Enzymes Questions in English

(D) The mathematical model describing the rate of enzymatic reactions by relating reaction rate $v$ to the concentration of a substrate $[S]$ was developed by Leonor Michaelis and Maud Menten in $1913$. This is known as the Michaelis-Menten kinetics,represented by the equation $v = \frac{V_{max}[S]}{K_m + [S]}$,where $V_{max}$ is the maximum velocity and $K_m$ is the Michaelis constant.

(A) Organophosphates act as potent inhibitors of the enzyme $Cholinesterase$.
This enzyme is essential for the breakdown of the neurotransmitter $Acetylcholine$ at the synaptic cleft.
By inhibiting this enzyme,organophosphates cause an accumulation of $Acetylcholine$,leading to overstimulation of the nervous system and eventual paralysis or death of the organism.

(D) The enzyme diastase was the first enzyme to be discovered. It was identified by Anselme Payen and Jean-François Persoz in $1833$. They isolated it from a malt extract and named it 'diastase' from the Greek word for 'separation'.

(D) Enzyme immobilisation is a technique used to restrict the mobility of enzymes to a fixed space.
$(a)$ Cross-linking involves binding enzyme molecules to each other using bifunctional or multifunctional reagents.
$(b)$ Covalent attachment involves forming stable chemical bonds between the enzyme and a solid support matrix.
$(c)$ Entrapment involves trapping enzymes within a polymer matrix or gel (like alginate or polyacrylamide) while allowing substrates to diffuse in and products to diffuse out.
Since all these methods are standard techniques for enzyme immobilisation,the correct answer is $D$.

(B) Carrier proteins exhibit high specificity for the molecules they transport,similar to how enzymes bind to their specific substrates. This specificity is due to the unique shape and chemical properties of the binding site on the carrier protein,which allows it to recognize and bind only to a particular type of molecule. This mechanism is often referred to as the 'lock and key' or 'induced fit' model,which is a fundamental characteristic of enzyme-substrate interactions.

(B) Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy $(E_a)$ required for the reaction to proceed.
By providing an alternative reaction pathway with a lower energy transition state,enzymes allow a greater number of substrate molecules to reach the energy threshold at a given temperature,thereby increasing the rate of the reaction.

(B) The first enzyme to be discovered was $Zymase$. It was discovered by $Eduard$ $Buchner$ in $1897$ from cell-free extracts of $Yeast$ ($Saccharomyces$ $cerevisiae$). This discovery demonstrated that fermentation could occur outside of living cells,leading to the field of biochemistry.

(B) Cytochrome oxidase is an enzyme that functions within the cell,specifically within the mitochondria as part of the electron transport chain $(ETC)$.
Enzymes that function inside the cell where they are synthesized are known as endoenzymes.
Since cytochrome oxidase catalyzes the final step of the electron transport chain inside the mitochondrial membrane,it is classified as an endoenzyme.

(A) Succinate dehydrogenase is an enzyme that catalyzes the oxidation of succinate to fumarate in the Krebs cycle.
Malonate is a structural analog of succinate.
Because malonate closely resembles the substrate (succinate),it competes with the substrate for the active site of the enzyme.
This type of inhibition,where the inhibitor competes with the substrate for the active site,is known as competitive inhibition.

(D) Carbonic anhydrase is known as the fastest enzyme in the biological world.
It catalyzes the hydration of $CO_2$ to form bicarbonate and protons.
It can catalyze the conversion of about $36,000,000$ molecules of $CO_2$ per minute.
This reaction is $10$ million times faster than the rate of the same reaction occurring without the enzyme.

(B) Enzymes are biological catalysts that speed up chemical reactions in living organisms. Almost all enzymes are proteins,which are composed of amino acids linked by peptide bonds. While some $RNA$ molecules (ribozymes) can act as catalysts,the vast majority of enzymes found in biological systems are proteinaceous in nature.

(B) The term $enzyme$ was coined by the German physiologist Wilhelm $K$ühne in $1877$. He derived the term from the Greek words $en$ (in) and $zyme$ (leaven or yeast),referring to the process of fermentation.

(B) Enzymes are biological catalysts that speed up chemical reactions in living organisms.
Chemically,almost all enzymes are proteins with a specific three-dimensional structure (tertiary structure).
This specific structure is essential for the enzyme to bind to its substrate at the active site,forming an enzyme-substrate complex.
Therefore,enzymes are proteins with a specific structure.

(C) $1$. Enzymes are biocatalysts that are generally proteinaceous in nature.
$2$. Most enzymes are denatured at high temperatures,but enzymes isolated from thermophilic organisms (like thermophilic bacteria) remain stable and active at temperatures as high as $80 \ ^\circ C - 90 \ ^\circ C$. Thus,statement $A$ is correct.
$3$. Enzymes are highly specific in their action,meaning a particular enzyme acts on a specific substrate. Thus,statement $B$ is correct.
$4$. Almost all enzymes are proteins. While some nucleic acids (ribozymes) can act as enzymes,lipids do not function as enzymes. Thus,statement $C$ is incorrect.
$5$. Enzymes exhibit maximum activity at a specific $pH$ known as the optimum $pH$. Thus,statement $D$ is correct.

(C) Competitive inhibition occurs when the substrate and the inhibitor resemble each other in structure and compete for the same active site of the enzyme.
Because the inhibitor occupies the active site,the substrate cannot bind,thereby reducing the rate of the reaction.
This type of inhibition can be overcome by increasing the concentration of the substrate,which increases the probability of the substrate binding to the active site rather than the inhibitor.

(A) An enzyme is often composed of a protein part and a non-protein part.
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 coenzyme or metal ion) to become catalytically active.
Since enzymes are biological catalysts made of amino acid chains,the $Apoenzyme$ is essentially a protein.

(B) Enzymes that catalyze the transfer of electrons (or hydrogen atoms) from one substrate to another are classified as oxidoreductases.
Dehydrogenases are a specific type of oxidoreductase that catalyze the removal of hydrogen atoms from a substrate,effectively facilitating electron transfer.
Therefore,enzymes involved in the transfer of electrons are known as dehydrogenases.

(C) Enzymes are biological catalysts that speed up chemical reactions in living organisms. Most enzymes are proteins.
$A$. Oxidase is an enzyme that catalyzes oxidation-reduction reactions.
$B$. Pepsin is a digestive enzyme that breaks down proteins into peptides in the stomach.
$C$. Oxygen is a chemical element $(O_2)$ and a gas,not an enzyme.
$D$. Trypsin is a digestive enzyme that breaks down proteins in the small intestine.
Therefore,oxygen is not an enzyme.

(A) Competitive inhibition occurs when a substrate analogue (an inhibitor) resembles the substrate in molecular structure and competes for the active site of the enzyme.
In the case of the enzyme succinic dehydrogenase,the normal substrate is succinate.
Malonic acid is structurally similar to succinate and competes with it for the active site of the succinic dehydrogenase enzyme.
Therefore,malonic acid acts as a competitive inhibitor of succinic dehydrogenase.

(C) Enzymes are biological catalysts that speed up biochemical reactions within living organisms.
Since metabolic activities occur in all living cells to maintain life processes,enzymes are essential in every living cell of the plant body.
Therefore,enzymes are present in all living cells of the plant body.

(C) The minimum amount of energy required by the reactants to undergo a chemical reaction and form products is known as activation energy.
In biochemical reactions,enzymes function by lowering this activation energy barrier,thereby facilitating the reaction process.
Therefore,activation energy is the essential energy required to initiate any biochemical reaction.

(D) Most enzymes are proteins in nature. However,there are some nucleic acids that behave like enzymes. These are known as ribozymes. Ribozymes are $RNA$ molecules that possess catalytic activity. Therefore,they are non-proteinaceous in nature.

(B) The Michaelis-Menten constant,denoted as $K_m$,is defined as the substrate concentration at which the reaction rate is exactly half of the maximum velocity $(V_{max}/2)$.
This constant is a measure of the affinity of the enzyme for its substrate.
$A$ lower $K_m$ value indicates a higher affinity of the enzyme for the substrate.

(C) Hydrolytic enzymes are a class of enzymes that catalyze the hydrolysis of chemical bonds.
Many hydrolytic enzymes,particularly those found in lysosomes (such as acid hydrolases),are specifically adapted to function optimally at an acidic $pH$ (low $pH$).
These enzymes are collectively referred to as hydrolases.
While proteases are a specific type of hydrolase,the broader term for enzymes that catalyze hydrolytic reactions is hydrolases.

(B) Enzymes are classified into six classes based on the type of reaction they catalyze.
$1$. Oxidoreductases/Dehydrogenases: These enzymes catalyze oxidoreduction between two substrates $S$ and $S'$ by transferring electrons.
$2$. Hydrolases: These catalyze the hydrolysis of ester,ether,peptide,or $C$-$C$ bonds.
$3$. Transaminases: These catalyze the transfer of an amino group between substrates.
$4$. Proteases: These are a type of hydrolase that breaks down proteins.
Therefore,the enzyme involved in the transfer of electrons is Dehydrogenase.

(D) Enzymes,vitamins,and hormones are essential biological chemicals that act as biocatalysts or regulatory molecules.
Enzymes act as catalysts for biochemical reactions.
Vitamins act as co-factors or precursors for co-enzymes.
Hormones act as chemical messengers that regulate physiological processes.
Collectively,they are essential for the regulation and control of metabolic pathways in living organisms.

(A) The efficiency of an enzyme is often determined by its catalytic power,which is represented by the turnover number $(k_{cat})$.
However,in the context of comparing enzyme kinetics,the $K_m$ value (Michaelis constant) is a crucial parameter.
$K_m$ represents the substrate concentration at which the reaction rate is half of the maximum velocity $(V_{max}/2)$.
$A$ lower $K_m$ value indicates a higher affinity of the enzyme for its substrate,meaning the enzyme is more efficient at lower substrate concentrations.
Therefore,$K_m$ is the standard parameter used to compare the efficiency and affinity of different enzymes for the same substrate.

(A) Competitive inhibition occurs when a structural analogue of the substrate competes with the actual substrate for the active site of the enzyme.
Since the inhibitor resembles the substrate,it binds to the active site,preventing the substrate from binding.
This type of inhibition can be overcome by increasing the concentration of the substrate.

(A) Enzymes that catalyze the joining of two molecules by forming new chemical bonds (such as $C-O$,$C-S$,$C-N$,or $C-C$ bonds) are classified as Ligases. These reactions are typically endergonic (require energy) and are coupled with the exergonic hydrolysis of $ATP$ to provide the necessary energy for the synthesis process. Therefore,the correct answer is Ligases.

(C) The first enzyme to be discovered was $Zymase$.
It was isolated from yeast cells by $Eduard \text{ } Buchner$ in $1897$.
$Zymase$ is a complex of enzymes that catalyzes the fermentation of sugar into ethanol and carbon dioxide.

(C) The $Active$ $site$ of an enzyme is a specific pocket or cleft formed by the tertiary structure of the protein. This is the region where the substrate molecule binds to the enzyme to form an enzyme-substrate complex,facilitating the chemical reaction.

(D) An allosteric enzyme is an enzyme that contains a region to which small,regulatory molecules may bind in addition to the active site.
These regulatory sites are known as allosteric sites.
Binding of a molecule to an allosteric site can either increase the enzyme's activity (allosteric activation) or decrease the enzyme's activity (allosteric inhibition).
Therefore,allosteric sites serve as regulatory points for both activation and inhibition of the enzyme.

(B) An allosteric inhibitor binds to a site other than the active site of an enzyme,known as the allosteric site.
This binding induces a conformational change (change in shape) in the enzyme's structure.
As a result,the active site is distorted,preventing the substrate from binding,which renders the enzyme inactive.
Competitive inhibitors,by contrast,bind to the active site directly without necessarily changing the enzyme's overall shape.

(D) The proteinaceous nature of enzymes was first demonstrated by $John \ H. \ Northrop$ in $1930$. He crystallized the enzyme pepsin and proved that it is a protein. $T. Cech$ discovered ribozymes ($RNA$ enzymes),$Kuhne$ coined the term 'enzyme',and $E. Buchner$ discovered cell-free fermentation.

(B) In $1926$,James $B$. Sumner isolated the enzyme $Urease$ from jack bean seeds in a crystalline form. This was the first time an enzyme had been crystallized,proving that enzymes are proteins. This discovery earned him a share of the Nobel Prize in Chemistry in $1946$.

(C) The term 'enzyme' was coined by the German physiologist $Wilhelm$ $Kuhne$ in $1877$. The word is derived from the Greek words '$en$' (in) and '$zyme$' (yeast), meaning 'in yeast'.

(B) The enzyme urease is a nickel-containing metalloenzyme that catalyzes the hydrolysis of urea into ammonia and carbon dioxide. It was first crystallized by James $B$. Sumner in $1926$ from the jack bean plant,which belongs to the genus $Canavalia$. Therefore,$Canavalia$ is the primary source from which urease is obtained.

(C) Allosteric inhibition is a regulatory mechanism where an effector molecule binds to a site other than the active site of an enzyme,causing a conformational change that reduces its activity.
This concept was proposed and discovered by $François \text{ } Jacob$ and $Jacques \text{ } Monod$ in the early $1960s$ while studying the regulation of gene expression and enzyme activity in bacteria.
Therefore,the correct option is $C$.

(D) Chemically,almost all enzymes are proteins.
They are composed of one or more polypeptide chains folded into a specific three-dimensional structure.
These proteins act as biological catalysts that speed up chemical reactions in living organisms by lowering the activation energy.

(B) Proteins are essential components of the protoplasm. Their primary importance lies in their role as biological catalysts,known as enzymes. Enzymes speed up biochemical reactions within the cell,which are vital for metabolism and maintaining life processes. While proteins can provide structural support and serve as energy sources under extreme conditions,their most critical functional role in the protoplasm is enzymatic catalysis.

(D) RuBisCO (Ribulose$-1,5-$bisphosphate carboxylase-oxygenase) is the most abundant protein in the biosphere. It is a key enzyme involved in the Calvin cycle during photosynthesis,responsible for fixing atmospheric $CO_2$ into organic compounds in plants.

(D) The correct answer is $D$ (Ptyalin).
$Gastrin$, $Glucagon$, and $Secretin$ are all hormones.
$Gastrin$ is a hormone that stimulates gastric acid secretion.
$Glucagon$ is a hormone produced by the pancreas that raises blood glucose levels.
$Secretin$ is a hormone that stimulates the pancreas to release bicarbonate-rich fluid.
$Ptyalin$ (also known as salivary amylase) is an enzyme, not a hormone, which breaks down starch into maltose.

(B) The correct answer is $\alpha$-amylase.
Salivary amylase (also known as ptyalin) is an enzyme that breaks down starch into maltose.
It functions optimally at a neutral pH (around $6.7$ to $7.0$).
When it reaches the stomach,the highly acidic environment (low pH due to $HCl$) denatures the enzyme,causing it to lose its catalytic activity.
In contrast,proteases like pepsin are specifically adapted to function in low pH environments.

(B) The enzyme invertase (also known as sucrase) is responsible for the hydrolysis of the disaccharide sucrose into its constituent monosaccharides, glucose and fructose.
The chemical reaction is: $C_{12}H_{22}O_{11} (\text{Sucrose}) + H_2O \xrightarrow{\text{Invertase}} C_6H_{12}O_6 (\text{Glucose}) + C_6H_{12}O_6 (\text{Fructose})$.

(B) Feedback regulation (or feedback inhibition) is a mechanism in metabolic pathways where the end product of a series of enzymatic reactions acts as an inhibitor for one of the earlier enzymes in the pathway.
When the concentration of the end product increases beyond a certain level,it binds to an allosteric site on the regulatory enzyme,thereby slowing down or stopping the pathway to prevent the overproduction of the substance and conserve cellular resources.

(A) Riboflavin is a water-soluble vitamin,also known as Vitamin $B_2$.
Renin is a proteolytic enzyme secreted by the stomach of infants that helps in the digestion of milk proteins (casein).

(D) The enzyme $Glucose-6-phosphatase$ is an integral membrane protein located in the endoplasmic reticulum. Its activity is strictly dependent on the presence of membrane lipids, specifically phospholipids, which provide the necessary environment for the enzyme to function. If the lipids are removed or the membrane structure is disrupted, the enzyme loses its catalytic activity.

(A) The enzyme $Tyrosinase$ is a copper-containing enzyme that catalyzes the oxidation of phenols. It is known that $Tyrosinase$ activity can be significantly enhanced or activated in the presence of certain lipids or phospholipids,which act as essential cofactors or structural components for its optimal function. Therefore,among the given options,$Tyrosinase$ is the correct answer.

(A) Enzymes are biological catalysts that speed up chemical reactions in living organisms.
Most enzymes are globular proteins,which are composed of one or more polypeptide chains.
These chains are folded into specific three-dimensional shapes,which are essential for their catalytic activity.
While some $RNA$ molecules (ribozymes) can act as catalysts,the vast majority of enzymes found in biological systems are proteins.

(B) An enzyme is often composed of a protein part and a non-protein part.
The proteinaceous part of an enzyme is known as the $Apoenzyme$.
The non-protein part is called the $Cofactor$.
When the $Apoenzyme$ combines with the $Cofactor$,the complete functional enzyme is called a $Holoenzyme$.