Absorption of Water soluble molecules Flashcards
What are carbohydrates mainly?
starch and sucrose - dietary ones are glucose polymers, glycogen, cellulose
what does amylase do?
break long glucose polymers into smaller glucose chains and disacc maltose
Where does starch digestion start?
in the mouth with salivary amylase - then denatured by stomach acid
what does pancreatic amylase do?
resumes digestion of starch to maltose
What is maltose broken down by?
intestinal brush border enzymes like maltase, sucrase, lactase
What are absorbable end products of carb digestion?
glucose, galactose and fructose
What is intestinal carb absorption restricted to?
monosaccharides
what complex carbs can we digest and not digest?
can - starch and glycogen
cant - cellulose plant fibre and sucralose cant be digested due to chlorine atoms
what does intestinal glucose and galactose absorption use?
transports such as NA-glucose symporter and basolateral glut2
how does fructose move across the apical membrane?
by facilitated diffusion on glut5 transporter
what proteins are least digestible?
plant , egg is most digestible
What are enzymes for protein digestion groups called?
endopeptidases and exopeptidases
what are endopeptidases?
proteases are zymogens such as pepsin, trpsin and chymotrypsin
what are exopeptidases?
digest terminal peptide bonds to release AA - minly isoenzymes of carboxypeptidase
what are main products of protein digestion?
free AA, dipeptides, tripeptides
what are free AA carried by?
Na dependent cotransport proteins
where are di and tri peptides carried to?
enterocytes on oligopeptide transporter pept1
what are peptides larger than 3 AA absorbed by?
transcytosis after binding to membrane recepters
What is responsible for allergic reactions?
ingested proteins as small peptides can act as antigens
in newborns where are peptide absorption take place?
intestinal crypt cells
what is a common indigestible peptide drug?
DDAVP synthetic vasopressin
what is water soluble vitamins absorbed by?
mediated transport except v b12 as it has cobalt
where is intestinal transporter for b12 found?
only in ileum by protein intrinsic factor
where is mineral absorption done?
by active transport
How is heme iron absorbed?
by apical transporter on enterocyte leves cell on ferroportin
how is iron uptake regulated by the body?
by peptide hormone hepcidin
how is calcium absorbed?
in gut by passive paracellular pathways - regulated in duodenum by VitD3
