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Plants and food (Photosynthesis and respiration (Plant's uses for…

- - - - Too cold (close to 0°) – slows the reaction
      - Too hot (above ~35°) – enzymes denature
      - In glasshouses, limiting factors are used to provide the optimum amount of CO2 which is pumped in
  - - - Proteins contain these and nitrogen, obtained as nitrate ions from the soil
      - Chlorophyll contains magnesium as well – absorbed from water in soil
- - - - remove leaf
      - dewax in boiling water for 30sec – boil with bunsen burner
      - place in boiling tube containing ethanol in the beaker of hot water (turn bunsen burner off) – ethanol will boil
        –> removes chlorophyll and green colour
      - leaf turns colourless / pale yellow
        –> remove and wash in cold water
      - spread on tile and cover with a few drops of iodine solution
      - Result: will turn from yellow-brown to blue-black
- - - - 0.8g calcium nitrate
      - 0.2g magnesium sulfate
      - 0.2g potassium nitrate
      - 0.2g potassium dihydrogenphosphate
      - (trace) iron (III) phosphate
  - - - use: making amino acids, proteins, chlorophyll, DNA etc.
      - deficiency: limited growth of plant, older leaves turn yellow
    - - use: making DNA and other compounds, part of cell membranes
      - deficiency: poor root growth, younger leaves turn purple
    - - use: needed for enzymes of respiration and photosynthesis to work
      - deficiency: leaves turn yellow with dead spots
    - - deficiency: leaves turn yellow
      - use: part of chlorophyll molecule
- - - - Reduces water loss by evaporation
      - Acts as a barrier to the entry of pathogens
      - Upper epidermis
        
        Not many chloroplasts
        
        Transparent to let light through
    - - Allows carbon dioxide to diffuse into and oxygen and water vapour to diffuse out of the leaf.
      - Gap between two guard cells
        
        Change their shape to open or close to stoma
    - - Main gas exchange surface of the leaf
      - Absorb CO2 and release O2 & H2O
      - Rounded, loosely packed cells
      - Air spaces between cells to allow gases to diffuse in and out
    - - Tissue made of long, narrow cells – each containing hundreds of chloroplasts
      - Main site of photosynthesis
      - Close to the source of the light
  - - - Very sensitive to changes in carbon dioxide concentration
      - High CO2 concentration – yellow
        CO2 in normal air – orange
        Low CO2 concentration – purple
    - - 10cm3 of the indicator solution is placed in the bottom of each of four boiling tubes
      - 3 large leaves are detached from a suitable plant and placed in the tops of three of the tubes
      - Each tube is sealed with a rubber bung
      - Tube 1 – bright light
        Tube 2 – dark
        Tube 3 – covered in a translucent material to restrict light intensity
        Tube 4 – no leaf – control to show that it is the leaf that changes the colour
      - Four tubes are left for a few hours, indicator colour recorded
    - - Tube 1 – bright light – purple
        Tube 2 – dark – yellow
        Tube 3 – dim light – orange
        Tube 4 – control – orange