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  • Created on: 05-04-14 12:47

Production of glucose

Photoynthesis the procees that produces glucose in plant and algae

Photosynnthesis takes place in the chloroplasts

Chloroplasts contain a green substance called chlorophyll, absorbs sunlight and uses its energy to concert to carbon dioxide and water into glucose. Oxygen is a by-product

Photosynthesis happens in leaves of all green plants.Four raw materials need: 

1) Sunlight beating down on the leaf provides the energy for the process

2) Cholorophyll is contained in chloropasts

3) Water reaches the cell via the xylem

4) CO2 diffuses into the leaf

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How plant use glucose


  • Plants make glucose in their leaves
  • They use some for respiration
  • This release energy enabling them to convert the rest of the glucose inot various other substances, which they can use to build new cells and grow
  • Some substances require a few minerals from the soil

Making Cell Walls

  • Glucose is converted into cellulose for making strong cell walls, especially ina rapidly growing plant

Making Proteins

  • Glucose is combined with nitrate ions (absorbed from the soil) to make amino acids which are then made into proteins
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How plant use glucose continued

Stored in seeds

  • Glucose is turned into lipids (fats and oils) for storing in seeds.
  • Sunflower seeds for example contain a lot of oil- we get cooking oil and margarine from them

Stored as starch

  • Glucose is turned into strach and stored in roots, stems and leaves ready for use when photosynthesis isn't happening like in winter
  • Starch is insoluble - better for storing than glucose. A cell with lots of glucose in would draw in loads of water and swell up.
  • Potato and arsnip plants store a lot of starch underground over the winter so a new plant can grow the following spring
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The Rate of Photosynthesis

Not enough light slows the rate of photosynthesis down

  • Light provide the enegy needed
  • As the lght level is raised the rate of photosynthesis increases steadily but only up to a certain point
  • beyond the point won't make any difference as temperature or Co2 level will be th limiting factor.
  • Measure light intensity using a light meter

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The Rate of Photosynthesis 2

Too little Carbon Dioxide slows the rate

  • CO2 is one of the raw materials needed for photosynthesis
  • The amount of CO2 will only increase the rate of photosynthesis up o  a certain point. After this the graph flattens ut showing that CO2 is no longer a limiting factor.
  • Light or temperature needs to be increases
  • Lots of was to control the amount of CO2 one in which you dissolve different amount of sodium hydroxide in water- gives off CO2

A graph with rate of photosynthesis on the y axis and carbon dioxide concentration on the x axis. The plotted line rise steeply and then levels off to horizonal. During the steep part carobn dioxide is the limiting factor. During the horizontal part another factor has become limiting. (

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The Rate of Photosunthesis 3

The temperature has to be right

  • If temperature is the limiting factor nrmally it's because it's too low The enzymes needed for photosynthesis work slowly at low temperatures
  • But if a plant gets too hot the enzymes it needs fr photosynthesis and other reactions ecome damaged and are denatured. Happens at 45 degrees clecius.

A graph with rate of photosynthesis on the y axis and temperature on the x axis. The plotted line rises at a 45 degree angle and then drops back down to 0. (

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The Rate of Photosynthesis lab experiments

Canadian Pondweed.

  • Easily measure the amount of oxygen produced in a given time to show how fast photosynthesis is happening.
  • Either count the bubble given off or more accurately coolect the oxygen in a gas syringe

Keeeping variables constant apart from one investigating so it's a fair test:

  • Use a bench lamp to control the intensity of light
  • Keep the flask of water in a watwe bath to keep the temperature constant
  • Not much can do about CO2 levels- use a large fask, conduct exeriments quickly so the plant doesn't use up too much of the CO2 in the flask. Ensure sodium hydrogencarbonater changd each time
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Artificially creating Ideal Farming Conditions

  • Ideal environment= a greenhouse
  • Help trap th sun's heat and make sure temperature doesn't become limiting
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