June 6, 2019
Photosynthesis
- Plants make their own food by photosynthesis.
- The food that plants make through photosynthesis is a type of sugar called glucose.
- During photosynthesis, plants use carbon dioxide and water to produce glucose and oxygen, using sunlight as energy.
- Sunlight is absorbed by green pigments called chlorophyll, which is located in chloroplasts of plant cells.
👇 For IGCSE Biology, you should be familiar with the word and balanced chemical equation for photosynthesis 👇
Structure of Leaves
Most of the photosynthesis happens at leaves of plants, so structure of leaves are adapted for photosynthesis.
👇 Frequently asked in IGCSE Biology... 👇
How the structures of leaves🌿 are adapted for photosynthesis:
- Wide and flat leaves: Increases surface area to capture as much light as possible
- Thin leaves: Carbon dioxide can reach cells easily
- Network of veins in leaves: Transports water to leaves and glucose away from leaves
- Waxy cuticle: Prevents water loss through evaporation while still absorbing sunlight
- Thin and transparent epidermis: Allows more light to reach palisade mesophyll, where much of photosynthesis happens in leaves
- Numerous chloroplasts in palisade mesophyll: Increases the rate of photosynthesis with many chlorophylls capturing a lot of sunlight
- Air spaces in spongy mesophyll: Allows carbon dioxide and oxygen to diffuse in and out of leaves faster
- Guard cells and stomata: Opening stoma by controlling guard cells allows carbon dioxide to enter leaves and oxygen to go out of leaves
Factors that Affect the Rate of Photosynthesis
- Light intensity: As light intensity increases, the rate of photosynthesis increases until other factors start to limit the rate of photosynthesis.
- Carbon dioxide concentration: As concentration of carbon dioxide increases, the rate of photosynthesis increases until other factors start to limit the rate of photosynthesis.
- Temperature: Photosynthesis is controlled by enzymes. To a certain temperature, the rate of photosynthesis increases as temperature increases. However, when the temperature gets too high, enzymes denature and cannot function anymore, so the rate of photosynthesis drops.