Question 1: Define the word 'photosynthesis'.

Answer: Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose molecules.

Question 2: Write the overall chemical equation for photosynthesis, including states of matter.

Answer: 6CO₂ (g) + 6H₂O (l) → C₆H₁₂O₆ (aq) + 6O₂ (g)

Question 3: Which pigment is primarily responsible for capturing light energy in photosynthesis?

Answer: Chlorophyll a

Question 4: Fill in the blank: The light-dependent reactions of photosynthesis occur in the __________ of the chloroplast.

Answer: thylakoid membranes

Question 1: If a plant requires 120 molecules of CO₂ to produce 1 molecule of glucose, how many molecules of CO₂ are needed to produce 5 molecules of glucose?

Answer: 600 molecules of CO₂

Question 2: Calculate the amount of water (in grams) needed to supply 1 mole of water for photosynthesis, given that the molar mass of water is 18 g/mol.

Answer: 18 grams

Question 1: Describe a basic experimental setup to test the effect of light intensity on the rate of photosynthesis in aquatic plants.

Answer: An experiment can be set up using pondweed in a test tube with sodium bicarbonate solution, placed at varying distances from a light source to alter light intensity. The rate of photosynthesis can be measured by the amount of oxygen bubbles produced over a fixed time period.

Question 2: Identify two variables that must be controlled in the experiment described above and explain why.

Answer: Variables to control include temperature and carbon dioxide concentration, to ensure that changes in the rate of photosynthesis are due to light intensity alone.

Question 1: A researcher measures the oxygen output from aquatic plants under different light intensities. The data shows increased oxygen production with higher light intensities until a plateau is reached. Explain why the rate of photosynthesis levels off at high light intensities.

Answer: The rate of photosynthesis levels off because other factors such as carbon dioxide availability or temperature become limiting, or the photosynthetic machinery reaches its maximum capacity, preventing further increases despite higher light intensity.

Question 1: Explain how understanding photosynthesis reactions is important for improving crop yields in agriculture.

Answer: Understanding the reactions allows scientists to optimise conditions such as light, CO₂, and nutrients to enhance photosynthetic efficiency, leading to increased crop yields.

Question 2: Describe how artificial photosynthesis could be used as a sustainable technology for energy production.

Answer: Artificial photosynthesis mimics natural processes to convert sunlight, water, and carbon dioxide into chemical fuels like hydrogen or hydrocarbons, providing a renewable and clean energy source that reduces reliance on fossil fuels and decreases greenhouse gas emissions.