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Photosynthesis

Photosynthesis. The Carbon Cycle. Plants are carbon sinks removing carbon dioxide from the atmosphere and oceans by fixing it into organic chemicals. Plants also convert energy from light into chemical energy

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Photosynthesis

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  1. Photosynthesis

  2. The Carbon Cycle • Plants are carbon sinks removing carbon dioxide from the atmosphere and oceans by fixing it into organic chemicals. • Plants also convert energy from light into chemical energy • Animals produce carbon dioxide and get their energy from carbohydrates and other chemicals produced by plants

  3. The Carbon Cycle • The balance between plant carbon dioxide removal and animal carbon dioxide production is equalized by the formation of carbonates in the oceans. This removes excess carbon dioxide from the air and water. • Fossil fuels, such as petroleum and coal, peat and wood generate carbon dioxide when burned. • Fossil fuels are formed ultimately by organic processes, and represent a carbon sink. Human activity has greatly increased the concentration of carbon dioxide in air.

  4. Photosynthesis • Photosynthesis - the process by which plants, some bacteria, and some protistans use the energy from sunlight to produce sugar • The conversion of solar energy into chemical energy is associated with the green pigment chlorophyll • Most of the time, the photosynthetic process uses water and releases the oxygen

  5. Photosynthesis • We can write the overall reaction of this process as: • 6H2O + 6CO2 ----------> C6H12O6+ 6O2

  6. Photosynthesis • There are two stages in photosynthesis • The first stage, the light-dependent reaction – chlorophyll gathers the energy of light and uses it to make high-energy molecules NADPH & ATP • Light-dependent reactions use the high-energy molecules to gather carbon dioxide to produce the precursors of carbohydrates (Sugar)

  7. Light Dependent Reactions • Light reactions cannot take place unless light is present. They are the energy-capturing reactions • Chlorophyl within thylakoid membranes absorbs solar energy and energizes electrons • Energized electrons move down the electron transport system; energy is captured and used for ATP production • Energized electrons are also taken up by NADP+, becoming NADPH.

  8. Light Independent Reactions – the Calvin Cycle • The 2nd stage of photosynthesis is light independent. It does not need light. This stage is called the Calvin Cycle. • These reactions take place in the stroma; can occur in either the light or the dark. • These are synthesis reactions that use NADPH and ATP to reduce CO2.

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