(B) The mechanism of enzyme action involves the formation of an enzyme-substrate $(E \cdot S)$ complex.
$1$. The enzyme $(E)$ binds to the substrate $(S)$ to form a transient enzyme-substrate complex $(E \cdot S)$.
$2$. This complex then undergoes a chemical reaction to form the enzyme-product $(E \cdot P)$ complex.
$3$. Finally,the enzyme releases the product $(P)$ and returns to its original state,ready to bind with another substrate molecule.
$4$. The simplified representation is: $E + S \rightarrow E \cdot S \text{-Complex} \rightarrow E + P$.

(B) Isomerases are a class of enzymes that catalyze the conversion of a molecule into one of its isomeric forms. This involves the rearrangement of atoms within a single molecule without changing its molecular formula. For example,the conversion of glucose$-6-$phosphate to fructose$-6-$phosphate by phosphoglucose isomerase is a classic reaction catalyzed by an isomerase.

(C) Synthetases are a class of enzymes that catalyze the joining of two molecules together.
This process is coupled with the hydrolysis of a pyrophosphate bond in $ATP$ or a similar triphosphate.
Therefore,the correct statement is that it joins two molecules together with the help of $ATP$.

(C) The enzyme $Adenylate$ $kinase$ is a phosphotransferase that catalyzes the interconversion of adenine nucleotides. Its activity is primarily dependent on $Mg^{2+}$ ions as a cofactor. Unlike many signaling enzymes or kinases involved in calcium-dependent pathways,$Adenylate$ $kinase$ does not require $Ca^{2+}$ for its catalytic activity,and the presence of calcium does not activate or inhibit it in a regulatory manner compared to its dependence on magnesium. Therefore,it remains inactive in the context of calcium-dependent regulatory mechanisms.

(B) Statement $P$ is correct because enzymes are proteinaceous substances that act as biological catalysts,accelerating biochemical reactions without being consumed in the process.
Statement $Q$ is also correct because enzymes are synthesized by living cells and are required in very small quantities to effectively catalyze metabolic reactions within the organism.

(A) Enzymes are biological catalysts that speed up chemical reactions in living organisms.
Structurally,almost all enzymes are globular proteins.
Globular proteins have a complex $3D$ folded structure that creates an active site,which is essential for their catalytic activity.
Fibrous proteins are typically structural (e.g.,collagen,keratin),whereas enzymes require a specific shape to bind to substrates.

(C) The enzyme Acetyl $CoA$ synthetase catalyzes the reaction: $Acetate + ATP + CoA \rightarrow Acetyl-CoA + AMP + PP_i$.
This reaction involves the joining of two molecules (acetate and $CoA$) coupled with the hydrolysis of $ATP$.
Enzymes that catalyze the joining of two molecules by forming $C-O$,$C-S$,$C-N$,or $C-C$ bonds at the expense of $ATP$ are classified as Ligases.

(C) Assertion $(A)$ is false because while most enzymes are proteins,there are exceptions known as ribozymes ($RNA$ molecules that act as enzymes).
Reason $(R)$ is also false because proteins have various functions such as structural support,transport,and signaling; not all proteins function as enzymes.

(C) : Proteins are essential for life as they form the structural components of cells, act as hormones, antibodies, and transport molecules. Thus, life is not possible without proteins.
$R$: Most enzymes are proteins (biocatalysts). However, there are exceptions such as ribozymes ($RNA$ molecules that act as enzymes). Therefore, the statement "All enzymes are made of proteins" is technically false.
Conclusion: $A$ is true, but $R$ is false.

(A) Assertion $(A)$ is true because enzymes are biocatalysts,which are typically large,complex protein molecules with high molecular weights.
Reason $(R)$ is also true because almost all enzymes are proteins (with the exception of ribozymes). As proteins,they exhibit all characteristic properties of proteins,such as specific three-dimensional folding,sensitivity to temperature and pH,and the presence of peptide bonds.
Since enzymes are proteins,their high molecular weight and complex structure are direct consequences of their proteinaceous nature. Therefore,$R$ is the correct explanation of $A$.

(D) Assertion $(A)$ is false because in a feverish condition,the body temperature rises,which typically increases the rate of metabolic reactions up to a certain point,rather than decreasing them. However,if the temperature becomes excessively high,it can denature enzymes.
Reason $(R)$ is true because enzymes are proteins that are highly sensitive to temperature changes. They function optimally at a specific temperature (optimum temperature). High temperatures cause the denaturation of the protein structure,leading to a loss of enzymatic activity.

(D) Statement $X$ is false because enzymes are biological catalysts that can catalyze reactions in both directions depending on the concentration of substrates and products.
Statement $Y$ is true because enzymes are proteins,and proteins are composed of amino acids. Since amino acids contain both acidic $(-COOH)$ and basic $(-NH_2)$ groups,they exhibit amphoteric properties,meaning they can react with both acids and bases.

(A) The provided image illustrates the 'Lock and Key' model of enzyme action.
In this model,$P$ represents the substrate,$Q$ represents the enzyme,and the complex formed is the enzyme-substrate complex.
After the reaction,$R$ represents the product and $S$ represents the enzyme,which is released unchanged to catalyze further reactions.
Therefore,the mechanism shown is characteristic of enzymes.

(A) In the provided diagram,the process illustrates the mechanism of enzyme action.
$P$ represents the substrate molecule that binds to the active site of the enzyme.
$Q$ represents the enzyme.
$R$ represents the product formed after the reaction.
$S$ represents the enzyme released after the reaction is complete.
Therefore,$P$ is the substrate.

(B) In the provided diagram,the process illustrates the mechanism of enzyme action.
$P$ represents the substrate which binds to the active site of the enzyme.
$Q$ represents the enzyme,which has an active site where the substrate binds to form an enzyme-substrate complex.
$R$ represents the product formed after the reaction.
$S$ represents the enzyme released after the reaction,which remains unchanged and can catalyze further reactions.
Therefore,$Q$ represents the enzyme.

(D) The provided figure illustrates the mechanism of enzyme action,specifically the 'Lock and Key' or 'Induced Fit' model.
In this process:
$P$ represents the substrate.
$Q$ represents the enzyme.
The complex formed between the enzyme and substrate is the enzyme-substrate complex.
$R$ represents the product formed after the reaction.
$S$ represents the enzyme,which is released unchanged after the reaction to catalyze further substrate molecules.

(A) The correct statement is $Holoenzyme = Apoenzyme + Cofactor$.
An apoenzyme is the protein part of an enzyme,which is inactive on its own.
$A$ cofactor is a non-protein chemical compound that is required for the enzyme's activity.
When an apoenzyme binds with its specific cofactor,it forms a complete,catalytically active enzyme known as a $Holoenzyme$.
Coenzymes are a specific type of organic cofactor that bind loosely to the apoenzyme.
Therefore,$Holoenzyme = Apoenzyme + Coenzyme$ (where coenzyme acts as a cofactor) is the correct representation among the given options.

(B) : $A$ ribozyme is a ribonucleic acid $(RNA)$ enzyme that catalyses a chemical reaction in a similar way to that of a protein enzyme.
These are found in ribosomes and are also called catalytic $RNAs.$

(B) The graph shows the energy levels of reactants and products during a chemical reaction.
Since the energy level of the product is lower than that of the reactant,the reaction is exothermic.
Enzymes lower the activation energy of a reaction.
In the graph,$A$ represents the activation energy in the presence of an enzyme (lower peak),and $B$ represents the activation energy in the absence of an enzyme (higher peak).
Therefore,the correct description is an exothermic reaction with energy $A$ in the presence of an enzyme and $B$ in the absence of an enzyme.

(B) The correct answer is $B$. Competitive inhibition is a reversible process where the inhibitor competes with the normal substrate for the active site of the enzyme.
In competitive inhibition,the inhibitor is structurally similar to the substrate,allowing it to bind to the active site. This binding prevents the substrate from binding,thereby reducing the enzyme's affinity for the substrate.
The $K_m$ value (Michaelis constant) represents the substrate concentration at which the reaction velocity is half of the maximum velocity $(V_{max})$. $A$ higher $K_m$ indicates lower affinity. Since a competitive inhibitor reduces the apparent affinity of the enzyme for the substrate,it increases the $K_m$ value,not decreases it. Therefore,statement $B$ is incorrect.
Statement $A$ is correct because the inhibitor does not affect the catalytic step $(k_{cat})$ once the enzyme-substrate complex is formed. Statement $C$ is correct as the binding is reversible. Statement $D$ is correct because the inhibitor is not a substrate and is not chemically modified by the enzyme.

(B) The correct answer is $B$. The inhibition of succinate dehydrogenase by malonate is a classic example of competitive inhibition.
Competitive inhibition is a reversible process where the inhibitor competes with the substrate for the active site of the enzyme.
Because the inhibitor is structurally similar to the substrate,it occupies the active site,preventing the substrate from binding.
Since this binding is temporary and reversible,increasing the concentration of the substrate (succinate) allows it to outcompete the inhibitor (malonate) for the active site,thereby reversing the inhibition.
Therefore,the statement that adding a lot of succinate does not reverse the inhibition is incorrect.

(A) The transition state is the formation of an unstable intermediate structural state during an enzymatic reaction.
During this process,existing bonds in the substrate are broken and new bonds are established to transform the substrate molecules into products.
This state is transient (short-lived) and highly unstable due to its high energy level.

(B) The correct answer is $B$.
Enzymes are primarily proteinaceous in nature.
Some $RNA$ molecules also act as enzymes,which are known as ribozymes.
There are no known lipids that function as enzymes.
Therefore,the statement that enzymes are lipids is incorrect.

(D) The correct answer is $D$.
Most enzymes are proteins in nature, but some are $RNA$ molecules known as ribozymes.
There are no known lipids that function as enzymes.
Therefore, the statement that 'some enzymes are lipids' is incorrect.

(B) In the given graph representing the progress of an enzymatic reaction:
- $A$ represents the peak of the curve, which is the $Transition \text{ } state$.
- $B$ represents the energy level of the substrate, which is the $Potential \text{ } energy$.
- $C$ represents the energy barrier that must be overcome for the reaction to proceed without an enzyme, known as the $Activation \text{ } energy \text{ } without \text{ } enzyme$.
- $D$ represents the lowered energy barrier when an enzyme is present, known as the $Activation \text{ } energy \text{ } with \text{ } enzyme$.
Therefore, the correct identification is given in option $B$.

(B) The enzyme $Invertase$ (also known as $Sucrase$) catalyzes the hydrolysis of sucrose into its constituent monosaccharides,glucose and fructose. The chemical reaction is represented as:
$Sucrose + H_2O \xrightarrow{Invertase} Glucose + Fructose$.
Therefore,the correct option is $B$.

(C) The enzymes $Pepsin$, $Trypsin$, and $Dipeptidase$ are all involved in the process of protein digestion (proteolytic enzymes).
$Pepsin$ acts in the stomach to break down proteins into peptides.
$Trypsin$ acts in the small intestine to break down proteins into peptides.
$Dipeptidase$ acts in the small intestine to break down dipeptides into amino acids.
$Carbonic \text{ } anhydrase$ is an enzyme that catalyzes the interconversion of carbon dioxide and water to bicarbonate and protons, which is involved in acid-base balance and gas transport, not protein digestion. Therefore, it is the odd one out.

(D) Hydrolases are enzymes that catalyze the hydrolysis of chemical bonds.
Lipases catalyze the hydrolysis of lipids (fats).
Proteases catalyze the hydrolysis of proteins.
Carbohydrases catalyze the hydrolysis of carbohydrates.
Since all three types of enzymes mentioned function by adding water to break bonds,they are all classified as hydrolases.
Therefore,the correct answer is $D$.

(B) Enzymes are classified into six classes based on the type of reaction they catalyse.
$1$. $Lyases$ are enzymes that catalyse the removal of groups from substrates by mechanisms other than hydrolysis,which often results in the formation of double bonds.
$2$. $Transferases$ catalyse the transfer of a group between a pair of substrates.
$3$. $Ligases$ catalyse the linking together of two compounds.
$4$. $Isomerases$ catalyse the interconversion of optical,geometric,or positional isomers.
Therefore,the correct answer is $Lyases$.

(A) An enzyme is often composed of a protein portion and a non-protein portion.
The protein portion of an enzyme is called the $Apoenzyme$.
It is the inactive part of the enzyme that requires a cofactor (such as a co-enzyme,metal ion,or prosthetic group) to become catalytically active.
The complete,active enzyme complex consisting of the $Apoenzyme$ and the cofactor is known as the $Holoenzyme$.

(A) Nucleic acids that possess catalytic activity and function as enzymes are called $Ribozymes$.
Most enzymes are proteins,but $Ribozymes$ are $RNA$ molecules that can catalyze specific biochemical reactions,such as the removal of introns during $RNA$ splicing or the formation of peptide bonds during protein synthesis.

(B) The given reaction is $S-G + S' \rightarrow S + S'-G$.
In this reaction,a functional group '$G$' is transferred from one substrate '$S$' to another substrate '$S'$'.
Enzymes that catalyze the transfer of a group other than hydrogen between a pair of substrates are classified as Transferases.
Therefore,the correct type of enzyme is Transferase.

(A) Enzymes are biocatalysts that speed up chemical reactions in living organisms.
Most enzymes are globular proteins,which means they are composed of amino acid chains folded into specific three-dimensional shapes.
These proteins lower the activation energy required for metabolic reactions,thereby controlling the rate of these processes within the cell.
Therefore,the correct answer is $A$.

(D) $Trypsin$ is a proteolytic enzyme (protease) found in the digestive system of many vertebrates, where it breaks down proteins.
$Collagen$ is a structural protein found in connective tissues.
$Antibody$ is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses.
$Insulin$ is a peptide hormone produced by beta cells of the pancreatic islets.

(B) ribozyme is an $RNA$ molecule that possesses catalytic activity,meaning it can catalyze specific biochemical reactions.
Most enzymes are proteins,but ribozymes are unique because they are composed of ribonucleic acid $(RNA)$.
Therefore,a ribozyme functions as an enzyme.