What Are the Functions of Chlorophyll in Photosythesis?

Chlorophyll

• Chlorophyll is a complex molecule consisting primarily of carbon and hydrogen. Chlorophyll absorbs blue and red wavelengths of light very effectively, but reflects green; this reflection is what gives organisms that contain high levels of chlorophyll their characteristic green color. There are several different types of chlorophyll molecule, some of which absorb slightly different ranges of light. In plants, chlorophyll is heavily concentrated in structures called chloroplasts within the leaves. Leaves thus function like solar panels, bringing as many chloroplasts as possible into contact with sunlight.

Photosystems

• Each chloroplast is made up of a number of parts, including small disk-shaped structures called thylakoids, stacked into columns called grana. Most of the interior space of a chloroplast is taken up by thylakoids. The membranes of the thylakoids contain large concentrations of chlorophyll molecules organized into photosystems. In a photosystem, some of the chlorophyll molecules serve primarily to absorb light energy, while others, called reaction centers, are the starting points for the chemical reactions that make up photosynthesis.

First Stage Photosynthesis

• The process of photosynthesis is divided into two stages. In the first stage, also known as the light-dependent process, light strikes the chlorophyll molecules, exciting electrons into a higher energy state. This begins a series of chemical reactions that produce adenosine triphosphate or ATP, a nucleotide that carries energy within cells. This process also produces oxygen as a waste product. The energy stored by the ATP molecules will be used in the second stage of photosynthesis.

Second Stage Photosynthesis

• In the second stage of photosynthesis, also called the light-independent process, energy stored by ATP from the first stage is used to fuel a process called carbon fixation. In carbon fixation, hydrogen is added to carbon dioxide to create carbohydrates. Other cells within the organism can break down these molecules using metabolic processes, releasing the energy they contain. Through this process, plants and other organisms convert light energy, which they cannot directly use, into usable chemical energy.