Biology Revision Y10



                                     (light, chlorophyll)

carbon dioxide + water        -->          glucose + oxygen 

        6CO2        + 6H2O       -->        C6H12O6 + 6O2                                  

Testing a green leaf for starch

- place a leaf in boiling water for about 1 minute to soften it.

-turn off bunsen burner, place leaf into a test tube half full of ethanol (ethanol has boiling point of 78-80'c),place test tube in the hot water for 10 minutes.

- spread leaf out on ptridish and cover it in iodine solution.

- return the leaf to hot water for about a minute.

- if blue/black starch is present , if it stays brown starch is not present.

What is needed for photosynthesis?

- plants are destarched by placing them in a cupboard for two days meaning we can see if its being produced in our experiment.

- is chlorophyll needed?  We used a variagated leaf that is green and white. Starch is only found where the green chlorophyll is present, therefore we proved chlorophyll is needed.

- is light needed?  we used a leaf with a piece of foil over it, stopping light getting to it. Starch is only made in areas where light can reach the leaf, therefore proving light is needed.

- is CO2 needed? we tested a plant with sodium hydroxide (no CO2) and one with sodium hydrogen carbonate (has CO2). Starch is only made in the plant with carbon dioxide, proving CO2 is needed. 

How plants use glucose

Plants make glucose in their leaves. They then use some of this glucose for respiration. Glucose is also made into cellulose. This is used to build strong cell walls. Seeds can store glucose in the form of fats and oils. We can use these things to make things like margarine. 

Plants store glucose as starch. It is insoluble and can be stored in the stem, seeds etc. 

Plants use glucose to make protein. In order to produce protein plants need to absorb nitrate ions ( NO3-) from the soil.

Limiting factors

 A factor that is in the lowest amount and limits the rate of photosynthesis. The limiting factor can vary throughout the day or fro place to place. 

What factors will affect the rate of photosynthesis?

- lots of chlorophyll to absorb and catch the light energy.

- warm temperatures.

- lots of carbon dioxide to combine.

-lots of water to combine.

- sunlight.

3 environmenta factors which act as limiting factors are:

-low light intensity 

- low carbon dioxide levels

-low temperatures

Photosynthesis is an enzyme controlled reaction. Enzymes function fastest in warm conditions. If the temperature gets too hot they de-nature nd stop working.

What happens to glucose after photosynthesis?

-it is…


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