lecture 8 Flashcards
Proteins can stably associate with membranes via: (3)
Hydrophobic transmembrane segments
Posttranslationally added lipid groups that are covalently linked to proteins
Association with other membrane localized proteins
Phospholipids that have shorter fatty acid tails or tails which contain unsaturated hydrocarbons cause membranes to be
More fluid
When observing the movements of phospholipids in membranes, which of the following occurs least frequently
Movements between the leaflets of a membrane bilayer
DO All transmembrane proteins float and diffuse freely in the bilayer of the plasma membrane in the same manner as phospholipids?
NO
DO Membrane compartments in eukaryotic cells maintain lipid bilayers whose contents are typically symmetric in their distribution across both leaflets
NO the are asymmetric
Proteins that aid the movement of phospholipids from one leaflet of a membrane bilayer to another are known as:
Flippases
The best way to determine if a protein is able to move in a membrane would be
Fluoresence Recovery After Photobleaching Experiment (FRAP)
Membranes provide cells control over by
1 receiving info
2 import and export of molecules
3 capacity for movement and expansion
_____ is important for its role in ordering the _______ ________
that form
membrane bilayers
Water,amphipathic phospholipids
Formation of closed circular _____ and compartments
is energetically favored in aqueous environments
vesicles
Cholesterol is an ______ molecule. with an ___ polar head
amphipathic, OH
Two of the major components of the lipid bilayer
Phospholipids and Cholesterol
3 major phospholipids
Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine
how do Phospholipids move and __ ___ rareley occurs
- Rotation, Diffusion, Flip-flop
Proteins and Glycolipids - ____ most relevant parameter of movement
Diffusion
saturated = _______ = ________
better packing less fluid
Unsaturated = _______ = ________
worse packing more fluid
Length of tails short = _______ = ________
less well packed = more fluid
the Distribution membrane of subtypes are
in rafts or islands
An increase in cholesterol will tend to make membranes:
Stiffer/less permeable
Cholesterol and other sterols help control
fluidity, filling in spaces between
phospholipids
________is also important to the formation of ____ ____which are enriched in _____ ______whose diffusion is more limited
Cholesterol, lipid rafts, signaling proteins
what are some ways Proteins play major roles in modulating membrane dynamics and organization
flippases and scramblases
fusion catalysts
‘coupling’ proteins for other proteins
diffusion barriers
New membrane phospholipids are first synthesized and inserted into membranes where
The cytosolic surface of the ER
scramblases catalyzes
the transfer of random phopholipids from one monolayer to another
flippases catayzes
transfer of specific phospholids to cytosolic monolayer
______trafficking helps distribute phospholipids from the ER cytosolic face to other compartments.
Vesicle
Cellular membranes are __________. _______
also generate and maintain this
asymmetric –Flippases
Membranes form largely by ____ docking and fusion – this establishes and asymmetry of the contents
vesicle, polarity
vesticles can be tranfered fron the
Endoplasmic –>golgi
Reticulum vise versa
Glycolipids and glycoproteins occur only or mainly in the ___ ____ of the plasma membrane because of their synthesis on the ___ ___of the Golgi
outer leaflet, interior face
what are some examples of plasma membrane proteins
transporters, ion channels, anchors, receptors, enzymes
3 mechanisms for membrane localizatin of proteins
Integral Membrane Proteins
Lipid anchor addition Peripheral membrane proteins
Integral Membrane Proteins, are ofthen Membrane Associated by
alpha helix or beta sheet presentinga hydrophobic face to the lipid bilayer
in Transmembrane
domains in alpha helices
helices – hydrogen bonds “occupy” dipoles in peptide bonds hydrophobic R groups
Membrane spanning proteins are typically extracted from membranes by using:
Addition of detergents such as SDS
___ ____ can be used to
break protein-protein
interactions,
salts and urea, proteins in the periphery
lectin is a ____ receptor that ________ bind to
adhesion oligosaccarides bind to
proteins in the nucleus can directly go to
er
proteins made in the cytosal can go to what intracelluar comparments
neucleus, chloroplast,mitochondrion,peroxiome, er
