All Free Biology MCQs with Answers

4321. Proteins of hair, horns, feathers and other skin parts are:

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

Explanation: Proteins of hair, horns, feathers, and other skin parts are primarily structural proteins. Structural proteins provide support and shape to various body parts, such as hair, nails, horns, feathers, and the skin's outer layer. They have a fibrous and durable nature, which makes them well-suited for providing the necessary strength and integrity to these body parts.

4322. Usually a polypeptide chain bends and folds upon itself to form a globular shape. This is protein's:

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

Explanation: The tertiary conformation refers to the three-dimensional arrangement of a single polypeptide chain. The polypeptide chain bends, folds, and twists upon itself to form a specific globular shape stabilized by various types of interactions, such as hydrogen bonding, disulfide bridges, hydrophobic interactions, and ionic interactions. The tertiary structure is essential for the protein's overall stability and function.

4323. Which one of the following is used in synthesis of nucleic acid hormones, co-enzyme and amino acid for protein synthesis?

• A. Carbon
• B. Hydrogen
• C. Oxygen
• D. Nitrogen

Explanation: Carbon, hydrogen, and oxygen are also important elements in biological molecules, nitrogen stands out as the primary element associated with nucleic acids, co-enzymes, and amino acids, making it the correct answer in this context.

4324. Enzymes are molecules of one of the following group of biomolecules. Mark the correct answer which can also be defined as a biological catalyst:

• A. Protein
• B. Fats
• C. Carbohydrate
• D. Vitamins

Explanation: Enzymes are a type of biomolecule known as proteins. Proteins are large molecules composed of amino acids linked together in a specific sequence. Enzymes are biological catalysts, which means they facilitate and speed up chemical reactions in living organisms without being consumed in the process. Enzymes play a crucial role in various metabolic processes, and they are involved in breaking down substrates, building new molecules, and regulating biochemical pathways.

4325. Backbone of amino acid comprises of:

• A. C-C-N
• B. -NH2 Group
• C. -COOH group
• D. -H group

Explanation: The backbone of an amino acid is composed of a central carbon (C) atom, a hydrogen (H) atom, an amino (NH2) group, and a carboxyl (COOH) group. The central carbon atom is bonded to the amino group, the carboxyl group, and a hydrogen atom, forming a linear chain of C-C-N. Explanation are given below.

4326. Bonds present in alpha helix are:

• A. Hydrogen bonds
• B. Ionic bonds
• C. Disulphide linkage
• D. Peptide bonds

Explanation: The bonds present in an alpha helix are hydrogen bonds. In an alpha helix, the backbone of the polypeptide chain forms a helical structure stabilized by hydrogen bonds between the carbonyl oxygen atom of one amino acid and the amide hydrogen atom of another amino acid. These hydrogen bonds occur between the carbonyl group (C=O) of the nth amino acid and the amide group (N-H) of the (n+4)th amino acid along the chain, creating a stable and regular helical conformation.

4327. Sequence of amino acids is important in:

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

Explanation: The sequence of amino acids in a polypeptide chain, known as the primary structure, is crucially important for determining a protein's overall function and properties. The sequence dictates how the amino acids are arranged, and this specific order influences how the protein folds into its unique three-dimensional structure. The primary structure is the foundation upon which the higher-order structures of the protein, such as the secondary, tertiary, and quaternary structures, are built.

4328. The structure of a fibrous protein comprises of polypeptide chains in the form of:

• A. Cluster
• B. Spherical or curled up ball
• C. Flat uncoiled chains
• D. Long strands or librils

Explanation: Fibrous proteins are characterized by their long, elongated strands or fibrils. They have a repeating pattern of secondary structures, such as alpha helices or beta sheets, that align along the length of the protein. This arrangement imparts tensile strength and structural integrity, making fibrous proteins well-suited for providing support and structure in various tissues and cells.

4329. The structure given below is the constituent part of:

• A. Lipids
• B. Carbohydrates
• C. Vitamins
• D. Proteins

Explanation: The picture represents an amino acid, which is the building block of proteins. Proteins are large, complex molecules composed of one or more polypeptide chains made up of amino acids linked together by peptide bonds. The sequence of amino acids determines the primary structure of the protein, which then folds into its functional three-dimensional structure.

4330. Which of the following is a protease?

• A. Deaminase
• B. Rennin
• C. Oxidase
• D. Catalase

Explanation: Protease is an enzyme that cleaves peptide bonds. Rennin, also known as chymosin, is a protease enzyme that plays a crucial role in the digestion of milk proteins in the stomach of young mammals, especially in the early stages of life. Rennin helps coagulate milk, forming a curd that aids in the digestion and absorption of nutrients.