Lecture 1 Flashcards
What form do electrolytes and minerals need to be in in order to absorbed?
in solution in the free ionized form
What is absorbed on the apical membrane of villus cells?
chloride and sodium absorbed down the electrochemical gradient into cells, Na co-transported with amino acids and sugars across the apical membrane
What occurs at the basolateral membrane of villus cells?
Na is actively pumped out across the basolateral membrane into blood, chloride is co-transported across the basolateral membrane with potassium or exchanged for HCO3
How do some ionized atoms get through tight junctions and some do not?
for smaller ionized atoms if the concentration gradient across the tight junctions is great enough, this resistance is overcome and atoms leak through the tight junction
How is sodium transported across the apical membrane in all sections of the small and large intestine?
co-transported with chloride to maintain electrical balance (Na/Cl co-transport and Na/K/2 cl transporter)
How is sodium transported across the apical membrane in the duodenum and the jejunum?
co-transported with sugars and amino acids of the meal
In general how is sodium transported in the apical membrane?
down chemical and electrical gradient
In general how is sodium transported in the basolateral membrane?
against the chemical and electrical gradient
Specifically, what mechanisms transport sodium across the basolateral membrane?
electrogenic pump (3 Na out, 2 K in, cost 1 ATP) and Na and Cl ATPase pump
When does paracellular transport of Cl occur?
in the upper duodenum when Cl exits the stomach in high concentration
Generally, how is chloride transported across the apical membrane?
it moves down the concentration gradient and against the electrical gradient
Specifically, what mechanisms transport chloride in the apical membrane?
it is co-transported with Na, the Cl/HCO3 ATPase pump, and Na/K/2Cl co-transporter
Generally, how is chloride transported across the basolateral membrane?
against the chemical gradient, but down the electrical gradient
Specifically, what mechanisms transport chloride across the basolateral membrane?
co-transported with potassium, chloride channel (if concentration inside of the cell is great enough to help the electrical gradient trying to pull Cl-across) Na/Cl ATPase pump
Generally, how does potassium transport across the apical membrane?
K is going against the chemical gradient, but with the electrical gradient
