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.
true or false
proteins do flip-flop across membrane.
false
Such movement would be energetically unfavorable.
Many receptors in the plasma membrane are anchored through a single ___
alpha-helical transmembrane segment
Most transporters of solutes, pumps and channels are formed of ___ going through the membrane.
multiple (6-24) alpha-helical segments
___ for translocation of proteins through membranes consist of multiple (8 and 12) strands of beta-sheet structures.
Aqueous channels
8 and 12 strand transmembrane ____ are preferred transmembrane pores for translocation of proteins and large molecules through mitochondrial and ER membranes.
beta-barrels.
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)
Plasma membranes determine the ___, ___ and also the biological properties of cells.
size, shape
Plasma membranes of ____, exhibit a special type of architecture and cytoskeletal attachment needed for a high degree of flexibility.
erythrocytes (red blood cells),
Unlike red blood cells which are independent, free floating units, most animal cells are organized into ___
multicellular arrays that form solid tissues
___ are said to be polarized as different regions of these cells are specialized to carry out different function
Epithelial cells
The epithelial cells of pancreatic acinus and intestinal microvilli are two such examples.
Erythrocyte plasma membrane is highly ___ yet ___ to survive multiple long journeys from the lung to various tissues.
flexible
durable
The cytoskeleton of erythrocytes is a complex mesh or net like structure underneath the plasma membrane consisting of fibrous rod like proteins called ___
spectrins
Membrane associated cytoskeletal protein networks are involved in the control of erythrocytes ___, attachments to other cells and to the substrate.
shape,
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
Ankyrin attaches to
transmembrane protein Band 3 (anion exchanger protein)
Band 4.2 (palladin) helps stabilize the link between ankyrin and the anion exchanger.
Spectrin is also linked to a transmembrane protein called glycophorin C (25 kDa) by the protein known as ankyrin.
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)
spur cells or
acanthocytes
___ are irregular shaped erythrocytes with spiny projections
Acanthocytes
Acanthocytes can occur from an increase in ____content or from the presence of abnormal plasma lipoprotein composition.
blood cholesterol
A disproportionately high cholesterol in the outer leaflet of plasma membrane causes a disproportionately larger size of the outer leaflet, which is believed to be the cause of the disease.
In acanthocytes, a disproportionately high ____ in the outer leaflet of plasma membrane causes a disproportionately larger size of the outer leaflet, which is believed to be the cause of the disease.
cholesterol
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
Unlike the free floating erythrocytes, the pancreatic ___ cells are anchored on a basal membrane and form the epithelial layer of an ___.
acinar
acinus
Pancreatic acinar cells, In response to hormonal signals (cholecystokinine and secretin) will excrete ___ and ____ that are important in digestion.
zymogens
bicarbonate
Pancreatic acinar cells
The basolateral side of the cells lining the ___ (basal membrane) receives signals and the apical region, which is facing the acinus carries out the ____ function.
blood vessel
secretory
cells with distinctly different functional and structural domains at different parts of the cell surface are called____
polarized cells.
Erythrocytes, are ___ cells , since the functional membrane domains are evenly distributed around the cell surface.
non-polarized
____ and ____ are secreted into the blood stream from the intestinal mucosal cells to signal the incoming food material. The hormones travel through the blood stream and signal the pancreatic acinar cells to excrete zymogens and bicarbonate.
Cholecystokinine
secretin
