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Biology; Chemistry; Physics: Post your doubts here!

Discussion in 'Cambridge O Levels' started by scouserlfc, Sep 13, 2011.

  1. Ayesha Asif333

    Ayesha Asif333

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    Yea, that's exactly how the explanation goes....Thanx
     
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  3. Hasaan Issani

    Hasaan Issani

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    I want the soft copy of biology, chemistry and physics topical past papers of o levels
     
  4. Hasaan Issani

    Hasaan Issani

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    What are the properties of ionic and covalent substances? Can any one explain me.
     
  5. sameer Ul Haq

    sameer Ul Haq

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    Ionic substances have high Melting & boiling points and conduct electricity while Covalent substances have low melting & boiling points and do not conduct Electricity. Ionic bonds are formed between Metal and Non-metal while covalent bonds are formed between Non-metals and Non-metals
     
  6. A*****

    A*****

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    *Ionic substances conduct electricity in molten or aqueous form...u need to mention this...while covalent substances don't conduct electricity in any state.
     
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  7. MysticLightning

    MysticLightning

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    Would anyone happen to have a precise explanation to the production of cheese and yogurt using bacteria?
     
  8. A*****

    A*****

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    YOGHURT:
    *Warm milk and add the culture of bacteria.
    *Bacteria respires anaerobically and converts milk lactose to lactic acid.
    *Lactic acid causes milk protein(casein) to curdle, producing yoghurt.

    CHEESE:
    *Milk is fermented to lactic acid by bacteria.
    *This causes the milk protein to curdle.
    *Curdled milk + fats in the milk are removed and acted upon by a mixture of both bacteria and fungi to produce cheese.
    *Different types of cheese can be prepared by varying the conditions.
     
  9. A*****

    A*****

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    Can someone plz help me with this...

    IMG_20170316_231225.jpg
     
  10. Talha Jameel

    Talha Jameel

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    For first part, you have to write down 2 values of where graph intersects the x axis
     
  11. A*****

    A*****

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    Sorry I was asking about the (e) part
     
  12. cool.fireboy24

    cool.fireboy24

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    you have to find the variables which make the equation eqqual to x3+10x-80

    If we write 4-x in the place of y you would find that it results in x3+10x-80 showing that y=4-x is the equation
     
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  13. Nour29

    Nour29

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    Can someone send feb/mar 2017 question papers pleasee
     
  14. THE YELLOW FLASH

    THE YELLOW FLASH

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    Hello guys. I am new to this thread and I wanted to ask if anyone has Physics and Chemistry Past Papers in a form of e-book. Please reply and share it will be a great help
    -Thank You
     
  15. MnMz Mohammad-M

    MnMz Mohammad-M

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    hey,

    can somebody solve this question for physics on 0625/63/o/n/16

    the questions starts with something like that --> Plan an experiment which will enable you to compare the strengths of different samples of thin paper

    its the last question.

    please solve it in a brief and detailed way...
    and plz use the mark scheme
    :):):)
     
  16. ZainJamro

    ZainJamro

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    Here's my Question
    How does transpiration stream increase the production of protein?
     
  17. A*****

    A*****

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    Transpiration brings nitrates dissolved in solution up the plant....those nitrates are used to manufacture amino acids, which in turn are used to synthesis more proteins...
    Hope it helped :)
     
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  18. Zeerak 420

    Zeerak 420

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    "The best removal of stains is maintained by providing the optimum temperature for enzymes, presoaking to leave time for the enzymes to digest, putting the suitable amount of the powder", can someone briefly explain the presoaking and powder part?

    Also, why is water needed for activating enzymes in germination of seeds?
     
  19. whyareallnamestaken

    whyareallnamestaken

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    Detergent powders contain enzymes which digest the protein in food/blood stains. Increasing the enzyme concentration would speed up the process of protein digestion.

    Pre-soaking is required because enzymes need aqueous mediums to function (hydrolytic breakdown).

    In germination, you need water for the same reason. Enzymes allow break down to happen through hydrolysis, which quite obviously requires water.
     
  20. BlitzyDay

    BlitzyDay

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    For germination to occur, you need water to break down the stored food inside the cotyledon - enzymatic activity (hydrolysis) and also for the permeability of the seed coat for oxygen uptake.
     

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