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Alberts Cell Bio Chapter 10 Lecture 3
Terms in this set (39)
"Sidedness" refers to ___.
the asymmetrical distribution of proteins
Three classes of membrane proteins.
Related to the bilayer they:
a) Integral ___
b) Peripheral ____
c) Lipid-anchored ___
a) Integral --Transmembrane--penetrate bilayer
b) Peripheral --occur outside bilayer attached noncovalently
c) lipid-anchored --occur outside, but attached to (glyco)lipid
In comparison, myelin has _a___ protein than lipids, and the inner mitochondrial membrane has _b__ protein than lipids.
b. much more
Transmembrane proteins have 3 basic structures:
a. single helix
b. several helices
c. beta barrel
"One sided" proteins can be anchored directly to lipids, proteins or carbs--4 types: a-d
b) covalently attached lipid
c) oligosaccharide linker to lipid (GPI anchor)
d) non-covalent binding to anchored protein
How does the attachment of cytoplasmic lipid-anchored proteins differ from the external ones? What are some examples of each?
Cytoplasm --attach by long fatty acid carbon chains
--examples -- signaling mlcls
External surface proteins--are linked to GPI
GPI-anchored proteins have what functions? (GPI= glycosyl-phosphatidylinositol)
--receptors, enzymes, cell adhesion mlcls
Lipoproteins are formed by what kind of bonds?
a fatty acid or prenyl group in the bilayer attaches to the protein.
Integral membrane proteins are ___a___. Why? b
Are these membranes stable out of a membrane? c
a--amphipathic (polar/nonpolar domains)
b--portion within bilayer is hydrophobic, portion in aqueous environment is hydrophilic
c--no, they are unstable d/t hydrophobic regions
A charged AA chain is going to be in which region of an integral membrane protein? a.
How many AAs are in the embedded helix ? b
a. Charged AAs are found near the end of helix in the transmembrane area
b. about 20-30 AA
Examples of hydrophilic uncharged AAs
Ser (S), Tyr (Y), Thr (T), Gln (Q), Asn (N)
Examples of hydrophilic charged AAs
His (H), Asp (D), Lys (K), Glu (E), Arg (R)
Why do polar residues tend to be on surface? a.
Why would they project into hydrophobic region? b.
a. Because of interactions with water
b. To create an enzyme's catalytic activity
Mnemonic for hydrophobic AAs
Frail lovers insert airborne pharmacists when cakes grow mold
A hydropathy plot measures __a__. It predicts _b__, and is useful for only _c_(alpha helix/beta barrel)_.
The x-axis is ___d___ and y-axis is __e__, with the amino terminal on the left side.
b. predicts the regions of potential for protein to span membrane ---20-30 hydrophobic AA in a row
c. Alpha helices
d. the hydropathy index (+ up, - down)
e. the amino acid number
alpha helix channels are formed from _a. __. Example: _a__
Lipase and iron transporter proteins are formed from ___b__.
a. multiple transmembrane domains. aquaporin
b. beta barrels
Multipass transmembrane proteins can be transcribed from 2 different genes. Does the function stop if it is clipped?
No, a protease can cut it and it will still work
Transmembrane proteins can be modified by adding __a__. Where does this occur and on what side of membrane? __b__
b. the ER or golgi will attach the carbs on the non-cytosolic side.
Carbs on cell surface (either glycolipid or glycoprotein) perform what functions?
regulate cell-cel interactions, protect from mechanical damage.
What is a proteoglycan?
The glycoprotein with a polysacc that has an amino sugar.
What function do peripheral proteins do? Are they stationary?
Form the ECM, act as enzymes to carry mlcls along, transmit signals.
They are placed on membrane when needed, then come off.
If salt or a high pH removes a protein, what type of protein is it?
How can an integral protein be removed?
Only by detergents that deaggregates a membrane.
If a protein has a fatty acid attachment, what type of protein is it?
A phospholipid attachment of protein is a _____protein.
A protein that requires phospholipids is NOT a ___ or ____ protein.
Peripheral (attach only to protein --not lipid anchored) or integral.
Membranes can be solubilized by ___.
A strong concentration of detergent will do what to the proteins?
Completely denature the protein (and prevent study)
If a weak concentration of detergent is used, what is possibly formed?
a phospholipid vesicle containing much of the original cell properties.
How is the movement of a protein through the membrane restricted?
Either by ECM domains, or by cortical skeleton proteins (peripheral proteins), assembly of aggregates.
FRAP refers to ____
Flourescent Recovery after Photobleaching. (apply flourescent dye to proteins, and then bleach an area and observe time for diffusion)
What is FLIP? a
What is the limitation of both FRAP and FLIP, and how can it be corrected?b
a--Flourescence loss in photobleaching (continuously hold laser beam on a phospholipid, and observe time for entirety of bleaching.
b--limits becase a large area is affected (so use single particle tracking)
SDS PAGE is an acronym for:
It is used for __.
How does it work?
SDS polyacrylamide-gel electrophoresis.
It uses SDS, a strong ionic detergent to solubilize proteins by binding to the hydrophobic core and applying a negative charge to each protein according to its mass.
Tight junctions restrict protein movement where?
on the exterior apical plan, but not along the basal membrane, and NOT along the inner monolayer.
Proteins move by the action of :
motors attached to membrane,
What is unique about the human RBC?
98% of the cell is plasma membrane
The majority of RBC protein is __a__. It's shape is _b_. What is function? c
c. provides structure
2 other proteins on outer surface of RBC are __a, b_, and used for (respectively)
a. Coupled anion transporter -- creates permeability to bicarb
b. Glycophorin -- bear antigens amoung other things
A limitation of an artificial membrane regarding protein mvmt is __
There is no cortical skeleton which can restrict a protein to a 'grid' area.
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