# The Rate of Photosynthesis

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• Created by: joshd
• Created on: 15-03-14 12:28
What slows down the rate of photosynthesis?
Not enough LIGHT, too little CARBON DIOXIDE, the TEMPERATURE (too low or hot)
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What does light provide? (1)
The energy needed for photosynthesis.
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What happens when the light level is raised? (2)
The rate of photosynthesis increases steadily, but only up to a certain point.
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Once light level does not make a difference to the rate, what does? (3)
It'll either be the temperature or the Co2 level which is the limiting factor.
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What can you do in a lab with light? (4)
You can change the light intensity by moving a lamp closer to or further away from your plant.
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What happens if you just plot the rate of photosynthesis against "distance of lamp from beaker"? How can you get an accurate graph? (5)
You get a weird-shaped graph. To get an accurate graph, you either need to measure the light intensity at the beaker using a light meter or use math to work it out.
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What is CO2 one of? (1)
The raw materials needed for photosynthesis.
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Describe how carbon dioxide affects the rate of photosynthesis (2)
It will only increase the rate of photosynthesis up to a point. After this the graph flattens out showing that CO2 is no longer the limiting factor.
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What is the limiting factor when light and CO2 are in plentiful supply? (3)
The factor limiting photosynthesis must be temperature.
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What is a way of controlling the concentration of Co2? (4)
Dissolve different amounts of sodium hydrogencarbonate (which gives off Co2) in the water.
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Why is temperature usually the limiting factor (if it is) and how ? (1)
Because the temperature is too low - the enzymes needed for photosynthesis work more slowly at low temperatures.
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What happens if the plant gets too hot? What temperature is this at (about)? (2)
The enzymes it needs for photosynthesis and other reactions will be denatured. This happens at about 45 dC (hot for outdoors, but greenhouses can get this hot if you're not careful).
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What is the best way experimentally to control the temperature of the flask? (3)
Experimentally, the best way to control the temperature of the flask is to put it in a water bath.
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What do you have to try and do in all the experiments and why?
You have to try and keep all the variables constant apart from the one you're investigating, so it is a fair test.
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How can you control the intensity of light?
Use a bench lamp to control the intensity of light.
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How can you help keep the temperature constant?
Keep the flask in a water bath.
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What must you do for CO2 levels? Why must you do the experiments as quickly as possible? Sodium hydrogencarbonate?
You can't really do anything - you just have to use a large flask and do the experiments as quickly as you can, so that the plant doesn't use up too much of the CO2 in the flask. If using sodium hydrogencarbonate make sure it's changed each time.
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## Other cards in this set

### Card 2

#### Front

What does light provide? (1)

#### Back

The energy needed for photosynthesis.

### Card 3

#### Front

What happens when the light level is raised? (2)

### Card 4

#### Front

Once light level does not make a difference to the rate, what does? (3)

### Card 5

#### Front

What can you do in a lab with light? (4)