All Free Biology MCQs with Answers

4671. The organic biomolecules that store the maximum amount of potential energy are:

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

Explanation: Lipids having a maximum number of C - H bonds are capable to store maximum potential energy as compared to equal amounts of carbohydrates and proteins. Lipids store 9kcal of energy.

4672. Lipids provide water barrier to:

• A. Birds
• B. Fur containing animals
• C. Insects
• D. Birds and fur containing animals

Explanation: A thin coating of fats on the fur of animals and the feathers of birds saves them from absorbing rainwater and enables them to thermoregulate in winter.

4673. All _ are proteins and in this way they control the whole metabolism of the cell.

• A. Hormones
• B. Antibodies
• C. Enzymes
• D. Immunoglobulins

Explanation: Enzymes are proteins that play a crucial role in controlling the entire metabolism of the cell. They function as biological catalysts, accelerating the chemical reactions necessary for various cellular processes, thus ensuring the cell's metabolic pathways operate efficiently. In contrast, hormones, while sometimes proteins, are primarily signaling molecules; antibodies and immunoglobulins are focused on immune response, not metabolism.

4674. The organic biomolecules that exhibit maximum physiological diversity in living being are:

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

Explanation: Proteins are the most versatile biomolecules, performing numerous functions such as enzymatic activity, structural support, transport, communication, and defense mechanisms. This diversity surpasses that of lipids, which are mainly involved in energy storage and membrane structure; nucleic acids, which focus on genetic information; and carbohydrates, primarily responsible for energy provision and structural roles.

4675. Some proteins work as carriers and transport specific substances for example:

• A. Immunoglobulins
• B. Enzymes
• C. Albumins
• D. Hemoglobin

Explanation: Hemoglobin is the correct answer because it is a specialized carrier protein designed to transport oxygen and carbon dioxide in the bloodstream. Immunoglobulins are involved in immune response, enzymes catalyze biochemical reactions, and albumins serve a more general transport role but are not specialized for a single substance like hemoglobin.

4676. The protein that prevent the loss of blood from the body after injury is:

• A. Albumin
• B. Fibrin
• C. Globulin
• D. Keratin

Explanation: Fibrin is the protein responsible for preventing blood loss after injury by forming a stable blood clot. It is an insoluble plasma protein which seals the ruptured blood vessels after injury and prevents the loss of blood.

4677. These are polymers of amino acids:

• A. Hormones
• B. Enzymes
• C. Hemoglobin
• D. Proteins

Explanation: Proteins are polymers of amino acids linked together by peptide bonds. They are essential biological molecules with diverse functions, such as enzymes catalyzing reactions, structural components providing support, hormones regulating processes, and transporters moving substances across membranes. Other options like hormones, enzymes, or hemoglobin are specific types of proteins or molecules that do not encompass the full scope of what proteins are.

4678. Amino acids mostly contain following elements:

• A. Carbon, nitrogen, oxygen, hydrogen
• B. Carbon, nitrogen, sulphur, oxygen, hydrogen
• C. Carbon, sulphur, oxygen, hydrogen
• D. Carbon, nitrogen, sulphur, oxygen

Explanation: Amino acids, the building blocks of proteins, are primarily composed of carbon, nitrogen, oxygen, and hydrogen. These elements form the backbone of the amino acid structure, with nitrogen being present in the amino group of each amino acid. Although some amino acids contain sulphur, it is not a common component in all amino acids, distinguishing them from the primary elements listed in Option A. Therefore, Options B, C, and D are incorrect as they include sulphur, which is not a primary element in all amino acids, and some options omit nitrogen and hydrogen, which are essential components.

4679. All the amino acids have an amino group and a carboxyl group attached to the same carbon atom, also known as:

• A. Central carbon
• B. Major carbon
• C. Alpha carbon
• D. Beta carbon

Explanation: The correct answer is alpha carbon. In amino acids, the alpha carbon is the central carbon atom to which the key functional groups-amino group (-NH2) and carboxyl group (-COOH)-are directly attached. The term 'alpha carbon' specifically refers to this position in the structure of amino acids. Other terms like 'central carbon' and 'major carbon' are not standard terms used to describe this feature. A 'beta carbon' refers to the second carbon atom in the chain, which is not directly attached to the amino or carboxyl groups.

4680. The _ group of one amino acid may react with the _ group of another releasing a molecule of water to form a dipeptide.

• A. Functional, Amino
• B. Amino, Amino
• C. Carboxyl, Carboxyl
• D. Carboxyl, Amino

Explanation: The correct answer is Carboxyl, Amino. The peptide bond is formed when the carboxyl group of one amino acid reacts with the amino group of another amino acid. This reaction results in the release of a water molecule, a process known as a condensation reaction. The other options are incorrect because they do not involve the correct groups for forming a peptide bond. Specifically, two amino groups or two carboxyl groups cannot form a peptide bond with each other.