Lecture 42 11/28/23 Flashcards
(22 cards)
What are the characteristics of absorption?
-process of moving digested nutrients/water/ions across intestinal mucosa and into bloodstream
-requires transporters for most substances
Which molecules are transported via co-transport with sodium?
-glucose
-amino acids
-vitamins
-bile acids
What allows for basal-lateral facilitated diffusion of glucose?
high glucose conc. within the cell
What are the two types of passive transport?
-transcellular through ion channels
-paracellular through tight junctions
What are the major ions absorbed?
-sodium
-bicarbonate
-potassium
-chloride
What are the mechanisms of sodium absorption?
-co-transport with proteins via secondary active transport
-Na+/H+ exchanger
-simple diffusion through ion channels
What are the characteristics of the Na+/H+ exchanger?
-high H+ drives Na+ exchange
-occurs at the same time as HCO3-/Cl- exchange
-occurs in ileum and colon
What are the mechanisms of chloride absorption?
-HCO3-/Cl- exchange coupled with Na+ transport
-paracellular absorption coupled with sodium co-transport
-direct HCO3-/Cl- exchange without Na+ transport
What are the products of the sodium bicarb. and HCl reaction?
-NaCl
-water
-CO2
What are the steps of bicarbonate absorption?
-H+ and HCO3- are formed in the cell
-H+ is neutralized in the lumen with HCO3-
-Na+ charge balances HCO3- in cell
-Na+ and HCO3- absorbed into bloodstream
What are the characteristics of potassium absorption?
-potassium conc. is often higher than sodium conc.
-as water and other solutes are absorbed, K+ conc. increases
-conc. gradient forms, favoring absorption
-paracellular
-coupled with water absorption
-some active reabsorption in distal colon
Where does sodium co-transport primarily occur?
duodenum and upper jejunum
Where does chloride-coupled sodium absorption primarily occur?
ileum and colon
Where does HCO3-/Cl- exchange occur?
ileum and colon
Where does bicarbonate absorption occur?
ileum and colon
Where does potassium absorption occur?
ileum and colon
What are the characteristics of water absorption?
-passive through osmosis
-can be transcellular through aquaporins
-can be paracellular through tight junctions
What are the basic characteristics of cobalamin?
-central cobalt atom
-synthesized by microbes
-meat-containing diets provide sufficient amounts
What are the characteristics of R-protein/Haptacorrin?
-produced in saliva or gastric juice
-binds to cobalamin in stomach to prevent degradation
-released from B12 in duodenum by pancreatic enzymes
What are the characteristics of vitamin B12 absorption?
-R-protein transfers cobalamin to intrinsic factor in duodenum
-ileum is major site of absorption
-transported systemically with transcobalamin
What is the main function of cobalamin?
function in coenzymes
What are the characteristics of cobalamin deficiency?
-bacterial overgrowth leads to decreases in absorption
-main symptoms are megaloblastic anemia, weight loss, diarrhea, and vomiting
