Question

Describe the ultra-structure of chloroplast.

Answer 1

The chloroplast is a heterogeneous structure surrounded by two unit membranes separated from one another by a space called periplastideal space. The heterogeneous nature of chloroplast is due to the presence of disc-like structures i.e., grana, in a colourless matrix called stroma. Grana are the sites for the light reaction and stroma is the site for the dark reaction of photosynthesis. Each granum is made up of a stock of closed compartment called thylakoids. Each thylakoid consists of two parallel membranes joined at their margins. The membranes of thylakoids contain the layer of particles called chlorophyll. In stroma, there are many membranes running parallel to each other throughout the length of chloroplast which is called lamellae. The stacks of thylakoids sacs are connected by stroma lamellae. Each chloroplast contains nearly 40-60 grana embedded in the stroma.