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Phase I Medicine > B3 Digestion and Absorption > Flashcards

B3 Digestion and Absorption Flashcards

1
Q

How much energy is derived from protein?

A

40%

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2
Q

What is the first macromolecule metabolised?

A

Protein

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3
Q

What is the last macromolecule metabolised?

A

Fat

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4
Q

What are essential amino acids?

A

Those that cannot be synthesised in the body

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5
Q

How are essential amino acids provided for the body?

A

Through the diet

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6
Q

What are non-essential amino acids?

A

Those that can be synthesised in the body

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7
Q

How are non-essential amino acids made in the body?

A

From common metabolic intermediates via transanimation

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8
Q

What are semi-essential amino acids?

A

Amino acids that become essential under conditions of metabolic stress or trauma

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9
Q

Why is glutamine important?

A

Used to make purines and pyrimidines in DNA synthesis

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10
Q

What are essential precursor amino acids?

A

Amino acids that can be made provided that there are enough of other amino acids

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11
Q

What are the two essential precursor amino acids?

A

Cysteine and tyrosine

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12
Q

What amino acid is important in surgical trauma and sepsis?

A

Glutamine

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13
Q

What amino acid is relevant at times of high protein intake

A

Arginine

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14
Q

What amino acid is important at times of high growth?

A

Arginine

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15
Q

What amino acid is present with high intakes of some xenobiotics?

A

Glycine

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16
Q

What amino acid is present in severe trauma?

A

Proline

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17
Q

Why is proline important in severe trauma?

A

It’s required for collagen synthesis

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18
Q

How are high concentrations of glycine gotten rid of?

A

Excreted as glycine conjugates

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19
Q

What macromolecule would you expect to see a decrease in after trauma?

A

Protein

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20
Q

What is amino acid metabolism closely related to?

A

Carbohydrate and fat metabolism

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21
Q

What does amino acid breakdown give rise to?

A

Intermediates of carbohydrate and fat metabolism

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22
Q

What are amino acids without their amino groups known as?

A

Carbon skeletons

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23
Q

Where do amino acids travel to from the small intestine?

A

Portal vein

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24
Q

What is an acceptor in amino acid metabolism?

A

A different keto-acid that takes the amino acid group from the transanimase enzyme

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25
Q

What vitamin is the co-factor for transaminase enzymes?

A

Vitamin B6

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26
Q

What does keto refer to in keto-acid?

A

The carbon skeleton

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27
Q

What are the 3 main transaminase enzymes?

A 
Alanine aminotransanimase (ALT)
Aspartate aminotransferase (AST)
Glutamate aminotransferase
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28
Q

What do raised levels of alanime aminotransferase and aspartate aminotransferase indicate clinically?

A

Liver damage

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29
Q

What is the consequence of cholestasis?

A

Bile can’t get out of the liver

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30
Q

What is ALP?

A

Alkaline phosphatase

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31
Q

What do increased ALP levels indicate?

A

Increased synthesis by bile cannaliculi
Infiltrative disease of liver
Cirrhosis

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32
Q

What is GGT?

A

Gamma glutamyl transpeptidase

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33
Q

What do increased GGT levels indicate?

A

Cholestasis

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34
Q

What does raised GGT but normal ALP indicate?

A

Alcohol damage

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35
Q

What does raised ALP with normal GGT indicate?

A

Bone disease (e.g. Paget’s)

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36
Q

What do small increases in aminotransferases with large increases in both ALP and GGT indicate?

A

Biliary obstruction

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37
Q

What would large increases in amino transferases and a small increase in ALP indicate?

A

Hepatocellular damage

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38
Q

What is the major protein of the liver and blood?

A

Albumin?

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39
Q

Why is it important that the amino group gets removed from amino acids?

A

The keto acid can then be added to glutamate and sent through the krebs cycle

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40
Q

What are glucogenic amino acids?

A

Amino acids which can be converted back to glucose and continue like that through the krebs cycle

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41
Q

What are ketogenic amino acids?

A

Give rise to ketones or lose their carbons in breakdown pathways

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42
Q

Where is ammonia concentration highest in the body?

A

Liver

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43
Q

True or false? Ammonia being converted into urea involves mitochondria?

A

True

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44
Q

What enzymes can be responsible for forming ammonia?

A

Glutamate dehydrogenase

Aspartate

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45
Q

What is appreciable recycling?

A

Urea diffusing into gut lumen then being hydrolysed by gut bacteria

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46
Q

True or false? Ammonia being made into urea is a reversible process?

A

True

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47
Q

What is responsible for the conversion of urea to ammonia?

A

Bacteria urease

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48
Q

What is insulin’s effect on gluconeogenesis and lipolysis?

A

Decreases it

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49
Q

What is glucagon’s effect on gluconeogenesis?

A

Increases it

50
Q

Where do short chain fatty acids come from?

A

Anything derived from milk

51
Q

Where do we get phospholipids from?

A

Cell membranes

52
Q

Where do we get cholesterol esters from?

A

Animal cell fat stores

53
Q

Where do we get cholesterol from?

A

Animal cell membranes

54
Q

Why does TAG need to be emulsified?

A

They are oil based which means they would otherwise be immiscible in the aqueous environments of the intestine and blood

55
Q

What is emulsification?

A

The breakdown of oils into smaller droplets

56
Q

How are fats emulsified?

A

Adding energy in the stomach via churning

Stabilise the droplets with bile salts

57
Q

Where does digestion of fats begin?

A

The mouth

58
Q

Which enzyme starts breaking TAG down?

A

Lingual Lipase

59
Q

What is secreted by the duodenum in response to fat?

A

CCK

60
Q

What is the purpose of fat?

A

Inhibits gastric secretion and motility; stimulates pancreatic bicarbonate and enzyme

61
Q

What are zymogens?

A

Inactive precursors which get activated after gastric secretion to avoid the stomach and duodenum from being digested away from all the secreted enzymes.

62
Q

Where does carbohydrate digestion begin?

A

The mouth via salivary amylase

63
Q

What do salivary and pancreatic amylase do?

A

Splits starch (and glycogen) into smaller fragments

64
Q

What happens to ingested disaccharide molecules?

A

They’re not acted on until they reach the small intestine

65
Q

What breaks down the disaccharides?

A

Their respective enzymes in the small intestine

66
Q

What happens to monosaccharides?

A

Absorbed by the small intestine

67
Q

How do monosaccharides get absorbed by the small intestine?

A

Facilitated diffusion through apical membrane from lumen

68
Q

How are glucose and galactose transported into absorptive cells of villi?

A

Secondary active transport via Na+/ glucose symporters

69
Q

What happens to monosaccharides after entering the absorptive cells of the villi?

A

Travelling via facilitated diffusion into the capillaries of the villi.

70
Q

What surfaces do the monosaccharides diffuse through to get to the capillaries

A

Basolateral

71
Q

Where are the majority of carbohydrates absorbed?

A

Ileum/ Jejunum

72
Q

What happens when there is excess carbohydrate intake?

A

It’s converted in the liver to fat - made by combining acetyl CoA from the link reaction

73
Q

What is the function of the mucous cells of the salivary gland?

A

Secrete a mcus which causes the food to stick together and acts as a lubricant to aid in swallowing

74
Q

True or false? No significant chemical digestion of protein occurs in the mouth?

A

True

75
Q

What protein is secreted in response to protein?

A

Gastrin

76
Q

What is the role of gastrin?

A

Stimulates acid, pepsinogen and gastric motility

77
Q

What is the name of the enzyme that breaks down phopholipids?

A

Phospholipase

78
Q

What is the brush border made from?

A

Microvilli

79
Q

Where are proteins first digested?

A

Stomach

80
Q

What is the enzyme that first breaks down proteins?

A

pepsin

81
Q

What are the main enzymes that digest carbohydrates?

A

Salivary amylase

Pancreatic amylase

82
Q

What are the different forms of gut motility?

A

Peristalsis

Segmentation

83
Q

What is peristalsis?

A

Moving the whole bolus from side to side

84
Q

What is segmentation?

A

The bolus is broken into little segments (like pushing the ends of toothpaste)

85
Q

What turns a bolus into chyme?

A

Segmentation

Stomach churning

86
Q

What is necessary to stop the stomach and duodenum from being digested by gastric acid?

A

Zymogens

87
Q

What is the name of the process that produces short chain fatty acids?

A

Fermentation

88
Q

Where are carbohydrates absorbed?

A

Ileum/ jejunum

89
Q

Where does triacylglycerol digestion begin?

A

Mouth

90
Q

What are zymogens?

A

Inactive precursors to protein

91
Q

Where are short chain fatty acids usually absorbed?

A

Stomach

92
Q

Why is pancreatic TAG lipase necessary in lipid metabolism?

A

To aid in emulsification

93
Q

Where do chylomicrons enter lymphatics?

A

Thoracic duct

94
Q

How do chylomicrons get into the fenestrations in capillaries?

A

Lipoprotein lipase in extrahepatic tissues

95
Q

What happens to chylomicron remnants after being exposed to lipoprotein lipase?

A

Taken up by liver for metabolism and recirculation

96
Q

What stabilises chylomicrons in the blood?

A

Ampipathic apoproteins, phospholipids and cholesterol

97
Q

Where is brown adipose tissue especially important?

A

Neonates

98
Q

What pairs with fatty acids in the fatty acid cycle in white adipose tissue?

A

Glycerol-3-P

99
Q

Is ATP produced by brown adipose tissue?

A

No

100
Q

What is the exogenous pathway of cholesterol metabolism?

A

When eating dietary cholesterol

101
Q

What is the endogenous pathway of cholesterol metabolism?

A

Happens everyday- LDL transported to extrahepatic tissues and macrophages

102
Q

How much of HDLs gets recycled when it returns to the liver?

A

95%

103
Q

What cell receptors recognise LDLs in extrahepatic tissues?

A

B-100

104
Q

What do HDLs interact with on the cell surface of extrahepatic tissues?

A

ABC transporters

105
Q

What is the role of LCAT in cholesterol metabolism?

A

Converts cholesterol into cholesterol ester

106
Q

What is the difference between cholesterol and cholesterol ester?

A

Cholesterol- ampipathic

Cholesterol ester - non-polar

107
Q

When HDL 3 gets bigger what does it become?

A

HDL 2

108
Q

What is the initial shape of HDL molecules?

A

Discoid

109
Q

What receptor in the liver recognises returning HDLs?

A

SR-B1

110
Q

What enzyme breaks up HDLs in the liver?

A

Hepatic lipase

111
Q

What things are necessary for cholesterol synthesis?

A

Acetyl CoA

HMG CoA reductase

112
Q

How do macrophages take up LDLs?

A

Scavenger system?

113
Q

Is the scavenger system controlled?

A

No

114
Q

What increases cholesterol uptake by macrophages?

A

Opsonization

115
Q

What enzyme converts haem to biliverdin?

A

Haem oxygenase

116
Q

Is bilirubin soluble?

A

No

117
Q

What enzyme makes bilirubin?

A

Biliverdin reductase

118
Q

What is bilirubin’s precursor?

A

Biliverdin

119
Q

What process makes bilirubin more soluble?

A

Conjugation

120
Q

Where does bilirubin migrate in its metabolism pathway?

A

Sinusoids to hepatocytes

121
Q

What is bilirubin converted to in the colon?

A

Stercobilogens and urobiligens

Phase I Medicine (46 decks)

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