All living things carry on the life function of transport: the absorption and distribution of materials!
2 types:
Intracellular (within a cell) -
An example of this is cyclosis (
also known as cytoplasmic streaming) - a passive process of cytoplasm moving
around the cell.
Intercellular (between cells)
This process involves nutrients
into cells and wastes out of cells. The selectively permeable cell
membrane regulates what goes in and out of the cell. In class,
we used a dialysis bag to represent the selectively permeable cell membrane.
PROCESSES:
PASSIVE TRANSPORT: does not require the expenditure of energy (ATP)
1. Diffusion - the movement of materials from an area of high concentration to an area of low concentration. This is also known as going WITH the concentration gradient.
2. Osmosis - the diffusion of WATER from an area of high concentration of water to an area of low concentration of water. When water leaves a cell (in salt water), the membrane shrinks (Plasmolysis). When water enters a cell (in distilled water), the membrane swells and expands. A plant cell will experience turgor pressure. An animal cell may burst.
3. Cyclosis - see intracellular transport (above)
ACTIVE TRANSPORT: requires ATP
1. Phagocytosis - large molecules enter the cell when the cell membrane wraps around the object and brings it in. This is the way white blood cells engulf bacteria. It is also the way ameobas ingest their food.
2. Pinocytosis - molecules of water enter the cell when the cell membrane creates a straw-like funnel (Pino-colada!)
3. Exocytosis - like the reverse of phagocytosis - large, undigested materials leave a cell (or ameoba)
By the way (both phagocytosis
and pinocytosis) are categorized as Endocytosis, simply meaning "going
into".