Photosynthesis in Higher Plants MCQs with Answers and Explanations

What is Photosynthesis in Higher Plants

Photosynthesis is the way plants make their own food. It happens in green leaves, inside the chloroplasts. These parts contain chlorophyll, which traps sunlight. The process has two steps. First, there is the light reaction. This step happens in the thylakoid part of the chloroplast. In this reaction, sunlight splits water into hydrogen and oxygen. Oxygen is released, and energy in the form of ATP and NADPH is stored.

The second step is the dark reaction, also called the Calvin cycle. It takes place in the stroma of the chloroplast. In this step, the plant uses carbon dioxide and the energy made in the light reaction to make glucose, a simple sugar. Some plants also follow the C4 cycle, which is a different way of fixing carbon dioxide. It is used by plants in hot and dry areas.

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Photosynthesis in Higher Plants MCQs with Explanations

Here are some MCQs from Photosynthesis in the Higher Plants chapter.

Q1 PEPcase & RuBisCO in C plants are present respectively in:

1. mesophyll cell & bundle sheath cell.

2. bundle sheath cell & mesophyll cell.

3. spongy cell & bundle sheath cell.

4. subsidiary cell & guard cell.

Answer: (A) mesophyll cell & bundle sheath cell

Explanation: In C₄ plants, PEPcase (PEP carboxylase) is found in the mesophyll cells where it fixes CO₂ into oxaloacetate. RuBisCO is present in the bundle sheath cells where the Calvin cycle occurs.

Q2 Choose the events that occur in non-cyclic photophosphorylation but not in cyclic photophosphorylation.
I. Synthesis of ATP
II. Water splitting
III. Involvement of PS I
IV. Formation of NADPH
V. Phosphorylation occurs due to cyclic flow of electrons
Choose the correct answer from the options given below option.

1. II and IV only

2. I, II and V only

3. II, III, IV and V only

4. II, IV and V only

Answer: (A) II and IV only

Explanation: Water splitting (II) and NADPH formation (IV) occur only in non-cyclic photophosphorylation. Cyclic photophosphorylation does not involve water or production of NADPH.

Q3 Which of the following features are correct for bundle sheath cells in C plants?
I. Thin walled
II. Impervious to gaseous exchange
III. Having a large number of chloroplasts
IV. Presence of intercellular spaces
V. Wreath like arrangement of cells
Choose the correct answer from the options given below option.

1. I, II, III, IV and V

2. II, III and V only

3. II, III, IV and V only

4. I, II and V only

Answer: (B) II, III and V only

Explanation: Bundle sheath cells are impervious to gas exchange (II), have many chloroplasts (III), and are arranged in a wreath-like structure around the vascular bundle (V).

Q4 Choose the odd one w.r.t. the steps of Calvin cycle.

1. Deamination

2. Carboxylation

3. Reduction

4. Regeneration

Answer: (A) Deamination

Explanation: Deamination is not part of the Calvin cycle. The main steps of the cycle are carboxylation, reduction, and regeneration.

Q5 Non-cyclic photophosphorylation:

1. is not associated with splitting of water.

2. occurs in stroma lamellae only.

3. results in formation of ATP, NADPH & evolution of O₂.

4. involves two photosystem that work in series, first PS I & then PS II.

Answer: (C) results in formation of ATP, NADPH & evolution of O₂

Explanation: Non-cyclic photophosphorylation involves both PS II and PS I, leading to ATP and NADPH formation and oxygen release from photolysis of water.

Q6 Identify the A, B & C in the given image below:

1. A-Chl b, B-Carotenoids, C-Chl a

2. A-Carotenoids, B-Chl a, C-Chl b

3. A-Chl a, B-Carotenoids, C-Chl b

4. A-Chl d, B-Carotenoids, C-Chl a

Answer: (B) A-Carotenoids, B-Chl a, C-Chl b

Explanation: Based on light absorption, carotenoids absorb different wavelengths than chlorophyll a and b. Chlorophyll a is the primary pigment, while chlorophyll b and carotenoids are accessory pigments.

Q7 FNR catalyses:

1. oxidation of NADPH.

2. oxidation of NADP⁺.

3. reduction of NADP⁺.

4. reduction of NADPH.

Answer: (C) reduction of NADP⁺

Explanation: FNR (Ferredoxin-NADP⁺ reductase) is an enzyme that catalyzes the reduction of NADP⁺ to NADPH using electrons from ferredoxin.

Q8 All of the following are plants or internal factors affecting photosynthesis, except:

1. internal CO₂ concentration.

2. orientation of leaves.

3. availability of water.

4. amount of chlorophyll.

Answer: (C) availability of water

Explanation: Availability of water is an external factor. Internal factors include chlorophyll content, CO₂ concentration inside the leaf, and leaf anatomy.

Q9 Match List-I with List-II:

Choose the correct answer from the options given below:

1. A-II, B-I, C-III, D-IV

2. A-III, B-I, C-II, D-IV

3. A-IV, B-II, C-I, D-III

4. A-III, B-II, C-I, D-IV

Answer: (C) A-IV, B-II, C-I, D-III

Explanation: Calvin cycle happens in stroma; NADP reductase on the stroma side of thylakoid; cyclic photophosphorylation in stroma lamellae; water splitting on inner thylakoid membrane.

Q10 How many molecules of ATP and NADPH are required for the synthesis of one molecule of glucose in the Calvin cycle?

1. 3 molecules of ATP and 2 molecules of NADPH

2. 2 molecules of ATP and 3 molecules of NADPH

3. 18 molecules of ATP and 12 molecules of NADPH

4. 12 molecules of ATP and 18 molecules of NADPH

Answer: (C) 18 molecules of ATP and 12 molecules of NADPH

Explanation: To make one glucose (6 carbon), the Calvin cycle turns 6 times. Each turn uses 3 ATP and 2 NADPH → total = 18 ATP & 12 NADPH.

Q11 The first stable product of C₃ and C₄ pathway are, respectively:

1. 3-phosphoglycerate (3C) and oxaloacetate (4C).

2. phosphoglycolate (2C) and malic acid (4C).

3. aspartic acid (4C) and 3-phosphoglycerate (3C).

4. malic acid (4C) and oxaloacetate (4C).

Answer: (A) 3-phosphoglycerate (3C) and oxaloacetate (4C)

Explanation: C₃ plants form 3-PGA (3C) as first stable product; C₄ plants form oxaloacetate (4C).

Q12 The first stable product of CO₂ fixation in plant sorghum is:

1. oxaloacetic acid.

2. succinic acid.

3. phosphoglyceric acid.

4. Phosphoenolpyruvate.

Answer: (A) oxaloacetic acid

Explanation: Sorghum is a C₄ plant, and its first stable product is oxaloacetic acid (4C compound).

Q13 Given below are two statements:
Statement I: The principle of limiting factor was proposed by Jan Ingenhousz.
Statement II: Action spectrum of photosynthesis was described by Julius von Sachs.
In the light of the above statements, choose the most appropriate answer from the options given below:

1. Statement I is correct but Statement II is incorrect.

2. Statement I is incorrect but Statement II is correct.

3. Both Statement I and Statement II are correct.

4. Both Statement I and Statement II are incorrect.

Answer: (B) Statement I is incorrect but Statement II is correct

Explanation: The principle of limiting factors was given by Blackman, not Ingenhousz. Sachs did describe action spectrum-related ideas.

Q14 Identify the incorrect statement w.r.t carboxylation.

1. Carboxylation is the fixation of CO₂ into a stable organic intermediate.

2. Carboxylation is the most crucial step of the Calvin cycle.

3. Carboxylation reaction is catalysed by the enzyme RuBP carboxylase.

4. As a result of carboxylation, ribulose 1,5-bisphosphate is formed.

Answer: (D) As a result of carboxylation, ribulose 1,5-bisphosphate is formed.

Explanation: RuBP is the CO₂ acceptor, not the product. The product of carboxylation is 3-phosphoglycerate (PGA).

Q15 Calvin pathway occurs in:

1. all photosynthetic plants.

2. photosynthetic plants which have C₃ pathway only.

3. photosynthetic plants which have C₄ pathway only.

4. tropical plants only.

Answer: (A) all photosynthetic plants

Explanation: Calvin cycle or C₃ pathway is common to all photosynthetic plants — including C₃, C₄, and CAM — for fixing CO₂ in the chloroplast.

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