Lecture 4 - Membrane Dynamics Flashcards
What are the six factors that affect diffusion?
-concentration
-temperature
-cross sectional area
-distance
-molecule size
-lipid solubility
What are different types of membrane dynamics?
direct diffsuion
facilitated fissuion
osmosis (via aquaporins)
ion channels
active transport
exocytosis and endocytosis
What does facillitated diffusion transfer?
sugars amino acids organic ions
What does GLUT1 transfer?
glucose++
galactose +
fructose -
-found in many cells
What does GLUT2 transfer?
glucose+
galactose+
fructose+
-high capacity small intestine liver (glucose sensor in pancreatic beta cells)
What does GLUT3 tranfser?
same as glut1
glucose ++
galactose +
fructose -
main glucose transporter in neurons - nerve cells do not store glycogen
What does GLUT4 tranfser?
glucose ++
galactose -
fructose -
insulin responsive in skeletal and cardiac muscle and adipocytes
What does GLUT5 transfer?
glucose -
galactose -
fructose +
many cells such as small intestine and sperm
What are the four primary active transports?
Na+/K+ ATPase
H+/K+ pump
Uniport - Ca2+ ATPase
H+ ATPAse
What are the eight total secondary active transports?
-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
Transepithial glucose transport occurs where?
small intesine or kidney tubule
What does the apical membrane face?
the lumen of an organelle
What does the basal membrane face?
the extracellular fluid
What membrane is the sodium potassium pump usually on?
basal membrane
What membrane is SGLT on?
apical membrane
In what direction does the absorption of glucose take place?
From the lumen of the kidney tubule or small intestine to the ECF
What are the three transport systems involved in the movement of glucose?
- 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
- sodium moves out by the sodium potassium pump
- glucose leaves the cells by GLUT carriers facilitated diffusion
What has the high concentration of glucose and low concentration of sodium?
the epithelial cell
Why does the apical side have microvilli?
to increase the SA
What happens in transpeithelial glucose transport?
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
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
-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
Reabsorption of fluid in colon
eat resisiatnt starch to get short chain fatty acids which cause sodium and chloride reabsorption to prevent excessive fecal output via water
