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GI > Digestion of Carbohydrates, Proteins and Lipids > Flashcards

Digestion of Carbohydrates, Proteins and Lipids Flashcards

1
Q

What drives the entire absorption process of carbs and proteins? What is the one exception to this?

A
  • Na+/K+ ATPase
  • Fructose is only one not dependent on ATPase, and has it’s own channel
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2
Q

Describe glucose absorption.

A
  • Glucose absorption is not directly dependent on energy
  • Glucose absorption is secondary to active transport
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3
Q

How does insulin affect glucose transport in the stomach and kidney?

A

It does not

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4
Q

What does insulin primarily affect?

A

Adipose tissue

resting muscles

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5
Q

Where is protein digested?

A

The lumen

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6
Q

Does glucose require digestion for absorption?

A

Nope

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7
Q

What digests sucrose prior to absorption?

A

Brush border enzymes

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8
Q

These are directly absorbed by cell then broken down inside cell, what are they?

A

Oligopeptides

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9
Q

These are broken down before absorption cell then resynthesize original molecule. What are they?

A

TAGs

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10
Q

All chemical digestion and nutrient absorption occurs in the small intestine, what developments allow for greater surface area?

A
  1. Circular folds of mucosa
  2. Villi
  3. Microvilli
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11
Q

Juice secreted by small intestine does not contain any digestive enzymes. The synthesized enzymes act within the brush-border membrane of epithelial cells. What are the three enzymes we covered?

A
  1. Enterokinase
  2. Disaccharidases
  3. Aminopeptidases
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12
Q

Peptidase

A

breaks down peptides into amino acids

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13
Q

Sucrase, maltase, lactase

A

break down disaccharides into monosaccharides

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14
Q

Lipase

A

breaks down fats into fatty acids and glycerol

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15
Q

Enterokinase

A

converts trypsinogen to trypsin

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16
Q

Somatostatin

A

hormone that inhibits acid secretion by stomach

17
Q

Cholescystokinin

A

hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, stimulates gallbladder to release bile

18
Q

Secretin

A

stimulates pancreas to release bicarbonate ions in pancreatic juice

19
Q

What does the small intestine absorb?

A
  • 80 % ingested water
  • Electrolytes
  • Vitamins
  • Minerals
  • Carbonates
    • active/facilitated transport
    • monosaccharides

•Proteins

   - di-/tripeptides
    - amino acids

•Lipids

   - monoglycerides
    - fatty acids
    - micelles
    - chylomicrons
20
Q

Fill in the boxes with the appropriate enzymes

A
21
Q

What are the two steps of carbohydrate digestion?

A
  1. Intraluminal hydrolysis of starch to oligosaccharides by amylases
  2. membrane digestion of oligo to mono by brush border disaccharidases
22
Q

What are the four brush border oligosaccharidases?

A
  1. Lactase
  2. Glucoamylase
  3. Sucrase
  4. Isomaltase
23
Q

What are the two steps of carbohydrate absorption?

A
  1. Uptake across apical membrane into epithelial cell
  2. coordinated exit across basolateral membrane
24
Q

Where does protein digestion begin?

A

In the stomach, when pepsin digests proteins to form polypeptides

25
Q

What are the endopeptidases of the duodenum and jejunum?

(3)

A
  1. Trypsin
  2. Chymotrypsin
  3. Elastase
26
Q

What are the exopeptidases of the duodenum and jejunum?

A
  1. Carboxypeptidases
  2. Aminopeptidase
27
Q

What are the brush border enzymes responsible for breaking down protein?

A
  1. Carboxypeptidase
  2. Aminopeptidase
  3. dipeptidase
28
Q

Fill in the boxes with the correct enzymes or compounds.

A
29
Q

How are aminoacides and polypeptides transported across the basolateral membrane of enterocytes?

A

Facilitated or simple diffusion

30
Q

What type of transporter is PepT1? What does it move?

A

H+/oligopeptide cotransporter

•dipeptides, tripeptides and tetrapeptides into enterocytes across apical membrane

31
Q

What is the defect responsible for Hartnup disease?

A

Impaired a.a. transport in the SLC6A19 transporter across the apical brush border membrane of the small intestine. (Also impacts transport in the proximal tubule of the kidney)

32
Q

What are the symptoms of Hartnup disease?

A
  1. Pellagra like skin eruptions
  2. cerebellar ataxia
  3. gross aminoaciduria
33
Q

How does Hartnup disease manifest in infancy?

A
  1. failure to thrive
  2. photosensitivity
  3. intermittent ataxia
  4. nystagmus
  5. tremor
34
Q

PepT1 also plays a major role in supplying what compound to the body?

A

Nitrogen

35
Q

Fill in the blanks with the appropriate compounds or enzymes.

A
36
Q

Describe steps 1-7 of the image.

A

Dietary fat (TGs) emulsified by

bile salts into fat droplets

  1. Lipase hydrolyses TGs into

mono-glycerides & free FAs

  1. These water insoluble products

are carried in interior of water-

soluble micelles to luminal

surface of S.I. epithelial cells

  1. Micelle in epithelial surface,

mono-glycerides & free FAs

leave micelles & passively diffuse

through luminal membranes

  1. Mono-glycerides & free FAs

resynthesized into TGs inside

epithelial cells

  1. TGs aggregate & coated with

lipoprotein to form water

soluble chylomicrons

  1. Chylomicrons enters lacteals
37
Q

What does the large intestine secrete into the colonic lumen?

A

K+ and HCO3-

38
Q

Hartnup disease can be overcome by a high protein diet. Why is this is possible?

A

The presence of PepT1 allows for the uptake of dietary di and tripeptides from the small intestinal lumen.

GI (26 decks)

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