Chloroplasts are organelles of plants and algae. Each chloroplast is delimited by two membranes (an outer and an inner - arrowed on image below) sometimes referred to as the 'envelope'. A section of a chloroplast shows that chloroplasts contain superimposed layers of double membrane lamellae known as thylakoids (T on image below) embedded in and separated from each other by an amorphous stroma (S on image below). At intervals the thylakoids are stacked rather like a pile of coins. Such stacks are called grana (GR on image below). These are interconnected by frets (FR on smaller but higher magnification image). There may be up to 100 thylakoids per granum. The photosynthetic pigment, chlorophyll is attached to the thylakoid membranes.
The image below is a section through a chloroplast and viewed with a transmission electron microscope.
Last Modified: Wed, 21 Jun 2017 11:24:03 SAST