CHAPTER: 10 (A)
Photosynthesis
Introduction
to Photosynthesis:
• The synthesis of complex organic material
using carbon dioxide, water, inorganic salts, and light energy (from
sunlight) captured by light-absorbing pigments, such aschlorophyll and
other accessory pigments.
• The
use of light energy to produce carbohydrates from carbondioxide and a reducing
agent such as water is known as photosynthesis.
• Photosynthesis consists
of light reactions and dark reactions.
• This
process can be simplified in this equation:
• It
means photosynthesis is a process in which carbon dioxide (CO2), water (H2O)
and light energy are utilized to synthesize an energy-rich carbohydrate like glucose (C6H12O6)
and to produce oxygen (O2) as a by-product.
• Photosynthesis is
a vital process among photoautotrophs, like plants, algae and
some bacteria that are able to create their own food directly from
inorganic compounds using light energy so that they do not have to eat or rely
on nutrients derived from other living organisms.
• Photosynthesis occurs
in plastids (e.g.chloroplasts), which are membrane-bounded organelles containing
photosynthetic pigments (e.g. chlorophyll), within the cells of plants and algae.
• In photosynthetic bacteria (cyanobacteria)
that do not have membrane-bounded organelles, photosynthesis occurs
in the thylakoid membranes in the cytoplasm.
Significance
of Photosynthesis:
(1) It
is the primary source of organic food and food energy (ATP) for all forms of
life, either directly or indirectly.
(2) Excess
sugars produced in photosynthesis are either stored in the form of
carbohydrates or used in the biosynthesis of other organic compounds.
(3) In
any ecosystem, green plants represent the most essential biotic components as
they are the primary producers.
(4) Photosynthesis
helps to purify air and also maintain balance of oxygen and carbon dioxide in
the ecosystem.
(5) Oxygenic
photosynthesis was responsible for converting the totally anaerobic condition
on earth into aerobic atmosphere present now.
(6) The
fossil fuels (e.g. natural gas, coal, petroleum (oil), etc.) are all
energy-rich materials of an organic origin. The energy stored in all these
fuels is basically solar energy which was trapped and stored during
photosynthesis in the geological past.
