Lecture 4 - Membrane Dynamics

Question 1

What are the six factors that affect diffusion?

Answer 1

-concentration
-temperature
-cross sectional area
-distance
-molecule size
-lipid solubility

Question 2

What are different types of membrane dynamics?

Answer 2

direct diffsuion
facilitated fissuion
osmosis (via aquaporins)
ion channels
active transport
exocytosis and endocytosis

Question 3

What does facillitated diffusion transfer?

Answer 3

sugars amino acids organic ions

Question 4

What does GLUT1 transfer?

Answer 4

glucose++
galactose +
fructose -
-found in many cells

Question 5

What does GLUT2 transfer?

Answer 5

glucose+
galactose+
fructose+
-high capacity small intestine liver (glucose sensor in pancreatic beta cells)

Question 6

What does GLUT3 tranfser?

Answer 6

same as glut1
glucose ++
galactose +
fructose -
main glucose transporter in neurons - nerve cells do not store glycogen

Question 7

What does GLUT4 tranfser?

Answer 7

glucose ++
galactose -
fructose -
insulin responsive in skeletal and cardiac muscle and adipocytes

Question 8

What does GLUT5 transfer?

Answer 8

glucose -
galactose -
fructose +
many cells such as small intestine and sperm

Question 9

What are the four primary active transports?

Answer 9

Na+/K+ ATPase
H+/K+ pump
Uniport - Ca2+ ATPase
H+ ATPAse

Question 10

What are the eight total secondary active transports?

Answer 10

-3 sodium in 1 calcium out
-one sodium in one h+ out
-one chloride in one bicarbonate out (can go either way depending on concentration)
-one sodium in and one chloride in
-one sodium in, 2 chloride in, ine K+ in
-one potassium out one chloride out
-one sodium in and sugars amino acids and neurotransmitters in - SGLUT

Question 11

Transepithial glucose transport occurs where?

Answer 11

small intesine or kidney tubule

Question 12

What does the apical membrane face?

Answer 12

the lumen of an organelle

Question 13

What does the basal membrane face?

Answer 13

the extracellular fluid

Question 14

What membrane is the sodium potassium pump usually on?

Answer 14

basal membrane

Question 15

What membrane is SGLT on?

Answer 15

apical membrane

Question 16

In what direction does the absorption of glucose take place?

Answer 16

From the lumen of the kidney tubule or small intestine to the ECF

Question 17

What are the three transport systems involved in the movement of glucose?

Answer 17

1. the SGLT-mediated secondary active transport of glucose with Na+ from the lumen into the epithelial cell at the apical membrane followed by the movement of glucose and sodium out of the cell into the ECF
2. sodium moves out by the sodium potassium pump
3. glucose leaves the cells by GLUT carriers facilitated diffusion

Question 18

What has the high concentration of glucose and low concentration of sodium?

Answer 18

the epithelial cell

Question 19

Why does the apical side have microvilli?

Answer 19

to increase the SA

Question 20

What happens in transpeithelial glucose transport?

Answer 20

from the lumen of the kidney tubule or small intestine via SGLUT1 sodium comes into the epithelila cell woth glugocse and then glucose levaes the epithelial cell to the ECF into the blood via GLUT2
-sodium leaves the epithelial cell into the ECF vioa the sodium potassium pump against its ocncentration gradient
-potassium comes in via the pump but then leaves via a potassium channel if it is teh small intestine potsassium can leave via a channel; on the apical membrane into the lumen of the small intestine down its concentratioon gradient but if it is the kidney this will not happen cause do not want to get rid of potassium

Question 21

In a type II alveolar cell to make mucusu you bring in sodium two chlorides and potassiium and cAMp and PKA and phosphorylate chliride channel on apical membrane and bring chloiride into mucus and sodium comes in via paracellula trasnprot and water follows and make mucus - in CFTR there is no phosphorylation so teh mucus is stagnant

Answer 21

-in the colon cholera and e coli strains have adapted and evolved the mechanism to spread through host populations by inducing diarrhea which are watery stools which have these bacteria to contaminate water and food and environment - so these bacteria strongly phsopahorylate the chloride channel so they are open all the time and the toxins they produce cause the channels to open for longer and this causes sodium and chloride and water to leave and cholera is 50% death rate due to hyponatremia due to excess secretion of sodium and cause diarhhea

Question 22

Reabsorption of fluid in colon

Answer 22

eat resisiatnt starch to get short chain fatty acids which cause sodium and chloride reabsorption to prevent excessive fecal output via water