Biology: Plants

Biology: Plants

Photosynthesis
1. CO2 + H2O = C6H12O6 + O2
  1. Sunlight would be where the equals sign is, and provides energy for the whole process
  2. CO2 diffuses into the leaf from the air
    1. Water is absorbed from the ground by the xylem
2. Photosynthesis occurs inside chloroplasts in the leaves of a plant
  1. The chloroplasts are filled with chlorophyll which is actually where photosynthesis occurs
3. Rate of photosynthesis is affected by light intensity, CO2 volume and temperature. Amount of water available can also affect the rate but this is often a limiting factor
  1. Limiting factors are things that prevent photosynthesis happening any faster
    1. At night, the limiting factor is light
    2. In the winter, the limiting factor is temperature
  2. For example, you can continue increasing light intensity, however the rate will stop increasing at a certain point because then the temperature or CO2 volume needs to increase too
Water is taken through the plant from the ground by the xylem
1. The phloem is responsible for "translocation", the movement of food and nutrients to all tissues and organs throughout the plant
Plants use glucose for multiple purposes
1. Respiration
  1. Respiration releases energy which allows the plant to convert the rest of the glucose into other useful substances
2. Making Cell Walls
  1. Here glucose is converted into cellulose which is used to make strong cell walls
3. Making Proteins
  1. Glucose is combined with nitrate ions to make amino acids which are then made into proteins
4. To be stored in seeds
  1. Here glucose is turned into "lipids" (fats and oils) to be stored in seeds
5. To be stored as starch
  1. Starch is stored in the roots, stem, leaves and seeds as a glucose reserve for when photosynthesis isn't happening (eg. the winter)
Guard cells are adapted to open and close the "stomata" (pores) in a leaf. Their function is gas exchange and controlling water loss in a leaf.
1. When the plants has lots of water, the guard cells go turgid which open the stomata so gases can be exchanged for photosynthesis
  1. When the plant is lacking water, the guard cells become flaccid which causes the stomata to close which prevents too much water vapour from evaporating
    1. Guard cells are sensitive to light and close the stomata at night to save water without losing out on photosynthesis

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	Created by Tom Johnson over 9 years ago

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