Chlorophyll

Chlorophyll is the green photosynthetic pigment present in chloroplasts, which provides the energy necessary for photosynthesis. The intense green color of chlorophyll is due to its strong absorbence in the red and blue regions of the electromagnetic spectrum, which causes the light it reflects and transmits to appear green. Light absorbance by chlorophyll is the first step in transforming the energy of sunlight into chemical energy in the process of photosynthesis. The energy absorbed by chlorophyll is eventually used to convert carbon dioxide and water into carbohydrates and oxygen.

Chemical structure

Chlorophyll is a chlorin pigment, which is structurally similar to the iron-containing porphyrin compound known as heme. At the center of the chlorin ring is a magnesium ion. The sidechains vary somewhat between the different forms of chlorophyll found in different organisms. Chlorophyll a is present in all green plants, but chlorophylls b and c also occur in various groups.

Common structure of chlorophyll a and b

Absorbtion spectra

Absorbance of light by chlorophyll a (green) and b (red)

Evidence for chlorophyll

Chlorophyll can be shown to be vital for photosynthesis by destarching a leaf from a variegated plant and exposing it to light for several hours. (Variegated leaves have green areas that contain chlorophyll and white areas that have none.) When tested with