All Free Biology MCQs with Answers

• A. Glycolysis
• B. Pyruvic acid oxidation
• C. Krebs cycle
• D. Electron transport chain

Explanation: Glycolysis is the metabolic pathway that occurs in the cytoplasm of cells and is the first stage of cellular respiration.

• A. C55 H10 O4 N6 Mg
• B. C55 H70 O6 N5 Mg
• C. C55 H71 O6 N4 Mg
• D. C55 H70 O6 N4 Mg

Explanation: C55H70MgN4O6 is the correct formula of chlorophyll b.

• A. Animals
• B. Plants
• C. Both A and B
• D. None of these

Explanation: Cartenoids perform a protective function in both plants and animals. Carotenoids are essential compounds along with chlorophylls in…

• A. 20%
• B. 15%
• C. 10%
• D. 1%

Explanation: 50% of the light from the sunlight supports the process of photosynthesis.

• A. T.W.Engleman
• B. Julius von Sachs
• C. Gregor Mendel
• D. Robert Koch

Explanation: The first action spectrum, which shows the relationship between the rate of a biological process (like photosynthesis) and the wavelength…

• A. High concemration of NADH
• B. Low concentration of citrate
• C. High concentration of ATP
• D. Pyruvate decarboxylase

Explanation: Phosphofructokinase is a key regulatory enzyme in the glycolysis pathway, and it is inhibited by high concentrations of ATP.

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

Explanation: The correct answer is Option B: Chlorophyll - a. Chlorophyll a is fundamental to the photosynthetic process across all photosynthetic…

• A. Alpha ketoglutaric acid
• B. Citric acid
• C. Glyceric acid
• D. Acetyl-CoA

Explanation: Before entering the Krebs cycle, pyruvate is converted into acetyl-CoA through the link reaction, where it is decarboxylated and oxidized.

• A. Cytochrome a
• B. Oxygen
• C. Cytochrome a3
• D. Cytochrome c

Explanation: In the electron transport chain, oxygen serves as the final electron acceptor.

• A. 680 nm
• B. 100 nm
• C. 700 nm
• D. 670 nm

Explanation: This wavelength of light is red and red colour light is highly absorbed because it carries out most of the synthetic reaction.

• A. Carbon tetrachloride (CCl4)
• B. Alcohol
• C. Organic Solvents
• D. None of these

Explanation: Chlorophyll is a hydrophobic molecule, meaning it does not dissolve in water, a polar solvent.

• A. Bioenergetics
• B. Laws of thermodynamics
• C. Laws of thermochemistry
• D. Laws of chemical energetics

Explanation: The correct answer is the laws of thermodynamics. These laws provide the essential framework for understanding how energy is conserved and…

• A. 0.2%
• B. 0.15%
• C. 0.05%
• D. 1%

Explanation: 1% is the amount of percentage the leaf absorbs the sunlight.

• A. Fructose-6-Phosphate
• B. Glucose-6-Phosphate
• C. Fructose-1,6 biphosphate
• D. Dihydroxyacetone phosphate

Explanation: A. Glucose-6 phosphate is converted into its isomer fructose -6-phosphate, by an isomerase enzyme.C.

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

Explanation: The first action spectrum was made by T. W. Engelmann, who split light into its components by the prism and then illuminated Cladophora…

• A. C6H12O6 + 6O2
• B. (CH2O)n + H2O + 2S
• C. C6H12O6 + 6O2 + H2O + Energy
• D. C6H12O6 + 6O2 + 6 H2O

Explanation: A.6 molecules of water are also released. B.These are the products of photosynthetic bacteria which use H2S instead of water and release…

• A. A head of phytol and tail of four pyrrole rings
• B. A head of linked carbons and tail of four pyrrole rings
• C. A head of four pyrrol rings and tail of linked nitrogen
• D. A head of four pyrrol rings and a phytol tail

Explanation: A chlorophyll molecule has two main parts; one flat, light absorbing hydrophilic head and the other long, anchoring, hydrophobic…

• A. Chl.a has different types while Chl.b has single type
• B. Chl.a have functional group -CH3 but Chl.b has CHO
• C. Chl.a is necessary pigments but Chl.b is accessory pigments
• D. Chl.a is present in antenna complex while Chl.b is in reaction center

Explanation: Chlorphyll b is not found in reaction center.

• A. Absorbs wavelength of 680 nm
• B. Discovered earlier than PS-II
• C. Absorbs wavelength of 700 nm
• D. Slightly located upward than PS-II

Explanation: Photosynthetic pigments are organized into clusters, called photosystems. There are two photosystems found in plants, PS-I and PS-II.

• A. 1
• B. 4
• C. 2
• D. 6

Explanation: Each photon of light is able to excite a singlc electron during light reactions of photosynthesis.