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| Question | Answer |
| Photosynthesis 1 Give the word equation for photosynthesis | Carbon dioxide+water->glucose +oxygen |
| Where exactly does photosynthesis occur? | In the chloroplasts of the mesophyll layer of the leaf |
| What molecules could a plant convert the glucose made in photosynthesis into? | Starch, cellulose, fatty acids, amino acids |
| If the plant makes amino acids using glucose, what other ion is needed from the soil to do so? | Nitrate ions |
| What adaptations do leaves usually have for photosynthesis? | Large surface area, stomata, many chloroplasts, veins to supply water |
| Is the photosynthesis reaction endothermic or exothermic (and why)? | Endothermic – it uses light energy from the environment |
| Photosynthesis 2 How do you test a leaf to see if it contains starch? | By adding iodine solution. It will turn blue/black |
| Why do you put a plant in a dark place for a period of time before doing a photosynthesis experiment where you will test for starch? | So that any starch already present will be broken down into glucose before the experiment starts |
| When do plants respire? | All the time as respiration releases energy for chemical reactions |
| What will happen to the rate of photosynthesis if you increase the light intensity? | It will increase |
| How might very high temperatures (between 30 and 40 degrees C) affect the rate of photosynthesis? | The rate of photosynthesis could decrease as the plant closes its stomata to prevent water loss |
| Why is 25 degrees C a better temperature for photosynthesis than 15 degrees C? | The molecules involved in the reaction (including enzymes) have more kinetic energy so are more likely to react |
| Photosynthesis 3 If you keep increasing the carbon dioxide available to a plant, why does the rate of photosynthesis stop increasing after a certain concentration of carbon dioxide? | Another factor (probably light) becomes limiting |
| Besides light, what else could be a limiting factor? | The amount of chlorophyll to trap light, temperature, carbon dioxide |
| A deficiency in which ion would reduce the amount of chlorophyll a leaf has? | Magnesium ions |
| In winter, which factors would limit the rate of photosynthesis? | Light and temperature |
| In a greenhouse, how could you increase the carbon dioxide concentration in the air? | By burning fuel eg paraffin |
| Photosynthesis 4 If you do an experiment with pond weed, what can you measure to see the rate of photosynthesis? | The number of bubbles of oxygen per minute/volume of oxygen produced per minute |
| If you were investigating the effect of changing light intensity on rate of photosynthesis, what would your control variables be? | Carbon dioxide concentration, temperature, size of plant/surface area of plant leaves, time plant is left to photosynthesise |
| How can you add carbon dioxide to the water for the pond weed in this experiment? | By dissolving sodium hydrogen carbonate in the water |
| Why might you put the test tube with your pond weed into a large beaker of water for your experiment? | The large volume of water will absorb heat, therefore keeping the temperature constant. |
| What is the equation that links light intensity and distance? | Light intensity α 1/d2 |
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