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Biochemistry and Cell Biology Semester 1 > Membrane Transport > Flashcards

Membrane Transport Flashcards

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1
Q

features of membrane

A

thin film of lipid and protein held by covalent attractions
lipid bilayer
5nm
impermeable barrier

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2
Q

fatty acids and lipids structure

A

long hydrocarbon with carboxyl one end and methyl other
free or covalent bonds to glycerol

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3
Q

phospholipid structure

A

typical bilayer
2 fatty acids covalently bonded to glycerol (1 unsaturated)
3rd hydroxyl group on glycerol bonded to phosphate

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4
Q

what is phosphate bonded to in a phospholipid

A

choline
ethanol amine
serine

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5
Q

amphipathic

A

hydrophobic head and hydrophilic tail
(fatty acid non polar uncharged, phosphate polar and charged)

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6
Q

thermodynamics and bilayers

A

polar dissolve = energetically favourable = more disordered / increased entropy
non polar opposite

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7
Q

formation on bilayer due to amphipathic nature

A

avoids water exposing the head causing a cage and energetically favourable (all spontaneously form sealed compartments)

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8
Q

why are bilayers dynamic

A

phospholipids can move laterally, flex and rotate

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9
Q

what regulates fluidity

A

low temp = phase transition = rigid and packed closer together

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10
Q

how is ridgity prevented

A

by cis double bonds and cholesterol

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11
Q

cis double bonds

A

causes a kink as double bind on same side so cant be rigid and is thinner

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12
Q

cholesterol

A

steroid ring region of cholesterol stiffens upper region of fatty acid chain = immobilised, less able to move laterally, less fluid

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13
Q

issue of too much cholesterol

A

prevent phospholipid compacting together and too rigid

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14
Q

what are lipid rafts

A

randomly distributed
van der Waals not string enough to hold molecules together
sphingolipids are long saturated getting closer together and attract forces strong enough to hold adjacent molecules

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15
Q

purpose of lipid rafts

A

independent monolayers can interact with each other in lipid rafts
proteins congregate here to prepare for transport

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16
Q

glycoproteins

A

proteins glycosylated in RER and golgi

17
Q

glycolipids

A

lipids from SER glycosylated in golgi

18
Q

where are glycoproteins and lipids found

A

non cytoplasmic side of membrane = cho coating = protective

19
Q

what % of nuclear genome encodes membrane proteins

A

20

20
Q

examples of membrane proteins

A

alpha helix
single pass
multi pass
transmembrane proteins
beta sheet
covalently bonded to lipid
embedded into membrane
peripheral membrane proteins

21
Q

what is it called when membranes are coated in carbohydrate

A

glycocalyx

22
Q

how do non polar molecules get transported across membranes

A

diffuse across

23
Q

how do small uncharged polar molecules get transported across membranes

A

slowly diffuse

24
Q

how do large uncharged polar molecules get transported across membranes

A

probably with transporter

25
Q

how do ions molecules get transported across membranes

A

need mechanism

26
Q

membrane transport proteins

A

transmembrane multi pass proteins (no contact with hydrophobic core) allowing ions through

27
Q

carrier proteins

A

bind solute and undergo conformational change to transfer

28
Q

channel proteins

A

interact only weakly with solute from aqueous pore they pass through

29
Q

what causes an electrochemical gradient

A

ions (have a concentration and charge)

30
Q

active transport - coupled carriers

A

symporters (same direction) and antiporters (opposite direction)

31
Q

coupled carriers - symporters

A

electrochemical gradient = stored energy
transports ion = releases free energy
used to pump molecules eg glucose in same direction against conc gradient by a conformational change in shape

32
Q

coupled carriers - antiporters

A

eg malate moves in against while kept out with gradient causing malate to move in

33
Q

active transport - ATP driven pumps

A

Na K pump.
uses free energy from atp hydrolysis to actively pump out 3 k and 2 Na in by a phosphate group attaching causing a conformational change in shape

34
Q

2 types of active transport

A

coupled carriers
atp driven pumps

35
Q

channel proteins

A

form pores
can cause poor regulation
can be gated
transport ions by facilitated diffusion

36
Q

how is acidity of lysosomes maintained

A

pumping of H ions across membrane by ATPase pump

37
Q

what types of gated channels are there

A

voltage
ligand extra or intracellular
mechanically

Biochemistry and Cell Biology Semester 1 (12 decks)

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