Transport Across the Cell Membrane Diffusion Diffusion Movement

Transport Across the Cell Membrane

Diffusion • Diffusion = Movement of particles from high to low concentration • Example: air freshener • This is called moving DOWN the concentration gradient (high to low!)

• Molecules diffuse until they reach equilibrium (No net movement in any direction!) • Are molecules still moving around though? • Yes!

Diffusion

Passive Transport • Passive Transport is movement across a membrane that does not require energy to be used by the cell • Diffusion is an example of passive transport • What about molecules that cannot pass Cell Membrane easily through membrane? How do Will molecules diffuse left to right or right to left? ? they get across?

Passive Transport • Facilitated Diffusion: When Channel proteins help large molecules or charged molecules pass through the membrane • No energy required! Transport Protein

Osmosis – A Special Kind of Diffusion • Osmosis = the diffusion of water across a membrane • Water goes through channel proteins in the membrane called aquaporins • Water goes from High to Low concentration • No energy required!!

Osmosis Water easily passes through membrane but the sugar does not!

Osmosis Which way is water moving and why? ? ? Use concentration, solute, and osmosis in your answer!!!

Types of Solutions • Hypertonic- Solution with a higher concentration of solute than the cell • Hypotonic- solution with a lower concentration of solute than the cell • Isotonic- equal concentrations of solute • Draw examples!

• Hypo –Hippo! Cell in hypotonic solution will get fat like a hippo! • Iso -Equal! Equal amounts of solute in solution and in cell • Hyper- Too much! Higher concentration of solute outside of the cell, so cell will shrivel up! Types of Solutions

Osmosis in Hypertonic Solution

Active Transport • Cell uses energy to move molecules across membrane • From LOW to HIGH concentration • Protein Pump: Specific transport protein PUMPS solute against the concentration gradient

Active Transport • Very important in sending nerve signals!! • Na+/K+ pump – has PUMP right in the name!

Transport of Large Molecules • Exocytosis – vesicle fuses with membrane and releases contents

Exocytosis

Transport of Large Molecules • Endocytosis- Membrane pinches inward and takes in particles

Sledding Analogy!