Chloroplast

From WikiTextbook

Chloroplasts are organelles found within eukaryotic cells that photosynthesise. This generally refers to green plants. The function of the chloroplast is to produce energy by photosynthesis (autotrophy). The chroloplasts come in the form of flat disks. Each disk is usually between 2 and 10 nanometres in diameter, and 1 nanometer in thickness.

Chloroplasts are made up of a number of differnt parts:

Chloroplast Envelope This is a double membrane surrounding the chloroplast. The inner membrane is folded into a series of lamellae. The chloroplast envelope controls the entry and exit of substances in the chloroplast

Grana Grana are involved in the light dependant stage of photosynthesis. They resemble stacks of coins; each granum is made up of about 100 of these flattened sacs, known as thylakoids. Thylakoids have chlorophyll molecules attached to them. There are usually 50 or so grana in a chloroplast.

The Stroma The stroma is a gelatinous matrix which is responsible for the light independant stage of photosynthesis. The stroma mainly contains the enzymes needed for photosynthesis, but also contains oil droplets, and traces of DNA.

Starch grains act as a temporary store of the carbohydrate produced during photosynthesis.