Photosynthesis -
Life on earth ultimately depends upon energy derived from the sun. Photosyn
is essentially the only mechanism of energy input into the living world
thesis
.The only exception occurs in chemosynthetic bacteria, that obtain energy by oxic
inorganic substrates such as ferrous ions and sulfur in the earth's crust, or by oxidizing
hydrogen sulphide released from volcanic action. In addition, thermal vents on
ocean floor are a source of energy for biological systems in the form of heat
the
. Photosynthesis is a chemical process that converts carbon dioxide into organic
compounds, especially sugars, using the energy from sunlight
Photosynthesis is simply defined as, "formation of carbohydrates from carbon dioxi
and water by illuminated green cells of plants, oxygen and water are the by-product
It is also defined as the capture of photons of light by green plant cells, and conversion
of their radiant energy into chemical form of energy
. Earlier, photosynthesis was considered to be reverse of respiration, i.e
Light
Chlorophy
Respiration.
But Ruben and Kamen (1941)jexperimentally verified that source of liberated oxygern
in photosynthesis is water, and not carbon dioxide.
2
. So, it has led to a change in overall general equation of photosynthesis, because 6
water molecules are not sufficient to evolve 6 oxygen molecules.
6co2+ 12H,0
Light
Chlorophyll
H,20,+ 60,T+ 6H,0
Photosynthesis occurs in plants, algae, and many species of bacteria, but
not i
. About 90% of total photosynthesis in the world is performed by algae in ocean
. Carbon dioxide fixed annually through photosynthesis is about 7.0 x 1013 k
archaea
and in freshwater
Photosynthetic organisms are called photoautotrophs, since they can
their own food
Each day, the radiant energy that reaches the earth equals about 1 milion Hirosh
sized atomic bomb
