Dynamic Cells Membrane Properties Transport Across Cell Membranes Cell Size and Functions

Membrane Properties Membrane Structure Membrane Function

Cell membranes are phospholipid bilayers

What are phospholipids?

Phospholipids self assemble into different structures because their hydrophobic and hydrophilic ends repel each other

What’s a Phospholipid Bilayer? 2 layers of phospholipids

Each layer has: a hydrophilic phosphate end (hydro = water, philic = loving) and a hydrophobic lipid tail (phobic = fears, repels)

Cell membranes are like mosaics Lots of phospholipid tiles with protein, carbohydrate chain and cholesterol tiles thrown in!

Why the different tiles?

Membranes are responsible for an incredible number of things!

carbohydrate chains are for cell to cell communication.

Proteins are crucial for the transport of substances in and out of the cell

Membrane Proteins can be peripheral (on surface) or integral (spans the membrane)

Cholesterol maintains proper membrane flexibility, and also is crucial for cell signaling and nerve conduction.

Cholesterol is not just a bad guy!

Fluid Mosaic Model Cell membranes are constantly MOVING and CHANGING.

Gives cell flexibility, movement RBC membrane Fluid Mosaic Model Gives cell flexibility, movement RBC membrane

Changes the positions of the proteins, lipids and carbohydrates embedded in the membrane, changing the “mosaic” to meet changing needs

3 Functions of the Cell Membrane 1. Barrier – keeps “baddies out, cell organelles in Bacteria pollution resistant bacteria

3 Functions of the Cell Membrane Organization – membranes surround and package materials in vesicles, lysosomes E.R.

2. Organization – membranes 2. Organization – membranes organize complex reactions like photosynthesis and cellular respiration

3. Selective Filter – SEMI-PERMEABLE – only allows certain substances in or out Regulated by particle size and by selective transport by membrane proteins

Clips http://www.youtube.com/watch?v=Rl5Em UQdkuI&feature=fvwrel fluid mosaic model http://www.youtube.com/watch?v=G W0lqf4Fqpg&feature=related how a hormone communicates to the cell through the membrane