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10 Cards in this Set
- Front
- Back
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What is the formula for photosynthesis?
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Carbon Dioxide + Water --(Light Energy)--> Glucose + Oxygen
6CO2 + 6H2O --(Light Energy)--> C6H12O6 + 6O2 |
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How do we test for starch?
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Iodine solution is a yellow brown liquid that turns blue-black when it reacts with starch. You can use this to prove photosynthesis has taken place in a plant.
Take a leaf from a plant and keep it in the dark for 24 hours and one from a plant kept in the light. The leaf must be prepared so the waterproof cuticle doesn't keep the iodine out. The green chlorophyll would mask colour changes so you must boil the leaf to destroy the cuticle and remove the colour. Rinse it in hot water to treat it. Add iodine solution to two leaves, the one kept in the dark stays orange-red but the one kept in the light turns blue-black. |
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What are adaptations in a leaf which help with photosynthesis?
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Most are broad, giving them a big surface area for light to fall in.
They have chlorophyll in the chloroplasts to absorb the light energy. They have air spaces that allow carbon dioxide to get to the cells and oxygen to leave them by diffusion. They have veins which bring water in the xylem to the cells of the leaves and remove the products of photosynthesis in the phloem. |
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What are limiting factors in photosynthesis?
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In low light, photosynthesis stops.
As the temperature rises the rate increases but after 40-50°C the enzymes denature and the rate falls. Plants need carbon dioxide to make glucose. Increasing carbon dioxide levels increase the rate. |
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How do plants use glucose?
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They need it for respiration, the energy released from it builds up smaller molecules into bigger ones.
Some is changed to starch for storage. They build up glucose into more complex carbohydrates like cellulose to strengthen their cell walls. They make amino acids by combining sugars with nitrate ions and other mineral ions. They build up fats and oils to use as an energy store. |
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How are carnivorous plants adapted to live in nutrient-poor soil?
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They obtain most of their nutrients from the animals such as insects that they catch.
They have special enzymes to digest the insects or animals. |
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How are leaves adapted to only allow carbon dioxide in when it is needed?
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They are covered with a waxy cuticle which is waterproof and gas-proof.
Stomata are opened when the plant needs to allow air into and out of the leaves. They can be closed by guard cells to limit the loss of water. |
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What is transpiration?
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The loss of water vapour through the stomata by evaporation and then diffusion. This causes more water to be pulled up through the xylem to take its place.
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How does the environment affect the rate of transpiration?
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If it's sunny more stomata open up and therefore more water is lost by evaporation and then diffusion. Warm, sunny conditions increase the rate.
Hot, dry, windy conditions increase the rate of evaporation and therefore the rate of transpiration. Water evaporates more if the temperature is higher and diffusion happens more quickly. Water vapour diffuses more rapidly into dry air. Windy conditions remove the water vapour straight away as it diffuses out. |
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If a plant loses water faster than it is replaced, what will it do?
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It will wilt. The leaves collapse and hang down to reduce the surface area available for water loss by evaporation.
The stomata close which stops photosynthesis but risks overheating. This prevents further water loss and wilting. |
