nutrition And Digestion Flashcards
what enzymes in the small intestine breakdown the disaccharides ?
lactase, sucrase, maltase
what bonds link two monosaccharides ?
glycosidic bonds
where is amylase found ?
saliva and pancreas
how are glucose polymers broken into monosaccharides ?
glucose polymers are broken into dissacharides by amylase in the saliva and pancreas
disaccharides are broken down to monosaccharide by lactase, sucrase and maltase
how does glucose get absorbed into a cell ?
1- glucose and Na+ simultaneously bind to SGLT1 on the apical surface due to sodium electrical chemical gradient
2- this causes a conformational change in SGLT1 and the molecules enter the cell
3- Na+ leaves the cell via the NaK+ pump, glucose leaves the cell by GLUT2
sodium is highly osmotic so this gradient causes water to leak through the tight junctions
how does fructose get absorbed ?
enters the cell via GLUT 5 then leaves the cell via GLUT 2
what are polymers of amino acids linked together by ?
peptide bonds
what molecules hydrolyse peptide bonds and breakdown proteins ?
proteases
peptidases (endopeptidases and exopeptidase)
endopeptidase - breaks molecules from internal amino acids
exopeptidase - breaks molecules from carboxy (carboxypeptidase) and the amino end (amino peptidase)
how can dipeptides and tripeptides enter a cell ?
they can enter the cell using PEPT1 which used proton motive force to drive the molecules in
NHE3 allows H+ to leave the cell and replenishes the H+ concentration outside the cell to allow PEPT1 to continue its job
what does emulsification require ?
mechanical disruption by smooth muscle contraction
emulsifying agents
- bile salts and phospholipids
- amphiphatic molecules (polar and non polar)
what is inside a micelle ?
bile salt, phospholipids, monoglyceride and fatty acids
how small is a micelle ?
4-7 micrometres
how does fat digestion work ?
1- emulsification breaks down the triacylglycerol into droplets using bile salts and phospholipids
2- pancreatic lipase breaks down the droplet further into monoglyceride and fatty acids
3- these go into micelles which are constantly undergoing formation and breakdown
4- the molecules in the micelle move to the acid microclimate and become neutral charge so can diffuse into the cell
how are monoglycerides and fatty acids absorbed in the cell ?
1- enter the SER where they become triacylglycerols again(still coated with amphiphatic protein)
2- transport through the Golgi apparatus in vesicles then exocytosed
3- once outside the cell they become chylomicrons which pass into lacteals between endothelial cells
4- lacteals pass the fat into lymph
what are the fat soluble vitamins ?
Vitamins ADEK
follow same path as fat absorption
what are the water soluble vitamins ?
B,C,folic acid
absorbed by passive transport or carrier-mediated transport
how is B12 absorbed ?
binds with intrinsic factor protein in the stomach
this complex travels to the distal ileum and is absorbed via the specific transport mechanism
what is the B12 deficiency known as ?
pernicious anaemia (failure of red blood cell maturation)
how is iron absorbed ?
1- transported into duodenal enterocytes via DMT1
2- inside the cell they can bind into ferritin or unbound iron can cross the basolateral membrane and bind into transferrin in the blood
what is hyperaemia and anaemia ?
hyperaemia - increased ferritin levels (more iron bound enterocytes)
anaemia - decreased ferritin levels (more iron released into the blood)
