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
Glucose transporter consists of a cluster of ___ going through the membrane forming a central cavity or pore through which glucose is transported across the plasma membrane
alpha-helixes (10 in some cases)
spectrin
framework of erythrocyte
Two isoforms of spectrin, alpha (260 kDa) and beta (225 kDa), form a loosely wound helix. Two alpha-beta helixes are linked end to end to form a single tetramer, which has binding sites for several other proteins, including other spectrin molecules.
attached to the membrane/outside of cell by ankyrin (band 3)
COOH of one chain attaches to the NH2 of another chain
Framework of RBC
very complicated- attached at multiple points
spectrin tetramers attach to ankyrin and actin
ankyrin attach to band 3 and glycophorin C
band 4.2 helps ankyrin attach to band 3
Band 4.1 and adducin helps actin attach to spectrin
actin, tropomyosin and tropomodulin all form together with help from Band 4.9 (dematin)
Acanthocytosis
liver disease, anorexia, cystic fibrosis, and hypothyroidism.
It also is linked with hereditary neurological disorders neuroacanthocytosis.
In cirrhotic liver disease, the liver produces abnormal lipoproteins with a high cholesterol content. This excess cholesterol is readily transferred to the outer hemileaflet of the erythrocyte cell membrane, resulting in the formation of flat scalloped cells.
This cellular deformity ultimately leads to destruction of acanthocytes by the spleen and, consequently, an extravascular hemolytic anemia.
Another serious condition associated with acanthocytosis in dogs is hemangiosarcoma.
band 3
transmembrane protein-
14 turns
NH3 end -extends into cytoplasm and has binding sites for ankyrin and band 4.1, glycolytic enzymes and hemoglobin
has glycoprotein attached on outside (oligosaccharide)
spectrin tetramers attach to ankyrin and actin
ankyrin attach to band 3 and glycophorin C
band 4.2 helps ankyrin attach to band 3
Band 4.1 and adducin helps actin attach to spectrin
actin, tropomyosin and tropomodulin all form together with help from Band 4.9 (dematin)
in systemic capillaries in red blood cells
outside of RBC high CO2 , Low O2
CO2 comes into RBC
CO2(carbonic anhydrase)= H+ and HCO3-(bicarbinate)
H+ will bind to N of histone of heme- will let go of O2 and will leave cell
HCO3- will leave cell and Cl- will enter cell (by band 3 protein)
in pulmonary capillaries in red blood cells
outside of RBC low CO2 , high O2
O2 comes into RBC
O2 binds to heme- H+ will get kicked off the N
HCO3- will come into cell and Cl- will leave cell (by band 3 protein)
H+ and HCO3- (Carbonic anhydrase) = H20 and CO2
CO2 leaves cell
