Investigating Photosynthesis

Investigating Photosynthesis

In its essence, photosynthesis is the process by which plants make

their chemical energy.

Most people think that the equation for photosynthesis is the complete

process, though there are several steps until the ATP can be made. To

produce ATP, light energy must first be captured. Within the leaf,

there are two sets of pigments that are responsible for this. The

first set is Chlorophyll;

Ø Chlorophyll A which absorbs the yellow-green part of the spectrum

Ø Chlorophyll B which absorbs the blue-green part of the spectrum

The second set is Carotenoids;

Ø β Carotene which absorbs the orange in the spectrum.

Ø Xanthophyll which absorbs yellow from the spectrum.

The reason for these pigments is that each pigment can absorb a

certain wavelength or group of wavelengths. Without these pigments,

these wavelengths would pass through the leaf and their chemical

energy would be lost instead of harnessed. Chlorophylls generally

absorb the red and blue-violet regions of the spectra hence the fact

that they look green as they reflect green light. The carotenoids in

mainly absorb the blue-violet wavelengths which is why they tend to

look red/orangey.

Chloroplasts are the organelle responsible for trapping the light.

Within the chloroplasts are a structure called Grana which consist of

several Thylakoids. It is inside this thylakoid membrane that the

process begins, there is a ‘funnel’ in which at the bottom there is

primary pigment (Reaction Centre), along the side are many primary

pigments, these absorb the various different wavelengths in the light

and pass down the chemical energy down to the reaction centreÂ…this

ensures that no energy is lost during the process, it also makes the

process more efficient, as it ensures that no light energy passes

through without being harnessed.

There are two types of reactions, Light Dependant and Light

Independent. Light dependant is the more common reaction as the light

independent reaction only occurs when the light is made unavailable,

the light independent reaction is also known as the Calvin Cycle.