Photosynthesis

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  • Created by: ewilford
  • Created on: 27-11-16 14:15

Photosynthesis

The Word equation:
                     light
carbon + water ---> glucose + oxygen

The Symobol equation:
                           light
6CO6H2O ---> C6H12O+ 6O2

  • Takes place in the chloroplasts
  • Is an endothermic reaction that requires light

It produces glucose which plants can use for:

  • Respiration
  • Making cellulose - used for plant cell walls
  • Making amino acids - These are made into protein
  • Storing oils or fats: Glucose is turned into lipids for storing in seeds
  • Storing as starch - This is stored in roots, stems and leaves so it can be used for when photosynthesis is not happening.Starch is insoluble so it is better to store than glucose.
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Adaptations of the leaf

Adaptations that leaves have for Photosynthesis:

  • Leaves are green as they contain chlorophyll which absorbs the light in the chloroplasts
  • The stomata is on the bottom of the leaf to stop loosing as much water vapour. It is also used for gas exchange. Carbon dioxide passes through the stomata and oxygen leaves through the stomata
  • The phloem transports glucose to the rest of the plant
  • A large surface area to trap most of the surface area
  • Waxy cuticle prevents water loss
  • Spongy mesophyll means there are air spaces for gas exchange
  • The palisade cells have lots of chloropasts

The Leaf Structure (http://www.bbc.co.uk/staticarchive/9096f4876ea334b17cefc43963304ae282061a97.gif)

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Limiting Factors of Photosynthesis

The rate of Photosynthesis can be limited by: 

  • Light Intensity 
  • Carbon dioxide
  • Temperature

Light Intensity - As the light intensity increases, the rate of photosynthesis increases steadily but only up to a certain point. After this, the rate no longer increases as either the temperature or carbon dioxide level is now a limiting factor not light.

Carbon Dioxide - Like light intensity, the amount of carbon dioxide will only increase the rate of photosynthesis up to a point. The graph flattens out as the rate no longer increases therefore carbon dioxide is no longer a limiting factor. If there is a good supply of light and carbon dioxide then temperature must be the limiting factor.

Temperature - The temperature has to be just right as if it's too low then the enzymes needed will work slower. If it is too hot then the enzymes will become denatured. This would happen at around 45 degrees. If this happens, photosynthesis stops.

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Rate of Photosynthesis graphs

Light intensity graph (http://www.bbc.co.uk/staticarchive/afa3f2b16b4d58d077943c96929c9a4020fea83a.gif)temperature graph (http://www.bbc.co.uk/staticarchive/32b3b8ad49fe959ff58ac5611559c0c4480cc33b.gif)carbon dioxide graph (http://www.bbc.co.uk/staticarchive/020c4bb33ca143df87adc99bc1afa29bb95a1688.gif)   

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The Inverse square law

The inverse square law equation is:

light intensity =          1
                       ------------------
                    distance (d) squared (2)

You can use this equation to measure light intensity as the distance and light intensity are inversely prportional to each other.

You would use this when you have moved the lamp away from the pondweed. 

Example:

Use the inverse square law to caluclate the light intesity when a lamp is 20cm away from the pondweed

=    1                 = 0.0025 a.u (arbitary units)
    ------
20 squared

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