Chapter 4 Flashcards
Plasma membrane
the outer boundary of a cell that separates it for external environment. It is 5-10 mm thick
The basic characteristic of a biomembrane
they contain lipids, proteins and carbohydrates arranged in a bilayer. It is stabilized by van der waal interactions
Ratio lipid-protein assemblies in mitochondrial membranes
high proteins:low fats as protein carriers are needed for electron transport chain.
Ratio lipid-protein assemblies in myelin sheath
low protein: high lipids used as electrical insulation for nerve impulses
3 basic type of lipids in cell membranes
- phosphoglycerides
- sphingolipids
- cholesterol
sphingolipid/ceramide
a type of sphingosine that is linked to a fatty acid by its amino group
Phosphoglyceride
lipids with a phosphate group (phospholipid) and built on a glycerol backbone
characteristic of a phospholipid
- net negative charge
- amphipathic
- usually one saturated and unsaturated chain
difference between a phosphoglyceride and sphingolipid
The backbone of a phosphoglyceride is a glycerol but the backbone of a sphingolipid is a spingosine
sphingosine
an amino alcohol that contains a long hydrocarbon chain
cerebroside glycolipid
sphingolipid linked to 1 sugar
ganglioside glycolipid
sphingolipid linked to multiple sugars
sphingomyelin
a phosphorlcholine added to a ceramide (a sphingolipid and a phospholipid together)
synthesis of membrane phospholipids
- they are produced in the ER
- acyl transferase successfully adds 2 fatty acids to glycerol phosphate producing phosphatidic acid
the orientation of glycolipids and glycoproteins
they are exoplasmic because the lumen will become the exoplasmic face
3 groups of membrane proteins
- integral proteins
- peripheral
- lipid anchored
integral proteins
amphipathic as they go through the bilayer and is usually the target for drugs
peripheral
on the outsides (extracellular or cytoplasmic side) of the bilayer held by non covalent bonds
lipid anchored membrane protiens
covalently bound to the extracellular or cytoplasmic side and distingue by the type of lipid
3 types of lipid anchored protiens
- GPI: glycosylphopatidylinositol
- acylation
- prenylation
what is a hydropathy plot used for?
It measures the hydrophobicity of amino acids
- negative: hydrophilic
- positive: hydrophobic
what contributes to membrane fluidity?
- temperature
- sterol content
- length and saturation or fatty acyl chains
- phospholipid content
what is a lipid raft and what is it used for?
When cholesterol and sphingolipids pack together to make highly ordered microdomains when the environment is disorder or more fluid.
what is a FRAP and what is it used for?
fluorescence recovery after photobelaching is used to measure the rate of diffusion for membrane proteins
what determines lipid permeability?
- molecular size
- polarity
- partition coefficient (solubility in a non polar solvent vs water)
4 ways to move across a membrane
-simple diffusion
- simple diffusion by ion channels
- facilitated diffusion
- active transport
facilitated diffusion
no energy but a protein changes conformation allow solute to go through the lipid bilayer
simple diffusion
no energy, does down the gradient through the lipid bi layer
simple diffusion by ion channel (protein mediated)
no energy, ions go down the gradient through a channel
- voltage gated
- ligand gated
- mechanically- gated
active transport
energy required to allow transport up the gradient
primary active transport
directly uses energy to pump against the gradient
secondary active transport
indirectly uses energy by using a gradient made by active pump
Km value of glucose transporters and why
they are there to maintain a concentration of glucose in the body
symporter
simultaneously pumping in the same directions
antiporter
simultaneously pumping in opposite directions
function of the Na- glucose symporter
help move glucose out of the gut lumen
why is the Na-Glucose symporter considered a secondary active transport
it uses the gradient set up by the Na/K pump to transport the glucose
how does glucose get out the gut lumen and into circulation
it gets cotransported with sodium. every 2 sodium ion brings one glucose ion. once inside the membrane, it a GLUT 2 transporter facilitates diffusion into the blood
Lipid- anchor membrane: acylation
A palmitoyl or myristal group connected to a cytosololic protein
prenylation protein
A lipid-anchored membrane protein connected to a prenyl group bulit from 5 carbons
GPI: glycosylphospatidylinositol
Attaches to the carboxyl terminus of sugars exoplasmically used as receptor and enzymes
