Membranes Flashcards
What effects do Hydrophobic molecules have on the adjacent water molecules?
They Cause the water molecules to reorganize into icelike cages which increase the free energy
How can we follow movements within the membrane?
Use a nitroxyl spin label with an unpaired electron to follow movements within the membrane by “electron spin resonance spectroscopy (ESR)”
What does membrane fluidity depend on?
Composition and temperature
What happens at the “phase transition” point?
a liquid to gel transformation
How is fluidity altered?
by lipid tail length and cis double bonds
What is a lipid raft?
subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids
What are Glycolipids derived from?
Glycerol
Intrinsic or Integral Proteins
travers the membrane at least once or are covalently linked to the membrane
Extrinsic or Peripheral Proteins
attached to the membrane by ionic interactions
What effect does corralling have on membrane proteins?
Concentrates signaling complexes, increasing signaling speed and efficiency
How is Ras anchored to the plasma membrane?
Acylation
How is Src anchored to the plasma membrane?
Prenylation
What is the structure of a transmembrane segment?
20 to 30 amino acids cross the membrane in a alpha helix
Hydropathy Mapping
mapping of transmembrane proteins using the hydropathy index. Hydropathy index of an amino acid is a number representing the hydrophobic or hydrophilic properties of its sidechain
Why are proteins and lipids clycosylated?
Increase the hydrophilic nature of lipids and proteins and stabilize protein and lipid conformation
How can you solubilize peripheral membrane proteins?
High salt concentrations
What are used to solubilize integral proteins?
Detergents
Freeze Fracturing
Freezing a tissue or cell with nitrogen to rupture the cell in order to visualize and study the internal components
FRAP
Fluorescence Recovery after Photobleaching, a method for determining the kinetics of diffusion through tissue or cells. It is capable of quantifying the two dimensional lateral diffusion of a molecularly thin film containing fluorescently labeled probes, or to examine single cells
Prenylation
Addition of a hydrophobic molecule to a protein
Acylation
the process of adding an acyl group to a compound
