Membrane Structure and Function Ch 7 Membrane Protein

Membrane Structure and Function Ch. 7

Membrane Protein Functions

Types of Transport • • • Diffusion Osmosis Facilitated Diffusion Active Transport Endocytosis/exocytosis • Which are passive transport? ?

Types of Transport • • • Diffusion Osmosis Facilitated Diffusion Active Transport Endocytosis/exocytosis Passive = does not require energy • Which are passive transport? ?

Diffusion • Movement of molecules from high concentration to low concentration • “down a concentration gradient” • Brownian movement = natural movement of molecules • Oxygen, carbon dioxide, alcohol and urea move by simple diffusion in cells

Examples of diffusion • Perfume opened in a room • Drop of food coloring in glass of water • Lung cell: carbon dioxide diffuses from lungs to the air, oxygen diffuses into cells

Rate of diffusion • Temperature: Increased temperature, increases diffusion rate • Size of molecule: smaller molecules diffuse faster • Concentration gradient: bigger difference in concentration, faster diffusion

Osmosis • The movement of water across a semipermeable membrane in response to a concentration gradient • Osmolality = solute concentration Hyper = more Hypo = less Iso = same • Tonicity = movement of water in response to solute concentration

crenation

Osmometer • Sugar concentration in tube • Sugar cannot pass out of tube, so water moves into tube • Pushes fluid level up • Pull of water into the tube = “osmotic pressure” • Water moves from hypo hyperosmotic solution

Osmoregulation • Control of water balance • Paramecium uses contractile vacuole • We use our kidneys • Our kidneys filter our blood and maintain salt and water balance

Transport by Carriers Facilitated Diffusion Active Transport Uses specific membrane proteins Substances transported from high to low concentration Substances transported from low To high concentration Passive Requires energy input (ATP) Sugars, amino acids Ions, sugars, amino acids Both use lock and key mechanism to move molecules using membrane proteins that span the membrane

Facilitated Diffusion

Active Transport

Summary

Endocytosis = using the cell membrane to move materials into cell

Phagocytosis: Amoeba engulfing a bacterium

Receptor Mediated Transport

Exocytosis = using cell membrane to move materials out of cell