All Free Biology MCQs with Answers

• A. Protein part of enzyme
• B. Non-protein part of enzyme
• C. Complete enzyme
• D. Inactive enzyme

Explanation: A holoenzyme is the complete, active form of an enzyme. It is composed of an apoenzyme, which is the protein portion, and one or more…

• A. Irreversible inhibition
• B. Reversible inhibition
• C. Competitive inhibition
• D. Non competitive inhibition

Explanation: Non-competitive inhibitors obstruct enzymatic reactions by binding to a part of the enzyme away from the active site.

• A. Carbohydrates
• B. Proteins
• C. Lipids
• D. Can be lipid or proteins

Explanation: Enzymes are biological molecules that catalyze chemical reactions in living organisms.

• A. Changing conditions within the active site
• B. Changing conditions within the protein framework
• C. Rearranging the fatty acids in active site
• D. Distorting the molecules in the allosteric site

Explanation: Enzymes lower the activation energy by changing conditions within the active site.

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

Explanation: Enzymes are primarily proteins that serve as biological catalysts, facilitating and accelerating biochemical reactions by lowering the…

• A. By adding activation energy requirements.
• B. By lowering the activation energy requirements.
• C. By decreasing the concentration of products.
• D. By increasing the concentration of products.

Explanation: Enzymes are biological catalysts that increase the rate of reaction by lowering the activation of the energy of the reactions.

• A. Enzyme
• B. Substrate
• C. Allosteric side
• D. All of these options are correct

Explanation: c) ES-complex:This option is correct. Uncompetitive inhibition is characterized by the binding of the inhibitor to the enzyme-substrate…

• A. Vitamin B
• B. Vitamin B2
• C. Vitamin C
• D. Vitamin B1

Explanation: Coenzymes are organic molecules that help in the catalysis of chemical reactions by binding to the active sites.

• A. Binding site
• B. Allosteric site
• C. Catalytic site
• D. None of the above

Explanation: The enzyme-substrate complex is formed in the binding site of the enzyme molecule.

• A. Emil Fischer
• B. Koshland
• C. Watson and Crick
• D. Rosalind Franklin

Explanation: The lock and key model was proposed by Emil Fischer in 1894. Emil Fischer, a German chemist, introduced this concept in the late 19th…

• A. Non-competitive
• B. Un-competitive
• C. Allosteric Enzyme
• D. Competitive inhibition

Explanation: Correct answer is option D.A type of enzyme inhibition in which enzyme activity is blocked by the presence of a chemical that competes…

• A. Enzymes are sharp in action than catalyst
• B. Catalysts used in large amount than enzymes
• C. Catalysts are inorganic while enzymes are organic in nature
• D. Enzymes need pH while catalysts do not

Explanation: Enzymes are organic chemical substances while catalysts are inorganic. Catalysts are substances that increase or decrease the rate of a…

• A. Cause chemical reaction that would not otherwise take place
• B. Change the rate of a chemical reaction
• C. Change the direction of a chemical reaction
• D. Raise the activation energy of a chemical reaction
• E. None of the given reactions

Explanation: Option A: Enzymes can not initiate a chemical reaction.They can only accelerate a chemical reaction.So,option A is incorrect.Option B…

• A. Feedback inhibition
• B. Feedback regulation
• C. Positive Feedback
• D. Enzymes activation

Explanation: B. A process through which the product of a reaction controls its own synthesis C. If a product increases its own synthesis D.

• A. Metallic ions
• B. Organic molecules
• C. Inorganic molecules
• D. Radicals
• E. A, B and C

Explanation: Inorganic cofactors are activators while organic cofactors may be coenzymes or prosthetic groups.

• A. Enzymes require optimum pH for maximal activity
• B. Enzymes are denatured at high temperatures but in certain exceptional organisms, they are effective even at temperatures such as 80° and­ 90°C
• C. Enzymes are highly specific
• D. Most enzymes are proteins but some are lipids

Explanation: Enzymes are mostly proteins but some are RNA (ribozymes). No lipid which works as an enzyme is known.

• A. A
• B. B
• C. C
• D. D

Explanation: Every enzyme work best at its optimum pH. Pepsin optimum pH is 2. In the pH above 2 pepsin will be denatured.

• A. Hydrogen, Ionic
• B. Hydrogen, Covalent
• C. Ionic, Hydrogen
• D. Covalent, lonic

Explanation: Enzymes are protein in nature and different types of bonds (Hydrogen and Ionic) maintain their structure.

• A. Fibrous proteins
• B. No effect on end product
• C. Use in reaction
• D. Non-specific

Explanation: Ezymes are globular proteins, which act as biocatalyst and speed up biochemical reactions and their presence does not affect the nature of…

• A. Substrate
• B. Prosthetic Group
• C. Coenzymes
• D. Co-factors

Explanation: Co-factors are molecules that bind to enzymes, aiding in their function by altering the enzyme's shape, and are essential for catalytic…