MCQ (Practice) - Enzyme (Level 1) - Class 11 MCQ

Indispensable Role in Energy Metabolism: Phosphorus
Phosphorus plays a vital role in energy metabolism. It is a crucial component of various molecules involved in energy transfer and storage within cells. Here is a detailed explanation of how phosphorus contributes to energy metabolism:
1. ATP (Adenosine Triphosphate) Production:
- Phosphorus is an integral part of ATP, which is often referred to as the "energy currency" of cells.
- ATP is formed through the phosphorylation of adenosine diphosphate (ADP) by adding a phosphate group, and this process is essential for energy transfer in cells.
- The release of energy from ATP occurs when the terminal phosphate group is cleaved, forming ADP and inorganic phosphate (Pi).
2. Phosphorylation Reactions:
- Phosphorus is involved in phosphorylation reactions, where phosphate groups are transferred from ATP to other molecules, such as glucose, during processes like glycolysis.
- These phosphorylation reactions provide energy to drive various metabolic pathways and cellular functions.
3. Nucleotide and Nucleic Acid Synthesis:
- Phosphorus is a key component of nucleotides, the building blocks of DNA and RNA.
- Nucleotides contain phosphate groups, and their synthesis is essential for energy metabolism and cell division.
4. Phospholipids and Cell Membranes:
- Phosphorus is present in phospholipids, which are major components of cell membranes.
- Phospholipids play a crucial role in maintaining the integrity and fluidity of cell membranes, facilitating energy-related processes such as nutrient uptake and waste removal.
In conclusion, phosphorus is indispensable for energy metabolism due to its involvement in ATP production, phosphorylation reactions, nucleotide synthesis, and cell membrane structure.

Mineral activator needed for the enzyme aconitase of TCA cycle is:

The correct answer is B: Fe (Iron).
Explanation:
The enzyme aconitase plays a crucial role in the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle or citric acid cycle. This cycle is an essential metabolic pathway involved in the production of energy in cells.
Function of aconitase:
Aconitase catalyzes the conversion of citrate to isocitrate in the TCA cycle. This step is important for the subsequent reactions in the cycle.
Mineral activator for aconitase:
The mineral activator needed for the enzyme aconitase is iron (Fe). Iron acts as a cofactor for aconitase, which means it is required for the enzyme to function properly. It helps in the binding of the enzyme to its substrate and facilitates the enzymatic reaction.
Other mineral activators:
While iron is the primary mineral activator for aconitase, other minerals can also play a role as cofactors for different enzymes in the TCA cycle. Some examples include:
- Magnesium (Mg): Magnesium is involved in the activation of enzymes like pyruvate dehydrogenase and isocitrate dehydrogenase in the TCA cycle.
- Manganese (Mn): Manganese is required for the activity of enzymes like pyruvate carboxylase and malate dehydrogenase in the TCA cycle.
- Copper (Cu): Copper is an essential cofactor for enzymes like cytochrome c oxidase, which is involved in the electron transport chain, a part of cellular respiration.
However, for the specific enzyme aconitase, the mineral activator needed is iron (Fe).
Conclusion:
In summary, the mineral activator needed for the enzyme aconitase in the TCA cycle is iron (Fe). Iron acts as a cofactor for aconitase and is required for its proper functioning. Other minerals like magnesium (Mg), manganese (Mn), and copper (Cu) also play roles as cofactors for different enzymes in the TCA cycle.

The effect of increased temperature on the rates of respiration and photosynthesis can be explained as follows:
1. Photosynthesis:
- Photosynthesis is the process by which plants convert sunlight into energy in the form of glucose.
- It is a temperature-dependent process, and the rate of photosynthesis generally increases with an increase in temperature, up to a certain point.
- However, when the temperature exceeds a certain threshold, usually around 35°C, the rate of photosynthesis starts to decline.
- This decline in photosynthesis is primarily due to the denaturation of enzymes involved in the process, which are sensitive to high temperatures.
2. Respiration:
- Respiration is the process by which organisms convert glucose into energy for their cellular functions.
- Like photosynthesis, respiration is also temperature-dependent, and the rate of respiration generally increases with an increase in temperature.
- However, unlike photosynthesis, the rate of respiration continues to increase even beyond 35°C, as long as oxygen and glucose are available.
- This is because respiration is a vital metabolic process for the survival of organisms, and it needs to continue even under unfavorable conditions.
Conclusion:
Based on the above information, we can conclude that when the temperature is increased above 35°C:
- The rate of decline of photosynthesis will be earlier than the decline of respiration.
- This is because photosynthesis is more sensitive to high temperatures and starts to decline sooner due to enzyme denaturation.
- On the other hand, respiration can continue at an increased rate, as long as oxygen and glucose are available.
Therefore, the correct answer is B: Rate of decline of photosynthesis will be earlier than the decline of respiration.

Coenzyme-II:
Coenzyme-II refers to the reduced form of NADP (Nicotinamide adenine dinucleotide phosphate). It is a coenzyme involved in many biological reactions, particularly those involved in anabolic processes such as lipid and nucleic acid synthesis.
Detailed
NADP and NAD are coenzymes that play crucial roles in cellular metabolism. However, only one of them is referred to as Coenzyme-II. Let's examine the options to identify the correct answer:
A: NAD (Nicotinamide adenine dinucleotide) - This is not Coenzyme-II.
B: NADP (Nicotinamide adenine dinucleotide phosphate) - This is the correct answer. NADP is the reduced form of NADP+ and is often referred to as Coenzyme-II.
C: FAD (Flavin adenine dinucleotide) - FAD is a different coenzyme involved in redox reactions, but it is not Coenzyme-II.
D: None of the above - This is not the correct answer since NADP is indeed Coenzyme-II.
In conclusion, the correct answer is B: NADP as it is the coenzyme referred to as Coenzyme-II.

Synthesis of Enzymes in a Cell
Enzymes are protein molecules that act as catalysts in biochemical reactions. They are essential for various cellular processes. The synthesis of enzymes occurs in a specific location within the cell. Let's explore where this synthesis takes place:
1. Location:
The synthesis of enzymes takes place on the surface of ribosomes, which are small organelles found in the cytoplasm of a cell.
2. Ribosomes:
Ribosomes are composed of two subunits: a large subunit and a small subunit. They can be found either free in the cytoplasm or attached to the endoplasmic reticulum (ER).
3. Protein Synthesis:
The process of enzyme synthesis, like any other protein synthesis, occurs in two main steps: transcription and translation.
- Transcription: In the nucleus, the DNA sequence that codes for a specific enzyme is transcribed into a messenger RNA (mRNA) molecule.
- Translation: The mRNA molecule carries the genetic information to the ribosomes in the cytoplasm or attached to the ER. The ribosomes use this information to synthesize the enzyme by linking together amino acids in a specific sequence.
4. Post-Translational Modifications:
After synthesis, enzymes may undergo post-translational modifications such as folding, cleavage, or addition of functional groups to become fully active. These modifications can occur in various cellular compartments, including the endoplasmic reticulum, Golgi apparatus, or specific enzyme organelles.
In conclusion, the synthesis of enzymes occurs on the surface of ribosomes in the cytoplasm of a cell. This process involves transcription of the DNA sequence into mRNA in the nucleus and subsequent translation of the mRNA by ribosomes to synthesize the enzyme. Post-translational modifications may further modify and activate the newly synthesized enzymes in different cellular compartments.

Excess of ATP inhibits the enzyme Phosphofructokinase.
Explanation:
- Phosphofructokinase (PFK) is an important enzyme in glycolysis, a metabolic pathway that converts glucose into pyruvate.
- PFK is regulated by the levels of ATP in the cell. ATP is an energy molecule that is produced during the process of glycolysis.
- Excess ATP indicates that the cell has sufficient energy and does not need to produce more ATP through glycolysis. Therefore, the enzyme PFK is inhibited to prevent unnecessary energy production.
- This inhibition of PFK by ATP is an example of feedback inhibition, where the end product of a pathway regulates the activity of an enzyme earlier in the pathway.
- When ATP levels are high, ATP binds to the allosteric site of PFK, causing a conformational change that reduces the enzyme's activity.
- This inhibition of PFK helps to maintain energy homeostasis in the cell by preventing excessive ATP production and conserving resources.
Therefore, the correct answer is A: Phosphofructokinase.

Enzyme Cytochrome Oxidase Inhibition:
Cytochrome oxidase is an enzyme found in the mitochondria of cells, and it plays a crucial role in cellular respiration. It is responsible for the final step in the electron transport chain, where it transfers electrons to oxygen to produce water.
The enzyme cytochrome oxidase can be inhibited by various substances, including:
1. Iodoacetate: Iodoacetate is a chemical compound that can irreversibly inhibit cytochrome oxidase by binding to its active site. This prevents the enzyme from functioning properly, leading to a disruption in cellular respiration.
2. Cyanides: Cyanides, such as potassium cyanide or sodium cyanide, are potent inhibitors of cytochrome oxidase. They bind to the active site of the enzyme and prevent it from transferring electrons to oxygen. This inhibition halts the production of ATP, which is the main energy source for cells.
3. Oligomycins: Oligomycins are a group of antibiotics that can inhibit cytochrome oxidase by blocking the flow of protons through the mitochondrial membrane. This disruption in the proton gradient prevents the synthesis of ATP, leading to a decrease in cellular energy production.
4. Dinitrophenol: Dinitrophenol is a chemical compound that can uncouple oxidative phosphorylation by disrupting the proton gradient across the mitochondrial membrane. This uncoupling prevents ATP synthesis and inhibits cytochrome oxidase activity.
Overall, the inhibition of cytochrome oxidase by these substances can have severe consequences on cellular respiration and energy production. It can lead to a decrease in ATP synthesis and impair various cellular processes that rely on energy.

Different steps in respiration are controlled by enzymes. Enzymes are biological catalysts that speed up chemical reactions in living organisms. In respiration, enzymes play a crucial role in breaking down glucose and other molecules to produce energy. Here is a detailed explanation of how enzymes control the different steps in respiration:
1. Glycolysis:
- Enzymes such as hexokinase and phosphofructokinase catalyze the conversion of glucose to glucose-6-phosphate and fructose-6-phosphate, respectively.
- Enzymes like aldolase and triose phosphate isomerase facilitate the breakdown of fructose-1,6-bisphosphate into two molecules of glyceraldehyde-3-phosphate.
2. Pyruvate decarboxylation:
- Enzymes like pyruvate dehydrogenase complex convert pyruvate into acetyl-CoA, releasing carbon dioxide in the process.
3. Krebs cycle:
- Enzymes such as citrate synthase, isocitrate dehydrogenase, and alpha-ketoglutarate dehydrogenase catalyze various reactions in the Krebs cycle, leading to the production of energy-rich molecules such as NADH and FADH2.
4. Electron transport chain:
- Enzymes like NADH dehydrogenase, cytochrome c reductase, and cytochrome c oxidase are involved in the transfer of electrons during the electron transport chain. This process generates a proton gradient, which is used to produce ATP through ATP synthase.
Overall, enzymes play a critical role in controlling the different steps of respiration by facilitating the necessary chemical reactions. Without enzymes, these reactions would occur too slowly to sustain life.

Structural & Functional Protein: Myosin
Myosin is a protein that exhibits both structural and functional (catalytic) properties. Here's a detailed explanation of why Myosin fits this criteria:
1. Structural Role:
- Myosin is a major component of muscle fibers, where it plays a crucial role in muscle contraction.
- It forms thick filaments that interact with actin, a thin filament, to generate movement.
2. Functional (Catalytic) Role:
- Myosin acts as an enzyme that hydrolyzes ATP (adenosine triphosphate) to ADP (adenosine diphosphate) and inorganic phosphate (Pi).
- This ATP hydrolysis provides the energy required for muscle contraction.
- Myosin acts as an ATPase, catalyzing the breakdown of ATP into ADP and Pi.
3. Other Functions of Myosin:
- Myosin also participates in various cellular processes, such as cell division, organelle transport, and cell motility.
- It is involved in the movement of vesicles, organelles, and other cargoes within cells.
In summary, Myosin is a protein that not only provides structural support in muscle fibers but also acts as an enzyme, catalyzing the hydrolysis of ATP to generate the energy necessary for muscle contraction.

Full Form of NAD: Nicotinamide Adenine Dinucleotide
NAD stands for Nicotinamide Adenine Dinucleotide, which is a coenzyme found in all living cells. It plays a crucial role in energy metabolism and cellular respiration. Here is a detailed explanation of the full form of NAD:
Nicotinamide:
- Nicotinamide is a form of vitamin B3, also known as niacin or nicotinic acid.
- It is an essential nutrient that is involved in various metabolic processes in the body.
Adenine:
- Adenine is one of the four nucleobases that make up DNA and RNA.
- It is a purine base, meaning it has a double-ring structure.
Dinucleotide:
- A dinucleotide is a molecule composed of two nucleotides joined together.
- In the case of NAD, it consists of two nucleotides: nicotinamide and adenine.
Role of NAD:
- NAD is involved in redox reactions, where it acts as an electron carrier.
- It participates in both catabolic and anabolic reactions, helping to transfer energy between molecules.
- NAD can exist in two forms: NAD+ (oxidized) and NADH (reduced).
- NAD+ accepts electrons and becomes reduced to NADH, which can then donate those electrons to other molecules in metabolic reactions.
Importance of NAD:
- NAD is essential for cellular respiration, which is the process by which cells convert glucose into energy.
- It is involved in the citric acid cycle and oxidative phosphorylation, which are key steps in energy production.
- NAD also plays a role in DNA repair, gene expression, and various signaling pathways.
In conclusion, the full form of NAD is Nicotinamide Adenine Dinucleotide. It is a vital coenzyme involved in energy metabolism and numerous cellular processes.

First discovered Enzyme was -

Answer: C. Zymase

Explanation:
Enzymes are biological catalysts that speed up chemical reactions in living organisms. The discovery of enzymes has been a significant milestone in the field of biochemistry. The first discovered enzyme is known as zymase.
Here is a detailed explanation of the options and why zymase is the correct answer:
A. Isomerase:
- Isomerase is an enzyme that catalyzes the conversion of one isomer to another.
- While isomerases are important enzymes, they were not the first discovered enzyme.
B. Transaminase:
- Transaminase is an enzyme that catalyzes the transfer of an amino group from one molecule to another.
- Although transaminases play a crucial role in various metabolic pathways, they were not the first discovered enzyme.
C. Zymase:
- Zymase is an enzyme complex that catalyzes the fermentation of glucose into ethanol and carbon dioxide.
- Zymase was the first enzyme to be discovered by Edward Buchner in 1897.
- Buchner's discovery of zymase led to the understanding of fermentation and paved the way for further research on enzymes.
D. Transferase:
- Transferase is a generic term for enzymes that transfer functional groups from one molecule to another.
- While transferases are essential for various biochemical reactions, they were not the first discovered enzyme.
In conclusion, the correct answer is C. Zymase, as it was the first enzyme to be discovered.

The Discovery of Enzymes
Enzymes were discovered for the first time in yeast. Here is a detailed explanation of the discovery:
1. Introduction
Enzymes are protein molecules that act as catalysts in biological reactions. They play a vital role in speeding up chemical reactions in living organisms. The discovery of enzymes was a significant milestone in the field of biochemistry.
2. Historical Background
The discovery of enzymes dates back to the late 19th century. During that time, scientists were studying the process of fermentation, which is the conversion of sugar into alcohol by yeast. It was observed that certain substances present in yeast extract could catalyze the fermentation process.
3. The Contribution of Eduard Buchner
In 1897, the German chemist Eduard Buchner conducted experiments that led to the discovery of enzymes. Buchner extracted a cell-free extract from yeast and found that it could still ferment sugar, indicating the presence of a non-living substance responsible for the fermentation process. He named this substance "zymase," which we now know as enzymes.
4. Significance of the Discovery
The discovery of enzymes in yeast had a profound impact on the field of biochemistry. It provided evidence that biological reactions could occur outside of living cells and could be attributed to specific substances. This discovery laid the foundation for further research on enzymes and their role in various biochemical processes.
5. Further Research
After the discovery of enzymes in yeast, scientists began exploring other sources of enzymes. They found enzymes in bacteria, algae, plants, and animals. Today, enzymes are widely studied and utilized in various industries, including food, medicine, and biotechnology.
In conclusion, enzymes were first discovered in yeast by Eduard Buchner in 1897. This discovery revolutionized our understanding of biochemical reactions and opened up new avenues for research in the field of enzymology.

Who coined the term enzyme?
The term "enzyme" was coined by a German physiologist named Wilhelm Kuhne in the year 1878. Kuhne was studying the digestive process and discovered a substance in saliva that had the ability to break down starch into simpler molecules. He named this substance "enzyme" from the Greek words "en", meaning "in", and "zyme", meaning "yeast" or "ferment". This term was chosen because enzymes were initially believed to be produced by living organisms such as yeast.
Details of the individuals mentioned:
Here are brief details about the individuals mentioned in the options:
- Pasteur: Louis Pasteur was a French chemist and microbiologist. While he made significant contributions to the field of microbiology and fermentation, he did not coin the term "enzyme".
- Buchner: Eduard Buchner was a German chemist who discovered that fermentation could occur in the absence of living cells, leading to the identification of enzymes as catalysts. However, he did not coin the term "enzyme".
- Kuhne: Wilhelm Kuhne was a German physiologist who coined the term "enzyme" in 1878. He made important contributions to the understanding of enzymes and their role in digestion.
- Summer: It is unclear who "Summer" refers to in this context. There is no prominent individual associated with the name "Summer" in relation to the term "enzyme".
Therefore, the correct answer is C: Kuhne.

Vitamin serves the function of -
A coenzyme:
- A coenzyme is a non-protein compound that is necessary for the proper functioning of enzymes.
- Vitamins often serve as coenzymes, which means they assist enzymes in carrying out their specific biochemical reactions.
- Coenzymes are organic molecules that bind to enzymes and help them catalyze reactions in the body.
- Vitamins act as coenzymes by binding to specific enzymes and facilitating their activity.
- Without vitamins acting as coenzymes, many essential biochemical reactions in the body would not occur efficiently.
Examples of vitamin coenzymes:
- Vitamin B1 (thiamine) acts as a coenzyme in the metabolism of carbohydrates.
- Vitamin B2 (riboflavin) is a coenzyme for various metabolic reactions, including energy production.
- Vitamin B3 (niacin) is a coenzyme involved in energy metabolism and DNA repair.
- Vitamin B6 (pyridoxine) is a coenzyme in the metabolism of amino acids.
- Vitamin B12 (cobalamin) is a coenzyme involved in the synthesis of DNA and red blood cells.
Conclusion:
Vitamins serve the function of being coenzymes in various biochemical reactions in the body. They assist enzymes in carrying out their specific functions, thus playing a crucial role in overall metabolism and cellular processes.

Coenzymes:
Coenzymes are small molecules that work alongside enzymes to facilitate various biochemical reactions in the body. They act as carriers of specific functional groups or electrons during metabolic processes. Some examples of coenzymes include NAD, NADP, and FAD.
NAD (Nicotinamide Adenine Dinucleotide):
- NAD is a coenzyme involved in redox reactions.
- It can accept electrons (reduced form: NADH) or donate electrons (oxidized form: NAD+) during metabolic reactions.
- NAD is used in processes such as glycolysis, the citric acid cycle, and oxidative phosphorylation.
NADP (Nicotinamide Adenine Dinucleotide Phosphate):
- NADP is a phosphorylated form of NAD.
- It is involved in anabolic reactions, such as nucleotide synthesis and lipid biosynthesis.
- NADP can accept electrons (reduced form: NADPH) or donate electrons (oxidized form: NADP+) during these reactions.
FAD (Flavin Adenine Dinucleotide):
- FAD is another coenzyme involved in redox reactions.
- It can accept electrons (reduced form: FADH2) or donate electrons (oxidized form: FAD) during metabolic processes.
- FAD is used in reactions such as the citric acid cycle and electron transport chain.
Conclusion:
All three options, NAD, NADP, and FAD are examples of coenzymes. They play essential roles in various metabolic processes and are involved in redox reactions. Therefore, the correct answer is D: All the above.

NADP - Nicotinamide Adenine Dinucleotide Phosphate
NADP is a coenzyme that plays a crucial role in various metabolic reactions. It exists in two forms: NADP+ (oxidized form) and NADPH (reduced form). Here is a detailed explanation of what NADP is and its role in cellular metabolism:
1. Definition:
NADP stands for Nicotinamide Adenine Dinucleotide Phosphate. It is a coenzyme derived from niacin (vitamin B3) and is involved in numerous biochemical reactions.
2. Structure:
NADP consists of two nucleotides, nicotinamide adenine dinucleotide (NAD) and a phosphate group (P). It contains a ribose sugar, adenine base, and a pyrophosphate group. The phosphate group can accept and donate electrons during redox reactions.
3. Role:
NADP acts as an electron carrier and plays a vital role in cellular metabolism. It is primarily involved in anabolic reactions, including biosynthesis of fatty acids, cholesterol, and nucleotides. Some key functions of NADP are:
- H2 Acceptor: NADP acts as a hydrogen ion (H2) acceptor, which means it can accept two electrons and a proton to form NADPH. This reduced form of NADP is vital for many biosynthetic reactions.
- Redox Reactions: NADP participates in redox reactions by accepting and donating electrons. It can be oxidized to NADP+ by losing electrons or reduced to NADPH by gaining electrons.
- Enzyme Co-Factor: NADP serves as a co-factor for several enzymes involved in various metabolic pathways. It aids in the transfer of electrons and the synthesis of high-energy molecules like ATP.
- Antioxidant: NADPH acts as a reducing agent and plays a crucial role in cellular antioxidant defense. It helps regenerate other antioxidants like glutathione, which protects cells from oxidative damage.
4. NADP vs. NAD:
NADP and NAD (Nicotinamide Adenine Dinucleotide) are structurally similar, but they have different roles in cellular metabolism. NAD is primarily involved in catabolic reactions, such as glycolysis and the Krebs cycle, whereas NADP is more focused on anabolic reactions.
In summary, NADP is an essential coenzyme involved in various metabolic reactions. It acts as a hydrogen ion acceptor, participates in redox reactions, serves as an enzyme co-factor, and plays a crucial role in cellular metabolism and antioxidant defense.

Prosthetic Group of Various Respiratory Enzymes
The prosthetic group of various respiratory enzymes is Mg (Magnesium). This group plays a crucial role in the function of these enzymes. Here are the details:
1. Prosthetic Groups
- Prosthetic groups are non-protein molecules that are bound to enzymes and are necessary for their proper functioning.
- They can be either inorganic or organic molecules.
2. Role of Prosthetic Groups in Respiratory Enzymes
- Respiratory enzymes are involved in the process of respiration, which includes the breakdown of nutrients to produce energy.
- These enzymes require prosthetic groups for their catalytic activity and stability.
3. Magnesium (Mg) as a Prosthetic Group
- Magnesium (Mg) is an important prosthetic group found in various respiratory enzymes.
- It is involved in the electron transfer reactions and ATP synthesis during respiration.
- Mg ions coordinate with other molecules and stabilize the enzyme structure, allowing them to carry out their specific functions.
4. Examples of Respiratory Enzymes with Mg as Prosthetic Group
- Cytochrome C Oxidase: This enzyme, found in the electron transport chain, contains Mg as a prosthetic group.
- ATP Synthase: Mg ions are required for the proper functioning of this enzyme, which synthesizes ATP during respiration.
5. Other Prosthetic Groups
- While Mg is an essential prosthetic group in respiratory enzymes, there are other groups found in different enzymes.
- For example, some enzymes may contain iron (Fe), copper (Cu), or molybdenum (Mo) as their prosthetic groups.
In conclusion, the prosthetic group of various respiratory enzymes is Mg (Magnesium). It plays a vital role in the catalytic activity and stability of these enzymes during the process of respiration.

Explanation:
Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are composed of two parts:
1. Apoezyme: Also known as the protein component, this is the main part of the enzyme that provides the catalytic activity. It is made up of amino acids and determines the specific function of the enzyme.
2. Prosthetic group: This is the non-protein component of the enzyme, which may be a metal ion or an organic molecule. It is tightly bound to the apoezyme and is essential for the enzyme's activity. It helps in stabilizing the enzyme structure and/or participating in the catalytic reaction.
To summarize, enzymes consist of two parts - the apoezyme (protein component) and the prosthetic group (non-protein component). These two parts work together to catalyze specific chemical reactions in living organisms.
Therefore, the correct answer is option D: Apoezyme and prosthetic group.

Answer:
The first enzyme that was isolated in crystalline form was Urease. Here is a detailed explanation:
Introduction:
- Enzymes are biological catalysts that speed up chemical reactions in living organisms.
- Isolating enzymes in crystalline form is an important step in studying their structure and function.
Explanation:
- Urease is an enzyme that catalyzes the hydrolysis of urea into ammonia and carbon dioxide.
- In 1926, James B. Sumner successfully isolated and crystallized urease from jack bean seeds.
- Sumner's work was groundbreaking as it was the first time an enzyme had been isolated and purified in a crystalline form.
- This achievement provided evidence that enzymes are proteins, as the crystals obtained were pure and had well-defined structures.
- Sumner's work laid the foundation for further research on enzymes and their role in biochemical reactions.
Conclusion:
- The first enzyme to be isolated in crystalline form was Urease.
- This achievement by James B. Sumner in 1926 played a crucial role in advancing our understanding of enzymes and their functions.

Enzymes in plants are present in:
- All the living cells of plant body: Enzymes are present in all the living cells of the plant body. This includes cells in the leaves, stems, roots, flowers, and other plant organs.
- Enzymes in flowers: Enzymes are also present in flowers, where they play a role in various processes such as pollination, fertilization, and petal coloration.
- Enzymes in leaves: Leaves are one of the major sites of enzyme activity in plants. Enzymes in leaves are involved in processes such as photosynthesis, respiration, and the synthesis and breakdown of various compounds.
- Enzymes in parenchyma: Parenchyma cells are a type of plant tissue that are involved in various metabolic activities. Enzymes are present in parenchyma cells and play a role in processes such as storage, metabolism, and defense.
In summary, enzymes are present in all the living cells of the plant body, including flowers, leaves, and parenchyma cells. They are involved in various metabolic and physiological processes essential for plant growth and development.

An enzyme is made up of:
- Protein: Enzymes are biological catalysts that are composed of proteins. Proteins are made up of amino acids, and the sequence of amino acids determines the structure and function of the enzyme.
- Cofactors: Some enzymes require additional non-protein molecules called cofactors to function properly. Cofactors can be inorganic ions, such as iron or zinc, or organic molecules called coenzymes.
- Active Site: Enzymes have a specific region known as the active site where the substrate binds and the catalytic reaction takes place. The amino acid residues within the active site contribute to the enzyme's specificity and catalytic activity.
- Secondary and Tertiary Structure: Enzymes have a complex three-dimensional structure due to the folding of the protein chain. The secondary structure is formed by interactions between amino acids, such as alpha-helices and beta-sheets. The tertiary structure is the overall three-dimensional arrangement of the protein.
- Enzyme Classification: Enzymes are classified into different classes based on their catalytic mechanism, such as oxidoreductases, transferases, hydrolases, isomerases, ligases, and lyases.
- Enzyme Kinetics: Enzymes follow specific kinetic properties, such as Michaelis-Menten kinetics, which describe the relationship between substrate concentration and reaction rate.
In summary, enzymes are primarily composed of proteins, with additional cofactors or coenzymes required for their proper functioning. The specific amino acid sequence, active site, and three-dimensional structure of the protein contribute to the enzyme's catalytic activity.

To determine which of the following is not an enzyme, we need to understand what enzymes are and then analyze each option.
Enzymes:
- Enzymes are proteins that act as catalysts in chemical reactions within living organisms.
- They accelerate the rate of specific biochemical reactions without being consumed or permanently altered in the process.
- Enzymes are highly specific, meaning they will only catalyze a particular reaction or a set of similar reactions.
Now let's analyze each option:
A: Oxidase:
- Oxidase is an enzyme that catalyzes oxidation reactions by transferring electrons from a substance to an electron acceptor.
- It is an example of an enzyme.
B: Pepsin:
- Pepsin is an enzyme that breaks down proteins into smaller peptides in the stomach.
- It is an example of an enzyme.
C: Auxin:
- Auxin is not an enzyme but a plant hormone.
- It plays a role in plant growth and development, including cell elongation and differentiation.
- It is responsible for phototropism and gravitropism in plants.
D: Trypsin:
- Trypsin is an enzyme that breaks down proteins in the small intestine.
- It is an example of an enzyme.
Conclusion:
- Among the given options, C: Auxin is not an enzyme but a plant hormone.
- Therefore, the answer is C.

Enzyme capable of changing their shape are called allosteric enzymes.
Allosteric enzymes are enzymes that can undergo a change in shape or conformation in response to the binding of a molecule at a site other than the active site. This change in shape can either enhance or inhibit the enzyme's activity.
Explanation:
1. Allosteric enzymes:
- Allosteric enzymes have multiple binding sites, including the active site and allosteric sites.
- The binding of a molecule, known as an allosteric effector, to the allosteric site causes a conformational change in the enzyme's shape.
- This conformational change can either increase or decrease the enzyme's activity, depending on the specific enzyme and allosteric effector involved.
2. Active site:
- The active site of an enzyme is the region where the substrate binds and undergoes a chemical reaction.
- The conformational change in allosteric enzymes can affect the active site's accessibility and/or the enzyme's ability to bind and catalyze the substrate.
3. Regulation of enzyme activity:
- Allosteric enzymes play a crucial role in regulating metabolic pathways and maintaining homeostasis in cells.
- The binding of an allosteric effector can either activate or inhibit the enzyme, depending on the metabolic needs of the cell.
4. Examples:
- One example of an allosteric enzyme is phosphofructokinase, which is involved in the regulation of glycolysis.
- In the presence of high levels of ATP, phosphofructokinase undergoes a conformational change that inhibits its activity, preventing the further production of ATP.
- Another example is hemoglobin, which can change its shape in response to the binding of oxygen, enabling efficient oxygen transport in the blood.
Conclusion:
Allosteric enzymes are a class of enzymes that can change their shape in response to the binding of a molecule at an allosteric site. This conformational change can have significant effects on the enzyme's activity and play a crucial role in the regulation of metabolic pathways.

The Chemical Nature of Prosthetic Groups
Prosthetic groups are non-protein molecules that are tightly bound to proteins and are essential for their function. They can be divided into several categories based on their chemical nature. The majority of prosthetic groups are organic in nature.
Organic Prosthetic Groups:
- Organic prosthetic groups are derived from organic compounds and are composed of carbon, hydrogen, and other elements such as oxygen, nitrogen, and sulfur.
- These groups are covalently attached to proteins and play a crucial role in the protein's structure and function.
- Examples of organic prosthetic groups include heme, which is found in hemoglobin and myoglobin, and flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD+), which are involved in redox reactions.
Lipoidal Prosthetic Groups:
- Lipoidal prosthetic groups are lipid-based molecules that are associated with proteins.
- These groups are often found in membrane proteins and play a role in membrane structure and function.
- Examples of lipoidal prosthetic groups include fatty acids and cholesterol.
Metallic Prosthetic Groups:
- Metallic prosthetic groups are metal ions that are tightly bound to proteins.
- These groups are involved in various enzymatic reactions and can act as cofactors or coenzymes.
- Examples of metallic prosthetic groups include iron in hemoglobin and copper in cytochrome c oxidase.
Alkaloidal Prosthetic Groups:
- Alkaloidal prosthetic groups are derived from alkaloids, which are a class of naturally occurring nitrogen-containing compounds.
- These groups are found in some proteins and can have diverse functions.
- Examples of alkaloidal prosthetic groups include pyridoxal phosphate, which is involved in amino acid metabolism.
In conclusion, the majority of prosthetic groups are organic in nature, although lipoidal, metallic, and alkaloidal prosthetic groups also exist. These groups play a crucial role in protein structure and function and are essential for various biological processes.

Coenzyme derived from pantothenic acid (vitamin B complex)
Coenzyme A (Co-A) is a derivative of pantothenic acid, which is a member of the vitamin B complex. Co-A is an essential cofactor involved in various metabolic reactions in the body. It plays a crucial role in energy production and the metabolism of carbohydrates, fats, and proteins.
Explanation:
Pantothenic acid, also known as vitamin B5, is a water-soluble vitamin found in various food sources. It is a precursor to Coenzyme A, which is derived from pantothenic acid through a series of enzymatic reactions.
Coenzyme A is involved in numerous metabolic pathways, including:
1. Energy production: Co-A is a key component in the citric acid cycle (also known as the Krebs cycle) and the electron transport chain, which are responsible for generating ATP, the energy currency of the cell.
2. Fatty acid synthesis: Co-A is required for the activation of fatty acids, allowing them to be incorporated into triglycerides, phospholipids, and other lipid molecules.
3. Amino acid metabolism: Co-A is involved in the breakdown and synthesis of amino acids, which are the building blocks of proteins.
4. Detoxification: Co-A participates in the detoxification of various substances, including drugs and xenobiotics, through conjugation reactions.
Conclusion:
In summary, Coenzyme A (Co-A) is a coenzyme derived from pantothenic acid, which is a member of the vitamin B complex. Co-A is involved in various metabolic reactions, including energy production, fatty acid synthesis, amino acid metabolism, and detoxification.

Not Consumed in a Biochemical Process:
The correct answer is B: Enzyme.
Explanation:
In a biochemical process, various substances are consumed to carry out the necessary reactions. However, enzymes themselves are not consumed in the process but rather act as catalysts to facilitate the reactions. Here's a breakdown of the options:
A: Hormone: Hormones are signaling molecules that are produced by glands in the endocrine system. They are involved in various biochemical processes and are consumed in these processes.
B: Enzyme: Enzymes are proteins that speed up chemical reactions in living organisms. They are not consumed in the process but rather remain unchanged and can be used repeatedly.
C: Vitamin: Vitamins are organic compounds that are essential for normal functioning and metabolism. They are consumed in biochemical processes as coenzymes or cofactors.
D: Nucleotide: Nucleotides are the building blocks of DNA and RNA. They are consumed in various biochemical processes, such as DNA replication and protein synthesis.
In conclusion, enzymes are not consumed in a biochemical process, as they function as catalysts and remain unchanged after the reactions.

How the presence of an enzyme affects the activation energy of a reaction?
Introduction:
Activation energy is the minimum amount of energy required for a chemical reaction to occur. Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy. Let's understand how the presence of an enzyme affects the activation energy of a reaction.
Explanation:
When an enzyme is present in a reaction, it influences the activation energy in the following ways:
1. Formation of enzyme-substrate complex:
- Enzymes have a specific active site where the substrate binds.
- The binding of the substrate to the enzyme forms an enzyme-substrate complex.
- This complex stabilizes the transition state, reducing the energy required to convert reactants into products.
2. Inducing strain or distortion:
- Enzymes can induce strain or distortion in the substrate, making it easier for the reaction to occur.
- This strain or distortion weakens the existing bonds in the substrate and facilitates the formation of new bonds.
3. Providing an alternative pathway:
- Enzymes can provide an alternative reaction pathway with a lower activation energy.
- They can create a microenvironment that is more favorable for the reaction to take place.
4. Lowering the energy barrier:
- Enzymes stabilize the transition state of the reaction, reducing the energy barrier.
- This allows the reactants to overcome the activation energy barrier more easily and proceed to form products.
Conclusion:
In summary, the presence of an enzyme in a reaction lowers the activation energy by forming an enzyme-substrate complex, inducing strain or distortion, providing an alternative pathway, and lowering the energy barrier. This allows the reaction to occur more quickly and efficiently. Therefore, the correct answer is B: It becomes decreased.

The chief enzyme found in yeast cell is Zymase.
Zymase is an enzyme complex found in yeast cells that plays a crucial role in the process of fermentation. It is responsible for converting glucose into ethanol and carbon dioxide.
Here is a detailed explanation of why Zymase is the chief enzyme found in yeast cells:
1. Definition: Zymase is a complex of enzymes that catalyzes the conversion of glucose into ethanol and carbon dioxide during the process of fermentation.
2. Function: Zymase helps yeast cells produce energy by breaking down glucose molecules and releasing energy-rich compounds like ethanol and carbon dioxide.
3. Fermentation: Zymase is crucial for fermentation, which is the anaerobic process in which yeast cells convert sugars into alcohol and carbon dioxide. This process is used in the production of alcoholic beverages and bread making.
4. Other enzymes: While yeast cells also contain other enzymes like invertase, maltase, and amylase, these enzymes have different functions. Invertase and maltase are involved in the breakdown of specific sugars, while amylase breaks down starch into simpler sugars.
5. Importance: Zymase is considered the chief enzyme in yeast cells because it is directly involved in the key metabolic process of fermentation, which is integral to the survival and energy production of yeast cells.
In conclusion, the chief enzyme found in yeast cells is Zymase. It plays a crucial role in the process of fermentation by converting glucose into ethanol and carbon dioxide.

Enzyme That Joins Broken Strands of DNA: Ligase

• Nuclease: Nuclease is an enzyme that degrades or breaks down DNA.


• Kinase: Kinase is an enzyme that adds a phosphate group to molecules.


• Ligase: Ligase is the enzyme responsible for joining or sealing the broken strands of DNA.


• Endonuclease: Endonuclease is an enzyme that cleaves the phosphodiester bond within a DNA strand.

Explanation:
When DNA strands are broken, it is necessary for them to be joined back together in order to maintain the integrity of the DNA molecule. This repair process is carried out by the enzyme called ligase. Ligase catalyzes the formation of phosphodiester bonds between the sugar-phosphate backbones of the DNA strands, effectively sealing the break and restoring the continuity of the DNA molecule.
It is important to note that ligase is involved in various DNA repair processes, including DNA replication, recombination, and the repair of DNA damage. It plays a crucial role in maintaining the stability and function of the genetic material.
In summary, the enzyme responsible for joining the broken strands of DNA is ligase.

Explanation:
The inhibition of succinic dehydrogenase by malonate is an example of competitive inhibition.
Here's a detailed explanation:
Competitive inhibition:
- In competitive inhibition, the inhibitor molecule competes with the substrate for binding to the active site of the enzyme.
- In this case, malonate acts as the inhibitor, and it competes with the substrate (succinate) for binding to the active site of succinic dehydrogenase.
- Malonate and succinate have similar structures, and they both bind to the active site of the enzyme.
- However, only one molecule (either malonate or succinate) can bind to the active site at a time.
- When malonate binds to the active site, it prevents succinate from binding and inhibits the enzyme's activity.
- The inhibition can be overcome by increasing the concentration of succinate, which increases the chances of succinate binding to the active site instead of malonate.
Other types of inhibition:
- Non-competitive inhibition: In non-competitive inhibition, the inhibitor binds to a site other than the active site and causes a conformational change in the enzyme, reducing its activity.
- Allosteric inhibition: In allosteric inhibition, the inhibitor binds to an allosteric site on the enzyme and causes a conformational change that reduces the enzyme's activity.
- Enzyme repression: Enzyme repression refers to the control of enzyme activity by regulatory mechanisms, such as the repression of enzyme synthesis.
In conclusion, the inhibition of succinic dehydrogenase by malonate is an example of competitive inhibition, where malonate competes with the substrate for binding to the active site of the enzyme.