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ESA 2 > M+R > Flashcards

M+R Flashcards

1
Q

What are the important functions of membrane bilayers

A

Highly selective, permeable barrier

Control of the cellular environment

Communication

Recognition

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2
Q

What is the rough composition of the membrane bilayer?

A

40% lipid
60% protein
1-10% carb

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3
Q

What type of bonding allows phospholipids to form bilayers?

A

VDW forces, hydrophobic interaction, hydrogen bonding

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4
Q

What are the four types of motion possible in a phospholipid bilayer?

A

Flexion
Rotation
Laterial diffusion
Flip flop

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5
Q

What type of double bond is common in the fatty acids of phospholipids? What effect does this have?

A

Cis - introduces a kink

Reduces membrane packing, so fluidity is increased

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6
Q

What is the most common head group?

A

Choline

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7
Q

What is sphingomyelin?

A

The only phospholipid not derived from glycerol - phosphocholine group can be replaced by a sugar to produce a glycolipid

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8
Q

What is a cerebroside?

A

A glycolipid with one sugar head monomer

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9
Q

What is a ganglioside?

A

A glycolipid with multiple sugar head monomers

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10
Q

What is cholesterol’s role within the bilayer?

A

To maintain the correct fluidity, both:

  • forms interactions with hydrophobic fatty acids to decrease fluidity
  • reduces phospholipid packing to increase fluidity
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11
Q

What are the functions of membrane proteins?

A

Relating signals between the internal and external environment of the cell
Transportation of ions/molecules across the membrane
Cellular adhesion

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12
Q

How can peripheral proteins be removed?

A

Changes in pH or ionic strength

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13
Q

How can integral proteins be removed?

A

Detergents, or substances which compete for non polar interactions

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14
Q

What is the evidence for membrane proteins?

A

Functional - facilitated diffusion, ion gradients, specificity of cellular response
biochemical - membrane fractionation and freeze fracture

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15
Q

What motion is possible for membrane proteins?

A

Conformational change
Rotational
Lateral

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16
Q

What motion is not possible for membrane proteins and why?

A

Flip flop - not energetically possible and would destroy the membrane and the protein would not function (asymmetry)

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17
Q

Why are proteins more restricted in their mobility?

A 
Size
aggregation to other proteins
tethering to EC matrix or IC cytoskeleton
interactions with other cells
lipid mediated effects (cholesterol)
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18
Q

What is protein topology?

A

The orientation of a protein - essential for proper function

19
Q

Which proteins involved in the erythrocyte cytoskeleton are integral?

A

Band 3 and glycophorin A

20
Q

Which proteins involved in the erythrocyte cytoskeleton are peripheral?

A 
Spectrin
Actin
Ankyrin
Adducin
Band 4.1
21
Q

How does membrane protein synthesis differ from the normal synthesis of a secretory protein?

A

Presence of a strop transfer signal which releases the membrane protein from the protein translocator into the lipid bilayer, so that synthesis continues in the cytoplasm

22
Q

What are the two types of haemolytic anaemias?

A

hereditary spherocytosis is a depletion of spectrin by 40-50% so that the erythrocyte shape is distorted and is lysed

Hereditary elliptocytosis is an ability to form spectrin a2b2 heterotetramers so the erythrocytes are elliptical shaped

23
Q

What types of molecules can diffuse through the plasma membrane?

A

Hydrophobic molecules (resp gases) and small uncharged polar molecules (water)

24
Q

What types of molecules cannot diffuse through the plasma membrane?

A

Large uncharged polar molecules (glucose)

Ions

25
Q

What does the rate of diffusion depend upon?

A

The concentration gradient and the permeability of the barrier

26
Q

I/O concs of Na+

A 
I = 12mM  
O= 145mM
27
Q

I/O concs of K+

A

I= 155mM

O=4mM

28
Q

I/O concs of Cl-

A

I=4mM

O=123mM

29
Q

I/O concs of Ca2+

A

I=10-7M

O=1.5mM

30
Q

Compare the rate of simple and facilitated diffusion

A

Facilitated is faster - however it is saturable and so produces a hyperbolic curve (conc of substrate v rate)

31
Q

delta G in passive diffusion

A

negative

32
Q

delta G in active diffusion

A

positive

33
Q

what is primary active transport?

A

Energy from hydrolysis of ATP is directly used

34
Q

what is secondary active transport?

A

Energy from provided from the movement of a more thermodynamically favourable molecule - in a cotransporter

35
Q

what is a uniport/symport/antiport

A

uniport - one species
symport - same direction of two species
antiport - different direction of two species

36
Q

How is Na+ K+ ATPase activated?

A

phospohrylation of aspartate residue of alpha subunit

37
Q

What is the function of the beta subunit?

A

targeting of the protein

38
Q

Compare the affinity of PMCA/SERCA/NCX

A

NCX = lower affinity but higher capacity - main transport of ions
PMCA/SERCA have high affinity but low capacity and so transport residual ions

39
Q

When can the reversibility of NCX be dangerous?

A

ischemia > low O2 > low ATP > Na+ K+ pump cannot function > Na+ builds up intracellularly > depolariaztion > NCX reverses > calcium enters

40
Q

What two transporters are mainly involved in maintenance of pH?

A

Na+ H+ exchanger

Cl- HCO3- exchanger

41
Q

How is the control of intracellular pH regulated?

A

any deviation from the ‘set point’ pH will stimulate activity of the necessary transporter

42
Q

How is the resting membrane potential maintained?

A

Na/K+ pump removes Na+ from cell - membrane is impermeable to Na+. K+ builds up in the cell but then diffuses out via a K+ channel
producing a negative membrane potential of -70mV

43
Q

How is bicarbonate reabsorbed in the proximal tubule?

A

NaHCO3 in proximal tubule splits into Na+ and HCO3-. Na+ enters the epithelial cell via NHE, and then into the capillary via an Na+K+ pump
HCO3 combines with H+ to form H2O and CO2, and then diffuses into the epithelial cell
The two molecules recombine to produce HCO3- and H+ again. HCO3- enters the capillary via the anion exchanger

44
Q

How is Na+ absorbed in the cortical collecting duct?

A

Aquaporins remove any remaining water from the filtrate
Na+ enters the epithelial cell via ENaC, then into the capillary via Na+H+ pump
Spironolactone can be used to reduce water absorption - anti diuretic?

ESA 2 (4 decks)

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