Plasma Membrane Functions

Selective Permeability

The property of a cell membrane that allows certain molecules and ions to pass through while blocking others.

Passive Processes

Transport substance across the cell membrane from a high concentration to a low concentration without using cellular energy.

Diffusion

There two types: Simple and Facilitated

Simple Diffusion

Substances pass directly through the plasma membrane and diffuse into the cell.

Facilitated Diffusion (carrier, channel)

Molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers.

Osmosis

The movement of water from an area of high water concentration to an area of low water concentration.

Filtration

The process in which water and solutes are forced through the membrane by hydrostatic(fluid) pressure.

Concentration Gradient

The difference in the amount of a substance between two connected areas.

Pressure Gradient

Drives fluid flow and filtration, and forces water and dissolved solutes from an area of high hydrostatic pressure to an area of lower hydrostatic pressure.

Tonicity

The ability to make water move into or out of a cell by osmosis.

Isotonic

No net flow of water into or out of the cell.

Hypertonic

An extracellular fluid has a higher osmolarity than the fluid inside the cell.

Hypotonic

When there is a net flow of water into the cell.

Active Transport

The movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration.

ATP

It is required for active transport. It is used as energy.

ion Concentration Gradient

The difference between the inside and outside number of charge molecules of a cell membrane.

Vesicular Transport

A membrane proteins that regulates the movement of specific moleculesa vesicle’s membrane.

Exocytosis

The process by which a large amount of molecules are released.

Endocytosis

The active process by which cells engulf large molecules or particles by forming vesicle from the cell membrane.