Photosynthetic pigments | a2-level-level-revision, …
There are four things that are required by the plant before it can carry out photosynthesis, they are light, chlorophyll, carbon dioxide and water ....
A2 - AQA Biology (Unit 4) - Photosynthesis - …
Photosynthesis occurs inside chloroplasts. Chloroplasts contain chlorophyll, a green pigment found inside the thylakoid membranes. These chlorophyll molecules are arranged in groups called photosystems. There are two types of photosystems, Photosystem II and Photosystem I. When a chlorophyll molecule absorbs light, the energy from this light raises an electron within the chlorophyll molecule to a higher energy state. The chlorophyll molecule is then said to be photoactivated. Excited electron anywhere within the photosystem are then passed on from one chlorophyll molecule to the next until they reach a special chlorophyll molecule at the reaction centre of the photosystem. This special chlorophyll molecule then passes on the excited electron to a chain of electron carriers.
The action spectrum of photosynthesis is a graph showing the rate of photosynthesis for each wavelength of light. The rate of photosynthesis will not be the same for every wavelength of light. The rate of photosynthesis is the least with green-yellow light (525 nm-625 nm). Red-orange light (625nm-700nm) shows a good rate of photosynthesis however the best rate of photosynthesis is seen with violet-blue light (400nm-525nm).
Electron Transport Chain Photosynthesis Animation
So how can these factors have an effect on the rate of photosynthesis? Lets start off with the light intensity. When the light intensity is poor, there is a shortage of ATP and NADPH, as these are products from the light dependent reactions. Without these products the light independent reactions can't occur as glycerate 3-phosphate cannot be reduced. Therefore a shortage of these products will limit the rate of photosynthesis. When the carbon dioxide concentration is low, the amount of glycerate 3-phosphate produced is limited as carbon dioxide is needed for its production and therefore the rate of photosynthesis is affected. Finally, many enzymes are involved during the process of photosynthesis. At low temperatures these enzymes work slower. At high temperatures the enzymes no longer work effectively. This affects the rate of the reactions in the Calvin cycle and therefore the rate of photosynthesis will be affected.
The leaf is the main photosynthetic structure
Furthermore, I predict that if the light intensity increases, the rate of photosynthesis will increase at a proportional rate and more oxygen will be produced and therefore the oxygen levels will increase.
Photosynthesis GCSE by Sabir1 - Teaching Resources - Tes
A limiting factor is a factor that controls a process. Light intensity, temperature and carbon dioxide concentration are all factors which can control the rate of photosynthesis. Usually, only one of these factors will be the limiting factor in a plant at a certain time. This is the factor which is the furthest from its optimum level at a particular point in time. If we change the limiting factor the rate of photosynthesis will change but changes to the other factors will have no effect on the rate. If the levels of the limiting factor increase so that this factor is no longer the furthest from its optimum level, the limiting factor will change to the factor which is at that point in time, the furthest from its optimum level. For example, at night the limiting factor is likely to be the light intensity as this will be the furthest from its optimum level. During the day, the limiting factor is likely to switch to the temperature or the carbon dioxide concentration as the light intensity increases.
Complete lesson on introducing the topic of Photosynthesis
As we can see, there is a close relationship between the action spectrum and absorption spectrum of photosynthesis. There are many different types of photosynthetic pigments which will absorb light best at different wavelengths. However the most abundant photosynthetic pigment in plants is chlorophyll and therefore the rate of photosynthesis will be the greatest at wavelengths of light best absorbed by chlorophyll (400nm-525nm corresponding to violet-blue light). Very little light is absorbed by chlorophyll at wavelengths of light between 525nm and 625 (green-yellow light) so the rate of photosynthesis will be the least within this range. However, there are other pigments that are able to absorb green-yellow light such as carotene. Even though these are present in small amounts they allow a low rate of photosynthesis to occur at wavelengths of light that chlorophyll cannot absorb.