cell permeability and transport

What makes a solution

Solvent and solute.

Plasma membrane

Selectively permeable boundary separating the cell from the surroundings.

Hydrophobic

Repels water.

Hydrophilic

Attracts water.

Diffusion

The passive movement of molecules from higher to lower concentration until equilibrium is reached.

Simple diffusion

Diffusion that happens automatically.

Facilitated diffusion

Molecule can’t cross the membrane by itself and needs a special pathway across.

Osmosis

Diffusion of water across a semipermeable membrane. Water passes through special channels called Aquaporins.

Hypotonic

Lower solute concentration. Cell will swell and possibly burst in this type of solution.

Hypertonic

Higher solute concentration. Cell will shrink in this type of solution.

Isotonic

Two solutions have equal concentration of solutes. Cell will act as normal in this type of solution.

Tonicity

A measure of the solutions of ability to change the volume of cell cells by altering their water content.

Phospholipid bilayer

Two back to back layers of phospholipids arranged with hydrophilic heads facing outward and hydrophobic lipid tails facing inward.

Peripheral proteins

Proteins only found on one side of the membrane

Carbohydrate chain

Extend from outer surface of membrane. Functions as a signal, coating, or receptor.

Transmembrane proteins

Proteins that extend all the way through the lipid bilayer.

Channel protein

Protein that helps facilitate diffusion, mildly discriminate between their cargo based on size and charge

Carrier protein

Protein that facilitates diffusion, only allow one particular type of molecule to cross.

Active transport

Requires ATP to move substances across the membrane. Usually moves against concentration gradient.

Passive transport

Does not require ATP to move substances across the membrane (ex: diffusion and osmosis)