All Free Biology MCQs with Answers

3621. Molecular formula of chlorophyll b is:

• A. C55 H10 O4 N6 Mg
• B. C55 H70 O6N5 Mg
• C. C55 H71 O6 N4 Mg
• D. C55 H70 O6N4 Mg

Explanation: "The explanation for this question will be added soon!".

3622. Carbon dioxide released by respiration just equals the quantity required by photosynthesizing cells. At this moment there is no net gas exchange between the leaves and the atmosphere. This is termed as?

• A. Bacteriochlorophyls
• B. Redox process
• C. Photosystems
• D. Compensation point

Explanation: A. There are known many different kinds of chlorophylls. Chlorophyll a,b,c,d are found in eukaryotic photosynthetic plants and algae, while the others are found in photosynthetic bacteria and are known as bacteriochlorophylls B.The reaction in which one reactant is oxidized and other reactant is reduced C. Photosynthetic pigments are organized into clusters in thylakoid membrane called photo systems.

3623. A graph plotting absorption of light of different wave lenghts by a pigment is called as:

• A. Absorption spectrum
• B. Spectrophotometer
• C. Carotenoids
• D. Xanthophylls

Explanation: B. It is an instrument which is used to measure relative abilities of different pigments to absorb different wavelenght of lightC. These are accessory photosynthetic red ,orange and yellow pigments present in chloroplast.D. These are yellow colour accessory pigments present in chloroplast.

3624. The water splitting step of photosynthesis that releases oxygen is called as:

• A. Plastoquione
• B. Photolysis
• C. Plastocyanin
• D. Ferredoxin

Explanation: A. It is an electron acceptor in photosynthesis pathway. C. A copper containing protein acting as electron acceptor in photosynthesis pathway. D. An iron containing protein also acting as electron acceptor in photosynthesis pathway.

3625. A process that uses membranes to couple redox reactions to ATP production is termed as:

• A. Chemiosmosis
• B. Atp Synthase
• C. Dark Reactions
• D. Light Reactions

Explanation: B. It is an enzyme required for synthesis of ATP during which hydrogen ions move down their gradient. C. These reactions do not require lightD. these reaction do require light

3626. Initial incorporation of carbon dioxide into organic material refers to which reaction?

• A. Calvin cycle
• B. Carbon fixation
• C. Reduction phase of calvin cycle
• D. Regeneration of RUBP

Explanation: A. In this reaction, carbon is fixed and reduced resulting in the synthesis of sugars during dark reactionsC. PGA receives an additional phosphate from ATP of light reaction forming 1,3- bisphosphoglycerate and this product reduces to G3PD. five molecules of G3P are used to generate 3 molecules of five carbon RuBP.

3627. What is the end product of glycolysis that does not enter the Kreb's cycle directly?

• A. Acetic acid
• B. Alpha-ketoglutarate
• C. Pyruvic acid
• D. Citrate

Explanation: A. It is a carboxylic acid of 2 carbon. It is not the end product of glycolysis.B. Removal of Co2 from isocitrate forms Alpha ketoglutarate, which is the step of Krebs cycle.D. Acetyl CO-A and water combine with oxaloacetate to form citrates. This is the first step of Krebs cycle.

3628. Which one of the following is light-gathering?

• A. Antenna complex
• B. Reaction centre
• C. Photosystem
• D. None of these

Explanation: The antenna complex is a light-harvesting membrane-associated aggregate of proteins and photosensitive pigments such as chlorophyll and carotenoids.

3629. In which of the following component of the body, does lactic acid fermentation takes place:

• A. Brain
• B. Heart
• C. Liver
• D. Muscles

Explanation: Lactic acid fermentation occurs in the skeletal muscles. When oxygen is inadequate, pyruvate is converted to lactic acid by lactate dehydrogenase. It results in the accumulation of lactic acid and muscle fatigue. A.Lactic acid accumulates in muscles during anaerobic respiration causing muscle fatigue. B.Heart muscles donot fatigue and so lactic acid doesnot accumulate. C.Lactic acid doesnot accumulate in liver

3630. About _ % of photosynthesis is carried by terrestrial plants, while the rest occurs in oceans, lakes, and ponds.

• A. 10%
• B. 20%
• C. 30%
• D. 40%

Explanation: About 10% of photosynthesis is carried by terrestrial plants, while the rest occurs in oceans, lakes, and ponds. Terrestrial plants, including trees, grasses, and other land-based vegetation, play a significant role in capturing sunlight and converting it into chemical energy through the process of photosynthesis