epithelial transport

Question 1

Absorbing NaCl and H2O

Answer 1

Na+ is picked up on apical membrane (high permeability) and is transported into the cell. Na/K pump exchanges K and Na. Cl- passively follows Na+ into cell to equalize electrical potential. H2O follows NaCl influx to balance osmolarity.

Question 2

glucose and amino acid absorbtion

Answer 2

Epithelium in GI pumps AA, sugars, and glucose (seconary active transport) through the apical membrane and diffuse out the basolateral side passively into blood. AA and sugars use secondary active transport to go to target cells. Glucose diffuses along concentration gradient.

Question 3

tight epithelia

Answer 3

more junction proteins, tighter seal between cells. Used in distal tubules of kidneys. Strictly control substance transport at lower levers where you don?t want a “backflux”

Question 4

loose epithelia

Answer 4

less juction proteins. Quantity over quality, needs lots of tranporters and is not too picky about equal amounts

Question 5

trans-epithelial potential difference

Answer 5

transPD = Vm (basolateral) - Vm (apical)

Question 6

epithelial cell fluid secretion

Answer 6

chloride-selective channel in apical membrane in some spithelial cells, cAMP-gated on the inside of cell to open and allow the effluc of Cl- back out (takes Na+ and H2O with it). Driven by receptors on the basolateral side triggered by acetylcholine.

Question 7

cystic fibrosis

Answer 7

chloride channels are not properly implanted in cell membrane, thus no dilution of mucus secreations.

Question 8

Cholera

Answer 8

cholera toxin gets into cells and opens the Cl- channels without regulation. Massive efflux of water out of the apical membrane into the epithelial system (diarrhea)

Question 9

4 substances that are never pumped

Answer 9

H2O, O2m CO2, and urea. All move passively dwon concentration gradients

Question 10

CO2 excreation

Answer 10

alveoli of the lungs

Question 11

Urea excretion

Answer 11

urine after being picked up out of blood in the kidneys.

Question 12

kidney

Answer 12

gets rid of non-volatile metabolic wastes and regulates ECF composition by adjusting the activity of the transporters that do the reabsorbing.

Question 13

GI tract

Answer 13

absorbs just about everything presented to it, regardless of the needs of the ECF

Question 14

how kidneys function

Answer 14

forms unltrafiltrate of plasma in the glomerulus (contains H2O, salts, AA, sugars, etc as well as non-volatile metabolic waste). Passes renal tubules, the epithelial cells lining tubules reabsorb the good stuff. Requires loads of ATP

Question 15

CBIGK

Answer 15

treatment for hyperkalemia! Calcium, bicarbonate, insulin, glucose, kayexolate