Biomolecules

There are number of cases in which non-protein constituents called co-factors are bound to the enzyme to make the enzyme catalytically active.

In these instances, the protein portion of the enzymes is called the apoenzyme.

Three kinds of co-factors are identified prosthetic groups, co-enzymes and metal ions. Prosthetic groups are organic compounds and they are tightly bound with apoenzyme. Co-enzymes are also organic compounds but their association with apoenzyme is only transient.

The correct answer is A-III, B-II, C-I, D-IV

$\bullet$ Adenosine - It is a nucleoside which is composed of nitrogen base and sugar only.

$\bullet$ Adenylic acid - It is a nucleotide which is composed of nitrogen base, sugar and a phosphate group is esterified to the sugar.

$\bullet$ Adenine - Nitrogen base (Purine).

Alanine - An amino acid that contains a methyl group as the ' $R$ ' group.

The statement that best captures Reductionist Biology is:

Option C

• Physico-chemical approach to study and understand living organisms

Why?

Reductionism breaks complex systems into simpler parts.

In biology, it means explaining life processes in terms of physics and chemistry (molecules, atoms, reactions).

“Physico-chemical” explicitly combines physical laws with chemical interactions—the hallmark of a reductionist stance.

In enzymes like peroxidase and catalase, which facilitate the conversion of hydrogen peroxide into water and oxygen, 'haem' functions as the prosthetic group and is integral to the active site of these enzymes.

In contrast, zinc acts as a cofactor in the enzyme carbonic anhydrase.

RuBisCo is noted as the most abundant protein across the biosphere.

Succinate serves as the substrate for the enzyme succinate dehydrogenase.

In eukaryotes, packaging of DNA is much more complex. There is a set of positively charged, basic proteins called histones.

Histones are organised to form a unit of light molecules called histone octamer.

They are rich in the basic amino acid residues lysine and arginine.

Enzymes that catalyze the transfer of a group $ G $ (other than hydrogen) between a pair of substrates, $ S $ and $ S^{\#} $, are known as transferases. The general reaction is:

$ S-G + S^{\#} \rightarrow S + S^{\#}-G $

Transferases are responsible for transferring functional groups between molecules. In this reaction, the group $ G $ is being transferred from one substrate to another.

Ligases catalyze the linking together of two compounds, such as forming $ \mathrm{C}-\mathrm{O} $, $ \mathrm{C}-\mathrm{S} $, or $ \mathrm{C}-\mathrm{N} $ bonds.

Lyases facilitate the removal of groups from substrates, typically in a manner that leaves double bonds, and they achieve this without hydrolysis.

Hydrolases are enzymes that aid in the hydrolysis of various bonds, including ester, ether, peptide, glycosidic, $ \mathrm{C}-\mathrm{C} $, $ \mathrm{C}- $ halide, or $ \mathrm{P}-\mathrm{N} $ bonds.

The correct answer is Option B: Adenylic acid. Here's why:

Let's break down the components of a nucleotide:

• Sugar: A five-carbon sugar, either ribose (in RNA) or deoxyribose (in DNA).
• Phosphate Group: A molecule containing phosphorus and oxygen, often attached to the sugar.
• Nitrogenous Base: A molecule with nitrogen-containing rings, such as adenine (A), guanine (G), cytosine (C), thymine (T), or uracil (U).

Now let's analyze the options:

• Option A: Uridine is a nucleoside. It consists of the nitrogenous base uracil and the sugar ribose but lacks the phosphate group.
• Option B: Adenylic acid is a nucleotide. It consists of adenine, ribose, and a phosphate group.
• Option C: Guanine is a nitrogenous base, a component of nucleotides, but not a complete nucleotide itself.
• Option D: Guanosine is a nucleoside. It comprises guanine and ribose but lacks the phosphate group.

Therefore, Adenylic acid is the only option that contains all three components (sugar, phosphate, and nitrogenous base) required to be a complete nucleotide.

Option (A) is the correct answer because, ligases are the enzymes that catalyse the linking together of 2 compounds, e.g., enzymes which catalyse joining of C – O, C – S, C – N, P – O etc. bonds.

$\Rightarrow$ Options (B), (C) and (D) are wrong as ligase catalyse the joining of P – O, C – O & C – N bonds.

To determine which of the options are not fatty acids, we need to understand the nature of each compound mentioned:

Glutamic acid (A): This is an amino acid, not a fatty acid. Amino acids are the building blocks of proteins and have a structure completely different from that of fatty acids.

Arachidonic acid (B): This is a polyunsaturated omega-6 fatty acid, commonly found in the phospholipids of the cell membranes.

Palmitic acid (C): This is a saturated fatty acid that is commonly found in animals and plants. It is one of the most common fatty acids in body lipids.

Lecithin (D): Also known as phosphatidylcholine, lecithin is not a fatty acid but a fatty substance consisting of phospholipids. It is a major component of cell membranes.

Aspartic acid (E): This is another amino acid, not a fatty acid. Similar to glutamic acid, it is part of proteins and has a distinct structure from that of fatty acids.

Based on the information above:

Glutamic acid (A), Lecithin (D), and Aspartic acid (E) are not fatty acids.

Therefore, the correct option is:

Option C: A, D and E only

Option (1) is the correct answer because with the increase in substrate concentration, the velocity of enzymatic reaction rises at first. The reaction ultimately reaches maximum velocity (V$_{\mathrm{max}}$) which is not exceeded by any further rise in concentration of the substrate. This is because the enzyme molecules are fewer than substrate molecules and after saturation of these molecules, there are no free enzyme molecules to bind the additional substrate molecules

Option (2) is incorrect as velocity of reaction is continuously increasing in the given graph. In option (3) after reaching at Vmax, velocity declines while in option (4) velocity of reaction declines from high on increasing substrate concentration. So, option (3) and (4) are incorrect.

The correct answer is Option D: Lyases.

Here's why:

Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are classified into six main classes based on the type of reaction they catalyze.

Lyases are enzymes that catalyze the breaking of chemical bonds by means other than hydrolysis or oxidation. This typically results in the formation of a double bond or a new ring structure. They do not require water for the reaction and often produce a new double bond, ring, or a molecule of water.

Let's look at why the other options are incorrect:

Option A: Transferases These enzymes catalyze the transfer of functional groups (like methyl, phosphate, or amino groups) between molecules.

Option B: Oxidoreductases These enzymes catalyze oxidation-reduction reactions, where electrons are transferred between molecules.

Option C: Dehydrogenases These are a specific type of oxidoreductase that catalyze the removal of hydrogen atoms from a substrate.

In summary: Lyases are the enzymes responsible for breaking chemical bonds without using hydrolysis or oxidation, often creating double bonds or rings. This sets them apart from the other enzyme classes.

The correct answer is Option A: A-III, B-IV, C-II, D-I.

Here's a breakdown of the protein structures and their corresponding characteristics:

1. Primary Structure:

The primary structure refers to the linear sequence of amino acids in a polypeptide chain. This sequence is determined by the genetic code and is crucial for the protein's function.

Match: A - III (Polypeptide chain)

2. Secondary Structure:

The secondary structure arises from the hydrogen bonding between amino acids within the polypeptide chain. This results in the formation of regular, repeating patterns such as:

• Alpha-helix: A coiled structure resembling a spring.
• Beta-sheet: A sheet-like structure formed by hydrogen bonding between adjacent polypeptide segments.

Match: B - IV (Alpha helix and $\beta$ sheet)

3. Tertiary Structure:

The tertiary structure describes the three-dimensional shape of a single polypeptide chain. This structure is formed by interactions between various amino acid side chains, including:

• Hydrogen bonds
• Ionic bonds
• Hydrophobic interactions
• Disulfide bonds (formed between cysteine residues)

Match: C - II (Disulphide bonds)

4. Quaternary Structure:

The quaternary structure refers to the arrangement of multiple polypeptide chains (subunits) into a functional protein complex. This structure is stabilized by the same interactions responsible for the tertiary structure.

Match: D - I (Human haemoglobin)

Human haemoglobin is a classic example of a protein with a quaternary structure. It is composed of four polypeptide chains (two alpha and two beta chains), each of which binds to a heme group, enabling oxygen transport.

The correct answer is option (2).

Some lipids have phosphorous and a phosphorylated organic compound in them. These are phospholipids. They are found in cell membrane. Lecithin is one example.

Option (3) is incorrect as glycerides are another group of lipids in which both glycerol and fatty acids are present.

Option (1) and (2) are incorrect as amino acids and carbohydrates are separate groups of biomolecules.

The enzyme carboxypeptidase is well-known for its utilization of a zinc ion as a cofactor in its catalytic mechanism. The zinc ion plays a crucial role in the hydrolysis of peptide bonds, the reaction facilitated by carboxypeptidase. The presence of zinc allows for proper stabilization of water molecules which are necessary in the catalysis, making the hydrolysis of the peptide bond effective. This zinc dependency categorizes carboxypeptidase as a metalloenzyme.

Therefore, the correct answer is:

Option A: Zinc

Other options mentioned, such as Niacin, Flavin, and Haem, serve as cofactors for different enzymes. For example, Niacin is involved in the formation of NAD+ (Nicotinamide adenine dinucleotide) which acts as an electron carrier in many enzymatic reactions. Flavins (like FMN and FAD) are involved in a myriad of oxidation-reduction (redox) reactions. Haem, found in hemoglobin and cytochromes, also plays crucial roles primarily in electron transfer processes and oxygen transport. These are not associated with the functioning of carboxypeptidase, which specifically requires zinc for its enzymatic activity.

The inhibition of the enzyme succinic dehydrogenase by malonate is a classic example of competitive inhibition. To understand why this is the case, let's explore the mechanism and dynamics of this specific type of inhibition in the context of the given enzyme and inhibitor.

Competitive Inhibition: This type of enzyme inhibition occurs when an inhibitor compound resembles the substrate's structure and competes with the substrate for binding to the active site of the enzyme. If the inhibitor binds to the active site, it prevents the substrate from binding, temporarily blocking the enzyme’s activity. Importantly, competitive inhibition can typically be overcome by increasing the concentration of the substrate, as this can displace the inhibitor from the active site.

Succinic Dehydrogenase and Malonate: Succinic dehydrogenase is an enzyme that plays a critical role in the citric acid cycle, an essential metabolic pathway for energy production. It catalyzes the oxidation of succinate into fumarate. The structure of malonate is closely similar to that of succinate, the natural substrate of succinic dehydrogenase. Because of its structural similarity, malonate competes with succinate for the active site on succinic dehydrogenase. When malonate binds to the active site, it effectively inhibits the enzyme from catalyzing the reaction to convert succinate into fumarate.

Conclusion: Considering these points, Option C, Competitive inhibition, is correct for describing the inhibition of succinic dehydrogenase by malonate, as it directly competes with the substrate for the active site of the enzyme.

Other options such as cofactor inhibition, feedback inhibition, and enzyme activation do not accurately describe the situation with malonate and succinic dehydrogenase. Cofactor inhibition involves inhibition by substances that affect the enzyme's cofactors, feedback inhibition generally pertains to the regulation of biochemical pathways by their product, and enzyme activation is a process that increases the enzyme's activity, none of which apply in this context.

To solve this matching question, we need to correctly identify what each item in List I represents and match it with its corresponding description in List II:

• GLUT-4 is a glucose transporter protein that allows glucose to be absorbed into cells when insulin is present. Hence, it should be matched with "Enables glucose transport into cells."
• Insulin is a hormone produced by the pancreas that helps regulate blood glucose levels by facilitating the uptake of glucose into tissues. It should be matched with "Hormone."
• Trypsin is an enzyme that aids in the digestion of proteins in the digestive system. It should be matched with "Enzyme."
• Collagen is a primary structural protein that forms connective tissues throughout the body, including the extracellular matrix. It should be matched with "Intercellular ground substance."

Here's how we match each term with the correct description from List II:

A-IV, B-I, C-II, D-III

This corresponds to:

• A (GLUT-4) - IV (Enables glucose transport into cells)
• B (Insulin) - I (Hormone)
• C (Trypsin) - II (Enzyme)
• D (Collagen) - III (Intercellular ground substance)

Therefore, the answer is Option A:

A-IV, B-I, C-II, D-III

The task here is to correctly match the enzymes listed in List I with their corresponding type of bond they hydrolyze or act on, as listed in List II. To do this, we need to understand the function of each enzyme:

• Lipase: This enzyme catalyzes the breakup of fats (lipids), primarily working on the ester bonds in triglycerides. Thus, Lipase corresponds to Ester bond (II).
• Nuclease: Nucleases are enzymes that cleave the phosphodiester bonds within the nucleic acids, DNA and RNA. Therefore, Nuclease corresponds to Phosphodiester bond (IV).
• Protease: These enzymes hydrolyze proteins by breaking peptide bonds between amino acids. Thus, Protease matches with Peptide bond (I).
• Amylase: Amylase acts on starches, breaking down the glycosidic bonds in carbohydrate molecules to produce simple sugars. Hence, Amylase corresponds to Glycosidic bond (III).

Matching these to the given options:

• A - Lipase corresponds to Ester bond (II).
• B - Nuclease corresponds to Phosphodiester bond (IV).
• C - Protease corresponds to Peptide bond (I).
• D - Amylase corresponds to Glycosidic bond (III).

This matches with Option C, hence the correct response is:

Option C: A-II, B-IV, C-I, D-III.

The correct order of the steps in the catalytic cycle of enzyme action involves the following key events:

1. Substrate binding to the active site: Before any reaction can take place, the substrate must bind to the enzyme's active site. This is where the substrate is correctly positioned for the reaction.
2. Formation of the substrate-enzyme complex: Once the substrate binds to the active site, a substrate-enzyme complex is formed. This complex stabilizes the transition state of the reaction and lowers the activation energy required for the reaction.
3. Chemical bonds of the substrate broken : Within the substrate-enzyme complex, the specific chemical reaction occurs, leading to the breaking of bonds within the substrate. This step often involves changes to the chemical structure of the substrate, turning it into the product(s) of the reaction.
4. Release of products: After the reaction occurs, the product(s) of the reaction are released from the enzyme, leaving the enzyme unchanged.
5. Free enzyme ready to bind with another substrate: Once the product is released, the enzyme is free again to bind with another substrate, repeating the cycle.

Given the correct sequence and your provided options, the correct answer is:

Option A: E, A, D, C, B

This sequence correctly describes the steps involved in the catalytic cycle of enzyme action, from substrate binding to the release of products and the readiness of the enzyme to start a new cycle.

The correct matchings are :

(A) Protein - This is a polymer made up of amino acids linked by peptide bonds. So, (A) matches with (IV) Peptide bonds.

(B) Unsaturated fatty acid - These have one or more C=C double bonds in their hydrocarbon chain. So, (B) matches with (I) C=C double bonds.

(C) Nucleic acid - These are polymers made up of nucleotides linked by phosphodiester bonds. So, (C) matches with (II) Phosphodiester bond.

(D) Polysaccharide - These are polymers made up of monosaccharides linked by glycosidic bonds. So, (D) matches with (III) Glycosidic bonds.

So, the correct answer is Option C : (A)-(IV), (B)-(I), (C)-(II), (D)-(III).

Secondary metabolites are organic compounds produced by organisms that are not directly involved in the normal growth, development, or reproduction of the organism. Examples include antibiotics, pigments, and toxins.

Curcumin, morphine, and anthocyanin are all examples of secondary metabolites.

Lecithin, however, is a type of phospholipid, which is a primary metabolite as it is directly involved in the normal growth and development of cells by being a key component of cell membranes.

So, the correct answer is Option : Lecithin.

List I contains a list of categories of secondary metabolites or proteins, while List II contains examples of specific compounds.

Terpenoids are a large class of organic chemicals similar to terpenes, and diterpenes are a type of terpenoids. So, A matches with II.

Lectins are a type of protein that can bind specifically to certain sugars and so play a role in recognizing carbohydrates. Concanavalin A is a lectin. So, B matches with IV.

Alkaloids are a class of naturally occurring organic compounds that mostly contain basic nitrogen atoms. Codeine is an alkaloid found in opium poppy. So, C matches with I.

Toxins are poisonous substances produced within living cells or organisms. Ricin is a toxin. So, D matches with III.

Therefore, the correct answer is Option D : A-(II), B-(IV), C-(I), D-(III).

Option (B) is the correct answer because cellulose does not contain complex helices and hence cannot hold iodine molecules.

Option (A), (C) and (D) are not correct as cellulose is a polysaccharide.

The correct answer is option (C) as a protein is imagined as a line, the left end represented by the first amino acid and the right end is represented by the last amino acid. The first amino acid is also called N-terminal amino acid. The last amino acid is called the C-terminal amino acid.

Statement I : Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat.

• This statement is true. Low temperatures can slow down enzyme activity but do not typically denature the enzyme, essentially preserving it in an inactive state. High temperatures, on the other hand, can cause the enzyme (which is a protein) to denature, or lose its structure, which leads to a loss of enzymatic activity.

Statement II : When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as a competitive inhibitor.

• This statement is also true. A competitive inhibitor is a substance that binds to the active site of an enzyme, preventing the substrate from binding and thus inhibiting the enzyme's activity. Because it competes with the substrate for the same active site, a competitive inhibitor often has a structure that closely resembles that of the substrate.

So, the correct answer is :

Option D : Both Statement I and Statement II are true.

A symport is the transport of two types of molecules across the membrane in same direction.

Antiport is the transport of two different molecules in opposite directions.

Uniport is transport of a molecule across the membrane independent of other molecule.

Option (b) is the correct answer as adenine is a purine, anthocyanin is a pigment, chitin is a homopolysaccharide and codeine is an alkaloid.

Option (4) is the correct answer because primary proteins are heteropolymers containing strings of amino acids linked by peptide bonds.

Option (1) and (2) are incorrect as primary proteins are called polypeptides due to the presence of many monomers linked via peptide bonds, not due to the presence of many conformations.

Option (3) is incorrect because proteins are polymers of amino acid monomers.

The free living nitrogen fixing aerobic microbes are Azotobacter and Beijernickia

Rhizobium and Frankia are symbiotic nitrogen fixers.

Rhodospirillum is anaerobic nitrogen fixer.

Pseudomonas and Thiobacillus are denitrifying bacteria.

Option (b) is the correct answer because maltose is a disaccharide which on hydrolysis gives two molecules of glucose.

Maltose $\buildrel {\mathrm{Maltase}} \over \longrightarrow $ Glucose + Glucose

Options (a), (c) and (d) represent correct enzymatic reactions so they are not the answer.

In Hershey-chase experiment when radioactive sulphur was in protein capsule and radioactive phosphorus was in DNA then, no sulphur radioactivity detected in the cells as protein coat remains outside the bacterial cell after infection.

In the given question, sulphur is shown in the DNA and phosphorus in the protein coat. Hence radioactive sulphur will be seen in bacterial cells.

Option (d) is the correct answer as statement I is correct but statement II is incorrect.

A particular property of amino acids is the ionizable nature of $-$NH₂ and $-$COOH groups. Hence, in solutions of different pH, the structure of amino acid changes. Amino acid exists as a dipolar ion called a zwitterion at a particular pH called isoelectric point.

(B) is called zwitterionic form.

Option (c) is the correct answer because peroxidase is the enzyme that catalyzes the breakdown of hydrogen peroxide to water and oxygen; haem is the prosthetic group of this enzyme.

Option (a) and (b) are incorrect because co-enzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.

Option (d) is incorrect because zinc is a co-factor for the proteolytic enzyme carboxypeptidase.

Option (c) is the correct answer because statements (c), (d) and (e) correct as oils have lower melting point and hence remain oil in winters. Lipids are generally insoluble in water but soluble in some organic solvents.

Option (a), (b) and (d) are incorrect because statements (a) and (b) are incorrect. Lecithin is a type of phospholipid found in plasma membrane. Saturated fatty acids are without double bond.

Option (c) is correct because maltose is a disaccharide formed by dehydration process i.e., synthesis by elimination of one water molecule to form a glycosidic bond in between two glucose molecules. So, its molecular formula is

C₆H₁₂O₆ $\times$ 2 $\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{{H_2}O}} $ C₁₂H₂₂O₁₁

Option (d) is the correct answer as glycogen is a polysaccharide and is a storage product in animals.

$\bullet$ Globulins form antibodies which are also known as immunoglobulins.

$\bullet$ Steroids form hormones like testosterone.

$\bullet$ Thrombin is a biocatalyst which converts soluble fibrinogen to insoluble fibrin.