AQA - B2 2 - How plants produce food

These cards will tell you about photosynethesis, limiting factors,how plats use glucose and why plants need minerals. It includes everything you need to know for the additional biology AQA GCSE.

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  • Created by: Ruth
  • Created on: 06-12-10 20:10


carbon dioxide + water (+ light enegry) ------> glucose + oxygen

How the products are used
The glucose (carbohydrate) is useful but the oxygen is given off as a waste gas.  
Plants use some of the glucose straight away for processes like respiration and protein synthesis but some is converted into starch and stored for later - winter/times of low light.

Where the 'ingredients' for photosynthesis come from
~Carbon dioxide gets taken in by the leaves.
Light gets absorbed by the chlorophyll in the cloroplasts in the cells in the leaves.
~Water gets taken in by the roots.

How leaves are adapted to do their job
~Leaf structure - upper epidermis, palisade layer, spongy layer, lower epidermis. You could remember this by unusual people sing lots.
~Waxy cuticle stops water loss                                                    ~air spaces-oxygen get to cells - respiration
~Palisade cells in upper epidermis have lots of chloroplasts-lots of photosynthesis
~Cells not tightly packed-lots of surface area for lots of gas exchange and chloroplasts.
~Guard cells open and close the stomata to control water loss.
~Stomata allow gasses to move in and out.

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Limiting Factors

Limiting factors are things that affect the rate of photosynthesis.

Limiting factors:
Light - slow down rate of photosynthesis. Not as much glucose made so plant can't do as much - less energy. THis is why plants with green leaves (they are the ones that photosynthesise) do not work as well when you try to grow them in a dark cupboard.

Cold - enzymes dont work effectively. Cold so things are moving slowly so not as many things bump into each other and make a chemical reaction happen. So this then slows down the processes in the plant because chemical reactions aren't happening lots. This is why some instructions tell you to leave your plant in a warm place like near a radiator, so chemical reactions can happen lots.

Carbon dioxide - it is needed for respiration which gives energy. Without it, not as much respiration can take place so there is less glucose. Therefore the plant can't do as much. There may be a lack of CO2 in an enclosed space like in a greenhouse on a sunny day in the rainforest - hot so lots of photosynthesis but the CO2 gets used up.

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good;but font is little bit to small

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