Source: https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-7-photosynthesis-and-plant-responses [Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [GCSE](https://senecalearning.com/en-gb/revision-notes/gcse.md) › [Science Practicals](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals.md) › [National Curriculum](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum.md) › Photosynthesis & Plant Responses # Photosynthesis & Plant Responses Science Practicals: GCSE, topic 1.1.7 ## Photosynthesis Photosynthesis takes place inside chloroplasts found in plants and algae. The reaction is endothermic, meaning that it requires energy. The source of this energy is sunlight, which is trapped by a chemical called chlorophyll inside chloroplasts in plant cells. ### Photosynthesis [GIF: Photosynthesis](https://media.giphy.com/media/BCiNqZxPOFe6s/giphy.mp4) ## The Rate of Photosynthesis The four key factors affecting the rate of photosynthesis are: ### Temperature ![Temperature](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/1.3.1%20Diffusion%20and%20active%20transport/thermometer-1614708_640-min%20-%20Edited-min.png) - Increasing the temperature increases the rate of photosynthesis because more energy is provided. - However, if the temperature is increased to above about 45°C, the enzymes that catalyse (speed-up) the reaction begin to denature (not work anymore). - This causes the rate of the reaction to drop sharply until it stops altogether. ### Light intensity ![Light intensity](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/4.1.1%20Photosynthesis/forest-2178187_640-min.jpg) - Increasing light intensity increases the rate of photosynthesis because more energy is provided. - However, if the light intensity is increased above a certain threshold, the rate of photosynthesis will not increase because another factor (such as temperature) is limiting the rate of the reaction. ### Carbon dioxide concentration ![Carbon dioxide concentration](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/4.1.1%20Photosynthesis/car-exhaust-1902909_640-min.jpg) - Increasing the carbon dioxide concentration increases the rate of photosynthesis. - However, above a certain threshold, further increases in the carbon dioxide concentration do not increase the rate of photosynthesis because another factor (such as light intensity) is limiting the rate of reaction. ### Chlorophyll concentration ![Chlorophyll concentration](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/3.3.1%20-%20magnesium%20deficient%20plant.jpg) - High chlorophyll concentration gives a high rate of photosynthesis. ## Limiting Factors A limiting factor restricts the rate of a reaction. The identity of the limiting factor in photosynthesis depends on the conditions faced by the plant. ### Winter ![Winter](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/4.1.1%20Photosynthesis/wintry-2993370_640-min.jpg) - In winter, temperature is usually the limiting factor. ### Night ![Night](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/4.1.1%20Photosynthesis/moon-1859616_640-min.jpg) - At night, light intensity is usually the limiting factor. ### Warm and bright ![Warm and bright](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/4.1.1%20Photosynthesis/sunflower-1127174_640-min.jpg) - In warm and bright conditions, carbon dioxide concentration is usually the limiting factor. ### Mineral-deficient soil ![Mineral-deficient soil](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/4.1.1%20Photosynthesis/ground-1247893_640-min.jpg) - If plants are grown in mineral-deficient (lacking minerals) soil, they may not absorb enough minerals to produce lots of chlorophyll. - In this case, chlorophyll concentration can be the limiting factor. ## Test yourself on Photosynthesis & Plant Responses - Where does photosynthesis take place? - What are the key factors affecting the rate of photosynthesis? - CO2 concentration, light levels and temperature are all at optimum values. What might be the limiting factor of rate of photosynthesis, and why? - Which of these could be a limiting factor for photosynthesis on a warm, sunny day? - What do you think is most likely to be the limiting factor on photosynthesis in a dark forest? [Practise this topic for free](https://app.senecalearning.com/classroom/course/35d9e7b0-1dfb-11e8-b5b7-7546c70e1a36/section/f4fbaa80-1dff-11e8-b5b7-7546c70e1a36/session) - Previous topic: [1.1.6 Enzymes 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-6-enzymes-2.md) - Next topic: [1.1.8 Photosynthesis Experiments](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-8-photosynthesis-experiments.md) ## Science Practicals: GCSE contents ### 1 Biology - 1.1 Practicals - [1.1.1 Microscope & Bacteria](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-1-microscope-and-bacteria.md) - [1.1.2 Bacteria](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-2-bacteria.md) - [1.1.3 Osmosis Tests](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-3-osmosis-tests.md) - [1.1.4 Osmosis & Food Tests](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-4-osmosis-and-food-tests.md) - [1.1.5 Enzymes](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-5-enzymes.md) - [1.1.6 Enzymes 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-6-enzymes-2.md) - [1.1.7 Photosynthesis & Plant Responses](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-7-photosynthesis-and-plant-responses.md) - [1.1.8 Photosynthesis Experiments](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-8-photosynthesis-experiments.md) - [1.1.9 Reaction Time](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-9-reaction-time.md) - [1.1.10 Quadrats](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-10-quadrats.md) - [1.1.11 Decay](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/1-1-11-decay.md) ### 2 Chemistry - 2.1 Practicals - [2.1.1 Salts](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-1-salts.md) - [2.1.2 Neutralisation](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-2-neutralisation.md) - [2.1.3 Titration](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-3-titration.md) - [2.1.4 Electrolysis](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-4-electrolysis.md) - [2.1.5 Electrolysis 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-5-electrolysis-2.md) - [2.1.6 Rate of Reaction](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-6-rate-of-reaction.md) - [2.1.7 Rate of Reaction 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-7-rate-of-reaction-2.md) - [2.1.8 Chromatography](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-8-chromatography.md) - [2.1.9 Identifying Gases](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-9-identifying-gases.md) - [2.1.10 Identifying Gases 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-10-identifying-gases-2.md) - [2.1.11 Identifying Ions](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-11-identifying-ions.md) - [2.1.12 Carbonates, Halides & Sulfates](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-12-carbonates-halides-and-sulfates.md) - [2.1.13 Flame Emission Spectroscopy](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-13-flame-emission-spectroscopy.md) - [2.1.14 Water Purification](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-14-water-purification.md) - [2.1.15 Water Purification 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/2-1-15-water-purification-2.md) ### 3 Physics - 3.1 Practicals - [3.1.1 Specific Heat Capacity](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-1-specific-heat-capacity.md) - [3.1.2 Thermal Capacity & Insulation](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-2-thermal-capacity-and-insulation.md) - [3.1.3 Latent Heat](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-3-latent-heat.md) - [3.1.4 Resistance & Current](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-4-resistance-and-current.md) - [3.1.5 Resistance & Current 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-5-resistance-and-current-2.md) - [3.1.6 Density](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-6-density.md) - [3.1.7 Density 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-7-density-2.md) - [3.1.8 Force & Extension - Springs](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-8-force-and-extension-springs.md) - [3.1.9 Waves - Ripple Tank](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-9-waves-ripple-tank.md) - [3.1.10 Light](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-10-light.md) - [3.1.11 Light Reflection & Refraction](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-11-light-reflection-and-refraction.md) - [3.1.12 Radiation](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-12-radiation.md) - [3.1.13 Radiation 2](https://senecalearning.com/en-gb/revision-notes/gcse/science-practicals/national-curriculum/3-1-13-radiation-2.md)