Biological membrane structure Flashcards
what are the components of membranes?
lipid bilayer = structural backbone made up phospholipids, glycolipids, and cholesterol
proteins = transport, enzymatic, and signal transduction
carbohydrates = attached to proteins and lipids
Are carbohydrate chains found on the inside or outside of the cell membrane?
They are found on the outside of the cell membrane
how many rings does a sterol have?
4 rings
How do membranes contain different phospholipids?
phospholipids differ in their esterification to serine, ethanolamine, choline or inositol
What is cholesterol used for?
it maintains the fluidity fo the membrane and acts as a precursor to steroid hormones and Vitmain D
Is lateral diffusion or transverse diffusion faster?
Lateral and transverse diffusion of lipids in the bilayer (where they switch spots)
lateral difussion is faster
what is the fluid mosaic model of the membrane?
membranes are two dimensional solutions of oriented globular proteins and lipids
What are integral proteins?
integral proteins are fully integrated in the lipid bilayer - spanning the entire double layer
what are peripheral proteins?
They are proteins that only cushion into the bottom layer of the lipid bilayer
What are the functions of membrane proteins?
anchoring = attach cell membranes to eachtoerh or to external/internal structures
recognition proteins = identify the cell and prevent attack by immune system
enzymes = catalyze intracellular or extracellular reactions
receptors = bind to specific ligands in the extracellular matrix
carrier proteins = move solutes across membrane (may require ATP)
leak channels = permit continuous movement of water and ions
gated channels = close or open to regulate ion movement
Which membrane protein requires ATP to function?
carrier proteins
What is passive diffusion?
the unaided spontaneous movement of solute molecules down their concentration gradient, from high to low, until solutes equilibrate across the bilayer - entropically driven
When is maximum entropy reached?
at equilibrium… which is why equilibrium is the equilibrium
What types of faciliated diffusion occur in a lipid bilayer?
They occur down a concentration gradient and are dependent on integral proteins
we can have
- uniport - one molecule in one direction
- symport - two types of molecules in one direction
- antiport - two different molecules in opposite directions
What are the three forms of active transport?
- primary
- secondary
- group translocation
Give an example of a primary active transport
the Na+ K + pump/ ATPase ion pump
Where the sodium binds, then ATP is dephosphorylated giving the energy needed for the protein to change conformation and drive the sodium extracellularly
What classifies as a primary active transport?
requires ATP to move molecule against a concentration gradient
What type of transport does the hydrogen potassium ATPase require?
dead give away that the protein requires ATP
exchages K+ in the stomach for H+ in cytoplasm - works against con. gradient - therefore
PRIMARY active transport
What is the definition of a secondary active transport?
carrier protein that moves a specific substance against it’s concentration gradient, but uses the concentration gradient for one substance as the driving force
so the second substance gets a ‘free ride’
What is the definition of group translocation?
solute changes during transport -
ex) in the phosphotransferase system where the sugar is phosphorylated during transport into the cell therefore, it becomes sugar phosphate
What sort of transport does the glucose transport follow?
it follows secondary active transport because it tags along with the sodium that is moving with it’s normal concentration gradient
What is phagocytosis? How about Pinocytosis?
phagocytosis = cell bringing in material “eating”
pinocytosis = cell “drinking” fluid
