B4 - Photosynthesis
- Created by: Naomi
- Created on: 20-01-13 13:57
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- Photosynthesis
- Carbon Dioxide + Water ---> Glucose + Oxygen
- Glucose can be:
- Converted into cellulose (for cell walls)
- Used in respiration (to get energy)
- Converted into proteins (for growth and repair)
- Converted into starch, fats and oils (for storage)
- Starch is not used for storage because it is insoluable and does not move from storage areas.
- Unlike glucose it does not affect the water concentration of cells and cause osmosis
- Starch is not used for storage because it is insoluable and does not move from storage areas.
- Glucose can be:
- Historical understanding of Photosynthesis
- Greek scientists believed that plants took minerals out of the soil to grow and gain mass
- Van Helmot concluded from his experiment on a willow tree that plant growth must depend on something else as well as minerals
- Priestley's experiment showed that plants produce oxygen
- Greek scientists believed that plants took minerals out of the soil to grow and gain mass
- Photosynthesis is a 2 STAGE PROCESS
- Water is split up by light energy, releasing oxygen and hydrogen ions
- Carbon dioxide combines with hydrogen ions producing glucose
- Carbon Dioxide + Water ---> Glucose + Oxygen
- Glucose can be:
- Converted into cellulose (for cell walls)
- Used in respiration (to get energy)
- Converted into proteins (for growth and repair)
- Converted into starch, fats and oils (for storage)
- Starch is not used for storage because it is insoluable and does not move from storage areas.
- Unlike glucose it does not affect the water concentration of cells and cause osmosis
- Starch is not used for storage because it is insoluable and does not move from storage areas.
- Glucose can be:
- Water is split up by light energy, releasing oxygen and hydrogen ions
- The rate of photosynthesis can be increased by the plant having:
- More light
- More Carbon Dioxide
- Higher temperature, which increases enzyme action
- Since photosynthesis depends on light, temperature and carbon dioxide a lack of one of these factors will limit the rate of photosynthesis
- Called limiting factors
- Leaves are adapted for efficient photosynthesis
- The upper epidermis is transparent, so does not block out any light
- The upper palisade layer contains lots of chloroplasts as they will receive most of the light
- The spongy mesophyll cells are loosly spaced so diffusion of gases between the cells and outside atmosphere can take place
- The arrangement of mesophyll cells creates a large survace area:volume ratio so that large amounts of gases can enter and exit the cells
- Leaves are broad so that they have a large surface area
- Leaves are thin so gases can diffuse through easily and light can get to all cells
- They contain many pigments (chlorophyll a and b, carotene and xanthophylls) so the plant cells can maximise the use of the suns energy as they all absorb light of different wavelengths
- Have a network of vascular bundles (veins) for support and transport of chemicals such as water and glucose
- Have specialised guard cells which control the opening and closing of stomata, regulating the flow of carbon dioxide and oxygen as well as water loss
- Carbon Dioxide + Water ---> Glucose + Oxygen
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