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ICPP > ICPP S5 Membrane Permeability > Flashcards

ICPP S5 Membrane Permeability Flashcards

1
Q

What is a semipermeable membrane?

A

A layer through which only allowed substance can pass.

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2
Q

Can hydrophobic molecules pass through membrane?

A

Yes they diffuse through.

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3
Q

How do small uncharged polar molecules pass through membranes?

A

They can git through the gaps in between the phospholipid molecules.

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4
Q

How do large uncharged molecules pass through the membrane ?

A

They are too large to pass through and therefore their diffusion must be facilitated.

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5
Q

Can ions pass through the membrane and why?

A

No because ions cant interact with the hydrophobic region of the bilayer.

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6
Q

Define permeability coefficient.

A

Is the volume of a fluid that will flow through a unit cube of porous substance per unit time.

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7
Q

Gases have higher permeability coefficients that water true or false?

A

True.

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8
Q

How can we calculate rate of transport?

A

J=P(C1-C2)

P= permeability coefficient
C1 and C2 = concentration gradients on sides 1 and 2.
J= rate of transport.

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9
Q

What are the roles of transport processes?

A

Maintenance of ionic composition
Maintenance of pH
Regualtion of cell volume
Controlling concentration of metabolic fuels and biosynthetic precursors.
Excretion of metabolic waste and toxic substances.
Generation of ion gradient needed for electrical excitation.

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10
Q

It is thermodynamically likely that a protein will flip-flop.

True or false.

A

False

W

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11
Q

Why do proteins not flip-flop?

A

Too much energy required - large.
Disrupt the bilayer
Transport protein function would be randomly reversed.

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12
Q

What is the model of membrane transport proteins called?

A

Ping-pong transport.,

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13
Q

What is an advantage of ping-pong transport?

A

Promotes specificity.

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14
Q

What are the limitations to ping pong transport”?

A

Takes time for binding, conformational change and reversal back to native conformation to occur.

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15
Q

How does depolarisation cause a voltage gated channel to open?

A

They contain +ve AA residues on the intracellular portion of the channel.
As cell membrane depolarises these AA residues are repelled away from the intracellular region.
Causes channel to open.

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16
Q

What equation can we use to determine whether a process is active or passive?

A

deltaG=RTloge(C1/C2)

R=gas constant.
T= temperature in kelvin

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17
Q

How can we convert from Celsius to kelvin?

A

Add 273.

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18
Q

How can we convert from loge to log10?

A

Multiply everything by 2.303.

19
Q

How can we calculate deltaG is membrane potentials are involved?

A

Write it out and check lol too hard to type.

20
Q

If deltaG is less than 0 the process is passive.

True or false?

A

True.

21
Q

Define active transport.

A

The movement of ion or molecules against a concentration or electrical gradient.

22
Q

Describe how glucose/ galactose is absorbed in the small intestine.

A

SGLT - symport - Na and glucose into enterocyte.
Na+ pumped into capillary - Na K ATPase.

Glucose and galactose transported onto capillary through GLUT2.

23
Q

How does fructose enter and leave the enterocyte?

A

Enters on GLUT5 leaves via GLUT2.

24
Q

What are the electrolyte levels of Na+, K+, Cl- and Ca2+?

A

Na+ - 145mM
K+ - 4.5mM
Cl- - 123mM
Ca2+ - 1-1.5mM

25
Q

What is the difference between primary and secondary active transport?

A

Primary active transport - energy directly from ATP whereas secondary active transport energy is derived from energy that has been stored in the form of an ionic concentration gradient.

26
Q

What percentage of basal metabolic rate is used to keep Na K ATPase working?

A

~ 25%

27
Q

What does ATP hydrolysis when associated with Na K ATPase lead to?

A

Phosphorylation of an Asparginie AA residue on alpha sub unit of the ATPase.

28
Q

What binding sites does the alpha subunit of Na K ATPase contain?

A

Na+ K+ ATP and Oubain binding sites.

29
Q

What type of molecule is Oubain?

A

A cardiac glycoside

30
Q

What is a glycoside?

A

A sugar bound to another functional group.

31
Q

What is the effect of Oubain?

A 
Inhibits Na K ATPase. 
Leads to [Na+] in cell increasing. 
Reduction in NCX activity results 
Intracellular calcium rises. 
Leading to higher cardiac contractility and increased cardiac vagal tone aka decreased heart rate.
32
Q

What is the role if the beta subunit Na K ATPase?

A

Mainly regulatory

Guide pump to cell surface.

33
Q

What is fluoxetine’s therapeutic role?

A

Treats depression OCD and bulimia.

34
Q

What is fluoxetine also known as?

A

Prozac

SSRI - selective serotonin re-uptake inhibitor.

35
Q

Functional decrease in activity of amines such as serotonin and NA results in depression.

True or false.

A

True.

36
Q

What is the systematic name for serotonin?

A

5-HT

5-hydroxytryptamine

37
Q

How does fluoxetine work?

A

Inhibits 5-HT reuptake transporter SERT which symports5-HT back into presynaptic neurone along with Na+ ions.
Inhibition of SERT - increased interaction between 5-HT and serotonin receptors.

38
Q

What does CFTR stand for?

A

Cystic fibrosis transmembrane conductance regulator.

39
Q

Why do mutations in the CFTR gene result in thickened mucus?

A

Cl- not transported out into lumen and accumulates in the epithelium and therefore retains water along with it.

This means mucus is not sufficiently hydrated.

40
Q

What are the clinical complications associated with CF?

A

Thickened mucus
Frequent respiratory infections
Pancreatic insufficiency due to thick mucus blocking the ducts- diabetes and malnutrition

41
Q

What transported brings Cl- from the interstitium into the lung epithelia?

A

Na Cl K cotransporter.

42
Q

How does infection from Vibro cholerae result in diarrhoea?

A

Releases a toxin that ends up resulting in increased phosphorylation of PKA.
PKA phosphorylates CFTR increasing its activity.
CFTR pumps out Cl- and along with it H+ into gut lumen means more water is lost in the faeces.

43
Q

What transporter moves Cl- into gut epithelium?

A

Na Cl K transporter.

ICPP (17 decks)

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