All Free Biology MCQs with Answers

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

Explanation: The enzyme is a complex organic substance, which altered the rate of an already initiated biological reaction without itself being altered permanently during the reaction. Most of the enzymes are protein in nature and show all the properties of proteins. Hence, A is the correct option

• A. Dipeptide
• B. Protein
• C. Polypeptide
• D. Peptide

Explanation: OPTION A: When two amino acids are joined together, a dipeptide is formed. OPTION B: Proteins can be defined as polymers of amino acids or polypeptide chains. OPTION C: When several amino acids are linked together by many peptide bonds, the polypeptide bond is formed. Thus a peptide having 10000 amino acids is called a polypeptide. Hence, C is the correct option. OPTION D: A peptide bond links amino acids in a protein molecule to each other. The peptide bond is formed between a carboxyl group of one amino acid and an amino group of another amino acid.

• A. Maximum temperature
• B. Absolute temperature
• C. Critical temperature
• D. Optimum temperature

Explanation: Option B : Absolute temperature is temperature measured using the Kelvin scale where zero is absolute zero. The zero point is the temperature at which particles of matter have their minimum motion and can become no colder (minimum energy). Option C : The critical temperature of a substance is the temperature at and above which the vapour of the substance cannot be liquefied, no matter how much pressure is applied.Option : D The temperature at which enzyme activity is maximum is called the optimum temperature. Optimum temperatures have conditions in which a particular enzyme is most active.

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

Explanation: Option: A A dehydrogenase is an enzyme belonging to the group of oxidoreductases that oxidizes a substrate by reducing an electron acceptor, usually NAD+/NADP+ or a flavin coenzyme such as FAD or FMN. Option B: Hydrolases are a group of enzymes that catalyze bond cleavages by reaction with water. Option C: In biochemistry, a ligase is an enzyme that can catalyze the joining of two molecules by forming a new chemical bond. Option D: Transferase is any one of a class of enzymes that catalyse the transfer of specific functional groups from one molecule to another.

• A. Reaction site
• B. Active site
• C. Binding site
• D. None of these

Explanation: The active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction.

• A. Coenzyme
• B. Cofactor
• C. Apo-enzyme
• D. Prosthetic group

Explanation: Apoenzyme or apoprotein is an enzymatically inactive protein part of an enzyme, which requires a cofactor for its activity.

• A. Activator
• B. Coenzyme
• C. Co-factor
• D. Both A and B

Explanation: Following are definitions of each of the above terms: Coenzyme: A substance that enhances the action of an enzyme. (An enzyme is a protein that functions as a catalyst to mediate and speed a chemical reaction). Coenzymes are small molecules. They cannot by themselves catalyze a reaction but they can help enzymes to do soCofactors: can be metals or small organic molecules, and their primary function is to assist (not enhance) in enzyme activity. They are able to assist in performing certain, necessary, reactions the enzyme cannot perform alone. Activators: Enzyme activators are chemical compounds that increase a velocity (enhances) of enzymatic reaction

• A. Simple proteins
• B. Conjugated proteins
• C. Derived proteins
• D. None of these options are correct

Explanation: 'Simple proteins' are those that are made of amino acid units only, joined by peptide bonds. Upon hydrolysis, they yield a mixture of amino acids and nothing else. 'Conjugated proteins' are composed of simple proteins combined with a non-proteinous substance. The non-proteinous substance is called the 'prosthetic' group or cofactor. 'Derived proteins' are not naturally occurring proteins and are obtained from simple proteins by the action of enzymes and chemical agents. Since both conjugated and derived types arise from simple proteins, the amount of simple proteins in the body has to be the greatest. Moreover, the functionality of simple proteins is so vast that the quantity required for them is large.

• A. Amylase
• B. Urease
• C. Pectin
• D. None

Explanation: Is correct as it is a fact as urease is involved in hydrolysis of urea

• A. Reversible
• B. Irreversible
• C. Condensation
• D. Oxidation

Explanation: Reason: Reactions of enzymes are mostly reversible depending on the extent to which the products differ from the reactants.