3.1 The Plasma Membrane

The Plasma Membrane

The plasma membrane is a semi-permeable lipid bilayer found in all cells that controls water and certain substances in and out of the cell.

Function of the Plasma Membrane

  1. Protects the cell.
  2. Separates the intracellular components from the extracellular environment.
  3. Controls what enters and exits the cell

Necessities for the Movement of Substances across the Plasma Membrane

  1. To transport nutrients into the cell.
  2. For gases exchange
  3. To excrete metabolic waste.
  4. To maintain the pH value and ionic concentration of the cell.

Substances In and Out through the Membrane

Structure of the Plasma Membrane

Fluid Mosaic Model

Permeability of the Phospholipids Bilayer

The permeability of the phospholipids bilayer is determined by:
  1. the size
  2. the charge and
  3. the polarity
of the substances pass through it.

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