Cell Membrane Living Environment

Cell Membrane Fluid Mosaic Model – It is made up of a double layer of phospholipids containing imbedded proteins. It controls what can enter and leave the cell.

It is a fluid structure…not rigid. It is a semipermeable or selective membrane. Only certain molecules can pass through. Usually smaller ones can go through.

Structure of Cell Membrane

Movement Across the Cell Membrane 1. Active Transport requires energy (ATP) movement of molecules from an area of low concentration to high concentration Uses carrier proteins embedded in the cell membrane

Active Transport

Passive Transport / Diffusion Requires no energy Movement of molecules from an area of high concentration to an area of low concentration Establishes a dynamic equilibrium

Diffusion

Osmosis Osmosis is the diffusion of water. Water moves through gaps between the phospholipids. Concentration of solutes (dissolved particles) inside and outside of cells affects osmosis.

Hypertonic Solution Concentration of solutes in the solution is greater than inside the cell. Water moves out of cell; cell shrinks.

Isotonic Solution Concentration of solutes is the same in the solution and inside the cell. No net movement of water.

Hypotonic Solution Concentration of solutes in the solution is less than inside the cell. Water moves into the cell; cell swells.

Osmosis and Solute Concentration

Movement of Large Particles Endocytosis – brings large particles in by forming a sac of membrane around them

Movement of Large Particles Exocytosis – getting rid of materials from a sac at the cell’s surface