Green - Digestion And Absorption Of Carbs And Proteins Flashcards
Enzymes that cleave starches
Alpha-amylases
Rumbling or gurgling noise produced by the movement of gas thru the intestines
Borborygmi
Peptide produced by the liver that regulates iron transport from enterocytes
Hepcidin
Glucose and galactose absorbed into enterocytes by common Na-Dependent active transport system _____
SGLT-1
Why can your body use an Na cotransporter to move glucose and galactose into the enterocytes?
The intracellularNa is kept low by a Na-K ATPase, making a gradient for absorption
Fructose is absorbed exclusively by?
Facilitated diffusion
Explain the mechanism of lactose intolerance
Insufficient lactase to breakdown and absorb lactose. Lactose remains in GI tract. Water stays there with it (diarrhea)
This lactose is then digested by bacteria —> gas, distention, borborygmi, diarrhea
What is sucrase-isomaltase deficiency
Sucrose-isomaltase deficiency is an inherited disorder in which the body cannot digest sucrose and isomaltase
What happens in glucose/galactose malabsorption
There is a genetic defect in SGLT1, which absorbs both glucose and galactose. This means you can no longer absorb either of these
What transporter is genetically missing in glucose/galactose malabsorption
SGLT1
What are the sources for proteins for absorption?
Exogenous - dietary
Endogenous - proteins from cells shed into GI lumen
What does the class of peptidases called endopeptidases do?
They hydrolyze the interior peptide bond
Endopeptidases hydrolyze the interior peptide bonds of proteins. What are the endopeptidases we use
Trypsin
Chymotrypsin
Elastase. (First 3 all pancreatic enzymes, secreted inactive)
Gastric peptsin
What is the mechanism that exopeptidases use to digest proteins
They cleave one AA at a time from the C terminus of peptides and proteins
What are some exopeptidases?
Carboxypeptidase A
Carboxypeptidase. B
Secreted from pancreas in inactive form
Trypsin activates them
Starches are initially digested to ?
Maltose
How is fructose transported?
Facilitated diffusion
Most AA’s are absorbed into enterocytes by -__-_______
Na-dependent co-transport
The transport of Dipeptides and tripeptides is _____________ than for amino acids; using H-dependent co-transporter peptide protein 1 (PEPT1)
More efficient
Faster
The majority of protein absorbed after a meal is in form of ________
Di- and tri- peptides
What transports di and tri peptides from the lumen to the enterocytes?
H+ dependent co-transporter
Peptide transporter 1 (PEPT1)
________ affects uptake of Basic AA’s
Cystinuria
Cystinuria affects the uptake of ______ AA’s
Basic
_______ affects uptake of neutral AA’s
Hartnup’s disease
Hartnup’s disease affects the uptake of _______ AA’s
Neutral
Familial iminioglycinuria affects the uptake of what amino acids?
Proline
Hydroxyproline
Most easily absorbed form of iron is?
Heme iron
What are the 2 ways that heme-bound iron is taken up into enterocytes?
Thru receptor mediated endocytosis
Or
Transport protein HCP1
What happens to heme that is absorbed once it is in the enterocytic cytoplasm
It is broken down by heme oxygenase to release the free iron
What are the 2 forms of dietary free iron?
Ferrous (2+)
Ferric (3+)
What type of dietary free iron is more readily abosrbed?
Ferrous (Fe2+)
What type of free dietary iron is most common?
Ferric (Fe3+)
This form is insoluble and can precipitate
What do ascorbic acid and citric acid do to iron?
Promote absorption by forming soluble complexes w/ iron and reducing ferric iron to ferrous iron
What is duodenal cytochrome b?
Dcyt b is a brush border enzyme in the duodenum that reduces ferric iron to ferrous iron, making it more absorbable.
What transporter moves ferrous (Fe2+) iron from the brush border lumen into the enterocyte?
The DMT1 transporter
What does the ferrous iron go thru to get from enterocyte to blood stream?
Ferroportin
What happens to ferrous iron as it passes from the enterocyte thru the ferroportin into the bloodstream?
Ferroportin, along with ferrohephaestin convert ferrous to ferric iron
Body has no mech for removing excess iron, so absorption is regulated. This is based on body requirements. Much of this regulated orchestrated by liver derived peptide _______
Hepcidin
How does hepcidin regulate entry of iron into plasma?
By binding directly to ferroportin
What is the mechanism of action for the liver protein hepcidin
It regulates the entry of iron into the blood by binding directly to ferroportin. This causes the internalization of dedragation of ferroportin, cellular iron export and decreasing [plasma iron]
Low iron levels will have ___ hepcidin levels
Low
When iron levels are in excess, liver secretes ______ hepcidin
More
Most prevalent nutrient deficiency and most common cause of anemia
Iron deficiency
Explain hereditary hemochromatosis
Hereditary hemochromatosis is the most common genetic disorder in US. Characterized by defect in HFE gene which causes hepcidin levels to drop, leading to excess iron collection in liver.
Leads to cirrhosis and eventually liver cancer
Also can damage pancreas, leading to diabetes
Contributes to CAD
Treat by periodically removing blood
What are the two routes that electrolytes and H2O cross the intestinal epithelial cells?
Transcellular
Paracellular
What are the 4 ways which Na crosses the intestinal epithelium?
Restricted diffusion thru channels
Na-Glucose, Na-AA cotransport
Na-Cl cotransport
Na-H exchange
How is Na+ absorbed in the colon?
Na- restricted diffusion channels
How is Na absorbed in the ileum?
Na-AA, Na-Glucose cotransport
Na-H exchange
Na-Cl cotransport
How is Na absorbed in the jejunum?
Na-Gluc Na-AA cotransport
Na-H exchange
How is Na+ absorbed in the duodenum?
Mostly Na-Gluc and Na-AA cotransport
And Na-H exchange
What are the 3 methods for Cl- absorption in the GI tract?
Diffusion thru paracellular route w/ the elctrochemical gradient established by Na+
In cotransport w/ Na+ and K+
In exchange for HCO3-
