Transport Across Membranes

The Plasma Membrane A selectively permeable phospholipid bilayer with integrated proteins

Why do materials move into or out of cells? To maintain Homeostasis – Maintaining the cell's internal environment To gather nutrients from outside the cell To release waste products from the cell

Passive Transport no energy is required movement is along the concentration gradient

Diffusion The movement of molecules from an area of high concentration to an area of low concentration high concentration low concentration

Osmosis The movement of water molecules from an area of high concentration to an area of low concentration across a selectively permeable membrane.

Types of Solutions Hypertonic solutions the concentration of solute outside the cell is greater than inside the cell. water will move out to dilute the solution

Hypotonic solutions The concentration of solute outside the cell is less than inside the cell. water will move in to dilute the cell

Isotonic solutions The concentration of solute outside the cell is the same as inside the cell. water moves in and out but there is no net movement

Active Transport requires energy from the cell movement is against the concentration gradient – From low concentration to high

Carrier proteins Carrier proteins in the plasma membrane – recognize a specific needed material – changes its shape – provides an opening – the material can slip into the cell. (if with the gradient it’s called facilitated diffusion)

Vacuoles for transport Endocytosis – The cell surrounds and engulfs a large particle and brings it into the cell by creating a vacuole

Vacuoles for transport Exocytosis – The cell expels a large particle and by eliminating the vacuole