Download The Cell Membrane

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