Write short note on the following:
(a) Golgi apparatus
(b) Mitochondria
(a) Golgi apparatus
(i) Golgi apparatus consists of a set of membrane-bounded, fluid-filled vesicles, vacuoles, and flattened cisternae.
(ii) Cisternae are stacked together in parallel rows. They are formed at one end of the stack, called cis face of Golgi, and are budded off as vesicles at the other face, called trans face of Golgi.
(iii) Golgi apparatus arises from the membrane of smooth endoplasmic reticulum.
(iv) Golgi saccules (cisternae at cis and trans face) are constantly renewed. Distal saccules (trans face) disappear after vesicle formation.
(v) The main function of Golgi apparatus is to secrete vacuoles or secretory vesicles that contain cellular secretions such as enzymes, proteins, and cellulose.
(b) Mitochondria:
(i) Mitochondria are tiny bodies of varying shapes and sizes distributed in the cytoplasm.
(ii) They are bounded by a double membrane envelope.
(iii) The inner membrane is folded several times forming cristae. Each cristae are studded with small round bodies known as F1 particles or oxysomes.
(iv) The interior cavity of the mitochondria is filled with a proteinaceous (gel-like) matrix which contains a few small-sized ribosomes, a circular DNA molecule and phosphate granules.
(v) The main function of mitochondria is to synthesise ATP (energy-rich molecule) and provide energy to the cell via cellular respiration; hence, they are called as powerhouses of the cell.