B8: Photosynthesis Flashcards Preview

GCSE Combined Science: Biology (Higher) > B8: Photosynthesis > Flashcards

Flashcards in B8: Photosynthesis Deck (13)
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 - equation

 - what is it

Where plants make food using carbon dioxide, water and light. It is an endothermic reaction (energy taken from enviroment, temp goes up).


The process of Photosynthesis?

  • Uses energy to change Carbon Dioxide and Water into Glucose and Oxygen.
  • Takes place in chloroplasts 
  • Energy is transferred to the chloroplasts from the environment by light


Producing Oxygen


Leaf Adaptations

  • Broad leaves (bigger surface area for light to fall on)
  • leaves are thin (diffusion distance for gases are short)
  • Contain chlorophyll in chloroplasts (absorb light)
  • Have veins (bring plenty of water in xylem to cells of leaves, remove products of photosynthesis in the phloem)
  • Have air spaces (allow COto get to the cells and oxygen leave by diffusion)
  • Have guard cells that open and close the stomata (regulate gas exchange)


Uses of Photosynthesis?

 - other ways that plants use the glucose they produce during photsynthesis?

 - Plants use some of the glucose they produce to make a substance which strengthen their cell walls. What is it?

  • Respiration
  • Making cellulose
  • Making amnio acids
  • Stored as oils or fats
  • Stored as starch

Cellulose is answer to question because it supports the cell and strengthens it.


Required Practical...

Investigate the effect of light intensity on the rate of photosynthesis using pondweed.

Youtube: https://www.youtube.com/watch?v=hITp-60mqzg

              : Effect of a Varying Light Intensity on Rate of Photosynthesis-Updated


See A4 Booklet


How do you measure Light Intensity?


Limiting factors

 - what is meant by a limiting factor by the rate of photosynthesis?

Limit the rate of reaction, stops photsynthesis from happening any faster, e.g. photosynthesis


What factors affect the rate of Photosynthesis?

  • Light
  • Temperature - too hot, enzymes needed for photsynthesis and its other reactions will be damaged making them denatured causing a rapid decrease in photosynthesis
  • Carbon Dioxide concentration


Rate of Photosynthesis graphs...

  • Light
  • Temperature
  • Carbon Dioxide Concentration


  • More light, the more photosynthesis that takes place (only to a certain point)
    • Because as the light intensity increases, the rate will no longer increase because either the temperature or CO2 level is now the limiting factor not light
  • Provides energy needed for photosynthesis


  • Affects the enzymes involved
  • If this is the limiting factor, because the temp is too low
    • enzymes work a lot slower
  • too hot, enzymes can get damaged
  • Enzymes get destroyed at roughly 45oc

Carbon Dioxide:

  • Raw material needed for photsynthesis
  • More CO there is, will increase the rate of photosynthesis up to a cetain point.
  • At flat line, Light or temperature needs to be increased
  • Curve, plenty of light and warmth


How do plants use glucose?

  • During photosynthesis during respiration
  • broken down using oxygen to provide energy for the cells
  • Carbon dioxide and water are waste product


  • Plants and algae use some of the glucose from photosynthesis and energy tansferred to build up fats and oils
    • used in the cells as energy store
    • used in cell walls to make them stronger
    • energy store in their seeds
      • provide food for the new plant to respore as germinates 

Nitrates, Proteins and Carnivorous plants:

  • Plants use some of the glucose from photosynthesis to make amio acids
    • combining sugars with nitrate ions and other mineral ions from the soi
    • build up to proteins
    • be used in plant cells (enzymes)
  • Algae also make amnio acids
    • take nitrate ions from water they live in
  • Some carnivorous plants i.e. Venus Flytraps, are adapted to live in nitrate-poor soil.
    • Nutrients from animals i.e. insects
    • Plants produce enzymes to digest the insects they trap

Cellulose for strength, startch for storage:

  • Energy transferred in respiration may be used to build up smaller molecules into bigger ones
  • Plants convery some of the glucose they produce in photosynthesis into starch to be stored
    • Glucose is insoluble in water
    • Lots of glucose stored in the plant cells could affect the water balance if the whole plant
  • Starch is insoluble in water
    • no effect on the watter balance of plant making plant be able to store large amounts of starch in cells
    • Starch is stored in the cells of the leaves
    • Starch is kept in special storage areas of a plant



Ideal conditions for photosynthesis


  • trap suns heat
  • Temperature doesn't become limiting 
  • Artifical light after sun goes down to maintain photosynthesis
  • Can use it all year round
    • not depent on the weather
  • Increase level of Carbon dioxide
  • Keeping them enclosed limits the pests and diseases
  • it is very expensive but if done correctly, then it could save them money


What does C6H12O6 represent?