THE CELL MEMBRANE The Key to Cellular Transport
Characteristics of the Cell Membrane Made of phospholipids – arranged in two layers called a bilayer Selectively permeable - it controls “selects” what can enter or leave the cell -some materials are allowed through others aren’t Fluid Mosaic Model - made of different molecules – phospholipids, proteins, cholesterol - the molecules aren’t static but can move “fluid”
Lipid bi-layer – the heart of the membrane Phospholipids are arranged into 2 layers - called a bilayer
Phospholipids: Phosphate Heads Polar/hydrophillic – attracted to water and charged particles
Phospholipids: Lipid Tails Nonpolar/hydrophobic – repel water and charged particles
Cholesterol Found in bilayer – helps to hold the membrane together while adding to fluidity of the membrane
Glycoproteins Proteins with carbohydrates attached – identifies the cell type -allows it to bind with other cells of the same type
Receptor Proteins recognize and bind with substances outside of the cell, causing changes inside the cell
Enzymes Allow reactions to occur- light reactions and ETS occur with enzymes in membrane
Transport Proteins Proteins that extend across the membrane – provide a way for large or charged molecules to cross the membrane
Types of Transport Proteins Ion Channels- allow certain charged particles to cross the membrane – passive transport Carrier Proteins – bind to a specific molecule and carry it across the membrane - facilitated diffusion – proteins carry molecules with the concentration gradient /no cellular energy is required - active transport – proteins carry molecules against the concentration gradient/ cellular energy is required