All Free Biology MCQs with Answers

• A. T. W. Engelmann
• B. Darwin
• C. Robert Hooke
• D. Schwan

Explanation: The first action spectrum was obtained by German biologist T.W.England in 1833. He worked on Spirogyra.

• A. CO₂
• B. ATP
• C. Water
• D. Oxygen

Explanation: In cellular respiration, the final acceptor of electrons in the respiratory chain is oxygen (O₂).

• A. ATP synthesis
• B. Reduction of NADP
• C. Cyclic phosphorylation
• D. Oxidation of the reaction center of photosystem I

Explanation: Non-cyclic photophosphorylation is the light-dependent part of photosynthesis in higher plants, in which an electron donor is required…

• A. Stroma
• B. Grana
• C. Thylakoid
• D. lntergrana

Explanation: Chlorophylls are found embedded in the thylakoid membranes of chloroplasts.

• A. Leaf
• B. Stem
• C. Roots
• D. Branches

Explanation: The correct answer is 'Leaf'. In most plants, leaves are the primary sites for photosynthesis.

• A. Alcoholic fermentation
• B. Lactic acid fermentation
• C. Respiration
• D. Both A and B

Explanation: Pyruvate is produced in both of the processes as glycolysis continues to occur even in the absence of oxygen.

• A. ADP
• B. Reduced FAD
• C. Citric acid
• D. Pyruvate

Explanation: The end product of glycolysis is two molecules of pyruvate(3C compound).

• A. Glycolysis
• B. Pyruvic acid oxidation
• C. Krebs cycle
• D. None

Explanation: The Krebs cycle, also known as the citric acid cycle, is the stage of cellular respiration where FADH2 is produced.

• A. 5%
• B. 2%
• C. 7%
• D. 10%

Explanation: In anaerobic respiration, the process primarily involves glycolysis followed by fermentation, which yields only a small amount of ATP…

• A. Glycolysis
• B. Cellular respiration
• C. Fermentation
• D. None of the above

Explanation: This is the correct answer. Glycolysis is the metabolic pathway that breaks down one molecule of glucose into two molecules of pyruvate.

• A. Cytoplasm
• B. Mitochondria
• C. Nucleus
• D. Endoplasmic reticulum

Explanation: This is the correct answer. Glycolysis, the initial stage of cellular respiration, occurs in the cytoplasm of the cell.

• A. Stroma of chloroplast
• B. Guard cells of stomata
• C. Thylakoid membrane of chloroplast
• D. Cytoplasm of leaf cell
• E. None of the above

Explanation: The light-dependent reactions use light energy to make two molecules needed for the next stage of photosynthesis: the energy storage…

• A. Dawn
• B. Noon
• C. Dusk
• D. Dawn and dusk

Explanation: At dawn and dusk, when light intensity is low, the rate of photosynthesis and respiration may, for a short time, equal one another.

• A. Orange
• B. Grey
• C. Yellow
• D. Blue-Green
• E. Yellow-Green

Explanation: In paper chromatography, xanthophylls are pigments that are often responsible for giving a yellow color.

• A. Citrate
• B. Alpha-ketoglutarate
• C. Succinate
• D. Fumarate
• E. Oxaloacetate

Explanation: In the Krebs cycle, also known as the citric acid cycle, the formation of succinate involves a series of chemical reactions, and…

• A. Fe2+
• B. Mg2+
• C. Mn2+
• D. Ca2+

Explanation: The main difference between the chlorophyll molecule and the heme group of hemoglobin is that chlorophyll contains a magnesium ion (Mg2+)…

• A. ATP
• B. FAD
• C. FADH
• D. ADP

Explanation: During glycolysis, the oxidation of one molecule of 3-phosphoglyceraldehyde (PGAL or G3P, which stands for glyceraldehyde-3-phosphate)…

• A. Energy
• B. Electrons
• C. Hydrogen protons
• D. All of above

Explanation: When a molecule undergoes reduction, it gains electrons, hydrogen/protons, and often energy.

• A. Stroma and grana of chloroplast respectively
• B. Grana and stroma of chloroplast respectively
• C. Grana only
• D. Stroma only

Explanation: The light reactions occur in the thylakoid membranes, while the dark reactions (Calvin Cycle) take place in the stroma of the…

• A. T. W. Engelmann
• B. Malleus
• C. T. W. Inws
• D. W. Stapes

Explanation: The first action spectrum was obtained by German biologist T.W.England in 1833.