KERALA UNIVERSITY COLLEGE OF TEACHER

EDUCATION,NEDUMANGAD,

2013-2014.

SARATH.SReg. No. 13983026Natural Science

WELCOME

PHOTOSYNTHESIS

Green plants carry out ‘photosynthesis’ a physicochemical process by which they use light energy to drive the synthesis of organic compounds.

It is a process used by plants and other organisms to convert light energy, normally from the sun into chemical energy that can be later released to fuel the organisms activities.

This chemical energy is stored in carbohydrate molecules such as sugars, which are synthesized from CO2 and water hence the name ‘photosynthesis.’

Most plants, most algae and cyanobacteria perform photosynthesis and such organisms are called photoautotrophs.

Raw materials for photosynthesisCO2 - Enter the leaves through pores called stomata.Water - It is delivered to the leaves from the roots through a vascular system.

Chlorophyll - It is seen in the chloroplast.

Chloroplasts are the green plastids. They occur in all green parts of plants

mainly in the mesophyll cells of leaves. They are surrounded by a double

membrane system.

Inside the chloroplast is the stroma, a protein rich gel like material. Running through the stroma is a series of membranes called thylakoids. At certain regions the thylakoid membranes are stacked one above the another forming grana.

The process of photosynthesis can be divided into two parts.

1. Light reactions2. Dark reactions

It is takes place in the grana of the chloroplast. This occurs only in the presence of light. In this phase, light energy is converted to chemical energy contained in ATP molecule. In this phase water is broken down into hydrogen and oxygen utilizing light energy.

It is takes place in the stroma of the chloroplast.

In this phase do not require light. The hydrogen atoms that are released by

the break down of water molecules during the light reaction combines with the carbon atoms from CO2 molecules for the synthesis of glucose.

The overall process of photosynthesis can be represented by the formula.

6 CO2 + 12 H2O light energy

Chlorophyll C6 H12 O6 + 6H2O + 6O2