All Free Biology MCQs with Answers

3531. What is the color of the Chlorophyll-b molecule?

• A. Blueish green
• B. Yellowish green
• C. Dark Green
• D. Reddish green

Explanation: Chlorophyll-b is a secondary pigment that absorbs light primarily in the blue and red-orange wavelengths, giving it a yellowish-green colour.

3532. Which of the following is NOT a consequence of anaerobic respiration In humans muscles cells?

• A. Cramps
• B. High consumption of energy
• C. Pain
• D. Tiredness

Explanation: Anaerobic respiration is a less efficient process compared to aerobic respiration, which occurs in the presence of oxygen. Anaerobic respiration produces less energy, so it does not result in high energy consumption.

3533. In aerobic respiration, the glucose molecule is completely broken down into carbon dioxide (CO2), water (H2O) and _ energy.C6H12O6 + 6O2 ---> 6CO2 + 6H2O + ?

• A. 2 ATP
• B. 4 ATP
• C. 34 ATP
• D. 36 ATP

Explanation: Respiration is defined as the oxidation of food molecules that release energy in the form of ATP. Aerobic respiration involves the following stages: Glycolysis, Link Reaction, Kreb's Cycle, and Oxidative Phosphorylation.3 NADH2 = 3 ATPs1 FADH2 = 2 ATPsThe 2 NADH2 molecules formed during glycolysis remain in the cytoplasm as the mitochondrial membrane is impermeable to NADH2. They deposit hydrogen ions on the mitochondrial membrane. As a result, hydrogen will be gained by FAD to form 2 FADH2 molecules. When FADH2 gets hydrolysed, 4 ATP molecules are lost. Hence, 40 - 4 = 36 ATP molecules are formed during aerobic respiration.The yield is approximately 29−32 ATP molecules per glucose.

3534. In which part of the chloroplast the fixation of carbon dioxide results in the formation of sugars?

• A. Grana
• B. Stroma
• C. Intergranum
• D. Outer membrane of chloroplast

Explanation: Chloroplasts are biconvex disc-like organelles that are surrounded by a double membrane.

3535. The chloroplasts contain:

• A. Proteins only
• B. Ribosomes only
• C. Small circular DNA only
• D. Proteins, Ribosomes, and small circular DNA

Explanation: Chloroplasts are chlorophyll-containing organelles in plant cells; they play a vital role in life on Earth since photosynthesis takes place in chloroplasts. Chloroplasts develop from proplastids. Chloroplasts contain their own DNA and ribosomes and thus can make their own proteins. It is estimated that the chloroplast contains between 2000 and 5000 different proteins; thus, the majority of chloroplast proteins are encoded by the nuclear genome.

3536. The range of visible light is from:

• A. 300-650 nm
• B. 350-700 nm
• C. 380-750 nm
• D. 430-790 nm

Explanation: The visible light spectrum is the segment of the electromagnetic spectrum that the human eye can view. Cone-shaped cells in our eyes act as receivers tuned to the wavelengths in this narrow band of the spectrum. Other portions of the spectrum have wavelengths too large or too small and energetic for the biological limitations of our perception.Wavelength of visible light ranges from 380-750 nm.Visible light consists of seven colours - violet, indigo, blue, green, yellow, orange, and red. Each colour of the visible light spectrum has its distinct wavelength. The wavelengths are as follows:Violet: 380-450 nm Indigo: 450-485 nmBlue: 485-500 nmGreen: 500-565 nmYellow: 565-590 nmOrange: 590-625 nmRed: 625-750 nmDiagram:

3537. Which scientist among the following hypothesised that plant splits water to release oxygen as a by-product:

• A. Van Niel
• B. Lysenko
• C. Calvin
• D. Kreb

Explanation: Scientist Cornelius Van Niel first postulated in the 1930s that the oxygen released from photosynthesis comes from the water molecule. Through experiments with bacteria, he suggested by analogy that the O2 released in plant photosynthesis is derived from H2O rather than CO2.

3538. The Calvin Cycle is completed in _ stages:

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

Explanation: Calvin cycle is a cyclic enzyme-controlled process which involves the reduction of carbon dioxide in the presence of ATP and NADPH to form sugars. The process occurs in the stroma of the chloroplast. The Calvin cycle can be simplified into three stages:Carbon Fixation: A molecule of RuBP accepts CO2 in the presence of the enzyme rubisco to form an unstable 6-carbon intermediate which splits to form 2 molecules of glycerate-3-phosphate (GP). The combination of RuBP with CO2 is known as carbon fixation.Reduction of GP: Each phosphoglycerate molecule undergoes reduction using ATP and NADPH to form triose phosphate.Regeneration of RuBP: Most triose phosphate molecules use energy in the form of ATP to regenerate RuBP.One complete turn of the cycle consumes 9 ATP molecules and 6 NADPH molecules to form one molecule of triose phosphate.

3539. Each grana consist of _ thylakoids.

• A. 40 to 60
• B. 25 to 50
• C. 50 to 70
• D. 100 to 200

Explanation: Each granum consists of 25-50 thylakoids in it. Hence, option B is the correct option.

3540. Light independent phase of photosynthesis involves _.

• A. Formation of energy rich carbohydrates
• B. Hydrolysis of water
• C. ATP generation
• D. Production of reducing molecule

Explanation: Hydrolysis of water, ATP generation, and production of reducing molecules are all part of the light-dependent phase of photosynthesis. Light independent phase involves the reaction of G3P to form energy-rich glucose so option A is correct.