Test 2 Lecture 26-27 Flashcards
Biological membranes consist of lipid bilayers that are formed mostly through ___ lipids interacting through hydrophobic interaction.
amphipathic ( having both hydrophilic and hydrophobic parts)
Membrane lipids include ___, ___ and ___
Phospholipids, Sphingolipids and cholesterol
Cholesterol plays a dual role in membrane fluidity and excess cholesterol reduces fluidity
and affects protein function.
At high temp- prevents melting
At low temp- prevents freezing
Excess cholesterol causes the formation of ___ with spiny projections in a disease called ___
erythrocytes
acanthocytosis.
Red blood cell membrane contain CO2/HCO3- antiporter, which is critical in maintaining
the ____
blood pH.
Plasma membrane of pancreatic acinar cells is polarized with respect to protein
function—the side facing the exterior of acini, facing the ____, are designed to
receive signals while the other end facing the ___ of acini are designed to secrete
digestive enzymes and bicarbonate.
blood vessels
lumen
Lipids, carbohydrates and ____ are the most common constituents of biological membranes.
proteins
Carbohydrates are invariably associated with the ___ side of plasma membranes and ___ of endoplasmic reticular (ER) and golgi membranes.
exterior interior (lumen)
While the lipid bilayer provides a valuable barrier separating the extra- and intra-cellular ____, the membrane proteins are responsible for its dynamic properties.
compartments
Thus, although every membrane has the same basic structure of a phospholipid bilayer, a different set of ____enables each subcellular membrane to carry out its distinctive function.
membrane proteins
Membrane lipids are ___ molecules and spontaneously form a bilayer in an aqueous environment such that the ___ heads are exposed to the aqueous medium while the ___ tails are facing the core of the bilayer which contains very little or negligible water
amphipathic
hydrophilic
hydrophobic
The lipid bilayers provide an ___ barrier for various solutes, hydrophilic or charged compounds in addition to housing various functionally important proteins.
impermeable
In the lipid bilayer, the proteins are organized either as intrinsic (____) or extrinsic depending on their function
transmembrane
Three major classes of lipids generally found in the animal cell membranes are ___, ____ and ____
phospholipids (phosphoglycerides),
sphingomyelins, gylcolipids,
cholesterol
The ___ of biological membranes is determined by the nature of phospholipids and also the cholesterol contents.
fluidity
Phospholipids and sphingomyelin contain an ___ backbone with two attached fatty acid chains.
alcohol (glycerol) or ether
The length of the fatty acid chains and the degree of saturation are important factors in ___
membrane fluidity.
shorter bent= more fluidity more water
long straight= less water, more rigid
How does cholesterol effect membrane?
prevents freezing or melting of membrane
structure of phopspholipids vs sphingomyelin
sphingomyelin: straight chain of C
C attached to N
saturated hydrocarbon chains of phospholipids have a ___ membrane when compared to a unsaturated hydrocarbon chain with cis- double bonds
thicker, less flexible
___ spontaneously form a bilayer which assumes an energetically favorable conformation of an ___ with an aqueous interior. These enclosures can be quite extensive depending on the type of membrane.
Membrane lipids
enclosed structure
Membranes are ___ in that each leaflet of the bilayer contains different lipid composition.
asymmetric,
The ___ of gylcoproteins are on one face: projected outside in the case of plasma membranes, and projected to the luminal side in the case of endoplasmic reticulum and Golgi
carbohydrate groups
Similarly each membrane protein assumes a specific orientation with respect to cytoplasmic and exoplasmic of a cellular membrane depending on its _____
amino acid sequence.
