A typical plant cell (e.g., in the palisade layer of a leaf) might contain as many as 50 chloroplasts.

The chloroplast is made up of 3 types of membrane:
  1. A smooth outer membrane which is freely permeable to molecules.
  2. A smooth inner membrane which contains many transporters: integral membrane proteins that regulate the passage in an out of the chloroplast of
  3. A system of thylakoid membranes


The electron micrograph above on the right (courtesy of Dr. L. K. Shumway) shows the chloroplast from the cell of a corn leaf.

The electron micrograph on the left (courtesy of Kenneth R. Miller) shows the inner surface of a thylakoid membrane. Each particle may represent one photosystem II complex. In the functioning chloroplast, these particles may not be as highly ordered as seen here.
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7 January 2011