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2A - Alimentary System > Nutrient Digestion 1 > Flashcards

Nutrient Digestion 1 Flashcards

1
Q

What are the principle dietary constituents?

A

Carbohydrates

Protein

Fat

Vitamins

Minerals

Water

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2
Q

What are different classes of carbohydrates?

A

Monosaccharides

Disaccharides

Polysaccharides

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3
Q

What are monosaccharides?

A

Hexose sugars (6C)

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4
Q

What are examples of monosaccharides?

A

Glucose

Galactose

Fructose

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5
Q

Where are monosaccharides absorbed?

A

Small intestine

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6
Q

What bond connects disaccharides?

A

Glycosidic bond

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7
Q

What and where are disaccharides broken down into monosaccharides?

A

By brush border enzymes in the small intestine

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8
Q

Why are all complex carbohydrates broken down into monosaccharides?

A

Only monosaccharides can be absorbed

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9
Q

What is lactose formed from?

A

Glucose and galactose

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10
Q

What enzyme breaks lactose down into glucose and galactose?

A

Lactase

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11
Q

What is sucrose formed from?

A

Glucose and fructose

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12
Q

What breaks sucrose down into glucose and fructose?

A

Sucrase

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13
Q

What is maltose formed from?

A

Glucose and glucose

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14
Q

What breaks maltose down into 2 glucose monomers?

A

Maltase

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15
Q

What are some examples of polysaccharides?

A

Starch

Cellulose

Glycogen

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16
Q

What is starch?

A

Plant storage form of glucose

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17
Q

What are some examples of starch?

A

a-amylose (glucose linked in straight chains)

Amylopectin (glucose chains highly branched)

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18
Q

What are glucose monomers linked by in starch?

A

a-1, 4 glycosidic bonds

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19
Q

What are a-1, 4 glycosidic bonds broken down by?

A

Amylases

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20
Q

What is cellulose?

A

Constituent of the plant cell wall

Unbranched linear chains of glucose monomers linked by B-1, 4 glycosidic bonds

cannot be broken down naturally and needs bacteria to be broken down (bacteria in large intestine)

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21
Q

What are B-1, 4 glycosidic bonds broken down by?

A

Cellulase

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22
Q

What is cellulose also known as?

A

Dietary fibre

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23
Q

Why is cellulose only broken down by bacteria and not enzyme?

A

Animals do not synthesis cellulase which is required to break down B-1, 4 glycosidic bonds

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24
Q

What is glycogen?

A

Animal storage form of glucose

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25
Q

How are glucose monomers linked in glycogen?

A

a-1, 4 glycosidic bonds

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26
Q

Where are maltase, sucrase and lactase found?

A

Brush border of the small intestine

27
Q

What increases the surface area of epithelial cells?

A

Villi for absorption

28
Q

What are the 2 membranes of epithelial cells?

A

Apical membrane facing the lumen of the gut

Basal and lateral membranes facing the blood circulation

29
Q

What is transepithelial transport?

A

Travelling through both the apical and basal membranes of epithelial cells

30
Q

What is transport from the lumen to the blood circulation around the cells called?

A

Paracellular transport

31
Q

What is transport from the lumen to the blood circulation through the cells called?

A

Transcellular

32
Q

Which 2 of the 3 monosaccharides are absorbed by the same mechanism?

A

Glucose and galactose

33
Q

What is the process of glucose/galactose absorption?

A

1) Na/K ATPase found on basolateral membrane which hydrolyses ATP to pump Na out of the cell and Na into the cell created Na concentration gradient allowing SGLT1 to work
2) 1 Na and 1 glucose travel from gut lumen into cell through SGLT1 transporter protein
3) Glucose concentration develops inside cell to leaves down gradient into the circulation through GLUT-2 transport protein
4) Concentration gradient of Na causes water to travel from lumen of gut to blood through leaky membrane between cells

34
Q

What transport protein does 1 Na and 1 glucose use to travel from gut lumen into cell?

A

SGLT1 transporter protein

35
Q

Why does SGLT1 transporter protein need both Na and glucose to bind to transport molecules into the cell?

A

Both binding causes conformational change that flips the protein, having an extremely high affinity when facing gut lumen and extremely low affinity when facing inside the cell to release the molecules

36
Q

What allows SGLT1 to work?

A

The concentration gradient of Na created by Na/K ATPase pumping Na out of the cell and K into the cell

37
Q

What protein does glucose use to leave the cell to the blood cirulation?

A

GLUT-2 transport protein

38
Q

Why does water travel from the gut lumen into the blood circulation during glucose/galactose absorption?

A

Concentration gradient of Na affects the osmolarity

39
Q

What is the process of fructose absorption?

A

1) Fructose travels into the cell from the lumen through the GLUT-5 transport protein
2) Enters the circulation from the cell through the GLUT-2 transport protein

40
Q

What transport protein does fructose use to enter the cell from the gut lumen?

A

GLUT-5 transport protein

41
Q

What transport protein does fructose use to enter the blood circulation from the cell?

A

GLUT-2 transport protein

42
Q

Does water travel from the gut lumen to the blood circulation during fructose absorption?

A

No because fructose transporters do not rely on Na gradient created by Na/K ATPase so osmolarity remains unchanged

43
Q

What are proteins?

A

Polymers of amino acids linked together by peptide bonds (between amino and carboxy ends)

44
Q

What bonds connects the polymers of amino acids to form proteins?

A

Peptide bond

45
Q

What do proteins often undergo after being synthesised?

A

Post-translational modifications

46
Q

What are examples of post translational modifications?

A

Addition of CHO making glycoproteins

Addition of lipid making lipoproteins

47
Q

What are small proteins (3-10 amino acids in length) known as?

A

Peptides

48
Q

What enzymes hydrolyse peptide bonds to reduce proteins to amino acids?

A

Proteases or peptidases (known as peptidases when break down peptides which are small proteins)

49
Q

What are examples of proteases?

A

Trypsin and chymotrypsin

50
Q

What are the different categories of peptidases?

A

Endopeptidases

Exopeptidases (aminopeptidase and carboxypeptidase)

51
Q

What do endopeptidases do?

A

Break bond in the middle of a protein

52
Q

What do exopeptidases do?

A

Break bond at the end of a protein

53
Q

What do aminopeptidases do?

A

Break bond at the amino terminal of a protein

54
Q

What do carboxypeptidases do?

A

Breaks bond at the carboxy terminal of a protein

55
Q

How many naturally occuring amino acids are they?

A

20

56
Q

What can be said about the transporting mechanisms of amino acids?

A

They all have their unique transporting mechanisms

57
Q

What is the process of a typical absorption mechanism of a protein?

A

1) Na/K ATPase pumps Na from cell to circulation and takes in K
2) Due to Na concentration gradient Na and amino acid are transported into th cell by SAAT1 transporter protein
3) Amino acid enters the circulation through a transporter protein down its concentration gradient
4) Water travels from gut lumen into circulation due to Na concentration gradient created by Na/K ATPase

58
Q

What transporter protein takes in Na and amino acid from the gut lumen into the cell?

A

SAAT1

59
Q

Does water travel from the gut lumen to the circulation during protein absorption?

A

Yes due to Na concentration gradient created by Na/K ATPase

60
Q

What can be absorbed instead of individual amino acids?

A

Di and tri-peptides

61
Q

What is the process of di/tri peptides being absorbed?

A

1) Di/tripeptide enters the cell from lumen with H ion through PepT1 transporter protein
2) H ion leaves cell back into lumen through NHE3 so Na can enter the cell
3) This H ion entering the lumen acidifies it and creases an acidic layer
4) Na leaves the cell into circulation due to ATPase, whilst K enters the cell from the circulation
5) Di/tripeptide leaves the cell into the circulation through transporter protein
6) Water travels from lumen into circulation due to Na concentration gradient created by Na/K ATPase

62
Q

What transporter protein does di/tripeptide and H use to enter the cell from the gut lumen?

A

PepT1

63
Q

What transporter protein does H use to leave the cell and return to the gut lumen with Na coming in from the lumen?

A

NHE3 transporter protein

2A - Alimentary System (41 decks)

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