Passive Transport pp. 97-102

How does the cell membrane maintain homeostasis in a cell?

The cell membrane has many different macromolecules embedded within the phospholipids - Carbohydrates and lipids can be use for cell-to- cell communication or as cell markers - Peripheral proteins are attached to the surface of the cell membrane - Integral proteins are embedded in the bilayer and are often channel proteins. - Cholesterol makes the membrane more fluid and less rigid at colder temperatures

What characteristic does the cell membrane have? Cell membrane is nonpolar and tightly packed Small and nonpolar substances can easily pass through the cell membrane

Movement across the cell membrane without energy Passive transport: Movement across the cell membrane without energy

Diffusion: movement of molecules from area of high concentration (CONC) to area of low concentration

Osmosis: special diffusion of water (polar) across membrane

A solution is made of a solute dissolved in a solvent (like water). Water movement depends on the number of solutes outside the cell Water moves towards the greatest number of solutes or towards the highest concentration

Hypertonic: CONC of solutes is higher outside the cell and water moves out the cell- cell shrinks

Hypotonic: CONC of solutes is lower outside the cell and water moves into the cell cell swells

Isotonic: CONC of solutes inside = outside; so no net water movement

Facilitated Diffusion

Polar molecules or molecules too big to move across the membrane use carrier proteins EX. Glucose and Polar molecules Similar to enzymes in that the carrier protein is specific as to what it moves