All Free Biology MCQs with Answers

• A. Vitamins
• B. DNA
• C. Coenzyme
• D. None of these options are correct

Explanation: OPTION A: Vitamins are considered essential nutrients that are required in small amounts in the diet and are not classified as cofactors because they don't function as catalysts in enzymes and metabolic reactions, unlike organic and metallic organic molecules which are considered non-protein cofactors that help enzymes carry out their functions.OPTION B: DNA is not considered a non-protein part of a cofactor. It is the genetic material that contains the instructions for the development, functioning, and reproduction of all living organisms.OPTION C: The coenzyme is a type of cofactor that helps in the reaction completion by enhancing the enzyme activity. It is mostly present in enzyme-catalyzed reactions and is a non-protein part of the enzyme. The cofactors that are composed of organic constituents are called a coenzyme. They function as a catalyst in different reactions. They mostly contain vitamins as their essential components. For example, the coenzyme nicotinamide adenine nucleotide (NAD) and NADP contain the vitamin niacin in them.OPTION D: This option is not correct.

• A. LDH-1
• B. Protease
• C. Alkaline phosphatase
• D. None of these options is correct

Explanation: Alkaline phosphatase is used for the diagnosis of rickets and obstructive jaundice.

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

Explanation: Option A: A carbohydrate is a naturally occurring compound, or a derivative of such a compound, with the general chemical formula Cx(H2O)y, made up of molecules of carbon (C), hydrogen (H), and oxygen (O). Option B: Lipids are fatty, waxy, or oily compounds that are soluble in organic solvents and insoluble in polar solvents such as water. Lipids include: Fats and oils (triglycerides) Phospholipids.Option C: Proteins are polypeptide structures consisting of one or more long chains of amino acid residues. They carry out a wide variety of organism functions, including DNA replication, transporting molecules, catalyzing metabolic reactions, and providing structural support to cells.Option D: The molecule inside cells that contains the genetic information responsible for the development and function of an organism. DNA molecules allow this information to be passed from one generation to the next.

• A. Coagulation
• B. Dehydration
• C. Denaturation
• D. None of these options are correct

Explanation: Option A: Coagulation is defined as the change in the structure of protein (from a liquid form to solid or a thicker liquid) brought about by heat, mechanical action or acids.Option B: The water of hydration is essential to the structure of protein crystals; when they are completely dehydrated, the crystalline structure disintegrates. In some proteins this process is accompanied by denaturation and loss of the biological functionOption C: The secondary and tertiary structure of a protein can be disrupted by heating, by pH changes, by high concentrations of substances such as urea or by reducing agents that break the disulphide bonds. The process is calleddenaturation, and it destroys the protein's biological activity.

• A. Same sources
• B. Different organisms
• C. Same organisms
• D. None of these options are correct

Explanation: Isoenzymes are the enzymes that come from same organism and catalyse the same reaction but are chemically and physically distinct from each other

• A. Lyases
• B. Hydrolases
• C. Ligases
• D. Transferases

Explanation: Protease is an enzyme that hydrolyses the protein into amino acids. Hence it is a hydrolases enzyme.

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

Explanation: A peptide bond is made up of many amino acids condensing to form peptide bonds. Peptide chains are made up of many peptide bonds condensing to form chains. The sequence of amino acids is the primary structure and the hydrogen bonding between amino acids is the secondary structure. Various peptide bonds forming chains and joining together is the tertiary structure.

• A. Concentration of products
• B. Time
• C. Concentration of substrate
• D. Concentration of solvent

Explanation: The more the substrate, there is a higher chance that they will collide with the active sites of the enzymes and hence, the greater the rate of enzyme action. Hence, substrate concentration is directly proportional to enzyme action.

• A. Lyases
• B. Hydrolases
• C. Ligases
• D. Transferases

Explanation: Lyases are the enzymes responsible for catalyzing addition and elimination reactions. Lyase-catalyzed reactions break the bond between a carbon atom and another atom such as oxygen, sulfur, or another carbon atom.Lyase is an enzyme involved in glycolysis, hence lyase itself is the word for breaking down compounds

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

Explanation: Chemically, proteins are complex nitrogenous organic compounds, which are associated with the concept of life itself. By chemical composition, proteins are composed of carbon, hydrogen, oxygen, and nitrogen. Some proteins also contain smaller quantities of sulfur and phosphorus. The percentage of nitrogen is fairly constant and is about 16% of the molecular weight of protein. Hence, C is the correct option.