ICPP S5 Membrane Permeability

Question 1

What is a semipermeable membrane?

Answer 1

A layer through which only allowed substance can pass.

Question 2

Can hydrophobic molecules pass through membrane?

Answer 2

Yes they diffuse through.

Question 3

How do small uncharged polar molecules pass through membranes?

Answer 3

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

Question 4

How do large uncharged molecules pass through the membrane ?

Answer 4

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

Question 5

Can ions pass through the membrane and why?

Answer 5

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

Question 6

Define permeability coefficient.

Answer 6

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

Question 7

Gases have higher permeability coefficients that water true or false?

Answer 7

True.

Question 8

How can we calculate rate of transport?

Answer 8

J=P(C1-C2)

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

Question 9

What are the roles of transport processes?

Answer 9

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.

Question 10

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

True or false.

Answer 10

False

W

Question 11

Why do proteins not flip-flop?

Answer 11

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

Question 12

What is the model of membrane transport proteins called?

Answer 12

Ping-pong transport.,

Question 13

What is an advantage of ping-pong transport?

Answer 13

Promotes specificity.

Question 14

What are the limitations to ping pong transport”?

Answer 14

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

Question 15

How does depolarisation cause a voltage gated channel to open?

Answer 15

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.

Question 16

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

Answer 16

deltaG=RTloge(C1/C2)

R=gas constant.
T= temperature in kelvin

Question 17

How can we convert from Celsius to kelvin?

Answer 17

Add 273.

Question 18

How can we convert from loge to log10?

Answer 18

Multiply everything by 2.303.

Question 19

How can we calculate deltaG is membrane potentials are involved?

Answer 19

Write it out and check lol too hard to type.

Question 20

If deltaG is less than 0 the process is passive.

True or false?

Answer 20

True.

Question 21

Define active transport.

Answer 21

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

Question 22

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

Answer 22

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

Glucose and galactose transported onto capillary through GLUT2.

Question 23

How does fructose enter and leave the enterocyte?

Answer 23

Enters on GLUT5 leaves via GLUT2.

Question 24

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

Answer 24

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

Question 25

What is the difference between primary and secondary active transport?

Answer 25

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.

Question 26

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

Answer 26

~ 25%

Question 27

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

Answer 27

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

Question 28

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

Answer 28

Na+ K+ ATP and Oubain binding sites.

Question 29

What type of molecule is Oubain?

Answer 29

A cardiac glycoside

Question 30

What is a glycoside?

Answer 30

A sugar bound to another functional group.

Question 31

What is the effect of Oubain?

Answer 31

``` 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. ```

Question 32

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

Answer 32

Mainly regulatory | Guide pump to cell surface.

Question 33

What is fluoxetine’s therapeutic role?

Answer 33

Treats depression OCD and bulimia.

Question 34

What is fluoxetine also known as?

Answer 34

Prozac | SSRI - selective serotonin re-uptake inhibitor.

Question 35

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

Answer 35

True.

Question 36

What is the systematic name for serotonin?

Answer 36

5-HT | 5-hydroxytryptamine

Question 37

How does fluoxetine work?

Answer 37

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.

Question 38

What does CFTR stand for?

Answer 38

Cystic fibrosis transmembrane conductance regulator.

Question 39

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

Answer 39

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.

Question 40

What are the clinical complications associated with CF?

Answer 40

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

Question 41

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

Answer 41

Na Cl K cotransporter.

Question 42

How does infection from Vibro cholerae result in diarrhoea?

Answer 42

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.

Question 43

What transporter moves Cl- into gut epithelium?

Answer 43

Na Cl K transporter.