Membrane transport Flashcards
Phospholipid Bilayer
Hydrophilic heads face outwards towards the cytoplasm
Hydrophobic tails (fatty acid chains) face eachother
Fluid mosaics model
Phospholipid molecules are in constant motion e.g they’re fluid
Proteins are of different shapes and sizes and are distributed unevenly throughout the membrane eg form a mosaic pattern
Proteins in membranes
Some span the whole membrane (intrinsic proteins)
Some are confined to the inner or outer surface (extrinsic proteins)
What are transport proteins
-Channels and carrier
-span the whole membrane
-transport substances that cannot cross the phospholipid bilayer by simple diffusion
- specific tertiary structures -> determined which molecules they transport
What are transport proteins - protein carriers
Protein carriers
- transport water soluble substances
Facilitated diffusion and active transport
What are channel proteins
Channel ions
Charged channels
Facilitated diffusion
Other membrane proteins
Extra cellular side
Act as receptors (for hormones/neurotransmitters)
Involved in cell recognition
Act as antigens
Many are glycoproteins
Cytosolic side
send messages within the cell
some can dissociate from the membrane and move into the cytoplasm
Glycoproteins and Glycolipids
Branched carbohydrate chains stick out from the outer surface is some membranes like antenna
They are attached to lipids forming glycolipids or to proteins forming glycoproteins
What does cholesterol do in the bilayer?
makes the bilayer less fluid and helps maintain its shape
strength and fluidity
What does partial permeability mean
membranes don’t let every type of molecule theough
they’re partially permeable
What affects permeability
-Unsaturated fatty acids = Increased permeability
-Saturated fatty acids - decreased permeability
-Cholesterol - Increased strength, decreased fluidity and permeability l
- Number and distribution of channels and carriers
