Test: Biomolecules - 1 - NEET MCQ

Oils have lower melting point (e.g., gingely oil) and hence remain as oil in winters.

The given molecule is adenylic acid. It is a nucleotide found in RNA. It is an ester of phosphoric acid with the nucleoside adenosine. It consists of a phosphate group, a pentose sugar ribose, and the nucleobase adenine.

Proteins human haemoglobin consists of 4 subunits. Two of these are identical toeach other. Hence, two subunits of αα type and two subunits of ββ type together constitute the human haemoglobin (Hb).

The diagram shown is a uracil which is a pyramidine belonging to nitrogen bases.

• Proteins are polymers of amino acids undergo dehydration to form a peptide linkage.
• Dipeptides are formed by a single peptide bond and a tripeptide through two peptide bonds and so on.

Protein molecules get denatured due to high temperature, very high or low pH and high energy radiation but there is no effect due to high pressure.

Based on number of amino and carboxyl groups, there are acidic (e.g., glutamic acid), basic (lysine) and neutral (valine) amino acids. Similarly, there are aromatic amino acids (tyrosine, phenylalanine, tryptophan).

Uracil nitrogenous base is produces nucleoside only with ribose sugar. This nucleoside is present only inside the RNA and absent in DNA.

Enzymes have a particular optimum range of working temperature, below which their activity decreases.

• Primary structure of protein is formed by peptide linkages between two amino acids.
• Secondary structure, i.e. α-Helix and β-Sheath, of protein is formed by hydrogen bonds.
• Tertiary structure of protein is formed by disulphide linkages between different amino acids
• Quaternary structure is formed when multiple chains of polypeptides held together by hydrogen bonds.

Plant cell walls are made of cellulose. Paper made from plant pulp is cellulose.

Amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon, i.e. the α-carbon. Hence, they are called α-amino acids.

Assertion (A): The formation of the enzyme-substrate complex is indeed a transient phenomenon and is crucial for catalysis, as it facilitates the reaction by bringing the substrate into proximity with the active site of the enzyme and lowering the activation energy. This is true.
Reason (R): The transition state structure is actually the least stable state, not the most stable state, during the conversion of substrate to product. The transition state is an intermediate, high-energy configuration that occurs before the substrate is converted into the product. This makes the Reason false.
Thus, the Assertion is true, but the Reason is false.

Answer: C) If Assertion is true but Reason is false
The Assertion (A) is true because the acid-insoluble fraction indeed contains macromolecules like proteins, nucleic acids, and polysaccharides.
However, the Reason (R) is false because lipids are not included in the acid-insoluble fraction. Instead, they are part of the acid-soluble fraction due to their low molecular weight and solubility properties, despite forming structures like cell membranes.

- Statement i is correct because polysaccharides can indeed be classified as homopolymers (like cellulose, which is made only of glucose) or heteropolymers (which contain different types of monosaccharides).

- Statement ii is incorrect; while cellulose is a homopolymer of glucose, it does not form complex helical structures. Instead, it has a linear structure that forms microfibrils.

- Statement iii is correct; starch serves as an energy reserve in plants and forms helical structures that can bind iodine, resulting in a blue complex.

- Statement iv is incorrect; glycogen is a highly branched polysaccharide, not linear, which allows for rapid mobilization of glucose when needed.

Thus, the correct statements are those in Option B: i and iii.

To analyze the statements:

- Statement i is correct; it describes the slow reaction rate in the absence of an enzyme.

- Statement ii is also correct; it accurately describes the function of carbonic anhydrase and its dramatic acceleration of the reaction rate.

- Statement iii is accurate; it notes that the pathway from glucose to pyruvic acid consists of ten enzyme-catalyzed reactions.

- Statement iv is incorrect; under anaerobic conditions, lactic acid is produced in skeletal muscle, not pyruvic acid.

Therefore, the correct answer, which includes statements i, ii and iii, is Option B.

To determine the correct statements:

• Statement i is incorrect because lipids are generally water insoluble, not soluble.
• Statement ii is correct as it accurately describes the types of fatty acids.
• Statement iii is incorrect because glycerol is not a simple sugar; it is a trihydroxy alcohol (trihydroxy propane) that combines with fatty acids to form triglycerides.
• Statement iv is correct as phospholipids are indeed found in cell membranes and contain phosphorus.

Thus, the correct statements are ii and iv, making Option A the right choice.

• Statement i is correct because nucleic acids are indeed made up of polynucleotides that include ribose in RNA and deoxyribose in DNA.
• Statement ii is incorrect; the building blocks of nucleic acids are nucleotides, not amino acids (which are the building blocks of proteins).
• Statement iii is correct as it accurately lists the nitrogenous bases found in nucleic acids.
• Statement iv is incorrect; DNA contains deoxyribose, while RNA contains ribose.

Thus, the correct answer is C: i, iii, and iv.

- Statement i is correct because all amino acids indeed have an amino group (-NH2) and a carboxyl group (-COOH) attached to the same α-carbon.

- Statement ii is also correct as there are exactly twenty standard amino acids that are incorporated into proteins.

- Statement iii is correct because the R group (side chain) varies among amino acids and determines their unique chemical properties.

- Statement iv is incorrect; while amino acids can be classified as acidic or basic, they can also be neutral and aromatic, making this statement false.

Thus, the correct statements are i, ii, and iii, leading to the answer being Option A.

- Statement i is correct because enzymes do require cofactors to be catalytically active, and the protein part without the cofactor is indeed called the apoenzyme.

- Statement ii is incorrect; prosthetic groups are tightly bound to the apoenzyme, not loosely associated.

- Statement iii is correct because coenzymes are indeed transiently associated with the apoenzyme and are often derived from vitamins, such as NAD from niacin.

- Statement iv is correct as certain enzymes do require metal ions, which are essential for their catalytic activity, forming coordination bonds at the active site.

Thus, the correct combination of statements is i, iii, and iv, corresponding to Option C.

Transferases are enzymes that facilitate the transfer of functional groups from one substrate to another, which is essential for various metabolic processes.

- The Assertion is correct because competitive inhibitors indeed bind to the active site of an enzyme, which prevents the substrate from binding.

- The Reason is also correct as increasing the substrate concentration can outcompete the inhibitor for the active site, thereby restoring enzyme activity.

- Additionally, the Reason effectively explains the Assertion as it describes how competitive inhibition can be mitigated, confirming that both statements are true and that the Reason is the correct explanation for the Assertion.

To determine which statements are correct, let's analyze each one:

- Statement i: This statement describes the initial binding of the substrate to the enzyme's active site, which is accurate as enzymes typically have specific active sites that fit their substrates (the "lock and key" model).

- Statement ii: This statement is also correct. After the substrate binds, the enzyme undergoes an "induced fit," altering its shape for a tighter fit around the substrate.

- Statement iii: This statement correctly describes the formation of the enzyme-product complex, where the active site facilitates the breaking of chemical bonds in the substrate.

- Statement iv: This statement is incorrect. Enzymes are not permanently altered after the reaction; they can be reused to catalyze additional reactions.

Thus, the correct statements are i, ii, and iii, leading to the correct answer being Option D.