Chapter 11 Flashcards
Functions of the cell membrane
receiving information, import/export of small molecules, capacity for movement and expansion
Basic structure of the membrane and function
Lipid bilayer; serves as a permeability barrier to most water soluble molecules
which formation of phospholipids is energetically favorable
sealed compartments of bilayer membrane
fatty acid structure
carboxyl group attached to hydrocarbon tail
phospholipid structure
two fatty acid tails attached to a glycerol, which is attached to a phosphate group and a hydrophilic group
which functional group does a hydrocarbon chain need to have to be a fatty acid
carboxyl group (fatty acids are carboxylic acids)
triglyceride polarity
completely nonpolar; hydrophobic; only found in lipid droplets
lipase function
breaks TG into glycerol and fatty acids
saturated fatty acids
no double bonds between C atoms, straight line
monounsaturated fatty acids
1 double bonds between C atoms; causes kink
polyunsaturated fatty acids
2 or more double bonds between C atoms
fatty acid categorization (X:X)
(Carbons: Double Bonds)
what type of hydrocarbon chains are more rigid
saturated (pack tightly) and longer
what type of hydrocarbon chain is more fluid
unsaturated (less packed) and shorter
at a higher temp, mb fluidity is high– to reduce membrane fluidity . . .
longer and more saturated hydrocarbon chains
cholesterol impact on mb fluidity
acts as a buffer; increases fluidity in cold temps, decreases fluidity in warm temps
functions of membrane proteins
transporters and channels, anchors, receptors, and enzymes
integral membrane proteins
directly attached to lipid bilayer, only removable by disrupting membrane (transmembrane, monolayer associated, lipid-linked)
peripheral membrane proteins
attached to integral membrane proteins, can be removed without disrupting membrane bilayer
transmembrane protein
amphipathic; extend through bilayer; single pass or multi-pass; alpha helices or beta barrel
amphipathic helix in a multi-pass membrane protein/monolayer associated protein
hydrophilic side chains on one side of helix, hydrophobic on opposite side
multipass membrane channel structure
alpha helices in rings with hydrophilic side chains pointing in and hydrophobic side chains facing membrane. (act as channels for small hydrophilic molecules)
are alpha helices and beta sheets motifs or domains
motifs
alpha helices form hydrogen bonds within one peptide backbone with amino acids that are ____ amino acids away
4
beta sheets form hydrogen bonds between amino aicds _______
of adjacent peptide backbones
beta barrels are found in what type of protein
porin proteins (water filled pores in mitochondrial and bacterial outer membranes)
beta barrel structure and function
16-stranded beta-sheet in its tertiary structure; hydrophobic side chains on the outside, hydrophilic on the inside
allow small nutrients and inorganic ions across membranes
cell cortex structure
meshwork of fibrous proteins that is attached to cytosolic surface of membrane via anchor proteins
cell cortex function
determines shape and mechanical properties of the cell/PM
cortex is made largely of what protein
spectrin; consists of actin filaments as well; connected to PM by spectrin/transmembrane protein interaction
which part of the bilayer are glycolipids mainly found
non-cytosolic
where do glycolipids acquire their sugar groups
golgi
what is the glycocalyx composed of
sugars attached to both lipids and proteins in the extracellular surface of the PM
glycocalyx function
absorbs water, slimy surface, prevents blood cells sticking to one another/blood vessel walls, cell-cel recognition, motility
oligosaccharides on glycolipids and glycoproteins of neutrophils function
“ID tags” recognized by lectins of endothelial cells lining the blood vessels at infection site, allowing neutrophils through the tissue into infection site
new phospholipids are produced by what
enzymes bound to the cytosolic half of the ER membrane; causing curvature by addition of phospholipids only to cytosolic half
scramblase function
proteins that randomly transfer phospholipids from one monolayer to another, allow symmetric membrane growth
NONSPECIFIC, BIDIRECTIONAL, NO ENERGY required
flippases
enzymes in golgi membrane that remove specific phospholipids from the non-cytosolic side and flip to cytosolic side, making membrane asymmetrical
ENERGY REQUIRED
when vesicles form from an organelle and merge with the PM, how does the orientation of the bilayers change?
It doesn’t, cytosolic side remains cytosolic
how do cells contain proteins in specialized membrane domains on the surface of cells/organelles
anchor to cell cortex
anchor to ECM
surface proteins of 2 cells anchor each other
diffusion barrier restricts diffusion of proteins to certain side of cell
example of a lateral diffusion barrier
cells in the intestine have a side that uptake nutrients, and a side that exports solutes into the bloodstream
apical membrane proteins (uptake) are prevented from crossing to basal domain and vice versa by a tight junction
FRAP
used to measure the rate of lateral diffusion of membrane proteins
FRAP steps
fluorescently labeled (GFP) membrane proteins bleached in small area
fluorescent intensity recovers as unbleached proteins diffuse into area
rate of “fluorescent recovery” is direct measure of rate of lateral diffusion in the membrane
detergents
small amphipathic lipid-like molecules that from phospholipids by only have one tail
how do detergents work
single tail allows them to squeeze into membranes and aggregate into micelles trapping and separating lipids
how are detergents used to solubilize and reconstitute membrane proteins
detergent added to membrane solution, which solubilizes proteins and creates lipid-detergent micelles
protein of interest separated from solution
addition of pure phospholipids/detergent micelles creates protein/artificial bilayer complex
