YEAR 9 - Topic 5 - Photosynthesis And Plant Nutrition Flashcards
What is photosynthesis?
Photosynthesis is the chemical reaction that takes place inside a plant, producing food for the plant. It uses carbon dioxide, water and light to make glucose and oxygen.
Light
6CO2 + 6H2O —————> C6H12O6 + 6O2
Chlorophyll
Where does photosynthesis happen?
In chloroplasts, which contain a pigment (green) called chlorophyll that absorbs the sunlight and converts it to energy.
What does xylem tissue do?
Xylem tissue transports water and minerals.
What does phloem tissue do?
Phloem tissue transports glucose.
How are leaves adapted for photosynthesis?
- broad - large surface area to catch light
- chloroplasts - in the palisade layer which is near the top of the leaf
- transparent - the upper epidermis is transparent which means light can pass through easily
- waxy cuticle - prevents water loss by evaporation so the water can be used for photosynthesis
- stomata - holes to allow gas exchange (CO2 in, O2 out)
- guard cells - change the stomata’s shape to allow the right amount of gases in and out
What are the limiting factors of photosynthesis?
- light intensity
- CO2 concentration
- temperature
What is a limiting factor?
Substance that prevents the rate of reaction increasing when it is in short supply.
How does light intensity affect photosynthesis?
If light intensity increases the rate of photosynthesis will increase steadily but only up to a certain point.
beyond that it wont make any difference because either the temperature or the CO2 levels will become the limiting factor.
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How does CO2 levels affect the rate of photosynthesis?
CO2 is needed for photosynthesis. Only 0.04% of the air is CO2, so it is scarce.
As CO2 levels increase, the rate of photosynthesis will increase steadily.
But as it goes on the temperature will become the limiting factor (as for CO2 to be used we need light, so it can’t be light)
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How does temperature affect the rate of photosynthesis?
Temperature affects the rate of photosynthesis because enzymes are involved.
As the temperature increases the rate of photosynthesis increases until it is at its optimum temperature.
After the optimum temperature (over about 45°c) the enzyme starts to denature, so the rate of photosynthesis will rapidly decrease.
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Why do plants need mineral ions?
Mineral ions - growth
Why do plants need magnesium ions?
Magnesium ions - chlorophyll
Why do plants need nitrate ions?
Nitrate ions - amino acids
Light intensity practical…
You need: -lamp -metre ruler -pond weed in water (in test tube) -stop watch (1min) You will change the distance of the pond weed to the lamp (changes the light intensity). You will use the same type of pond weed. Repeat the experiment 3 times, get an average, to check results are reliable. Measure distance between lamp and the test tube, the amount of bubbles/minute and 1 minute. Keep time, pond weed, temperature, CO2 levels the same.
How are amino acids synthesised?
Amino acids are synthesised by ribosomes into proteins.
