Biological Membranes Flashcards
Membranes
Plasma and Organelle
Fluid - Phospholipid Bilayer
Mosaic - Proteins associated with membrane, move
locations over time
Phospholipids
Hydrophilic Heads
Hydrophobic Tails
Turn and move laterally along membrane, but rarely flip du
to being surrounded in water
Integral Proteins
Embedded in bilayer, difficult to remove
Some are transmembrane (membrane spanning)
ex: transport proteins
Peripheral Proteins
Not embedded, easy to remove
Held in place through interactions with phospholipids
Usually on outside face of membrane
Transport Proteins
Membrane spanning
Substrate specificity - only transports 1 kind of molecule
Diffusion
Solutes move down a concentration gradient
Solvents (water) move up the solute concentration gradient
Random mixing of molecules due to kinetic energy
Osmosis
Diffusion of water
Small, can diffuse through membrane despite hydrophobic
core of phospholipid bilayer
Aquaporins: Channel proteins, assists with diffusion of water
Channel Proteins
Allows specific molecules to diffuse down concentration
gradient
Specificity
Can open/close as needed
Carrier Proteins (Uniports)
Substrate binding site Specificity Opens to collect molecule, closes, and releases molecule across membrane Has maximum speed
Active Transport
Requires ATP
Uses ATP to pump molecule against concentration gradient
ex) H+ pump
Co-Transport
Indirectly uses ATP
Brings a molecule down a concentration gradient in order to
power the pumping of another against the concentration
gradient
Requires a active transport protein to create concentration
gradient, which uses ATP
Exocytosis
Vesicles moving molecules in and out of cell through fusion
of membrane
Pinocytosis
Endocytosis
Plasma membrane blebs inwards to catch molecule outside of cell
Least selective
Phagocytosis
Endocytosis
Membrane blebs forward to catch molecule
More selective then phagocytosis
Receptor-Mediated Endocytosis
Endocytosis
Coated pit inside membrane
When specific molecule enters pit, pit leaves as vesicle
