All Free Biology MCQs with Answers

4691. The example of structural protein is:

• A. Hemoglobin
• B. Albumin
• C. Antibodies
• D. Collagen

Explanation: Collagen is the correct answer as it is a structural protein that forms the framework of bones, cartilage, skin, and connective tissues, providing strength and support. Hemoglobin, Albumin, and Antibodies, on the other hand, are functional proteins involved in transport, maintaining osmotic balance, and immune response, respectively.

4692. One of the common secondary structure of protein is:

• A. α-helix
• B. β-helix
• C. γ helix
• D. Pi helix

Explanation: The α-helix is one of the most common secondary structures in proteins, known for its stability and regularity, due to hydrogen bonding between every fourth amino acid. This structure is found in many functional proteins. In contrast, the β-helix is not a secondary structure; it is a type of tertiary structure. The γ helix and Pi helix are rare and less stable helical forms, making them less prevalent in the secondary structures of proteins.

4693. It is formed by folding back of the polypeptide chain:

• A. α-helix
• B. β-helix
• C. α-pleated sheet
• D. β-pleated sheet

Explanation: The example of folded secondary protein is β − pleated sheetwhich is formed by folding back of polypeptide chain.

4694. This structural level of proteins is maintained by ionic, hydrogen and disulphide bonds:

• A. Primary structure
• B. Secondary structure
• C. Tertiary structure
• D. Quaternary structure

Explanation: The correct answer is the tertiary structure. Tertiary structure is the overall three-dimensional shape of a single protein molecule, and it is stabilized by various interactions, including ionic bonds, hydrogen bonds, and disulfide bridges. These bonds are crucial for maintaining the protein's functional shape. In comparison, primary structure is solely about the amino acid sequence, secondary structure involves regular patterns like alpha helices and beta sheets stabilized by hydrogen bonds, and quaternary structure refers to the arrangement of multiple protein subunits, which can include similar interactions as tertiary structure but also others like hydrophobic interactions.

4695. Stabilization of tertiary structure of proteins involve _ chemical bonds.

• A. One
• B. Two
• C. Three
• D. Four

Explanation: Tertiary structure is the overall folding of the polypeptide chain into a three-dimensional shape. This level of protein structure is stabilized by ionic bonds, hydrogen bonds, and disulfide bonds.

4696. Pick up the highly complex protein:

• A. Primary protein structure
• B. Secondary protein structure
• C. Tertiary protein structure
• D. Quaternary protein structure

Explanation: The quaternary structure of a protein is the most complex because it involves the organization of multiple polypeptide chains into a single functional unit. This complexity arises from the interactions between these chains, which can include various bonds and interactions. The primary structure is simply the sequence of amino acids, secondary structure involves local folding patterns like alpha helices and beta sheets, and tertiary structure is the three-dimensional configuration of a single chain. However, none of these are as intricate as quaternary structure, which integrates multiple polypeptide units.

4697. Polypeptide tertiary chains are aggregated and held together to give rise to:

• A. Primary structure
• B. Secondary structure
• C. Tertiary structure
• D. Quaternary structure

Explanation: More than one molecules of tertiary proteins are bonded to acquire a stable aggregated configuration called quaternary configuration e.g. hemoglobin.

4698. It involves all the four structural levels of proteins:

• A. Insulin
• B. α-helix
• C. Alpha chain of hemoglobin
• D. Hemoglobin molecule

Explanation: The correct answer is the Hemoglobin molecule. Hemoglobin is a complex protein consisting of four polypeptide chains, each having its primary, secondary, and tertiary structures. These chains come together to form a quaternary structure, thus involving all four structural levels of proteins. In contrast, Insulin is a single-chain peptide hormone, lacking quaternary structure. The α-helix is a secondary structural element, not a complete protein structure. Lastly, the Alpha chain of hemoglobin alone does not form a quaternary structure, as it is only part of the hemoglobin molecule.

4699. The amount of DNA is fixed for a particular species, as it depends upon the:

• A. Number of individuals
• B. Number of chromosomes
• C. Number of cells
• D. Number of genes

Explanation: The correct answer is the number of chromosomes. In a given species, the amount of DNA is determined by its chromosome number, which remains constant across all individuals of that species. This is why the DNA content is fixed. Other factors like the number of individuals, cells, or genes do not determine the fixed DNA amount, as each cell of the species typically contains the same DNA content based on its chromosome number.

4700. The amount of DNA in _ is one half to that of _.

• A. Somatic cells, Germ cells
• B. Gametocytes, Somatic cells
• C. Germ cells, Somatic cells
• D. Somatic cells, Gametocytes

Explanation: Germ cells (sperms and ova) are meiotic products, thus contain haploid number of chromosomes, whereas rest of the body cells are mitotic products.