Schedule Why was it so darn cold? Go over quizzes Current event Membranes Membranes worksheet (finish for HW as needed) Tomorrow: Review membranes, Osmosis/Diffusion Membranes Quiz next Monday Mini-unit test next Wednesday

DNA Draw how a water molecule surrounds a cation like Na+

Water Soluble

Membrane Structure and Function

Hydrophobic Vs. Hydrophilic Water-fearing Fats, oils, rubbers Non-polar Water-loving Polar, ionic Has some charge

Amphipathic Molecules Have both hydrophilic and hydrophobic regions Phospholipids have hydrophilic heads and hydrophobic tails

Soaps/Detergents

Phospholipids

Phospholipid Bilayer Phospholipids naturally arrange themselves to keep hydrophobic portions away from water

Membranes Both wrap the entire cell and individual organelles Very movable – like play-dough

Fluid Mosaic Model Proteins are embedded in the membrane These proteins have many different functions

Membrane Protein Functions Transport Enzymatic Activity Binding of messengers Intercellular connections Cell recognition Attachment

Membrane Carbohydrates Important in cell-cell recognition Short polysaccharides Often bonded to proteins (glycoproteins) Distinguish cells – i.e. blood types

What Makes Each Membrane Different? The proteins and carbohydrates present E.g. thylakoid membranes have chlorophyll proteins, red blood cells have A/B markers etc.

Special Membranes = Special Organelles Controls what gets into the organelle. So mitochondria has only the materials necessary for respiration – nothing else to get in the way!

Selective Permeability Membrane is selective in what molecules can pass through and how quickly they pass Energy must sometimes be used to transport molecules

Simple Permeability Small non-polar molecules rapidly pass through membrane Very small polar molecules can slip through Larger polar molecules cannot Very impermeable to ions

Cell Wall v. Plasma Membrane Rigid Carbohydrates Controls structure Not in animal cells Flexible Phospholipids Controls entry In all cells