membrane proteins Flashcards

1
Q

liquid-ordered (Lo) state

A

gel-like state in which all types of motion of individual molecules are strongly constrained

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2
Q

liquid-disordered (Ld) state

A

state in which individual hydrocarbon chains are in constant motion (lateral & rotational)

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3
Q

membrane dynamics

A

at mammalian physiologic temperatures (20-40 C) biological membranes are fluid and are maintained in a transition state between Lo & Ld

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4
Q

membrane proteins facilitate…

A

translocation of individual lipid molecules

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5
Q

flippase

A

(P-type ATPase) moves PE and PS from outer to inner leaflet

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6
Q

floppase

A

(ABC transporter) moves phospholipids from inner to outer leaflet

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7
Q

scramblase

A

moves lipids in either direction, toward equilibrium

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8
Q

membrane proteins are limited in movement by:

A

associating to form large aggregates (patches)
anchoring to internal structures

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9
Q

microdomains (rafts)

A

clusters of cholesterol and sphingolipids that make the bilayer slightly thicker and more ordered than neighboring, phospholipid-rich regions- can be up to 50% of the cell surface

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10
Q

_______________ are central to the ability of biological membranes to undergo fusion with other membranes w/o losing continuity

A

curvature changes

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11
Q

integrins

A

surface adhesion proteins that mediate a cell’s interaction with the extracellular matrix and with other cells
-> carry signals in both directions across membrane
-> heterodimeric proteins composed of two unlike subunits, a & B

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12
Q

cadherins

A

involved in surface adhesion
-> undergo homophilic interactions with identical cadherins in an adjacent cell

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13
Q

selectins

A

have extracellular domains that bind specific polysaccharides on the surface of an adjacent cell
-> requires Ca2+
-> essential part of the blood-clotting process

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14
Q

passive transporters

A

facilitate movement down a concentration gradient, increasing the transport rate
-> process is called passive transport or facilitated diffusion

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15
Q

active transporters

A

move substrates across a membranes against a concentration gradient or an electrical potential; process called active transport

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16
Q

simple diffusion

A

movement of a solute from the region of high concentration to the region of lower concentration

17
Q

membrane potential, Vm

A

a transmembrane electrical gradient that occurs when ions of opposite charge are separated by a permeable membrane

18
Q

transporter proteins reduce the energy of activation for diffusion by…

A

forming noncovalent interactions with the dehydrated solute; providing a hydrophilic transmembrane pathway