All Free Biology MCQs with Answers

• A. ADP
• B. PGAL
• C. DPGA
• D. NAD

Explanation: Option D is correct because NAD (Nicotinamide adenine dinucleotide) functions as a hydrogen carrier in glycolysis.

• A. Cyt "O"
• B. Cyt "a3"
• C. Cyt "b"
• D. Cyt "c"

Explanation: A membrane-bound cytochrome f-b complex participates in both respiratory and photosynthetic elevtron transport.

• A. Glucose phosphate → fructose diphosphate
• B. Fructose diphosphate → DAP
• C. PGAL→ PGAP
• D. PGAP→ PGA

Explanation: Energy transfer here occurs by the transfer of phosphate group from one compound to another.

• A. Glycosidic
• B. Peptide
• C. Ester
• D. None

Explanation: Covalent bond formed between the 1st carbon atom of one monosaccharide with 4 carbon atoms of the neighboring monosaccharide unit is known…

• A. It is reduced to water
• B. It is converted to gas
• C. It is used as an electron carrier
• D. It supplies energy to produce ATP

Explanation: Oxygen plays a crucial role in the electron transport chain as the final electron acceptor.

• A. Four ATPs
• B. Two ATPs
• C. One ATP
• D. Three ATPs

Explanation: Three ATPs: This is the correct option. Each NADH molecule generally leads to the synthesis of around three ATP molecules in the electron…

• A. photosynthesis
• B. digestion
• C. respiration
• D. circulation

Explanation: Respiration: Respiration is the biochemical process by which cells break down organic molecules, such as glucose, and convert them into…

• A. 2 ATP
• B. 3 ATP
• C. 4 ATP
• D. 32 ATP

Explanation: Glycolysis is the process of breaking down one molecule of glucose into two molecules of pyruvate.

• A. Glycolysis
• B. Lipogenesis
• C. Ketogenesis
• D. Glycogenesis

Explanation: The correct answer is lipogenesis, which refers to the conversion of excess glucose into fat.

• A. One ATP
• B. Two ATP
• C. 32 ATP
• D. 36 ATP

Explanation: The Krebs cycle, also known as the citric acid cycle, occurs in the mitochondria and is a critical part of cellular respiration.

• A. Respiration
• B. Photosynthesis
• C. Growth
• D. Both A and B

Explanation: Redox reactions are crucial in both respiration and photosynthesis. In respiration, glucose is oxidized to produce energy, and oxygen is…

• A. Electron transport chain
• B. Photophosphorylation
• C. Krebs cycle
• D. Glycolysis

Explanation: The correct answer is A, the electron transport chain, which occurs on the cristae of the mitochondria.

• A. 12-ATP
• B. 38-ATP
• C. 18-ATP
• D. 36-ATP

Explanation: An NADH molecule on oxidation theoretically releases sufficient energy to make 3 ATP molecules.

• A. 6 kcal
• B. 9 kcal
• C. 8 kcal
• D. 7 kcal

Explanation: When an ATP molecule is hydrolyzed into ADP and P, it undergoes a chemical reaction that releases about 7 kilocalories (kcal) of energy.

• A. Glycolysis
• B. Kreb's cycle
• C. Synthesizes of acetyl Co-A
• D. Electron transport chain

Explanation: Glycolysis is the metabolic pathway that is common to both fermentation and cellular respiration.

• A. Coenzyme
• B. Apoenzyme
• C. Holoenzyme
• D. Denatured enzyme

Explanation: The correct answer is apoenzyme. An apoenzyme is the protein part of an enzyme that is inactive on its own.

• A. They increase the activation energy
• B. They are specific in action
• C. They possess specific active site
• D. They possess dimensional shapes

Explanation: They increase the activation energy: This statement is incorrect. Enzymes actually decrease the activation energy required for a chemical…

• A. Proteins
• B. Carbohydrates
• C. Hydrocarbons
• D. None of the above

Explanation: Enzymes are specialized proteins that catalyze biochemical reactions, enabling them to occur more rapidly and efficiently.

• A. NAD
• B. FAD
• C. NADP
• D. ADP

Explanation: Coenzymes are non-protein, organic compounds required by many enzymes for catalytic activity.

• A. Protien
• B. Urea
• C. Lipid
• D. ATP

Explanation: Lipase is an enzyme that helps break down lipids, which are fats and oils.