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Flashcards in Digestion and Absorption Deck (74)
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1

What is digestion?

The process by which ingested food is broken down chemically into absorbable molecules.

2

What is absorption?

Is the movement of nutrients, water and electrolytes from the lumen of the intestine into blood.

3

What are the 2 pathways of absorption?

 Cellular path - the substances enter the intestinal epithelial cells via the apical (luminal
membrane) and are extruded via basolateral membrane to enter blood.

 Paracellular path - substances move across the tight junctions, through the lateral interspaces into blood.

4

What must carbohydrates be digested to in order to be absorbed?

Monosaccharides

5

What are the monosaccharides that can be absorbed?

Fructose, Galactose and Glucose

6

What is amylose?

It is the straight chain polymer

7

What is amylopectin?

It is the branched chain polymer

8

What does trehalose break down to?

2 Glucose

9

What does sucrose break down to?

1 Glucose 1 Fructose

10

What does lactose break down to?

1 Glucose 1 Galactose

11

Why can't cellulose be broken down?

It has beta-1,4 linkages which cannot be broken down in humans due to the lack of the enzyme

12

What is the function of the enzyme alpha-amylase?

Cleaves the α-1,4 linkages in carbohydrates

13

What is the result of digestion with pancreatic amylase?

It yields a mix of disaccharides, trisaccharides
and oligosaccharides

14

What further digests the saccharides after the amylase does?

These disaccharides are further digested to monosaccharides by intestinal brush border enzymes:
- α-dextrinase (isomaltase)
- maltase
- sucrase

15

What is unique about α-limit dextrins?

Alpha-dextrins have the α-1,6 linkage that
can only be broken with alpha-dextrinase

16

What is the function of SGLT1?

SGLT1 transports glucose and galactose against their concentration gradients by coupling their transport to that of Na+ (active process).

17

What is the function of GLUT5?

Transports fructose across the apical membrane and it does not require an Na+ ion

18

What is the function of GLUT2?

It transports glucose, galactose and fructose across the basolateral membrane

19

What is the function of sucrase?

Digests sucrose

20

What is the function of lactase?

Digests lactose

21

What is lactose intolerance and what are symptoms of it?

Lack or deficiency of lactase in the brush border- lactose is not digested to glucose and galactose. If lactose is ingested (in milk or milk products), lactose remains undigested and unabsorbed in the intestinal lumen – and retains water causing osmotic diarrhea.

22

What is congenital lactose intolerance?

It is a lack of jejunal lactase and is much rarer than normal lactose intolerance. It can be dangerous so replacement with a sucrose/fructose diet may be necessary

23

What is glucose-galactose malabsorption?

It is due to a mutation in SGLT1 and a fructose diet is recommended

24

What enzyme starts protein digestion in the stomach?

Pepsin

25

What are endopeptidases?

They hydrolyze the interior peptide bonds of proteins

Example – pepsin, trypsin, chymotrypsin, elastase.

26

What are exopeptidases?

They hydrolyze one amino acid at a time from the C-terminal ends of proteins and peptides

Example - carboxypeptidases A&B.

27

What activates trypsinogen?

Enterokinase. It will then become trypsin and activate the other proteases.

28

Is pepsin in the stomach essential for protein digestion?

Pepsin is not essential for normal protein digestion, since in people whose stomach has been removed or who d not secrete gastric H+, have normal protein digestion and absorption.

29

Where does the major protein digestion occur?

In the small intestine with the pancreatic enzymes

30

Besides enterokinase, what else can activate trypsinogen?

Trypsin. It can auto catalyze itself.

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