1. Passive Transport

2. The Cell Membrane There are 2 important parts of the cell membrane regarding transport: 1. Phospholipids 2. Proteins Cells need nutrients from the exterior environment. As cells process these nutrients, wastes build up in the cell = must eliminate them. 1.2. Ext. env. Inside cell CMs are selectively permeable – only certain substances can go in and out of them!

3. The Living Cell Membrane CM is composed of 2 layers of phospholipids each phospholipid molecule has a head and 2 tails –the head is hydrophilic (attracts water) and soluble in water –the tails are hydrophobic (repels water) and insoluble in water

4. The Living Cell Membrane A variety of protein molecules are embedded within the bilayer Many of these proteins carry special sugar molecules (glycoproteins) –help distinguish type A vs. type B blood cells The protein molecules serve different functions: 1.Gatekeepers - opening and closing paths through the cell membrane 2.Receptor sites for hormones - chemical messengers that allow cells to communicate with one another 3.Transport - pick up materials and move them into and out of the cells

6. Types of Passive Transport Transport of materials across CM without using energy. There are 3 types: Simple Diffusion Osmosis Facilitated Diffusion

7. 1. Simple Diffusion Movement of molecules from an area of high concentration to an area of low concentration Goal is to achieve equilibrium Affected by concentration, temperature and pressure *** HIGH  LOW ***

8. Examples of Simple Diffusion H 2 O, CO 2, O 2 molecules with cells (involved in life processes) Air freshener cones Perfume sprays

9. 2. Osmosis Diffusion of water molecules across a selectively permeable membrane Cells are ideally bathed in isotonic solutions (where conc. inside cell equals conc. outside cell) H 2 O molecules move from a side with low conc. to a side with high conc. across a selectively permeable membrane to obtain equilibrium –SP membrane allows water to go through, but not other molecules

10. Result: Equal conc. of sugar solution on BOTH sides SP membrane keeps sugar molecules from moving to other side! (impermeable to them) (solute) Osmosis happens when there is a difference in solute conc.

11. Types of Solutions Recall: A solution is a uniform mixture made up of a solvent (the bigger part) and a solute (the smaller part) 3 Types: 1.Isotonic – conc. of solute inside cell EQUALS conc. of solute outside the cell 2.Hypertonic – conc. of solute inside cell is HIGHER than conc. of solute outside the cell 3.Hypotonic – conc. of solute inside cell is LOWER than conc. of solute outside cell Now… if you have red blood cells in a beaker full of water and you add salt to the beaker… what would be the hypothetical situation for each of these solutions?

12. 1.Isotonic – conc. of salt inside cell EQUALS conc. of salt outside cell. Water moves in and out at equal rates. Nothing happens to cell size. 2.Hypertonic – conc. of salt inside cell LOWER than conc. Of salt outside cell. Water moves OUT to adjust conc. = cell SHRINKS 3.Hypotonic – conc. of salt inside cell GREATER than conc. Of salt outside cell. Water moves IN to adjust conc. = cell SWELLS & may burst 1.3.2.

15. 3. Facilitated Diffusion Protein carrier molecules speed up movement of molecules moving already The carrier proteins must be specialized to aid the diffusion of these molecules as it has a specific fit.

16. a) molecule bounces into a specific carrier protein b)carrier protein binds molecule d)carrier protein resumes its shape high concentration outside cell lower concentration inside cell c)carrier changes shape & flips over, bringing molecule into cell

17. 1. directly through phospholipid bilayer ex. O 2 CO 2 H 2 O diffusion and osmosis 2. protein channels charged ions & water ex. Na +, Ca 2+, K+, Cl - diffusion and osmosis 3.carrier protein facilitated diffusion larger molecules ex. glucose, amino acids higher concentration outside of the cell 123 Summary of Passive Transport