Cell Transport  Diffusion & Osmosis (aka Passive Transport)  Active Transport

Cells are very busy doing many things in order to keep organisms alive.

One important thing that the cell membrane does is to control cell transport-- what comes into and out of the cell through the cell membrane.

Picture the cell membrane as a slice of Swiss cheese. It has many small openings called pores. It is through these tiny pores that many small molecules like water, oxygen, and carbon dioxide enter and leave the cell.

The cell membrane is very “ choosy. ” It allows some materials to pass through quickly, some slowly, and some materials may not be allowed to pass through at all. Because of this “ choosiness, ” the membrane is said to be selectively permeable; it lets some substances through, but not all.

Concentration Concentration= the number of molecules in a given space Concentration = the number of molecules in a given space High concentration= ______________ number of molecules in a given space High concentration = ______________ number of molecules in a given space Low concentration= ______________ number of molecules in a given space Low concentration = ______________ number of molecules in a given space

Examples of Concentration If you use the example of people, which living area would be more highly concentrated, New York City or the Sahara desert? If you use the example of frogs, which area would have a low concentration of frogs: the Charles River in Needham, or the top of Mount Washington in New Hampshire?

Passive Transport Diffusionand Osmosis are called Passive Transport, because they do not require energy for them to take place. Diffusion and Osmosis are called Passive Transport, because they do not require energy for them to take place. A good analogy is that Diffusion and Osmosis are like riding a bicycle downhill … you don ’ t need to pedal!

Definition of Diffusion: Diffusionis the movement of molecules from an area of higher concentration (where there ’ s more) to an area of lower concentration (where there ’ s less.) Diffusion is the movement of molecules from an area of higher concentration (where there ’ s more) to an area of lower concentration (where there ’ s less.)

This movement of molecules also takes place across cell membranes. Which way will these molecules move?

Diffusionis the process that allows certain materials to enter and leave the cell. Diffusion is the process that allows certain materials to enter and leave the cell. Animation of Diffusion across cell membrane ge/modules/homeostasis_kidneys /kidneys3.cfm?coSiteNavigation _allTopic=1

We can see (and smell) diffusion all around us.

How does Diffusion occur? animation All molecules are in constant, random motion. Molecules are constantly colliding with each other. Molecules are constantly colliding with each other. As molecules collide, they push each other around, until they reach equilibrium. As molecules collide, they push each other around, until they reach equilibrium. animation Equilibriummeans“balanced”-- the molecules are evenly distributed. Equilibrium means “balanced”-- the molecules are evenly distributed.

Osmosis Osmosis is a special type of diffusion. Osmosisisthe movement of water molecules from an area of higher concentration to an area of lower concentration, across a membrane Osmosis is the movement of water molecules from an area of higher concentration to an area of lower concentration, across a membrane

Examples of Osmosis Mummification Putting salt on a slug grapes turning into raisins H2OH2O H2OH2O H2OH2O Sponge in a bucket of water H2OH2O

Osmosis The water molecules are small enough to fit through the pores, but the sugar molecules are too big to fit. The water molecules will move from the left (high concentration of water) to the right (low concentration of water), to try to reach equilibrium. J-bAiJcLdxI&feature=youtu.be

Osmosis Osmosis happens across cell membranes, just as diffusion does. swells

Osmosis in red blood cells Blood is slightly salty (3% salt). If red blood cells are put in salt water, they shrivel up (water leaves the cells). If they are put in pure water, they fill up with water and burst. H2OH2OH2OH2O H2OH2OH2OH2O H2OH2OH2OH2O pure water salty water Normal concentration (in blood) Advanced video on osmosis

Osmosis in red blood cells H2OH2OH2OH2O H2OH2OH2OH2O H2OH2OH2OH2O pure water salty water Normal concentration (in blood) omeostasis_kidneys/kidneys4.cfm?coSiteNavig ation_allTopic=1 Osmosis in red blood cells-- animation

Active Transport Animation of Active Transport is the movement of molecules across a cell membrane using energy, from an area of lower concentration to an area of higher concentration.

Active Transport A good analogy is that Active Transport is like riding a bicycle uphill … it takes energy!

Two Types of Active Transport Transport Proteins Endocytosis & Exocytosis Cell uses a vacuole or vesicle to move substances in & out of the cell. Transport or Carrier proteins carry a large molecule across the cell membrane, going from low to high concentration. This takes energy!

Endocytosis  Endo means “inside”. Cyto means “cell”. process of bringing Endocytosis is the process of bringing something inside a cell by enclosing it in a vacuole or vesicle.  Endo means “inside”. Cyto means “cell”. process of bringing Endocytosis is the process of bringing something inside a cell by enclosing it in a vacuole or vesicle.

Endocytosis Amoeba eats 2 paramecia

Exocytosis  Exo means “outside”. Cyto means “cell”. Exocytosis is the process of moving something outside a cell by means of a vacuole or vesicle.  Exo means “outside”. Cyto means “cell”. Exocytosis is the process of moving something outside a cell by means of a vacuole or vesicle.

Active Transport of Materials in & out of a cell _int_membraneweb/ Exocytosis in Paramecium video _place/biocoach/biomembrane1/diffusion. html s/homeostasis_kidneys/kidneys3.cfm?coSite Navigation_allTopic=1 Facilitated Diffusion & Active Transport Diffusion, Osmosis & Active Transport