All Free Biology MCQs with Answers

4011. Which of the following is the final acceptor of electron in respiratory chain?

• A. Cytochrome a
• B. Cytochrome b
• C. Oxygen
• D. Hydrogen

Explanation: The final electron acceptor in the respiratory chain is oxygen (O2). During oxidative phosphorylation, electrons are passed along a series of membrane-bound protein complexes, which pump protons (H+) across the inner mitochondrial membrane, creating an electrochemical gradient. At the end of the electron transport chain, the electrons are transferred to oxygen molecules, which combine with protons to form water (H2O). This process generates a large amount of energy, which is used to synthesize ATP from ADP and inorganic phosphate.

4012. Electron transport chain in mitochondria is used to:

• A. Synthesize NADP+
• B. Synthesize ADP
• C. Create electron gradient
• D. Create proton gradient

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

4013. ATP formation through oxidative phosporylation involves:

• A. Light reactions
• B. Dark reactions
• C. Chemiosmosis
• D. Fermentation

Explanation: ATP formation through oxidative phosphorylation involves the transfer of electrons from NADH and FADH2 to a series of electron carriers, which generates a proton gradient across the inner mitochondrial membrane. The energy stored in the proton gradient is then used by ATP synthase to produce ATP through the process of chemiosmosis. This is the final stage of cellular respiration and is responsible for producing the majority of ATP molecules (28-34 ATP molecules per glucose molecule).

4014. A aldo sugar that is intermediate between respiration and photosynthesis:

• A. Glucose
• B. Dihydroxyacetone
• C. Glyceraldehyde 3-phosphate
• D. Fructose

Explanation: The aldose sugar that is an intermediate between respiration and photosynthesis is glyceraldehyde-3-phosphate (G3P). G3P is a key intermediate in both the glycolysis pathway and the Calvin cycle of photosynthesis. In glycolysis, G3P is produced during the conversion of glucose to pyruvate, while in the Calvin cycle, it is produced during the fixation of carbon dioxide.

4015. An 18 carbon fatty acid is converted into how many acctyl-CoA molecules?

• A. 18
• B. 16
• C. 9
• D. 20

Explanation: When an 18-carbon fatty acid is broken down by beta-oxidation, it is first converted into 9 molecules of acetyl-CoA, which can then enter the citric acid cycle (also known as the Krebs cycle) to produce ATP.

4016. Deamination of amino acid takes place in:

• A. Liver
• B. Kidney
• C. Pancreas
• D. Gall bladder

Explanation: Deamination of amino acids takes place in the liver. The liver is a major site of amino acid metabolism, and it is responsible for processing amino acids that are derived from the breakdown of dietary proteins or from the turnover of proteins within the body. During deamination, the amino group (-NH2) is removed from the amino acid, and it is converted into ammonia (NH3) and then into urea, which is excreted by the kidneys.

4017. The reaction which occurs in thylakoid interior space:

• A. Photolysis
• B. ATP synthesis
• C. Transport of electrons
• D. Dark reaction

Explanation: Photolysis, also known as photodissociation or photodecomposition, refers to the process in which a substance is broken down or decomposed into smaller parts by absorbing light energy. In photosynthesis, photolysis occurs during the light-dependent reactions that take place in the thylakoid membranes of chloroplasts. Water molecules are photolyzed to release oxygen, electrons, and protons. This process is a crucial step in the generation of oxygen and the production of energy-rich molecules like ATP.

4018. In which of the following steps, NADH is formed without decarboxylation?

• A. Isocitrate → a-ketoglutarate
• B. Pyruvate → Acetyl CoA
• C. a-ketoglutarate → succinate
• D. Malate → oxaloacetate

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

4019. The oxidation of which of the following wilI produce FADH2?

• A. Malate
• B. Fumarate
• C. FAD
• D. Succinate

Explanation: Succinate is a dicarboxylic acid and a key intermediate in the citric acid cycle, also known as the Krebs cycle or tricarboxylic acid (TCA) cycle. This cycle is a central component of cellular respiration, occurring in the mitochondria of eukaryotic cells and the cytoplasm of prokaryotic cells.

4020. In which wavelength of light, photosynthesis is maximum?

• A. Red light
• B. Blue light
• C. Green light
• D. Ultra-violet light

Explanation: When light having a wavelength ranging between 400-and 700 nm is absorbed by the plant, the rate of photosynthesis is the highest. Red light is absorbed effectively by chlorophyll, which ranges within this wavelength. It is utilized in the maximum amount.