Endocytosis and exocytosis:

Endocytosis:

Molecules that need to be taken into the cell

bind with receptors.

cell membrane forms cavity around the molecules

breaks away from the membrane as a vesicle containing the substances.

Pinocytosis

Pinocytosis is for the movement of many small particles, often dissolved in water.

It is used by the cell to take in molecules that are too large to get through the membrane in the usual way,

Pinocytosis, examples

proteins, glycoprotein, vitamin B12 etc. All cells are capable of pinocytosis.

Exocytosis and why it is needed:

Exocytosis is the movement of large molecules from inside the cell to the outside of the cell.

The substances have been made by the ribosomes and are finished off in the Golgi apparatus. Vesicles bud off from the Golgi apparatus and make their way towards the cell membrane where they will undergo exocytosis and leave the cell. The membrane of the vesicle merges with the cell membrane and the substances are released on the outside of the cell.

Exocytosis Examples include

extracellular enzymes used for digestion, hormones, mucus and antibodies.

Mechanism and need for energy:

ATP needed to move vesicle to or from the cell membrane.

This process uses protein molecules actin and myosin. When calcium ions are released into the cell they contract and move the vesicle much like they contract in muscle.

Surface area

1x1x6 =6

2x2x6 = 24

Volume

1x1x1 = 1

2x2x2x = 8