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Gastrointestinal Case > Absorption > Flashcards

Absorption Flashcards

1
Q

What are the roles of crypt and villi in the small intestine?

A

Crypts- secretion

Villi- Absorption

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2
Q

What part of the small intestine absorbs?

A

Villi

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3
Q

What part of the small intestine secretes?

A

Crypts

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4
Q

What happens to glucose at the small intestine?

A

Absorbed without digestion by the villous epithelial cells into the bloodstream

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5
Q

What happens to sucrose at the small intestine?

A

Brush-border hydrolysis of oligomer to monomers glucose and fructose before being Absorbed by the villous epithelial cells into the bloodstream

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6
Q

What happens to proteins at the small intestine?

A

Luminal hydrolysis of polymer to monomer amino acid then Absorbed by the villous epithelial cells into the bloodstream

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7
Q

What is an oligomer

A

a molecule with a small number of monomers unlike a polymer which has large number of monomers

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8
Q

What are the only sugars allowed to be absorbed by villous epithelial cells?

A

Glucose
Fructose
Galactose

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9
Q

What enzyme breaks down sucrose?

A

Sucrase

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10
Q

What is sucrose broken down into?

A

Fructose

Glucose

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11
Q

What happens to peptides at the small intestine?

A

Absorbed into villous epithelial cell

Intracellular hydrolysis into amino acids before being absorbed into the bloodstream

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12
Q

What happens to peptides at the small intestine?

A

Luminal hydrolysis into mono-glyceride and fatty acids followed by intracellular resynthesis into triglyceride an then absorbed into lacteals of the lymphatic system

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13
Q

What is the difference between peptide and protein?

A

peptide is 2-50 amino acids

Protein is more than 50 amino acids

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14
Q

How is starch converted into simple sugars

A

alpha- amylase begins the process of carbohydrate digestion into maltose maltotriose and alpha-limit dextrins
These are further converted by maltase lactase and sucrase-isomaltase into one or both glucose and fructose

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15
Q

What is carbohydrate- starch initially digested into?

A

maltose maltotriose and alpha-limit dextrins

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16
Q

What is sucrase-isomaltase

A

two enzyme complex

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17
Q

Where are maltase lactase and sucrase-isomaltase located?

A

embedded in the apical membrane of the villous epithelial cells

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18
Q

What does maltase convert?

A

Maltose

Maltotriose

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19
Q

What is maltose broken down into?

A

Two glucoses

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20
Q

What converts alpha-limit dextrins

A

isomaltase of the sucrase-isomaltase

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21
Q

What is alpha-limit dextrins broken down into?

A

maltose maltotriose

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22
Q

What is lactose broken down into?

A

Galctose and glucose

23
Q

What maltotriose broken down into?

A

Three glucoses

24
Q

How is glucose absorbed by the bloodstream (process)

A

going to be transported across the apical membrane of the villous epithelial cell by transporter SGLT1 using the sodium concentration gradient across the cell membrane set up by the action of the sodium potassium ATPase
sodium moves down a favorable electrochemical gradient bringing glucose into the cell
Transported across basolateral membrane by GLUT2 facilitated diffusion

25
Q

What is SGLT1

A

Na+-coupled glucose transporter

26
Q

What is GLUT 2

A

Glucose transporter 2- facilitated diffusion

27
Q

How is galactose absorbed by the bloodstream (process)

A

going to be transported across the apical membrane of the villous epithelial cell by transporter SGLT1 using the sodium concentration gradient across the cell membrane set up by the action of the sodium potassium ATPase
sodium moves down a favorable electrochemical gradient bringing galactose into the cell
Transported across basolateral membrane by GLUT2 facilitated diffusion

28
Q

How is fructose absorbed by the bloodstream (process)

A

going to be transported across the apical membrane of the villous epithelial cell via transporter GLUT5 by facilitated diffusion
Transported across basolateral membrane by GLUT2

29
Q

What is GLUT 5

A

Glucose transporter 5 - facilitated diffusion pathway

30
Q

What transporter does glucose use to travel across apical membrane of the villous epithelial cells?

A

SGLT1

31
Q

What transporter does galactose use to travel across apical membrane of the villous epithelial cells?

A

SGLT1

32
Q

What transporter does fructose use to travel across apical membrane of the villous epithelial cells?

A

GLUT2

33
Q

From most to least what parts of the small intestine carry out sugar absorption

A

duodenum> jejunum» ileum

34
Q

How amino acids go across apical membrane(Digestion and Absorption of Proteins)

A

Seven mechanism
Some sodium dependant
sodium independent

35
Q

How dipeptides and tripeptides go across apical membrane(Digestion and Absorption of Proteins)

A

Coupled to protons to travel across apical membrane via a symporter (cotransporter)
Protons are moving down a favorable gradient across the apical membrane
As proton comes in so does peptide

36
Q

Digestion and Absorption of Proteins (mechanisms of breaking down protein)

A

Proteins by proteases are converted into sections of amino acids e.g (dipeptide, amino acids,etc)
Either travel across apical membrane in specific mechanism
Or longer peptides broken down at apical membrane to produce amino acids and then transported

37
Q

Ways of digesting and absobing proteins(Digestion and Absorption of Proteins)

A

Luminal enzymes (proteases) digest proteins to amino acids before absorption by villus epithelial cells.

Luminal enzymes digest proteins to peptides, but enzymes in the apical membrane (brush border enzymes) of villus epithelial cells digest the peptides to amino acids before absorption by villus epithelial cells.

Luminal enzymes digest proteins to peptides, which are absorbed by villus epithelial cells and then digested within the cell (intracellular enzymes) to amino acids.

38
Q

Digestion and Absorption of Proteins- Source of H+ ions

A

Sodium proton exchanger exploit the sodium concentration gradient setup by the sodium potassium ATPase
secondary active transport
acidifies unstirred layer on the apical lumen facing membrane of the villus epithelial cells

39
Q

What type of transporter is sodium proton exchanger?

A

Antiporter

40
Q

What is secondary active transport?

A

. Secondary active transport uses the energy stored in these gradients to move other substances against their own gradients.

41
Q

How amino acids go across basal lateral membrane(Digestion and Absorption of Proteins)

A

3 sodium independant mechanisms

42
Q

From most to least what parts of the small intestine carry out amino acid and peptide absorption?

A

duodenum> jejunum» ileum

43
Q

What form are fats in when they are being digested and absorbed?

A

triglycerides

44
Q

Digestion and Absorption of Fats

A 
Triglyceride first converted to emulsion droplets by bile salts 
 Become smaller droplets 
Pancreatic lipase  breaks down into fatty acid and monoglyceride
Combined with phospholipid and cholesterol into bile salt micelle
Transported into unstirred layer next to brush border partly by diffusion, partly by the non propulsive movements within the small intestine
Diffusion of fatty acids and monoglyceride (phospholipids and cholesterol) out of bile micelle cross into  the apical lumen facing membrane
 within the villous epithelial cells within the smooth endoplasmic reticulum resynthesis of fat within chylomicron
Chylomicron formation(emuslion droplets)
45
Q

What does production of emulsion droplets depend on>

A

heavily on mechanical activity within the gastrointestinal tract

46
Q

when and why are emulsion droplets made smaller?

A

Increase the surface area so that lipase can work on it

Happens in stomach and small intestine when churning up

47
Q

Where can lipase work?

A

between lipid environment of the emotion droplet and the aqueous environment of the small intestine so needs emulsion droplets not raw triglyceride
cross the basal lateral membrane by exocytosis
delivered into the central lacteal

48
Q

What do triglycerides break down into

A

Fatty acids

Monoglyceride

49
Q

What does fatty acid and monoglyceride with phospholipids and cholesterol make?

A

Bile salt micelle

50
Q

What is a bile salt micelle

A

Combination of
phospholipids, cholesterol
fatty acid and monoglyceride

51
Q

Where do phospholipids and cholesterol involved in digestion of fats come from ?

A

liver

52
Q

How is chylomicron formed?

A

With phospholipids and cholesterol

53
Q

What is emulsion?

A

Emulsion is a key preliminary step reducing size of lipid droplets and increasing greatly the oil-water interface

54
Q

From most to least what parts of the small intestine carry out amino acid and peptide absorption?

A

jejunum>duodenum&raquo_space; ileum

Gastrointestinal Case (11 decks)

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