Describe the structure and function of chloroplasts with a diagram.

(N/A) $ \Rightarrow $ The majority of the chloroplasts of green plants are found in the mesophyll cells of the leaves.
$ \Rightarrow $ These are lens-shaped, oval, spherical, discoid, or even ribbon-like organelles.
$ \Rightarrow $ They have a variable length $(5-10 \mu m)$ and width $(2-4 \mu m)$.
$ \Rightarrow $ Their number varies from $1$ per cell in Chlamydomonas, a green alga, to $20-40$ per cell in the mesophyll.
$ \Rightarrow $ Chloroplasts are double-membrane bound. Of the two, the inner chloroplast membrane is relatively less permeable.
$ \Rightarrow $ The space limited by the inner membrane of the chloroplast is called the stroma. A number of organized flattened membranous sacs called thylakoids are present in the stroma.
$ \Rightarrow $ Thylakoids are arranged in stacks like piles of coins called grana (singular: granum) or the intergranal thylakoids.
$ \Rightarrow $ There are flat membranous tubules called the stroma lamellae connecting the thylakoids of the different grana.
$ \Rightarrow $ The membrane of the thylakoids encloses a space called a lumen.
$ \Rightarrow $ The stroma of the chloroplast contains enzymes required for the synthesis of carbohydrates and proteins.
$ \Rightarrow $ It also contains small, double-stranded circular $DNA$ molecules and ribosomes.
$ \Rightarrow $ The ribosomes of the chloroplasts are smaller $(70S)$ than the cytoplasmic ribosomes $(80S)$.