Membrane Structure and Function
PLASMA MEMBRANE
SELECTIVE PERMEABILITY= allowing some substance to cross it more easily than others composed of: Phospholipids Proteins Carbohydrates
Cholesterol
FLUID MOSAIC MODEL Phospholipids are primary lipids(constantly moving, fluidly) AMPHIPATHIC-containing hydrophobic and hydrophilic regions
Mosaic part=not made of one thing
Freeze-fracture studies:way to view what's inside
FLUIDITY OF MEMBRANE Move within bilayer Most of lipids and some proteins, drift laterally Rarely does a molecule flip-flop transversely across the membrane Membrane held together by HYDROPHOBIC BONDS=weaker than covalent Temp affects fluidity
Cold temp:fluid-solid
The temp at which a membrane solidifies depends on the type of lipids
Membrane rich in unsaturated fatty acids are more fluid that those rich in saturated fatty acids Membranes must be fluid to work properly; they are usually about as fluid as salad oil. Cholesterol acts as a temp buffer At warm temp(such as 37*C), cholesterol restrains movement of phospholipids
At cool temp, it maintains fluidity by preventing tight packing (don't want cholesterol in bloodstream).
MEMBRANE PROTEINS determine the membrane’s function
Many diff. types of protein in plasma membrane
2 types of proteins Peripheral proteins-loosely bound to surface, not embedded in bilayer
Integral proteins-penetrate the hydrophobic core
Integral Proteins
Transmembrane proteins=integral proteins that span the membrane
The hydrophobic regions of an integral protein consists of one or more sections of non-polar amino acids, often coiled in alpha functions of membrane proteins
Transport
Allow passage of hydrophilic substances across the membrane
Channel proteins, have a hydrophilic channel that certain molecules or ions can use as a tunnel
Channel proteins called AQUAPORINS facilitate the passage of water
CARRIER PROTEINS, bind to molecules and change shape to shuttle them across the membrane
Enzyme activity
SELECTIVE PERMEABILITY= allowing some substance to cross it more easily than others composed of: Phospholipids Proteins Carbohydrates
Cholesterol
FLUID MOSAIC MODEL Phospholipids are primary lipids(constantly moving, fluidly) AMPHIPATHIC-containing hydrophobic and hydrophilic regions
Mosaic part=not made of one thing
Freeze-fracture studies:way to view what's inside
FLUIDITY OF MEMBRANE Move within bilayer Most of lipids and some proteins, drift laterally Rarely does a molecule flip-flop transversely across the membrane Membrane held together by HYDROPHOBIC BONDS=weaker than covalent Temp affects fluidity
Cold temp:fluid-solid
The temp at which a membrane solidifies depends on the type of lipids
Membrane rich in unsaturated fatty acids are more fluid that those rich in saturated fatty acids Membranes must be fluid to work properly; they are usually about as fluid as salad oil. Cholesterol acts as a temp buffer At warm temp(such as 37*C), cholesterol restrains movement of phospholipids
At cool temp, it maintains fluidity by preventing tight packing (don't want cholesterol in bloodstream).
MEMBRANE PROTEINS determine the membrane’s function
Many diff. types of protein in plasma membrane
2 types of proteins Peripheral proteins-loosely bound to surface, not embedded in bilayer
Integral proteins-penetrate the hydrophobic core
Integral Proteins
Transmembrane proteins=integral proteins that span the membrane
The hydrophobic regions of an integral protein consists of one or more sections of non-polar amino acids, often coiled in alpha functions of membrane proteins
Transport
Allow passage of hydrophilic substances across the membrane
Channel proteins, have a hydrophilic channel that certain molecules or ions can use as a tunnel
Channel proteins called AQUAPORINS facilitate the passage of water
CARRIER PROTEINS, bind to molecules and change shape to shuttle them across the membrane
Enzyme activity