QCM : Photosynthesis and Cellular Respiration — 9 questions

Questions et réponses du QCM

1. What is photosynthesis?

A process by which green plants convert light energy into chemical energy stored in glucose, using carbon dioxide and water, and releasing oxygen.
A pigment in chloroplasts that absorbs light energy for photosynthesis.
An organelle within plant cells where photosynthesis occurs.
A series of enzyme-assisted reactions that fix carbon dioxide into organic molecules.

A process by which green plants convert light energy into chemical energy stored in glucose, using carbon dioxide and water, and releasing oxygen.

Explication

Photosynthesis is the biochemical process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose, using carbon dioxide and water, and releasing oxygen as a byproduct. This process involves light-dependent reactions and the Calvin Cycle, occurring in chloroplasts.

2. What is the primary function of chlorophyll in photosynthesis?

It absorbs light energy, primarily in the blue and red wavelengths, to enable photosynthesis.
It converts light energy directly into glucose.
It stores chemical energy in the form of ATP.
It splits water molecules during photosynthesis.

It absorbs light energy, primarily in the blue and red wavelengths, to enable photosynthesis.

Explication

Chlorophyll's main role is to absorb specific wavelengths of light, mainly blue and red, which energizes the electrons necessary for photosynthesis to proceed.

3. What specific process occurs during the light-dependent reactions of photosynthesis that involves splitting water molecules?

Photolysis of water
Formation of glucose
Fixation of carbon dioxide
Conversion of NADP+ to NADPH

Photolysis of water

Explication

Photolysis of water is a key process in the light-dependent reactions of photosynthesis. It involves splitting water molecules into oxygen, protons, and electrons, which is essential for replenishing electrons in chlorophyll and producing oxygen as a byproduct. This process occurs in the thylakoid membranes and is driven by light energy.

4. In which part of the chloroplast do light-dependent reactions primarily occur?

Thylakoid membranes.
Stroma.
Outer membrane.
Nucleus.

Thylakoid membranes.

Explication

Light-dependent reactions occur in the thylakoid membranes where chlorophyll absorbs light energy to generate ATP and NADPH.

5. What is the primary role of the Calvin Cycle in photosynthesis?

To fix atmospheric CO₂ into organic molecules using energy from ATP and NADPH.
To convert light energy directly into glucose.
To generate ATP and NADPH during light-dependent reactions.
To produce oxygen as a byproduct of photosynthesis.

To fix atmospheric CO₂ into organic molecules using energy from ATP and NADPH.

Explication

The Calvin Cycle's main function is to fix atmospheric CO₂ into organic molecules like G3P, which can then be used to synthesize glucose. It uses ATP and NADPH from the light-dependent reactions to drive this process. It does not directly convert light energy into glucose nor produce oxygen; oxygen is released during the light-dependent reactions. ATP and NADPH are produced in the light-dependent reactions, not in the Calvin Cycle itself.

6. What is the overall chemical equation for photosynthesis?

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
6O₂ + C₆H₁₂O₆ → 6CO₂ + 6H₂O + energy
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ + light energy

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Explication

The correct equation shows carbon dioxide and water converting into glucose and oxygen using light energy, representing photosynthesis.

7. Which molecules are produced during the light-dependent reactions?

ATP and NADPH.
Glucose and oxygen.
G3P and ATP.
Carbon dioxide and water.

ATP and NADPH.

Explication

Light-dependent reactions produce ATP and NADPH, which are used in the Calvin Cycle to synthesize glucose.

8. What is a key difference between photosynthesis and cellular respiration?

Photosynthesis converts light energy into chemical energy, while respiration releases energy from glucose.
Photosynthesis occurs in animal cells, respiration occurs in plant cells.
Photosynthesis produces energy, respiration consumes it.
Photosynthesis only occurs at night, respiration only during the day.

Photosynthesis converts light energy into chemical energy, while respiration releases energy from glucose.

Explication

Photosynthesis captures light energy to produce glucose, whereas cellular respiration breaks down glucose to release energy as ATP.

9. Who is credited with describing the process of photosynthesis as a biochemical process?

Jan Ingenhousz in 1779.
Melvin Calvin in the 1950s.
Jan Ingenhousz, who demonstrated that sunlight is necessary for oxygen accrual in plants.
Joseph Priestly in 1772.

Jan Ingenhousz, who demonstrated that sunlight is necessary for oxygen accrual in plants.

Explication

Jan Ingenhousz showed that sunlight is necessary for plants to produce oxygen, thus contributing to understanding photosynthesis.

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Photosynthesis — overview?

Converts light into chemical energy in plants.

Photosynthesis — process?

Converts light into chemical energy in glucose.

Light-dependent reactions — role?

Produce ATP and NADPH using light energy.

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