Transport Across Cell Membranes pg. 297 - 307 3 Types 1. Passive Transport 2. Active Transport 3. Endocytosis/Exocytosis

Transport Across Cell Membranes pg. 297 - 307 1. Passive Transport

Brownian Motion and Concentration Gradients p. 297-298 Brownian Motion: matter is made up of tiny particles that are in constant motion

Molecules always move 1) randomly 2) from areas of high concentration to areas of low concentration This is called DIFFUSION

Concentration Gradient The difference in concentration between the high and low concentration areas. The greater the difference in concentration – the faster the particles move Eventually equilibrium is reached

Clips http://www.youtube.com/watch?v=STLAJ H7_zkY diffusion of food coloring http://www.youtube.com/watch?v=HIGEm TlNAT4 artistic

Why does this happen? At high concentrations the molecules ricochet off of each other and move towards the area of low concentration

Equilibrium Remember: at equilibrium the particles DO NOT stop moving, they continue to move back and forth across the concentration gradient.

Passive Transport pg. 297 - 303 NO ENERGY REQUIRED Small molecules move by diffusion (water, oxygen, carbon dioxide) When WATER molecules move by diffusion across a membrane we call it OSMOSIS

Tonicity of Solution pg. 299 Hypotonic more water than in the cell Hypertonic less water than in the cell Isotonic Same amount of water

Tonicity of Cell pg. 299 Hypotonic ? Hypertonic ? Isotonic ?

Clips http://www.youtube.com/watch?v=SSS3Et KAzYc egg cell osmosis

Should you drink salt water if you are lost at sea??? Potato Experiment

Should you drink salt water if you are lost at sea???

Facilitated Transport (also called facilitated diffusion) Another form of passive transport Used for molecules that are too large to cross the membrane by diffusion (i.e. glucose)

Facilitated Diffusion p. 303 Carrier proteins bind to larger molecules, and change their shape so molecules can diffuse through. Channel proteins provide water filled pores for charged ions to pass through

Transport Across Cell Membranes pg. 297 - 307 3 Types 1. Passive Transport 2. Active Transport 3. Endocytosis/Exocytosis

Active Transport pg. 303 - 304 Molecules move against the concentration gradient (low to high) Energy must be provided (even when we are resting, 40% of our energy is spent on active transport!)

Active Transport Uses specialized transport proteins and protein pumps

Why spend so much energy on active transport? Maintains internal cell environments (i.e. cell’s electrical gradient, roots pull in minerals from soil, filtering blood in your kidneys)

Transport Across Cell Membranes pg. 297 - 307 3 Types 1. Passive Transport 2. Active Transport 3. Endocytosis/Exocytosis

Endocytosis/Exocytosis For substances the cell needs to take in (endo = in) or expel (exo = out) that are too large for passive or active transport

Two Types of Endocytosis 1. phagocytosis (solids) 2. pinocytosis (liquids)

Test your transport knowledge! http://www.teachersdomain.org/asset/tdc 02_int_membraneweb/