To put this into perspective, a human hair is , nanometres thick. Photosynthesis is essentially the process of the plant converting atmospheric gas carbon dioxide CO 2 and water H 2 O into simple sugars, producing oxygen O 2 as a by-product.
To do this, it needs energy and it gets that energy from the light it absorbs. By absorbing light, the object also absorbs some of the energy carried by the light. In the case of plants, it is the pigment chlorophyll which absorbs the light, and it is picky about which wavelengths it absorbs — mostly opting for red light, and some blue light.
When electrons are excited, they are promoted from a level of low energy to a level of higher energy. The energy in the light makes the electrons excited and removes energy from the light — this is an example of the first law of thermodynamics — energy is neither created nor destroyed it can only be transferred or changed from one form to another.
That process takes place in specific compartments within cells called chloroplasts and is split into two stages;. During these reactions, CO 2 dissolves in the stroma and is used in the light-independent reactions. This gas is used in a series of reactions which results in the production of sugars.
Sugar molecules are then used by the plant as food in a similar way to humans, with excess sugars stored as starch, ready to be used later, much like fat storage in mammals. Therefore, the red end of the light spectrum excites the electrons in the leaves of the plants, and the light reflected or unused is made up of more of wavelengths of the complementary or opposite colour, green. The unused green light is reflected from the leaf and we see that light. Plants use glucose together with nutrients taken from the soil to make new leaves and other plant parts.
The process of photosynthesis produces oxygen, which is released by the plant into the air. Chlorophyll gives plants their green color because it does not absorb the green wavelengths of white light.
That particular light wavelength is reflected from the plant, so it appears green. Plants that use photosynthesis to make their own food are called autotrophs. Animals that eat plants or other animals are called heterotrophs. Because food webs in every type of ecosystem, from terrestrial to marine, begin with photosynthesis, chlorophyll can be considered a foundation for all life on Earth. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
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If no button appears, you cannot download or save the media. Text on this page is printable and can be used according to our Terms of Service. There are various types of chlorophyll structures, but plants contain chlorophyll a and b. These two types of chlorophyll differ only slightly, in the composition of a single side chain. Absorption spectra showing how the different side chains in chlorophyll a and chlorophyll b result in slightly different absorptions of visible light.
Light with a wavelength of nm is not significantly absorbed by chlorophyll a, but will instead be captured by chlorophyll b, which absorbs strongly at that wavelength. The two kinds of chlorophyll in plants complement each other in absorbing sunlight. Plants are able to satisfy their energy requirements by absorbing light from the blue and red parts of the spectrum.
However, there is still a large spectral region between and nm where chlorophyll absorbs very little light, and plants appear green because this light is reflected.
Chlorophyll is a compound that is known as a chelate. A chelate consists of a central metal ion bonded to a large organic molecule, composed of carbon, hydrogen, and other elements such as oxygen and nitrogen.
Chlorophyll has magnesium as its central metal ion, and the large organic molecule to which it bonds is known as a porphyrin. The porphyrin contains four nitrogen atoms bonded to the magnesium ion in a square planar arrangement. Chlorophyll occurs in a variety of forms. Chlorophyll does not contain chlorine as the name might suggest; the chloro- portion stems from the Greek chloros, which means yellowish green. The element chlorine derives its name from the same source, being a yellowish-green gas.
Vegetation will not appear to animals as it does to us. Although our color perception is the most advanced amongst mammals, humans have less effective color vision than many birds, reptiles, insects and even fish.
Humans are trichromats, sensitive to three fundamental wavelengths of visible light. Our brains interpret color depending on the ratio of red, green and blue light. Some insects are able to see ultraviolet light.
Birds are tetrachromatic, able to distinguish four basic wavelengths of light, sometimes ranging into ultraviolet wavelengths, giving them a far more sensitive color perception. It is hard for us to imagine how the world appears to birds, but they will certainly be able to distinguish more hues of green than we do, and so are far more able to distinguish between types of plants. We can speculate that this is of great benefit when choosing where to feed, take shelter and rear young.
Aquatic creatures, from fish to the hyperspectral mantis shrimp which distinguishes up to twelve distinct wavelengths of light are uniquely tuned to the colors of their environment. The pages on animals include more information on the variety of color vision in the animal kingdom. The vivid colors of fall leaves emerge as yellow and red pigments, usually masked by chlorophyll, are revealed by its absence.
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