Membrane function
Protect the cell
Controls the content of the cytoplasm
Senses molecules and other cells in the environment
Selectively permeable
Fluid mosaic
Bind to cytoplasm and extracellular matrix
Cell membranes
Phospholipids
Primary molecules that make up biological membranes.
- phosphate containing hydrophilic head
- hydrophobic lipid tail.
Amphipathic
A molecule containing both hydrophobic and hydrophilic regions
Phospholipid bilayer
2 large phospholipids
Arranged with the hydrophilic heads facing outwards
Hydrophobic tails facing inwards
Micelle
Forms spontaneously because it is the most energetically stable structure.
Ensures the hydrophobic regions face away from water
Animal cell membrane structure
- Phospholipids bilayer include sterols
- bilayer separates 2 aqueous regions- extracellular and intracellular
- proteins embedded in bilayer
- carbohydrates are attached to the exterior of the membrane
Carbohydrates
Hydrophilic
Located on the outside of the membrane
Bound to a membrane embedded molecule
Generates a wide variety of cellular messages
Glycoprotein
Carbohydrate bound to a protein on the outside of the cell membrane
Glycolipid
Carbohydrate bound to a lipid on the outside of the cell membrane
Sterols
Help membranes maintain fluidity and stability
Prevent membrane from solidifying at low temperatures
Hinder phospholipid movement in the membrane at moderate temperatures
Cell membrane exceptions to the rule
Psychrophilic organisms
Termophilic organisms
Mesophilic organisms
