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GI AM > Nutrient digestion > Flashcards

Nutrient digestion Flashcards

1
Q

What are the membranes of the small intestine?

A

Apical membrane

basolateral membrane

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2
Q

What are paracellular pathways?

A

Pathways between the cell to allow water to enter the cell

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3
Q

What are the principle dietary nutrients?

A

Carbohydrates
Protein
Fats

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4
Q

What are the forms of polysaccharides?

A

Starch
Cellulose
Glycogen

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5
Q

What is starch?

A

Plant storage form of glucose

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6
Q

What are the types of starch?

A

⍺ amylase

amylopectin

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7
Q

What is the difference between ⍺ amylase and amylopectin?

A

⍺amylase has glucose linked in straight chains while amylopectin has highly branched glucose chains

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8
Q

What is the structural makeup of starch?

A

Glucose monomers linked by ⍺-1,4 glycosidic bonds

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9
Q

How is starch broken down?

A

Amylase

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10
Q

What is cellulose?

A

Constituent of plant cell walls, dietary fibre

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11
Q

What is the structure of cellulose?

A

Unbranched linear chains of glucose monomers lined by β-1,4 glycosidic bonds

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12
Q

Why is cellulose a dietary fibre?

A

No enzymatic digestion in vertebrates

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13
Q

What is glycogen?

A

Animal storage form of glucose

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14
Q

What is the structure of glycogen?

A

Glucose monomers linked by ⍺-1,4 glycosidic bonds

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15
Q

How is starch and glycogen broken down?

A

by amylase

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16
Q

How are glucose and galactose absorbed into the cells of the small intestine?

A

Via SGLT1 accompanied by Na

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17
Q

How are glucose and galactose transported out of the small intestinal cells and into the bloodstream?

A

Via GLUT2

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18
Q

Why are glucose and galactose accompanied by Na?

A

Create a gradient to allow for passive absorption of water

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19
Q

How is water absorbed into the bloodstream?

A

Na/K pump created a gradient that allows water to passively pass through the paracellular pathway

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20
Q

How is fructose absorbed into the cells of the small intestine??

A

Via GLUT5 accompanied by Na

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21
Q

How is fructose transported out of the cells of the small intestine and into the bloodstream?

A

Via GLUT2

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22
Q

What are the transporter proteins of glucose and galactose?

A

Into cell= SGLT1

Out= GLUT2

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23
Q

What are the transporter proteins of fructose?

A 
in= GLUT5
out= GLUT2
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24
Q

What are proteins?

A

Polymers of amino acids linked together by peptide bonds of varying length

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25
Q

What are peptides?

A

Small proteins constituting of 3-10 amino acids

26
Q

What breaks down proteins and peptides?

A

Proteases and peptides

27
Q

How are amino acids absorbed into the bloodstream?

A

Via SAAT1 accompanied by Na then cross over into the bloodstream

28
Q

How are dipeptides absorbed into the bloodstream?

A

Taken into the cells via Pep1 accompanied by H
Na is taken into the cell by NHE3 as H is transported out
Dipeptides cross into the bloodstream

29
Q

Why is NHE3 essential?

A

maintains the Na gradient to allow water to enter the bloodstream via the paracellular pathway

30
Q

What is the most common form of ingested fat?

A

Triacylglycerol

31
Q

Where does fat digestion take place?

A

Small intestine

32
Q

What enzyme is involved in fat digestion?

A

Pancreatic lipase

33
Q

What does lipase break triacylglycerol down into?

A

Monoglyceride and 2 fat acids

34
Q

What makes lipase inefficient on triacylglycerol?

A

Triacylglycerol is insoluble in water while lipase is, so lipase can only work on the surface of lipid droplets

35
Q

What is done to make digestion of fats more efficient?

A

Emulsification

36
Q

What are the requirements of emulsification?

A

Mechanical disruption

Emulsifying agent

37
Q

What mechanical disruption is used in emulsification of fats?

A

Smooth muscle contraction of the stomach

Grinds and mixes lumenal contents

38
Q

What is the purpose of an emulsifying agent?

A

Prevents small droplets reforming into large droplets

39
Q

What emulsifying agent is used for fats?

A

Bile salts and phospholipids

40
Q

How do emulsifying agents work?

A

Have a polar and a non polar end

Non polar end associated with lipid droplet, leaving polar ends exposed at the water surface to repel each other

41
Q

What can emulsifying agents be classified as?

A

Amphipathic molecules

42
Q

What are micelles?

A

Bile salt, monoglyceride, fatty acid and phospholipid

43
Q

What is the structure of a micelle?

A

Polar portion at surface, non polar core

44
Q

How do micelles break down?

A

As micelles come into contact with the villi in the acid microclimate, they release the fatty acids and monoglyceride for passive diffusion across the intestinal cell membrane

45
Q

What happens to fatty acids and monoglycerides once they enter the small intestinal cells?

A

Smooth endoplasmic reticulum

46
Q

What do fatty acids and monoglycerides form into in the small intestinal cells?

A

Triacylglycerol

47
Q

How are fatty acids and monoglycerides formed into triacylglycerol?

A

Via enzymes in the smooth endoplasmic reticulum

48
Q

How is triacylglycerol transported in the cell?

A

In vesicles formed from the smooth endoplasmic reticulum membrane

49
Q

What happens to triacylglycerol in the small intestinal cells?

A

Processed through the Golgi apparatus and exorcised to the extracellular fluid at the basolateral membrane

50
Q

What are chylomicrons?

A

Coated extracellular fat droplet containing phospholipids, cholesterol and fat soluble vitamins

51
Q

What happens to chylomicrons in the small intestine?

A

Pass into lacteals between endothelial cells as they are too large to pass through the capillary basement membrane

52
Q

What are the fat soluble vitamins?

A

A, D, E, K

53
Q

How are fat soluble vitamins absorbed?

A

Via the same absorptive path as fat

54
Q

What are the water soluble vitamins?

A

B group, C, folic acid

55
Q

How are water soluble vitamins absorbed?

A

Passive diffusion

Carrier mediated transport

56
Q

How is B12 absorbed?

A

Binds to intrinsic factor in stomach to form a complex which is absorbed via a specific transport system in the distal ileum

57
Q

How much B12 can the body store?

A

3 years worth stored in liver

58
Q

What does a B12 deficiency cause?

A

Prenicious anaemia- failure of RBC maturation

59
Q

How is iron absorbed?

A

Transported across brush border membrane via DMT1 into duodenal enterocytes

60
Q

What are the 2 fates of iron in cells?

A

Incorporated into ferritin in the cell

Bound to transferrin in the blood for transport

61
Q

Why does iron bind to transferrin in the blood?

A

Cannot travel alone in the blood due to the charge and dangers of free radical creation

62
Q

How is ferritin expression controlled?

A

Depending on the body’s iron status

GI AM (34 decks)

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