Photosynthesis Reaction Stages 1 — Questions and Answers
Question 1: In which part of the plant cell do the light-dependent reactions of photosynthesis occur?
- Mitochondria
- Chloroplasts (thylakoid membranes) (Correct answer)
- Nucleus
- Ribosomes
Correct answer: Chloroplasts (thylakoid membranes)
The light-dependent reactions of photosynthesis, where light energy is captured and converted into chemical energy (ATP and NADPH), occur specifically within the thylakoid membranes inside the chloroplasts. These membranes contain the chlorophyll pigments and electron transport chains necessary for these initial energy conversion steps. The stroma is where the light-independent reactions (Calvin cycle) occur.
Question 2: What is the main product of the light-dependent reactions of photosynthesis?
- Glucose
- Oxygen
- ATP and NADPH (Correct answer)
- Carbon dioxide
Correct answer: ATP and NADPH
The light-dependent reactions of photosynthesis convert light energy into chemical energy. This energy is stored in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate). These energy-carrying molecules are then used to power the subsequent light-independent reactions (Calvin cycle) to synthesize glucose.
Question 3: During the light-dependent reactions, what molecule is split to provide electrons for the electron transport chain?
- Carbon dioxide
- Water (Correct answer)
- Glucose
- Oxygen
Correct answer: Water
During the light-dependent reactions, water molecules (H2O) are split in a process called photolysis. This splitting releases electrons, protons (H+), and oxygen gas. The electrons are then transferred to the electron transport chain, which is crucial for generating ATP and NADPH.
Question 4: Which of the following best describes the Calvin cycle?
- It occurs in the thylakoid membranes and uses sunlight to produce glucose.
- It occurs in the stroma of the chloroplast and synthesizes glucose using ATP and NADPH. (Correct answer)
- It is part of the light-dependent reactions that convert water into oxygen.
- It is a series of steps in which glucose is broken down into carbon dioxide.
Correct answer: It occurs in the stroma of the chloroplast and synthesizes glucose using ATP and NADPH.
The Calvin cycle, also known as the light-independent reactions, occurs in the stroma, the fluid-filled space within the chloroplast. It utilizes the ATP and NADPH produced during the light-dependent reactions to fix carbon dioxide from the atmosphere. This process ultimately synthesizes glucose, a sugar molecule.
Question 5: What is the role of NADPH in photosynthesis?
- It stores sunlight for later use.
- It provides energy to power the electron transport chain.
- It carries high-energy electrons to the Calvin cycle. (Correct answer)
- It absorbs carbon dioxide from the atmosphere.
Correct answer: It carries high-energy electrons to the Calvin cycle.
NADPH serves as an electron carrier in photosynthesis. It is reduced during the light-dependent reactions, picking up high-energy electrons and protons. These high-energy electrons are then transported by NADPH to the Calvin cycle, where they are essential for reducing carbon dioxide and building glucose molecules.
Photosynthesis Reaction Stages 1
In which part of the plant cell do the light-dependent reactions of photosynthesis occur?