Explain the structure of a granum.

(N/A) $\Rightarrow$ Thylakoids are arranged in stacks like piles of coins,which are called grana (singular: granum).
$\Rightarrow$ These stacks are interconnected by flat membranous tubules known as stroma lamellae.
$\Rightarrow$ The membrane of the thylakoids encloses a space called the 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 $(80S)$.