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6CO2 + 6H2O C6H12O6 + 6O2


In plants, light energy is transformed into the chemical energy of the molecules formed during
photosynthesis.

These molecules are used by the plant to produce ATP during respiration.
The leaf is the main photosynthetic structure.
The chloroplasts are the cellular organelles within the leaf…

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Photosynthesis is a complex metabolic pathway involving many intermediate reactions.
It is a process of energy transformation in which light energy is firstly changed into electrical energy
and then into chemical energy.

There are three main stages to photosynthesis:


Stage Process
1. Capturing light energy By chloroplast pigments such as…

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The light dependent reaction of photosynthesis involves the capture of light whose energy is used for
two purposes:

- To add an inorganic phosphate molecule to ADP thereby making ATP
- To split water by the process of photolysis, into H+ ions and OH- ions

The reaction needs light energy.…

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1. Light energy hits photosystem 2
This light energy excites the electrons and causes the chlorophyll to lose electrons
These electrons must be replaced
Light energy also causes water to split into protons, electrons and oxygen
The electrons from photolysis are used to replace the electrons lost from the chlorophyll…

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Chemiosmosis is the name of the process where the movement of H+ ions across a membrane
generates ATP ­ this also occurs in respiration.

The excited electrons lose energy as they move along the electron transport chain.

This energy is used to transport protons into the thylakoid so that the…

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The products of the light-dependent reaction of photosynthesis, ATP and reduced NADP are used to
reduce carbon dioxide in the second stage of photosynthesis.

The light-independent reaction takes place in the stroma of the chloroplasts.

The reaction is also called the Calvin cycle.




1. Carbon dioxide from the atmosphere diffuses…

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Site of the Light-Dependent Reaction

The light dependent reaction of photosynthesis takes place in the thylakoids of chloroplasts.

The thylakoids are disc like structures that are stacked together in groups called grana.


Chloroplasts are structurally adapted to their function of capturing sunlight and carrying out the
light-dependent reaction of photosynthesis…

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Factors Affecting Photosynthesis

A limiting factor limits the rate at which a process can take place.
Processes such as photosynthesis are made up of a series of small reactions.
It is the slowest of these reactions that determines the overall rate of photosynthesis.

The law of limiting factors is expressed…

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The rate of photosynthesis is measured in two
ways:
The volume of oxygen released by a plant
The volume of carbon dioxide taken up by a plant

Effect of Light Intensity on the Rate of
Photosynthesis
When light is the limiting factor, the rate of
photosynthesis is directly proportional to…

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Growers use information about limiting factors to increase plant growth
Commercial growers know the factors that limit plant growth.
This means that they can create an environment where plants get the right amount of everything that
they need, which increases growth and so increases yield.

Growers create optimum conditions in…

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