1950053
| Question | Answer |
| What is photosynthesis? | The process by which plants make their own food in the form of starch. |
| What is essential for photsynthesis? | Light energy from the sun. |
| Photosynthesis is a series of...reactions | Enzyme controlled |
| How many stages are there in photosythesis? | There are two stages. |
| Describe the first stage, and what is it called? | The first stage is called light reactions. It involves a reaction called photolysis. In this stage, light energy from the sun is trapped in chlorophyll and converted into chemical energy. |
| What is the chemical energy from the first stage used for? | Some of the energy is used to split the raw material water into hydrogen and oxygen. Oxygen diffuses out of the cell as a by-product. Hydrogen is needed for the second stage. The other energy is used to make ATP which stores chemical energy. |
| Describe the second stage, and what is it called? | The second stage is called carbon fixation. Hydrogen from the first stage and carbon dioxide from the air are use to make sugar (glucose). Carbon fixation is a series of reactions that needs energy. The energy comes from ATP. |
| What happens to iodine when it is added to starch? | It will turn blue/black. |
| Which indicator can be used to detect changes in CO2 concentration? | Hydrogen carbonate. |
| What can the chemical energy in sugar be used for? | It can be used for respiration, or it can be converted into plant products such as starch and cellulose. |
| What can starch be used for? | It can either be used by the plant immediately for energy, or it can be stored and converted back when sugar is need by the plant. It can also be used as a building material eg. to make the cell wall. |
| What is the rate of photosynthesis affected by? | Temperature, light intensity and carbon dioxide concentration. These are called limiting factors. |
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