How Plants Produce Food

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  • Created by: sophie
  • Created on: 18-11-10 20:52


  • carbon dioxide + water (+light energy) ---------> glucose + oxygen
  • During photosynthesis light energy from the sun is absorbed by the chlorophyll in the chloroplasts. It is used to convert carbon dioxide and water into sugar (glucose). Oxygen is produced as a by-product, which is released into the atmosphere.
  • Leaves have a wide surface area, which enables them to absorb as much light as possible during daylight hours, maximizing the amount of photosynthesis that takes place, increasing the amount of food they produce.
  • The food is either stored as starch or used straight away by the cells of the plant in respiration.
  • To test for starch in a plant, we use the iodine test. If starch is present the iodine will turn blue/black.

Limiting Factors:

  • Limiting factors are things that affect the rate of photosynthesis in plants.
  • There are three main limiting factors:
  • Light: If there's a lot of light, plenty of photosynthesis will take place in a plant, but if there's very little or no light, photosynthesis will stop regardless of other conditions affecting the rate of photosynthesis. The brighter the light, the faster the rate of photosynthesis.
  • Temperature: As the temperature rises, the rate of photosynthesis will increase. But, because photosynthesis takes place in living organisms, it is controlled by enzymes. Enzymes are destroyed at temperatures above 40-50 degrees.  This means that if the temperature gets too high, the rate of photosynthesis will slow down as more and more enzymes are denatured.
  • Carbon Dioxide Levels: As the atmosphere only contains 0.04% carbon dioxide, this is often the most limiting factor. Increasing carbon dioxide levels will increase the rate of photosynthesis.
  • We can artificially change the environment in


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