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| Question | Answer |
| Plants make their own food by way of Photosynthesis. the process produces glucose. photosynthesis happens in leaves of all green plants. |
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| Photosynthesis happens inside the chloroplasts. These are found in the green part of the leaf cell. Chloroplasts contain chlorophyll, this absorbs sunlight, this is used to convert C02 and H20 into glucose and 02. |
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| Carbon dioxide 6C02 + Water 6H20 -----> Glucose C6,H12,06 + 602 | |
| The equation shows that photosynthesis is important as it convert light energy to chemical energy, this energy is stored as glucose. | The chemical energy is released when glucose is broken down during respiration. Which is the photosynthesis equation in reverse. |
| Leave structure. Leaves are made of: A Waxy cuticle. Upper epidermis. Palisade mesophyll layer. Spongy mesophyll layer. lower epidermis. waxy cuticle. |
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| The Waxy cuticle helps to reduce water loss by evaporation. The upper epidermis is transparent so light can pass through to the palisade layer. The palisade layer contains most of the chloroplasts, as it close to the leaf's surface they get most of the light. | The spongy layer contains networks of vascular bunbles, these are the xylem and phloem, they deliver water and other nutrients to every part of the leaf. and take away the glucose produced by photosynthesis. |
| The lower epidermis contains the stoma or stomata of the leaf, these small holes allow C02 to diffuse directly into the leaf. The stoma are protected by guard cells. | Lower waxy cuticle performs the same function as the top waxy cuticle. Leaves are broad to create a large surface are to catch more light. The stoma in the leaf make the leaf adapted to increase the efficiency of photosynthesis. |
| Rate of Photosynthesis. This is dependant on three things. The amount of Light, the amount of C02 and the temperature of its surroundings. Photosynthesis will slow down or stop in incorrect conditions. | Light. Chlorophyll uses light energy to perform photosynthesis. It can do this as quickly as light energy arrives. as light intensity increases, so photosynthesis will increase steadily, but only up to s certain point. |
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Once this point is reached, the limiting factors of photosynthesis will either be the temperature of the conditions or the C02 levels. |
| C02. Is a raw material of photosynthesis. As with light intensity, increasing the C02 concentration will increase the rate of photosynthesis, up to a point. Showing that C02 is no longer the limiting factor. As long as there is plenty of light and C02, then temperature must be the limiting factor. |
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Temperature. This will increase the enzyme reactions involved up to a certain point. If it gets too hot then the enzymes will denature and become destroyed. making temperature the limiting factor. Enzymes have an optimal temperature to aid photosynthesis, this is below 45 degrees. usually around 37 degrees |
| Two main products of photosynthesis are glucose and oxygen. The glucose is stored as starch by plants. |
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| Before a leaf can be tested, its needs to be killed by dunking it in boiling water. This stops any chemical reactions from taking place. |
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| Once killed, heat the leaf in ethanol using a boiling tube and water bath. this gets rid of the chlorophyll and leaves the leaf a whit-ish colour. | Rinse the leaf off in cold water and add a few drops of iodine solution. If starch is present the leaf will turn blue-black from orange-brown |
| to test to prove chlorophyll is need for photosynthesis. Follow the same procedure for the starch test, kill, clean the leaf, but instead use a variegated green and white leaf. |
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| The white part of the leaf contains no chlorophyll, the green part contains chlorophyll. | The result should show the white part staying the iodine solution colour orange-brown and the green part turning blue-black as starch is present. This shows the leaf containing chlorophyll, photosynthesised and produced starch. |
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C02. To show C02 is need for photosynthesis. A plant can be placed in a bell jar with soda lime. Using a light source to create photosynthesis. The soda lime will absorb all the C02 from the jar. This means by leaving the plant for a while, it will not be able to photosynthesise as there is no C02. |
| Remove a leaf from the plant after a while, and perform a starch test as previously outlined. The leaf should not turn blue-black, as no starch will have been produced through photosynthesis. |
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| By performing a similar experiment where a plant has been kept away from light i.e in a cupboard, you can prove light is needed for photosynthesis. | Result. By stopping the light getting to the leaf, when tested for starch the leaf should not change to blue-black, showing light is need to photosynthesise starch. |
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