GCSE Biology

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  1. In a leaf experiment testing for starch we notice that the green part of the leaf turned black in the experiment . This was because
    Starch turns iodine solution a blue/black colour . This investigation proves that photosynthesis only happens in the presence of chlorophyll - startch from photosynthesis is present where there was chlorophyll . It proves that chlorophyll is needed for photosynthesis
  2. In a leaf experiment to try and prove that light is needed for photosynthesis we noticed that
    • Areas deprived oflight remained green and areas that were exposed to light turned black The areas that were black had startch unlike the green area proving that the black area 
    • (exposed to light) could photosynthesize unlike the green area (deprived or light) proving that light is needed for photosynthesis
  3. In a leaf experiment trying to prove that carbon dioxide is needed for photosynthesis ,
     the leaf That was placed in soda lime/pottasium hydroxide experienced no colour change however the leaf that was placed in the sodium bicarbonate changed to black . the black leaf contained starch showing it was able to photosynthesize suggesting that caron dioxide is needed for photosynthesis . the normal coloured leaf had a small amount of carbon dioxide because it had been absorbed by the soda lime from the air . this leaf produced no starch suggesting it was unable to photosynthesize . we can conlcude that carbon dioxide is needed for photosynthesis and when it is in short supply it limits photosythesis , so we call it a limitating factor 
  4. what does sodium bicarbonate do
    produces carbon dioxide
  5. what does soda lime do 
    absorbs carbon dioxide
  6. photosynthesis is the process by which green plants 
    • makes glucose . this process takes place near the upper surface of the leaf . Photosynthesis can be summarised as 
  7. for photosynthesis to take place the plant needs 
    • light
    • carbon dioxide
    • chloroplasts with chlorophyll
    • water 
  8. water enters the plant through the
    roots and travels to the leaves in the xylem 
  9. carbon dioxide enters the plant through the 
    stomata in the epidermis of the leaf 
  10. sunlight is absorbed by
    chlorophyll in the chloroplasts 
  11. leaves are especially adapted to help with photosynthesis in the following ways
    • the leaves are thin and flat to give a large surface area
    • palisade cells conatin lots of chlorplasts
    • the lower epidermis of the leaf has openings called stomata to allow gases to pass in and out of the air 
  12. during photosynthesis the two substances made are 
    glucose and oxygen 
  13. how is oxygen used
    it is a waste gas and some is used for respiration 
  14. list five ways in which plants use glucose made in photosynthesis
    • it can be converted to 
    • proteins 
    • lipids
    • starch 
    • cellulose 
    • it can also be used for respiration to produce energy 
  15. the upper epidermis has a 
    waxy cuticle which is waterproof layer which stops water loss
  16. the palisade layer has 
    palisade cells at the top of the leaf , close to light , tightly packed together and full of chloroplasts 
  17. the spongy layer has 
    air spaces and the cells are not tightly packed togther - they have a large surface areas available for gas exchange 
  18. the lower epidermis has
    • gurad cells which open and close the stomata to control water loss 
    • they also have stomata which allows gases to move in and out of the leaf 
  19. cross section of a leaf
  20. There are two layers in the mesophyll:
    • 1) the palisade layer - packed tight with oval cells
    • 2) the spongy layer - this area contains circular cells that are spread out --- allowing gases to circulate within the leaf
  21. a vascular bundle contains 
    xylem and phloem with cambium cells betwen them
  22. phloem tubes 
    they have thin walls and living cells 
  23. xylem vessels
    they have thick strong walls and are not living
  24. cambium cells 
    grow into new xylem and phloem 
  25. The xylem
    transport water & minerals from the roots, through the stem, & into the leaves  (remember ... we need water for photosynthesis)
  26. Phloem 
    are tubes that transport "food" through the plant.  This "food" is basically sugary water (sap).  The sugars are synthesized (made) during photosynthesis.
  27. If you've ever looked closely at a leaf you've noticed some pattern of lines running through it.  These lines are
    "vascular bundles" . Inside the vascular bundle are tubes that transport materials from place to place in the plant.
  28. vascular bundle
  29. lower epidermis
  30. starch
    is converted from glucose for storage
  31. limiting factors
    things which affect the rate of photosynthesis
  32. respiration
    the process carried out by all living things 

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GCSE Biology
2012-09-08 10:56:36
Photosynthesis part two

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