Photosynthesis Test

Multiple Choice Questions (MCQs)

1. Joseph Priestley’s experiment with a mint plant under a bell jar demonstrated that plants:
   1. Remove carbon dioxide from the air
   2. Release nitrogen into the air
   3. Restore oxygen to the air
   4. Absorb water vapour from the air
2. Who discovered that sunlight is essential for the purification of air by plants?
   1. Joseph Priestley
   2. Jan Ingenhousz
   3. Robert Hooke
   4. Antoine Lavoisier
3. In Jan Ingenhousz’s experiment, what did the bubbles formed around the green parts of the plant represent?
   1. Hydrogen
   2. Oxygen
   3. Carbon dioxide
   4. Nitrogen
4. Which of the following pigments is NOT an accessory pigment in photosynthesis?
   1. Chlorophyll b
   2. Xanthophylls
   3. Carotenoids
   4. Chlorophyll a
5. What is the absorption peak of chlorophyll a in Photosystem II?
   1. 700 nm
   2. 680 nm
   3. 720 nm
   4. 650 nm

Assertion-Reason Questions

In each of the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct answer from the following:

1. Assertion (A): Photosynthesis occurs mainly in the red and blue regions of the light spectrum.
   Reason (R): Chlorophyll a is the only pigment that absorbs light in photosynthesis.
   1. Both A and R are true, and R is the correct explanation of A
   2. Both A and R are true, but R is not the correct explanation of A
   3. A is true, but R is false
   4. A is false, but R is true
2. Assertion (A): Oxygen is released during the light reaction of photosynthesis.
   Reason (R): Water splitting occurs in Photosystem II, leading to the release of oxygen.
   1. Both A and R are true, and R is the correct explanation of A
   2. Both A and R are true, but R is not the correct explanation of A
   3. A is true, but R is false
   4. A is false, but R is true

One Word Answers

1. Which plant did Priestley use in his experiment to demonstrate the purification of air? Answer: Mint
2. Which pigment forms the reaction centre in Photosystem I? Answer: P700 (Chlorophyll a)
3. Name the scientist who showed that only the green parts of plants release oxygen. Answer: Jan Ingenhousz
4. What type of chemical intermediates are formed during the light reaction? Answer: ATP and NADPH
5. Which region of the light spectrum does Photosystem II absorb? Answer: 680 nm

Numerical Problems

1. If 4 bubbles of oxygen are produced by an aquatic plant in 2 minutes during bright sunlight, how many bubbles will be produced in 10 minutes?
   Answer: 20 bubbles (Assuming constant rate)
2. During photosynthesis, 6 molecules of CO₂ are required to produce one molecule of glucose. How many molecules of CO₂ are required to produce 10 molecules of glucose?
   Answer: 60 molecules of CO₂

Two Marker Questions on Photosynthesis

1. Explain the significance of Jan Ingenhousz’s experiment with an aquatic plant and the role of sunlight in photosynthesis.
   Answer: Jan Ingenhousz showed that sunlight is essential for the purification of air by plants. In his experiment with an aquatic plant, he observed that oxygen bubbles formed around the green parts of the plant in the presence of sunlight, indicating that photosynthesis occurs in the green parts and sunlight is crucial for oxygen release.
2. What is the role of accessory pigments in photosynthesis?
   Answer: Accessory pigments such as chlorophyll b, xanthophylls, and carotenoids absorb light and transfer energy to chlorophyll a. They enable a wider range of light wavelengths to be used in photosynthesis and protect chlorophyll a from photo-oxidation.
3. What happens during the light reaction of photosynthesis?
   Answer: During the light reaction, sunlight is absorbed by chlorophyll and other pigments, water is split into oxygen, protons, and electrons, and high-energy molecules like ATP and NADPH are formed. Oxygen is released as a by-product.
4. Why is the process of water splitting essential in Photosystem II?
   Answer: Water splitting in Photosystem II is essential because it provides the electrons needed to replace those lost by the excited chlorophyll molecules. It also releases oxygen as a by-product, which is essential for life on Earth.
5. Define the term ‘reaction centre’ in the context of photosystems.
   Answer: The reaction centre in a photosystem is a specific chlorophyll a molecule that absorbs light energy and releases excited electrons. In Photosystem I, it is called P700, and in Photosystem II, it is called P680, based on their absorption maxima.