All Free Biology MCQs with Answers

• A. Interior space of thylakoid
• B. Outside the thylakoid membrane
• C. Into the stroma
• D. At ATP synthase complex

Explanation: Water splits during photosynthesis in the interior space of thylakoid.

• A. It absorbs photons into PS-I
• B. It is a long pathway
• C. It produce ATP
• D. Carbon dioxide fixation

Explanation: Carbon dioxide fixation does not take place in light dependent phase of photosynthesis; rather its fixation occurs in light independent…

• A. Glycolysis
• B. The electron transport system
• C. Kerbs cycle
• D. Fermentation

Explanation: The cyclic reactions of Krebs cylce produce both NADH and FADH2, while in glycolysis, only NADH is produced.

• A. Pyruvate decarboxylase
• B. Phosphofructokinase
• C. Glucokinase
• D. Pyruvate phosphatases

Explanation: When excess NADH accumulates, the enzymes that produce NADH from NAD+ will be inhibited.

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Explanation: In a photosynthesizing cell exposed to high light intensity and low carbon dioxide concentration, the rate of photosynthesis may be…

• A. Acetyle coenzyme A
• B. Ribulose bisphosphate
• C. Fructose 1, 6-bisphosphate
• D. Triose phosphate

Explanation: Triose phosphate refers to a class of three-carbon sugar phosphates that play critical roles in cellular metabolism, particularly in…

• A. To cause the breakdown of citric acid
• B. To combine with glucose to produce carbon dioxide
• C. To combine with carbon from organic molecules to produce carbon dioxide
• D. To combine with hydrogen from organic molecules to produce water

Explanation: Function of molecular oxygen in cellular respiration is to combine with hydrogen from organic molecules to produce water.

• A. ADP from ATP
• B. ATP from ADP
• C. Glucose 6-phosphate from glucose
• D. NADP+ from NAD+

Explanation: During photophosphorylation, light energy is captured by chlorophyll and other pigment molecules in the thylakoid membranes of…

• A. Alpha ketogluteric acid
• B. Glyceric acid
• C. Citric acid
• D. Acetic acid

Explanation: Acetic acid, also known as ethanoic acid, is a simple organic acid with the chemical formula CH3COOH.

• A. 2 Electrons 1 proton
• B. 2 Electrons 2 protons
• C. Electron 2 protons
• D. 1 Electrons 1 proton

Explanation: Conversion of NAD+ into NADH requires 2 Electrons 1 proton.

• A. Glyceraldehyde-3-phosphate
• B. 3-Phosphoglycerate
• C. Ribulose bisphosphate
• D. 1,3-Bisphosphoglycerate

Explanation: 1,3-Bisphosphoglycerate (1,3-BPG) is a high-energy intermediate in glycolysis, a central metabolic pathway that breaks down glucose to…

• A. 6 carbon atoms
• B. 3 carbon atoms
• C. 5 carbon atoms
• D. 4 carbon atoms

Explanation: First stable compound during light-independent reactions contains 3 carbon atoms.

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Explanation: Peak of absorption spectrum of photosyntheis is narrow and valley is broad and deep.

• A. Same wavelength
• B. 380 - 750 nm wavelengths
• C. Different wavelengths
• D. 280 - 750 nm wavelengths

Explanation: As absorption spectra of pigments vary, they absorb light of different wavelengths.

• A. Red to orange
• B. Yellow and red to orange
• C. Yellow to orange
• D. Orange and red to yellow

Explanation: According to their absorption spectra carotenes are red to orange pigments.

• A. Green wavelength is reflected
• B. Green wavelength is transmitted
• C. Darker green color masks over the yellow color
• D. Green wavelength is reflected and transmitted

Explanation: Carotenoids are yellow and red to orange pigments which are masked over by green colored chlorophylls.

• A. Flat
• B. Long and anchoring
• C. Square shaped
• D. Flat and square shaped

Explanation: It is porphyrin head made up of tetrapyrole rings.

• A. Chlorophyll - a,Chlorophyll - b
• B. Carotenoids
• C. Bacteriochlorophyll
• D. Both A and B

Explanation: Option D is correct.Both chlorophyll a and chlorophyll b are located in the thylakoid membranes of chloroplasts.

• A. Few green plants and all algae
• B. All green plants and all algae
• C. All green plants and few algae
• D. Few green plants and green algae

Explanation: Option C is correct. Chlorophyll b occurs in all green plants right from bryophytes to angiosperms but it is found only in euglenoids and…

• A. Carbon tetrachloride
• B. Alcohol
• C. Carbon tetrachloride and alcohol
• D. Water

Explanation: Option C is correct.Chlorophylls are soluble in organic solvents, such as alcohol, ether, carbontetracholride and acetone.