All Free Biology MCQs with Answers

• A. Leaves
• B. Stems
• C. Roots
• D. Branches

Explanation: The leaves are the main sites of photosynthesis in plants, where the chloroplasts capture sunlight and convert it into energy and glucose…

• A. Stroma
• B. Chloroplast envelope
• C. Thylakoid membranes
• D. The intergrana

Explanation: Each granum is made up of coin-like thylakoids, whose membranes have photosystems.

• A. Leaves respire utilizes O2 and releases CO.
• B. Photosynthesis and respiration occur at the same rate. So there is no net exchange of gases between the atmosphere and plants.
• C. The rate of photosynthesis increases, and so does the O2 production, with a net release of oxygen coupled with the uptake of CO2
• D. The rate of respiration becomes more than the rate of photosynthesis.16 Net yield of H2O in Photosynthesis is

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

• A. A 5C carbohydrate accepts carbon dioxide and is then reduced by NADPH derived from photosynthesis
• B. A 3Ccarbohydrate is regenerated and reduced by hydrogen molecules derived from photophosphorylation
• C. Photolysis uses light to produce reduced NADP and oxygen which are used to reduce a 3Ccarbohydrate
• D. Photolysis produces NADPH and ATP which are used to reduce a 5C cartediadrate

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

• A. 45
• B. 35°C
• C. 15°C
• D. 25°C

Explanation: Despite the fact that the stomata open in response to light, they may close on a hot day in order to conserve water.

• A. p680,p700, water, NADP
• B. Water, p700, NADP, p68
• C. p700, p680, NADP, water
• D. Water, p680, p700, NADP

Explanation: In the presence of light the photolysis of water occurs in the water splitting centre within photosystem II, the electrons released are…

• A. ATP synthase
• B. Cytochrome B
• C. Oxygen
• D. Coenzyme Q

Explanation: NADH is oxidised by co enzyme Q and the reaction is catalyzed by NADH-ubiquinone oxidoreductase.

• A. Nucleus
• B. Cytosol
• C. Mitochondira
• D. Ribosomes

Explanation: Glycolisis is the 1st step of both aerobic and anaerobic respiration and takes place in cytosol of cell.

• A. Red blue
• B. Yellow orange
• C. Violet red
• D. Orange red

Explanation: Chlorophyll mainly absorbs violet-blue and orange-red wavelengths. Green, yellow and indigo are least absorbed and are transmitted or…

• A. Energized electron
• B. Energy
• C. Uncharged electron
• D. All of these

Explanation: NADPH2 is an energy-carrying molecule produced in the first stage of photosynthesis.

• A. It is a porphyrin ring or tetrapyrrole ring structure.
• B. It is flat, square and light absorbing.
• C. It is composed of carbon and nitrogen atoms with Magnesium as the central metal ion, which is coordinated with nitrogen.
• D. It is hydrophobic

Explanation: Chlorophyll is an asymmetrical molecule having a hydrophilic head made of four pyrrole rings bound to each other and forming a porphyrin.

• A. NADH
• B. DNA
• C. Oxygen
• D. None of these

Explanation: Option D is correct as CO2 is reduced to form carbohydrates which are not mentioned in the rest of the options.

• A. 600 nm
• B. 650 nm
• C. 680 nm
• D. 700 nm

Explanation: PSI (Photosystem I) is a complex of chlorophyll a pigment molecules that absorbs light at a wavelength of 700 nm, which is the far-red end…

• A. Ultra-Violet
• B. Blue
• C. Red
• D. None of the above options are correct

Explanation: Option A: Ultraviolet light is a different type of light and can not be seen by the naked eye hence it does not have a colour therefore…

• A. NAD
• B. ADP
• C. FADH
• D. RuBP

Explanation: The calvin cycle reactions fixes CO2 from the environment into carbohydrate molecules.

• A. Only heterotrophs require chemical compounds from the environment
• B. Cellular respiration is unique to heterotrophs
• C. Only heterotrophs have mitochondria
• D. Autotrophs but not heterotrophs can nourish themselves begining with nutrients that are entirely inorganic

Explanation: Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.

• A. 6.1
• B. 6.3
• C. 7.1
• D. 7.3

Explanation: The release of terminal phosphate in a single ATP molecule occurs using water, the energy released is equivalent to 7.3Kcal/mol.

• A. 1
• B. 6
• C. 3
• D. 0

Explanation: The equation for photosynthesis is as follows; 6CO2 + 6H2O → C6H12O6 + 6O2 Water appears on both sides of the equation because water is…

• A. It is a porphyrin ring or tetrapyrrole ring structure
• B. It is flat, square and light absorbing
• C. Composed of carbon and nitrogen atoms with magnesium as central metal ion.
• D. It is hydrophobic

Explanation: Chlorophyll molecules have a complex structure consisting of the hydrophobic tail region and hydrophilic head region because it needs to…

• A. Carbon fixation
• B. RUBP
• C. Reduction
• D. A and C

Explanation: Both carbon fixation and reduction are important stages in the Calvin cycle.