Page 63 - The Manga Guide to Biochemistry

Chloroplast Structure

This image (courtesy of RoboCat) shows green sacks, called chloroplasts, within a plant cell.
Inside a chloroplast, structures shaped like very thin pouches are stacked in multiple

layers to form peculiar structures. Each of these flat pouches is called a thylakoid, and a
stack of multiple thylakoids is called a granum.

Chloroplast outer membrane
(lipid bilayer)

inner membrane
(lipid bilayer)

Granum

Thylakoid

Chloroplast structure

The thylakoid membrane is a bilayer composed primarily of phospholipids, just like in
cell membranes.

Now let’s look at the surface of the thylakoid membrane.

Collection of
chlorophyll

molecules

Granum

Thylakoid

Thylakoid structure

Do you see the groups of tiny grains that appear to be embedded in the surface of the
thylakoid? Each of these is a collection of molecules called chlorophyll, as well as various
proteins that aid in photosynthesis.

Chlorophyll molecules absorb sunlight. However, they don’t absorb the entire spectrum;
they reflect the green portion of sunlight back outside, which is why plants appear green to us.

Photosynthesis and Respiration 49