GCSE OCR GATEWAY BIOLOGY : PHOTOSYNTHESIS COMPLETE REVISION

This page contains the detailed and easy notes for GCSE OCR Biology Photosynthesis for revision and understanding Photosynthesis .

Banner 1




GCSE OCR GATEWAY Photosynthesis Complete Revision Summary

PHOTOSYNTHESIS

Photosynthesis

  • What is photosynthesis ?

  • Factors affecting photosynthesis

  • Factors affecting the rate of photosynthesis

  • Historical experiments to investigate photosynthesis

  • Proving photosynthesis only occurs in the light

  • Interaction of factors limiting the rate of photosynthesis – Higher

  • Practical – effect of light intensity on photosynthesis in pondweed.

     

  • Scientific calculations – effect of light intensity on photosynthesis

  • Scientific calculations -distance and light intensity – Higher

  • The importance of limiting factors – Higher

Banner 2




PHOTOSYNTHESIS

It is the process by which green plants prepare their own food by using water, carbon dioxide in presence of sunlight to form glucose and oxygen.

  • Only leaves can photosynthesize as they have chloroplast which contains chlorophyll.
  • Chlorophyll is the green pigment that traps light for the leaves and helps them to photosynthesis.
  • Photosynthesis is ENDOTHERMIC
  • Endothermic as it takes in heat from the sunlight.
  • The energy released in making glucose and oxygen is less than the energy required to break the bonds of carbon dioxide and water.

_Photosynthesis

[download_after_email id=”9802″]

LEAF ADAPTATIONS FOR PHOTOSYNTHESIS

Mesophyll – Photosynthetic cells lies parallel to the surface to absorb maximum light and are closed to the stomata for quick diffusion of gases.

Chloroplast – They have chloroplast which contains chlorophyll and traps light for photosynthesis

Guard cell – They have stomata which are the pores for gas exchange

FACTORS AFFECTING PHOTOSYNTHESIS

  • As the light intensity increases the rate of photosynthesis increases and then it levels off.
  • Initially the rate increases an€ then it has no effect as at that point other factors become limiting.


    • As the light intensity increases the rate of photosynthesis increases and then it levels off.
    • Initially the rate increases and then it has no effect as at that point other factors become limiting

    • As the temperature increases the rate increases as the particles gain kinetic energy and moves faster causing greater collision and increase reaction rate.
    • Beyond optimum the rate decreases as at the higher temperature the enzymes get denatured. The enzyme changes shape and is not functions if the shape changes

    Banner 3




    LAW OF LIMITING FACTORS

    • The factor that limits the rate OF photosynthesis
    • Limiting factor is that factor that is present in a least amount than required and affect the rate of photosynthesis.

    As the pH increases the rate increases upto optimum. Beyond optimum the rate decreases as enzymes get denatured.

    Measuring Photosynthesis

    FATE OF GLUCOSE

    • Glucose is soluble in water and if present longer will disturb osmotic balance of the cell Starch is complex molecule which is insoluble and can store large amount of glucose.
    • Also starch being insoluble does not disturb the osmotic balance of the cell.

    GLUCOSE

    • Principle source of energy.
    • It broken down during respiration and produces energy for the plant to grow and reproduce.

    STARCH

    • Excess glucose is stored in the plant as starch and is used by the plant when needed.

    CELLULOSE

    • Excess glucose can be converted into structural carbohydrate called Cellulose
    • Cellulose is the component of the cell wall which provide shape and support to the plant.

    PROTEINS

    • Glucose is combined with nitrates and other mineral ions from the soil to form protein.
    • Proteins are responsible for growth and also to make enzymes for metabolic reactions.

    LIPIDS

    • Glucose can be converted to fats and oil to serve as energy source.
    • Fats and oil can form the component of the cell membrane
    • They are also stored in seeds as an energy store for germination.

     
    Banner 4




    TEST FOR STARCH

    • Add Iodine Solution
    • If the solution turns blue black it indicates the presence of starch.

    GREENHOUSE

    • It controls all the limiting factors to provide maximum yield of photosynthesize
    • Temperature, light, carbon dioxide and other factors affecting photosynthesis are controlled and monitored.
    • It works on the principle of greenhouse effect in which light is allowed to enter but is not allowed to escape thereby increasing light and temperature inside the greenhouse.

    Disclaimer:

    I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.

    References:

    BBC Bitesize

    Wikipedia

    Wikimedia Commons

    Image Source:

    Wikipedia

    Wikimedia

    Commons

    Flickr

    Pixabay

    Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.

    Photosynthesis