Passive Transport and Active Transport Chapter 7 Section 3

Passive Transport Movement of molecules across a cell membrane without the input of energy 2 Types of Passive Transport: Diffusion Osmosis

Key Terms to Know Concentration: the mass of solute in a given volume of solution Equilibrium: concentration of the solute is the same throughout the sytem Selectively Permeable Membrane: membrane that allows some substances to pass through the membrane while others cannot

Diffusion Movement of molecules from an area of higher concentration to an area of lower concentration Driven by the molecules kinetic energy until equilibrium is reached No Energy Needed!

Diffusion Molecules can diffuse across a cell membrane by: Dissolving in the phospholipid bilayer Passing through pores in the cell membrane

Osmosis Diffusion of water through a selectively permeable membrane

Osmosis Net direction of osmosis is determined by the solute concentrations on the two sides of the membrane When solute concentrations outside and inside the cell are equal, the two solutions are isotonic (which means same strength

Osmosis When the solute concentration is higher outside of the cell is higher than inside of the cell, it is hypertonic. Water will flow out of the cell When the solute concentration is higher inside of the cell than outside of the cell, it is hypotonic. Water will flow into the cell

Osmosis

Osmosis Hypertonic and Hypotonic solutions can cause osmotic pressure Osmotic pressure can cause serious problems-----cells may burst Vacuoles in plants help to regulate this process Humans do not have an organelle to regulate b/c they have so many cells to absorb water

Facilitated Diffusion In facilitated diffusion, a molecule binds to a carrier protein on one side of the cell membrane The carrier protein then changes its shape, allowing it to pass across the cell membrane and deposit the molecule inside or outside of the cell Still does not require energy!!!!

Facilitate Diffusion

Active Transport Molecules move across the cell membrane from an area of lower concentration to an area of higher concentration Active transport REQUIRES energy!!!! Most types of active transport is accomplished by using carrier proteins or cell membrane pumps Two Types: Endocytosis Exocytosis

Endocytosis Process of taking material into the cell by means of infoldings, or pockets, of the cell membrane Endo=“Inside” Breaks loose from the outer cell membrane to form a vesicle or vacuole in plants Large molecules, clumps of food, and even whole cells can be taken in this way

Endocytosis Endocytosis includes: 1) Pinocytosis: Process of endocytosis where the vesicle includes fluid or solutes 2) Phagocytosis: Process of endocytosis where the vesicle contains large particles or cells

Endocytosis

Exocytosis The membrane of the vesicle or vacuole fuses with the cell membrane, forcing the contents out of the cell Exo=“Outside” Removal of water by the contractile vacuole is an example

Exocytosis