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Membrane function
Separates cell interior from exterior environment.
Membrane proteins
Regulate movement of molecules across membranes.
Receptor proteins
Bind chemical signals and transmit messages.
Cell-to-cell interactions
Facilitate adhesion and communication between cells.
Energy storage
Creates voltage by separating charges.
Fluid Mosaic Model
Describes membrane structure with lipids and proteins.
Phospholipids
Most common membrane lipid, forms bilayer.
Sterols
Four-ringed hydrocarbons, stabilize membrane fluidity.
Glycolipids
Lipids with carbohydrate heads, determine blood types.
Membrane fluidity
Movement of phospholipids affects membrane state.
Transition temperature (Tm)
Temperature where membrane changes from gel to fluid.
Desaturase enzymes
Modify fatty acids by adding double bonds.
Membrane asymmetry
Different lipids on inner and outer leaflets.
Flippase
Protein that moves phospholipids between membrane sides.
Integral proteins
Span the membrane, involved in transport.
Peripheral proteins
Loosely attached to membrane, provide structural support.
Lipid-anchored proteins
Tethered to the membrane via lipid tails.
Lipid raft
Membrane section rich in cholesterol and sphingolipids.
Selectively permeable
Controls passage of ions and small molecules.
Concentration gradient
Difference in substance concentration across a membrane.
Electrochemical potential
Charge and concentration difference across a membrane.
Membrane potential (Vm)
Electrical potential difference maintained around -60 mV.
Simple diffusion
Molecules pass freely following concentration gradient.
Facilitated diffusion
Polar molecules move via channel or carrier proteins.
Active transport
Requires energy to move substances against gradient.
Channel proteins
Transmembrane proteins allowing specific ion passage.
Carrier proteins
Bind and transport specific substances across membranes.
Antiporter
Moves two molecules in opposite directions.
Symporter
Moves two molecules in the same direction.
Aquaporins
Channel proteins specifically for water transport.
Sodium-potassium pump
Active transport mechanism for Na+ and K+.
Membrane protein mobility
Variable movement, can be anchored or free.
Fluid state
Membrane condition allowing lateral lipid movement.
Rigid state
Membrane condition restricting lipid movement.
High temperature effect
Increases membrane fluidity, may destabilize structure.
Low temperature effect
Decreases membrane fluidity, may solidify structure.
Glycerol backbone
Structural component of phospholipids.
Sphingosine backbone
Alternative backbone for some membrane lipids.
Blood type determination
Based on glycolipid composition on cell membranes.
Membrane signaling
Communication initiated by receptor protein activation.
Chemical signals
Molecules that trigger cellular responses.
Cellular adhesion
Process by which cells stick to each other.
Membrane transporters
Proteins that facilitate movement across membranes.
Hydrophobic core
Barrier preventing polar molecules from passing.
Phospholipid bilayer
Basic structural unit of cell membranes.
Membrane structure
Composed of lipids, proteins, and carbohydrates.
