Photosynthesis

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.