AQA GCSE Biology: Photosynthesis
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This flashcard set covers photosynthesis, equations, limiting factors, and plant uses of glucose for AQA GCSE Biology students.
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Cards · 20
- Definition of photosynthesis
- An endothermic reaction where plants use light energy to convert carbon dioxide and water into glucose and oxygen.
- Word equation for photosynthesis
- Carbon dioxide + water -> glucose + oxygen (in the presence of light and chlorophyll)
- Balanced chemical equation for photosynthesis
- 6CO2 + 6H2O -> C6H12O6 + 6O2
- Site of photosynthesis in plant cells
- Chloroplasts, which contain the green pigment chlorophyll that absorbs light.
- Why is photosynthesis considered endothermic?
- It takes in energy from the environment (in the form of light) to break chemical bonds.
- Main limiting factors of photosynthesis
- Light intensity, carbon dioxide concentration, temperature, and amount of chlorophyll.
- Effect of increasing temperature on photosynthesis
- Increases rate up to an optimum; beyond this, enzymes denature and the rate drops rapidly to zero.
- Effect of increasing CO2 concentration
- Increases the rate of photosynthesis until another factor becomes limiting, causing the rate to plateau.
- Inverse square law for light intensity
- Light intensity is inversely proportional to the square of the distance from the light source (Light intensity is proportional to 1 / d^2).
- What happens if distance from a lamp is doubled?
- The light intensity decreases by a factor of four (quarter of the original intensity).
- Commercial use: controlling greenhouse conditions
- Farmers artificially supply light, heat, and CO2 to remove limiting factors and maximize crop yield and profit.
- Use of glucose: cellular respiration
- Broken down during respiration to release energy for cellular processes.
- Use of glucose: storage as starch
- Converted into insoluble starch stored in roots, stems, and leaves for use when light is unavailable.
- Why is glucose stored as starch rather than kept as glucose?
- Starch is insoluble, so it does not affect the water potential and osmotic balance of the plant cell.
- Use of glucose: cellulose production
- Joined into long chains to make cellulose, which strengthens and supports plant cell walls.
- Use of glucose: amino acid synthesis
- Combined with nitrate ions absorbed from the soil to produce amino acids, which make proteins.
- Use of glucose: lipids
- Converted into fats and oils stored in seeds as an energy store.
- Required Practical: pondweed variable measured
- The volume of oxygen produced per unit time or the number of oxygen bubbles produced per minute.
- Required Practical: why add sodium hydrogencarbonate to pondweed?
- To supply dissolved carbon dioxide so it does not become a limiting factor.
- Required Practical: controlling heat from the lamp
- Use an LED bulb or place a glass tank of water between the lamp and beaker as a heat shield.