All Free Biology MCQs with Answers

4021. Following is/are obtained during cyclic photophosphorylation:

• A. ATP
• B. NADPH2
• C. O2
• D. All A, B, C

Explanation: ATP (adenosine triphosphate) is produced through various cellular processes, primarily during cellular respiration and photosynthesis.The three main stages of cellular respiration are glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation (electron transport chain and chemiosmosis).Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. It consists of the light-dependent reactions and the light-independent reactions (Calvin cycle).

4022. Immediate source of energy for cellular metabolism is:

• A. Lipids
• B. Carbohydrates
• C. ATP
• D. Proteins

Explanation: ATP (adenosine triphosphate) is produced through various cellular processes, primarily during cellular respiration and photosynthesis.The three main stages of cellular respiration are glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation (electron transport chain and chemiosmosis).Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. It consists of the light-dependent reactions and the light-independent reactions (Calvin cycle).

4023. Krebs cycle in mitochondria takes place in:

• A. Cytosol
• B. Outer Membrane
• C. Matrix
• D. Inner Membrane

Explanation: The matrix of a mitochondrion refers to the central compartment enclosed by the inner mitochondrial membrane. Mitochondria are double-membraned organelles found in eukaryotic cells, and they are often referred to as the "powerhouses of the cell" due to their role in energy production.The two main compartments of a mitochondrion are the intermembrane space (between the outer and inner mitochondrial membranes) and the matrix (enclosed by the inner mitochondrial membrane).

4024. The one which is not correct about chlorophyll 'b'?

• A. Used in photosynthesis
• B. Soluble in organic solvents
• C. Present in plants
• D. Have different forms

Explanation: Chlorophyll 'b' does not have different forms.

4025. It is a five-carbon compound of the Krebs cycle:

• A. Oxaloacetate
• B. Succinate
• C. Alpha-ketoglutarate
• D. Isocitrate

Explanation: Alpha-ketoglutarate, also known as 2-oxoglutarate, is a key intermediate in several metabolic pathways, including the citric acid cycle (also known as the Krebs cycle or tricarboxylic acid cycle) and amino acid metabolism. It is a five-carbon compound with a keto group (C=O) at the second carbon.It is a five-carbon compound with a keto group (C=O) at the second carbon.: In the citric acid cycle, alpha-ketoglutarate is produced by the decarboxylation of isocitrate.

4026. Enzymes required for respiratory chain are present on/in:

• A. Cristae
• B. Mitochondrial matrix
• C. Inter-membrane space
• D. Cytoplasm

Explanation: Cristae (singular: crista) are internal, folded structures found in the inner mitochondrial membrane. Mitochondria are membrane-bound organelles known as the "powerhouses of the cell" due to their role in energy production through oxidative phosphorylation. Cristae provide an increased surface area for various mitochondrial activities, especially those related to the electron transport chain and ATP synthesis.

4027. Net gain of ATP molecule produced in algae after the complete breakdown of one glucose molecule during aerobic respiration is:

• A. 28
• B. 38
• C. 36
• D. 40

Explanation: Net gain of ATP molecule produced in algae after the complete breakdown of one glucose molecule during aerobic respiration is 36.

4028. During the Krebs cycle, carbon number is reduced by decarboxylation. It is repeated _ time/s during one cycle.

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

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

4029. Calvin cycle is also named as:

• A. C3 pathway
• B. Sugar synthesis phase
• C. Dark reactions
• D. All of these

Explanation: Calvin Cycle is also named as C3 pathway because the product of initial carbon fixation is a three carbon compound. It is also called sugar synthesis phase because it is that phase of photosynthesis in which sugar is synthesized using ATP and NADPH of light reaction. It is also called dark reaction because these reactions do not require light directly. So correct option is D i.e., all of these.

4030. In which stage of aerobic respiration, 2-carbon molecules are oxidized completely to carbon dioxide?

• A. Glycolysis
• B. Krebs cycle
• C. ETC
• D. Calvin cycle

Explanation: The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a central pathway in cellular respiration that takes place in the mitochondria of eukaryotic cells. It is a series of chemical reactions that ultimately leads to the complete oxidation of acetyl-CoA, derived from the breakdown of carbohydrates, fats, and proteins, producing carbon dioxide, energy-rich molecules, and reducing equivalents.