Physiology of Carbohydrate and Protein Digestion and Absorption Flashcards

1
Q

What type of digestion in the small intestine is mediated by pancreatic enzymes secreted into the duodenum?

A

Luminal

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2
Q

What kind og digestion in the small intestine is mediated by enzymes situated at the brush border of epithelial cells?

A

Membrane

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3
Q

Wat is the term for the overall process of digestion and absorption?

A

Assimilation

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4
Q

Give an example of luminal hydrolysis of polymer to monomers?

A

Protein to amino acids

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5
Q

Give and example of brushborder hydrolysis of oligomer to monomer?

A

Sucrose to glucose and fructose

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6
Q

Give an example of intracellular hydrolysis?

A

Peptide

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7
Q

Give an example of luminal hydrolysis followed by intracellular resynthesis?

A

Triacylglycerol to glycerol and fatty acids

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8
Q

Name two polymers of glucose?

A

Starch and glycogen

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9
Q

Name two oligosaccharides?

A

Sucrose and lactose

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10
Q

What does glucose + fructose give?

A

Sucrose

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11
Q

What does glucose + galactose give?

A

Lactose

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12
Q

What is more highly branched - amylopectin or glycogen?

A

Glycogen

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13
Q

What must all dietary carbohydrates be converted to for absorption?

A

Monosaccharides (glucose and fructose)

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14
Q

What is the process of starch being broken down to oligosaccharides?

A

Intraluminal hydrolysis

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15
Q

What are alpha-linit dextrins, maltotriose and maltose?

A

Oligosaccharides

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16
Q

What is the process for breaking down oligosaccharides to monosaccharides?

A

Membrane digestion (at brush border)

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17
Q

Name three oligosaccharidases?

A

Lactase
Maltase
Sucrase-isomaltase

18
Q

What accomplishes starch by intraluminakl hydrolysis to oligosaccharides?

A

Alpha-amylase (salivary and pacnreatic)

19
Q

What does a-amylase breakdown, and what does it not?

A

Breaks down linear internal alpha-1,4 linkages but not terminal alpha-1,4,linkages

20
Q

Does the endoenzyme a-amylase produce glucose?

A

No

21
Q

What enzyme, cannot cleave alpha-1,6 linkages at branch points (in amylopectin) ot alpha-1,4-linkages adjacent to branch points?

A

Alpha-amylase

22
Q

What are the main class of products from a-amylase?

A

Oligosaccharides

23
Q

What are integral membrane proteins with a catalytic domain that faces the lumen of the GI tract?

A

Oligosaccharidases

24
Q

Ohter than lactase, which breaks down lactose to glucose and galactose, what do all other oligosaccharidases cleave?

A

The terminal alpha-1,4-linkages of maltose, maltotriose and alpha-limit dextrins

25
Q

What oligosaccharidase is unique in that it is the only enzyme that can split the branching alpha-1,6,linkages of alpha-limit dextrins?

A

Isomaltase

26
Q

Give an example of a disorder caused by impaired carbohydrate digestion?

A

Lactose intolerance

27
Q

What insufficiency causes lactose intolerance?

A

Lactase deficiency

28
Q

What is primary lactase deficiency (primary hypolactasia) due to?

A

Lack of the lactase persistence (LP) allele

29
Q

What is secondary lactase deficiency due to?

A

Damage to/infection of/ the proximal small intestine

30
Q

Name a rare, autosomal recessive disease with no ability to digest lactose from birth?

A

Congenital lactase deficiency

31
Q

What are these produced in response to: short-chain fatty acids, hydrogen (can be detected in breath of lactase defiecient people), carbon dioxide and methane?

A

Produced by colonic microflora when lactose delivered to colon from ileum

32
Q

What are three symptoms of lactase insufficiency?

A

Bloating
Abdominal Pain
Flatulence

33
Q

What causes acidification of the colon and increased osmotic load - loose stools nad diarrhoea?

A

Undigested lactose

34
Q

What are the three final products of carbohydrate digestion?

A

Glucose, galactose and fructose

35
Q

Where does final product absorption occur?

A

In duodenum and jejunum

36
Q

What is absorbed by secondary active transport mediated by SGLT1?

A

Glucose and galactose

37
Q

What is absorbed by facilitated diffusion mediated by GLUT5?

A

Glucose and galactose

38
Q

How is exit for all monosaccharides mediated?

A

By facilitated diffusion by GLUT2

39
Q

For SGLT1 transport, what must the substrate be like?

A

A hexose in D conformation

Can form pyranose ring

40
Q

What products do endopeptidases produce?

A

Oligopeptides (2-6 amino acids)

41
Q

What products do exopeptidases produce?

A

Single amino acids