Lecture 2 (Mechanisms of Cell Transport)

Plasma membrane

The thin outer layer of a cell that controls what enters and leaves.

Transmembrane proteins

Proteins that go all the way through the cell membrane.

Integral proteins

Proteins embedded in the membrane (may go all the way through or partway).

Cholesterol

A lipid in the membrane that helps keep it stable and flexible.

Glycolipid

A lipid with a carbohydrate attached; helps with cell recognition.

Glycoprotein

A protein with a carbohydrate attached; helps cells communicate and identify each other.

Selectively permeable

Allows some substances to pass through but not others.

Concentration gradient

The difference in concentration of a substance between two areas.

Osmosis

The movement of water across a membrane from high water concentration to low.

Passive diffusion

Movement of molecules from high to low concentration without energy.

Facilitated transport (diffusion)

Passive movement through membrane proteins from high to low concentration.

Active transport

Movement of substances against the concentration gradient using energy.

Bulk transport

Movement of large amounts of material into or out of a cell using vesicles.

Endocytosis

The cell takes in material by forming a vesicle around it.

Exocytosis

The cell releases material by vesicles fusing with the membrane.

Vesicles

Small membrane-bound sacs that transport materials in the cell.