B3 Digestion and Absorption Flashcards Preview

Phase I Medicine > B3 Digestion and Absorption > Flashcards

Flashcards in B3 Digestion and Absorption Deck (121):
1

How much energy is derived from protein?

40%

2

What is the first macromolecule metabolised?

Protein

3

What is the last macromolecule metabolised?

Fat

4

What are essential amino acids?

Those that cannot be synthesised in the body

5

How are essential amino acids provided for the body?

Through the diet

6

What are non-essential amino acids?

Those that can be synthesised in the body

7

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

From common metabolic intermediates via transanimation

8

What are semi-essential amino acids?

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

9

Why is glutamine important?

Used to make purines and pyrimidines in DNA synthesis

10

What are essential precursor amino acids?

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

11

What are the two essential precursor amino acids?

Cysteine and tyrosine

12

What amino acid is important in surgical trauma and sepsis?

Glutamine

13

What amino acid is relevant at times of high protein intake

Arginine

14

What amino acid is important at times of high growth?

Arginine

15

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

Glycine

16

What amino acid is present in severe trauma?

Proline

17

Why is proline important in severe trauma?

It's required for collagen synthesis

18

How are high concentrations of glycine gotten rid of?

Excreted as glycine conjugates

19

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

Protein

20

What is amino acid metabolism closely related to?

Carbohydrate and fat metabolism

21

What does amino acid breakdown give rise to?

Intermediates of carbohydrate and fat metabolism

22

What are amino acids without their amino groups known as?

Carbon skeletons

23

Where do amino acids travel to from the small intestine?

Portal vein

24

What is an acceptor in amino acid metabolism?

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

25

What vitamin is the co-factor for transaminase enzymes?

Vitamin B6

26

What does keto refer to in keto-acid?

The carbon skeleton

27

What are the 3 main transaminase enzymes?

Alanine aminotransanimase (ALT)
Aspartate aminotransferase (AST)
Glutamate aminotransferase

28

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

Liver damage

29

What is the consequence of cholestasis?

Bile can't get out of the liver

30

What is ALP?

Alkaline phosphatase

31

What do increased ALP levels indicate?

Increased synthesis by bile cannaliculi
Infiltrative disease of liver
Cirrhosis

32

What is GGT?

Gamma glutamyl transpeptidase

33

What do increased GGT levels indicate?

Cholestasis

34

What does raised GGT but normal ALP indicate?

Alcohol damage

35

What does raised ALP with normal GGT indicate?

Bone disease (e.g. Paget's)

36

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

Biliary obstruction

37

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

Hepatocellular damage

38

What is the major protein of the liver and blood?

Albumin?

39

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

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

40

What are glucogenic amino acids?

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

41

What are ketogenic amino acids?

Give rise to ketones or lose their carbons in breakdown pathways

42

Where is ammonia concentration highest in the body?

Liver

43

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

True

44

What enzymes can be responsible for forming ammonia?

Glutamate dehydrogenase
Aspartate

45

What is appreciable recycling?

Urea diffusing into gut lumen then being hydrolysed by gut bacteria

46

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

True

47

What is responsible for the conversion of urea to ammonia?

Bacteria urease

48

What is insulin's effect on gluconeogenesis and lipolysis?

Decreases it

49

What is glucagon's effect on gluconeogenesis?

Increases it

50

Where do short chain fatty acids come from?

Anything derived from milk

51

Where do we get phospholipids from?

Cell membranes

52

Where do we get cholesterol esters from?

Animal cell fat stores

53

Where do we get cholesterol from?

Animal cell membranes

54

Why does TAG need to be emulsified?

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

55

What is emulsification?

The breakdown of oils into smaller droplets

56

How are fats emulsified?

Adding energy in the stomach via churning
Stabilise the droplets with bile salts

57

Where does digestion of fats begin?

The mouth

58

Which enzyme starts breaking TAG down?

Lingual Lipase

59

What is secreted by the duodenum in response to fat?

CCK

60

What is the purpose of fat?

Inhibits gastric secretion and motility; stimulates pancreatic bicarbonate and enzyme

61

What are zymogens?

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

62

Where does carbohydrate digestion begin?

The mouth via salivary amylase

63

What do salivary and pancreatic amylase do?

Splits starch (and glycogen) into smaller fragments

64

What happens to ingested disaccharide molecules?

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

65

What breaks down the disaccharides?

Their respective enzymes in the small intestine

66

What happens to monosaccharides?

Absorbed by the small intestine

67

How do monosaccharides get absorbed by the small intestine?

Facilitated diffusion through apical membrane from lumen

68

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

Secondary active transport via Na+/ glucose symporters

69

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

Travelling via facilitated diffusion into the capillaries of the villi.

70

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

Basolateral

71

Where are the majority of carbohydrates absorbed?

Ileum/ Jejunum

72

What happens when there is excess carbohydrate intake?

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

73

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

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

74

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

True

75

What protein is secreted in response to protein?

Gastrin

76

What is the role of gastrin?

Stimulates acid, pepsinogen and gastric motility

77

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

Phospholipase

78

What is the brush border made from?

Microvilli

79

Where are proteins first digested?

Stomach

80

What is the enzyme that first breaks down proteins?

pepsin

81

What are the main enzymes that digest carbohydrates?

Salivary amylase
Pancreatic amylase

82

What are the different forms of gut motility?

Peristalsis
Segmentation

83

What is peristalsis?

Moving the whole bolus from side to side

84

What is segmentation?

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

85

What turns a bolus into chyme?

Segmentation
Stomach churning

86

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

Zymogens

87

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

Fermentation

88

Where are carbohydrates absorbed?

Ileum/ jejunum

89

Where does triacylglycerol digestion begin?

Mouth

90

What are zymogens?

Inactive precursors to protein

91

Where are short chain fatty acids usually absorbed?

Stomach

92

Why is pancreatic TAG lipase necessary in lipid metabolism?

To aid in emulsification

93

Where do chylomicrons enter lymphatics?

Thoracic duct

94

How do chylomicrons get into the fenestrations in capillaries?

Lipoprotein lipase in extrahepatic tissues

95

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

Taken up by liver for metabolism and recirculation

96

What stabilises chylomicrons in the blood?

Ampipathic apoproteins, phospholipids and cholesterol

97

Where is brown adipose tissue especially important?

Neonates

98

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

Glycerol-3-P

99

Is ATP produced by brown adipose tissue?

No

100

What is the exogenous pathway of cholesterol metabolism?

When eating dietary cholesterol

101

What is the endogenous pathway of cholesterol metabolism?

Happens everyday- LDL transported to extrahepatic tissues and macrophages

102

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

95%

103

What cell receptors recognise LDLs in extrahepatic tissues?

B-100

104

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

ABC transporters

105

What is the role of LCAT in cholesterol metabolism?

Converts cholesterol into cholesterol ester

106

What is the difference between cholesterol and cholesterol ester?

Cholesterol- ampipathic
Cholesterol ester - non-polar

107

When HDL 3 gets bigger what does it become?

HDL 2

108

What is the initial shape of HDL molecules?

Discoid

109

What receptor in the liver recognises returning HDLs?

SR-B1

110

What enzyme breaks up HDLs in the liver?

Hepatic lipase

111

What things are necessary for cholesterol synthesis?

Acetyl CoA
HMG CoA reductase

112

How do macrophages take up LDLs?

Scavenger system?

113

Is the scavenger system controlled?

No

114

What increases cholesterol uptake by macrophages?

Opsonization

115

What enzyme converts haem to biliverdin?

Haem oxygenase

116

Is bilirubin soluble?

No

117

What enzyme makes bilirubin?

Biliverdin reductase

118

What is bilirubin's precursor?

Biliverdin

119

What process makes bilirubin more soluble?

Conjugation

120

Where does bilirubin migrate in its metabolism pathway?

Sinusoids to hepatocytes

121

What is bilirubin converted to in the colon?

Stercobilogens and urobiligens