Lecture 3: membrane transport III

Question 1

what things set up resting gradient for Sodium?

Answer 1

3Na/2K+ potassium pump (ATP)

Question 2

what things set up the resting gradient for calcium?

Answer 2

Ca-H pump and
Na/Ca exchanger
they keep intracellular calcium 4x lower

Question 3

what do change in cell volume do?

Answer 3

1. disrupt structural integrity which is important for ion channels
2. alter intracellular environment

Question 4

how does volume change affect function?

a) changes in intracellualr
b) changes in extracellular

Answer 4

a) intracellular:
metabolism, transport, and drugs
think TMD is inside your life (like TMZ) where d is for drugs bc celebs do drugs

b) extracellular: excessive water intake or loss, hormones, disease

Think HEED

Question 5

which things increase volume of cell (5) i.e. think about things that will let water move in

Answer 5

1. Na/H pump where Na comes in and H goes out
2. Cl/ HCo3 pump where Cl comes in and HCo3 goes out
3. K,Na, CL cotransporter where all come in. Na and CL go with gradient*** MOST EFFECTIVE esp for renal function

Question 6

which ion channels decrease cell volume (3)

i.e. think about things that will let water move out

Answer 6

1. Cl
2. K
3. K/CL co

Question 7

Na+/H+ exchanger

Cl/HCO3 exchanger

Answer 7

1 sodium in and 1 H out as sodium goes down gradient

Cl out and HCO3 in as CL goes down gradient

Question 8

What is IP3 receptor. where is it?

Answer 8

The IP3 receptor is a ligand-gated ion channel. When IP3 binds the receptor a calcium channel opens that allow calcium to diffuse down it’s concentration gradient from the ER to the cytosol.

Question 9

what is Ryandone receptor. where is it?

Answer 9

The way the ryanodine receptor works depends on the cell. In skeletal muscle, the ryanodine receptor is physically associated with the dihydropyridine receptor/voltage-gated calcium channel. When the cell is depolarized the ryanodine receptor opens to allow calcium to flow into the cytosol. In other cells, the ryanodine receptor is a calcium-sensitive calcium channel. Increases in cytosolic calcium will open the ryanodine receptor and let calcium flow from the ER into the cytosol.

Question 10

what things bring pH up by decreasing H concentration (4)

Answer 10

1) Na-H exhcanger
2) Na/HCO3 cotransporter
3. Na driven Cl/HCO3
4. voltage gated H pump (uses AtP)

Question 11

what things lower pH (3)

Answer 11

1. metabolism
2. Cl/HCO3 co exchanger bc Cl in and HCO3 out
3. Na/HCO3 bc sodium in and HCO3 out

Question 12

why do we have a blood brain barrier

Answer 12

bc capillaries have low permeability in the brain

Question 13

mechanisms for sodium ___ in proximal convoluted tubule

Answer 13

reabsorption of sodium

1. na/k atp ase pump
2. Na/HCO3 1:2 ratio cotransporter
3. Na/H exchanger

Question 14

what are ways / channels through which nutrients are absorbed in intestine?

Answer 14

1. na/amino acid cotransporter
2. H+/peptide cotransporter
3. aa transporter
4. na/k atpase transporter
5. endocytosis

Question 15

what are the channels in parietal cell of stomach

Answer 15

need to pump H into the lumen for acidic breakdown so use K/H which is atpase bc K is going against gradient

also have cl being pumped so that water will follow i guess which uses Cl/Hco3 where Cl enters lumen

Question 16

what are the channels in intestinal epithelial cell?

Answer 16

na/glucose symport while sodium goes down its gradient bc Na/K atpase pulls sodium out to keep that gradient. sodium and glucose make way to capillary

Question 17

what happens intracellularly during ischemi

Answer 17

ischemia causes decreased ATP supply. get products of ATP that build up and cause acidity.
So now Na/H is hyper activated and accumulate intracellular sodium.

intracellular sodium reverses the na/ca tranposrter such that instead of na enter the cell, it leaves the cell and calcium unders the cell.

Question 18

what is trnaseptithelial / endothelial transport?

Answer 18

transport across a layer of epithelial cells or endothelial cells

Question 19

Which of the following will double the permeability of a solute in a lipid bilayer?
A. Double the molecular radius of the solute
B. Double the oil/water partition coefficient of the solute
C. Double the thickness of the bilayer
D. Double the concentration difference of the solute across the bilayer

Answer 19

Increasing oil/water partition coefficient increases solubility in a lipid bilayer and therefore increases permeability.
Increasing molecular radius and increased membrane thickness decrease permeability.
The concentration difference of this solute has no effect on permeability.
Flux ∝ (D)(S.A.)(Conc. Difference)