All Free Biology MCQs with Answers

4241. A protein having secondary structure possesses:

• A. Hydrogen bonding
• B. Disulfide bond
• C. Peptide bond
• D. Both A and C

Explanation: All proteins have primary structure; amino acids are joined with each other through peptide bonds. In Secondary structure, polypeptide chains coil to form either a helixes or B pleated sheets or both through hydrogen bonds.

4242. All the following are examples of fibrous proteins, except:

• A. Silk fiber
• B. Keratin
• C. Myoglobin
• D. Fibrin

Explanation: Silk fiber, keratin and fibrin are examples of fibrous proteins while myoglobin has a tertiary structure and is a typical water soluble globular protein found in muscles.

4243. Which of the following is a complex of globular protein with non-proteinaceous material?

• A. Collagen
• B. Albumin
• C. Fibrinogen
• D. Haemoglobin

Explanation: Hemoglobin consists of 4 polypeptide chains forming a quaternary structure, and 4 haem groups containing 4 iron atoms as a non-protein part of the molecule.

4244. Which one of the following is a non-protein group covalently bonded to a few respiratory enzymes, among others?

• A. Nicotine adenine dinucleotide.
• B. Flavin adenine dinucleotide.
• C. Nicotinamide adenine dinucleotide phosphate.
• D. All of the above options are correct.

Explanation: Flavin adenine dinucleotide (FAD) is a non-protein group that is covalently bonded to a few respiratory enzymes, among others.FAD is a redox-active coenzyme that plays a crucial role in various metabolic reactions, particularly cellular respiration. It acts as a carrier of electrons and hydrogen atoms during oxidative reactions. FAD is derived from the vitamin riboflavin (vitamin B2) and consists of a flavin mononucleotide (FMN) molecule attached to an adenosine diphosphate (ADP) moiety. It can be covalently bound to certain enzymes, serving as a prosthetic group. In respiratory enzymes, such as flavoproteins, FAD is covalently attached to the enzyme's active site and participates in redox reactions, transferring electrons and hydrogen atoms between substrates. Therefore, FAD is a non-protein group covalently bonded to a few respiratory enzymes, among others, and functions as a vital cofactor for their catalytic activity.

4245. _ are defensive proteins.

• A. Antigens
• B. Antibodies
• C. Vaccines
• D. Fibrinogen

Explanation: Antibodies are also called immunoglobulins, they are the part of the immune system and protect the body against invading pathogens.

4246. Proteins of hair, horns, feathers, and other skin parts is:

• A. Storage Protein
• B. Enzymatic Protein
• C. Structural Protein
• D. Hormonal Protein

Explanation: Usually fibrous proteins containing secondary structure are structural proteins. Structural proteins are a class of proteins that provide physical support and maintain the structural integrity of cells, tissues, and organisms. They contribute to the form, shape, and mechanical strength of various biological structures.

4247. Identify the protein, which cannot be crystallized?

• A. Antibodies
• B. Fibrin
• C. Haemoglobin
• D. Enzymes

Explanation: Fibrin is an example of fibrous protein and cannot non-crystalline. Antibodies, hemoglobin and enzymes are globular proteins and can be crystalline.

4248. How many peptide bonds are present in an insulin molecule?

• A. 49
• B. 50
• C. 51
• D. 48

Explanation: There are two polypeptide chains in insulin. One containing 21 amino acids and the other containing 30 amino acids. The bond between the each chain is one less than the total number of the amino acids. In this way the number of peptide bonds will be 49 out of 51 amino acids. So 49 bonds

4249. All the following biomolecules are nutritious except:

• A. Carbohydrates
• B. Proteins
• C. Lipids
• D. Nucleic acids

Explanation: Through metabolism carbohydrates, lipids and proteins all can be the source of energy, while nucleic acids are not the source of energy.

4250. It contains nitrogenous base:

• A. Glycogen
• B. ATP
• C. Cellulose
• D. Haemoglobin

Explanation: ATP is a nucleotide which contains pentose sugar, nitrogenous base and three phosphate groups. Glycogen and cellulose are polysaccharides and hemoglobin is a quaternary protein.