1.3 Membrane Structure Flashcards
What are phospholipids?
-1 polar, hydrophilic head (composed of glycerol and a phosphate molecule)
-2 non-polar hydrophobic tails (composed of fatty acid hydrocarbon chains)
What does amphipathic mean?
Phospholipids are; they contain hydrophobic and hydrophilic regions.
What are the properties of the phospholipid bilayer?
-flexible so that individual phospholipids can float anywhere between both layers
-restricts the passage of unwanted substances
-through endocytosis and exocytosis, its membranes can break and reform
What are integral proteins?
They are permanently attached to the membrane across the bilayer.
What are peripheral proteins?
They are temporarily attached through non-covalence to the surface of the membrane.
How are proteins arranged inside of the membrane?
The non-polar, hydrophobic amino acids are close to the bilayer. The polar, hydrophilic amino acids are located internally (it’s like a tube) and face aqueous solutions that pass through.
What are the functions of membrane proteins?
JET RAT
Junction—joins 2 cells together
Enzyme—fixes to membranes to localise metabolic pathways
Transport—facilitated diffusion and active transport
Recognition—markers for cellular identification
Anchorage—attachment points for cytoskeleton and extracellular matrix
Transduction—receptors for peptide hormones
What are the different types of integral proteins?
Helix, helical bundle, and barrel.
What are the functions of each type of integral protein?
Helix—recognition, receptors
Helical bundle—enzymes, transporters, receptors
Barrel—transporters (channel proteins)
What are the functions of each type of peripheral protein?
Enzymes, anchorage, and transporters (carrier proteins)
Why is cholesterol important?
It maintains stability in animal cell membranes.
What are the properties of cholesterol?
It is amphipathic and interacts with the bilayer.
What are the functions of cholesterol?
-reduces fluidity and permeability to water-soluble molecules
-separate phospholipid tails to prevent crystallization of the membrane
-anchors peripheral proteins with lipid rafts
Why is it called the fluid mosaic model?
Fluid, because phospholipids can move around
Mosaic—different proteins make up a mosaic of components
What was the Davson-Danielli membrane model?
Trilaminar membrane; 3 layers recognized through an electron microscope; protein-lipid-protein layers, identified wrongly as protein layers
