LIFE ON EARTH ULTIMATELY DEPENDS ON ENERGY.

LIFE ON EARTH ULTIMATELY DEPENDS ON ENERGY.

Photosynthesis is the only process of biological importance that can harvest this energy.

• Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.

• The process is carried out by plants, algae, and some types of bacteria, which capture energy from sunlight to produce oxygen (O2) and chemical energy stored in glucose (a sugar).

• Herbivores then obtain this energy by eating plants; carnivores obtain it by eating herbivores.

• Carbon molecules that cannot be produced without the addition of energy are synthesized by photosynthetic organisms using sun energy. More specifically, the production of oxygen combined with light energy drives the synthesis of carbohydrates from carbon dioxide and water.

6 CO2 + 6 H2O → C6H12O6 + 6 O2

Energy stored in these molecules can be used later to power cellular processes in the plant and can serve as the energy source for all forms of life.

• The processes start with the stimulation of chlorophyll by light and end with the synthesis of ATP and NADPH, as well as the function of light in photosynthesis.

Plants absorb water (H2O) and carbon dioxide (CO2) from the soil and atmosphere during photosynthesis. Water is oxidized, which means it loses electrons, while carbon dioxide is reduced, which means it acquires electrons, inside the plant cell. Water is converted into oxygen and carbon dioxide into glucose as a result. After storing energy inside the glucose molecules, the plant releases the oxygen back into the atmosphere.

Chloroplasts, which are tiny organelles found inside plant cells, are there to store solar energy. Chlorophyll, a light-absorbing pigment found in the thylakoid membranes of the chloroplast, is what gives plants their green hue. Chlorophyll absorbs energy from blue and red-light waves during photosynthesis while reflecting green light waves, giving the appearance of a green plant.

The process of photosynthesis can be broken down into two major stages:

1. The light-dependent reaction takes place within the thylakoid membrane and requires a steady stream of sunlight, hence the name light-dependent reaction. The Chlorophyll absorbs energy from the light waves, which is converted into chemical energy in the form of the molecules ATP and NADPH.

2. The light-independent stage, also known as the Calvin Cycle, takes place in the stroma, the space between the thylakoid membranes and the chloroplast membranes, and does not require light, hence the name light-independent reaction. During this stage, energy from the ATP and NADPH molecules is used to assemble carbohydrate molecules, like glucose, from carbon dioxide.

LIFE ON EARTH ULTIMATELY DEPENDS ON ENERGY.

- BY K H AKHIL SRINIVAS.

(KHAS)