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Systems: Alimentary AB > Digestion of Fat, Vitamins and Minerals > Flashcards

Digestion of Fat, Vitamins and Minerals Flashcards

1
Q

What form is almost all ingested fat in?

A

Triacylglycerol

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2
Q

What is responsible for all fat digestion in the small intestine?

A

Pancreatic lipase

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3
Q

How does triacylglycerol present?

A

Large lipid droplets which are insoluble in water

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4
Q

What is lipase?

A

A water soluble enzyme

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5
Q

What does lipase break triacylglycerol into?

A

Monogylceride and 2 fatty acids

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6
Q

Why is the digestion of fat very slow?

A

Digestion can only take place at the surface of triacylglycerol droplets

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7
Q

Emulsification

A

Dividing large lipid droplets into smaller droplets

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8
Q

What is the purpose of emulsification?

A

To increase the surface area and accessibility to lipase action

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9
Q

What does emulsification require?

A
  • Mechanical disruption

- Emulsifying agent

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10
Q

How does mechanical disruption take place in emulsification?

A

Large lipid droplets mechanically disrupted into small droplets as smooth muscle contraction grinds and mixes luminal contents

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11
Q

What does the emulsifying agent do?

A

Prevents small droplets reforming into large droplets

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12
Q

What forms emulsifying agents?

A

Bile salts and phospholipids secreted in bile

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13
Q

What are emulsifying agents?

A

Amphiatic molecules (polar and non-polar portions)

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14
Q

How do the amphiatic molecules work as emulsifying agents?

A
  • The non-polar portions associate with non-polar interior of liquid droplet leaving polar portions exposed at water surface
  • Polar portions repel other small lipid droplets to prevent reforming into large droplets
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15
Q

How is absorption lipase digestion products enhanced?

A

By the formation of micelles

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16
Q

What are micelles?

A

Made up of:

  • Bile salt
  • Monoglycerides
  • Fatty acids
  • Phospholipids
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17
Q

How do micelles compare in size to emulsion droplets?

A

Much smaller

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18
Q

How are the components of micelles arranged?

A
  • Polar portions of molecules a micelle surface

- Non-polar portions form micelle core

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19
Q

What does micelle breakdown result in?

A

Release of small amounts of free fatty acids and monoglycerides into solution leading to diffusion across plasma membrane of absorbing cells

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20
Q

What does the dynamic equilibrium between fatty acids and monoglycerides in solution and in micelles result in?

A

Retains most of fat digestion products in solution while constantly replenishing supply of free molecules for absorption

21
Q

What does not get absorbed with the products of lipase digestion?

A

Micelles

22
Q

What happens to fatty acids and monoglycerides after entering epithelial cells?

A

They enter smooth endoplasmic reticulum where they are reformed into triacylglycerols

23
Q

What is responsible for the reforming of triacylglycerols?

A

Enzymes located in the smooth endoplasmic reticulum

24
Q

What happens to triacylglycerol droplets after they are reformed?

A

Emulsified by coating of amphiphatic proteins

25
Q

How are triacylglycerol droplets transported through the cell?

A

In vesicles formed from the smooth endoplasmic reticulum membrane

26
Q

What happens to the triacylglycerol droplets transported in vesicles?

A

They are processed through the Golgi apparatus and exocytosed into extracellular fluid at serosal membrane

27
Q

What are chylomicrons

A

Extracellular fat droplets

28
Q

Other than fat, what do chylomicrons contain?

A
  • Phospholipids
  • Cholesterol
  • Fat soluble vitamins
29
Q

What happens to chylomicrons?

A

They pass into lacteals between endothelial cells

30
Q

What can chylomicrons not pass through?

A

Capillary basement membrane

31
Q

What are the 2 classes of vitamins?

A
  • Fat soluble vitamins

- Water soluble vitamins

32
Q

What are the fat soluble vitamins?

A
  • A
  • D
  • E
  • K
33
Q

What happens to fat soluble vitamins?

A

Follow the same absorptive path as fat

34
Q

What are the water soluble vitamins?

A
  • B group
  • C
  • Folic acid
35
Q

What happens to water soluble vitamins?

A

Either absorbed by passive diffusion or carrier-mediated transporter

36
Q

What is vitamin B12?

A

A large charged molecule

37
Q

What happens to B12?

A

It binds to intrinsic factor in the stomach to form complex which is absorbed via specific transport mechanism is distal ileum

38
Q

What does B12 deficiency result in?

A

Pernicious anaemia

39
Q

What is pernicious anaemia?

A

Failure of red blood cells maturation

40
Q

What happen to 10% of our daily ingested iron?

A

Absorbed across intestine into blood

41
Q

How is iron transported across the brush border membrane?

A

Via DMT1

42
Q

Where does DMT1 transport iron to?

A

Duodenal enterocytes

43
Q

What are iron ions incorporated into?

A

Ferritin

44
Q

What is ferritin?

A

Protein-iron complex which acts as an intracellular iron store

45
Q

What happens to unbound iron?

A

Transported across serosal membrane to the blood

46
Q

What happens to iron in the blood?

A

Binds to transferrin

47
Q

How is ferritin expression regulated?

A

Depending on body’s iron status

48
Q

Hyperaemia

A

Increased ferritin levels which leads to more iron bound to enterocytes

49
Q

Anaemia

A

Decreased ferritin levels which leads to more iron released to blood

Systems: Alimentary AB (37 decks)

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