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GB lectures Flashcards

1
Q

Site of production of gastrin

A

g cells in antrum of the stomach

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2
Q

what receptor does gastrin bind to

A

CCK2 in the stomach but can also bind to CCK1 in the gallbladder

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3
Q

effect of gastrin binding to its receptor

A

binding with CCK2 increases acid production and mucosa thickening

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4
Q

what stimulates gastrin release

A

cephalic and gastric phase - vagovagal stimulation and distension caused by bolus of food
intestinal phase - by digested amino acids

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5
Q

what are the overall effects of gastrin release

A 
stimulates mucosa proliferation 
increases gastric acid release
increased growth of stomach mucosa
increased splanchnic blood flow 
causes the release of histamine
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6
Q

what hormone causes the release of histamine

A

gastrin

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7
Q

where is histamine released from

A

enterochromaffin- like cells

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8
Q

what stimulates the release of histamine

A

gastrin

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9
Q

effects of histamine

A

vasodilation

increased acid secretion

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10
Q

Site of production of CCK

A

I cells in the upper intestine (duodenum and jej.)

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11
Q

what receptor does CCK bind to

A

CCK1 in the gallbladder but can also bind to CCK2 in the stomach

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12
Q

effect of CCK binding to its receptor

A

causes the release of somatostatin from Delta cells

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13
Q

what stimulates CCK release

A

triggered by amino acids and peptides and monoglycerides and fatty acids
it is also activated by sensory afferents or by itself

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14
Q

what are the overall effects of CCK release

A

bind to CCK1 to inhibit acid secretion
bind to CCK2 to increase acid secretion
increases splanchnic blood flow

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15
Q

Site of production of secretin

A

S cells in the duodenum

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16
Q

Secretin has a similar structure to what other substances?

A

secretin is a peptide similar to VIP and glucagon

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17
Q

what stimulates secretin release

A

in response to acidic chyme of the stomach entering the duodenum
trigger - low pH and fatty acids
secretin- releasing- peptide activated by sensory afferents

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18
Q

what are the overall effects of secretin release

A

induces exocrine secretions from gallbladder and pancreas
stimulates insulin release form pancreas
decreases acid secretion via the release of somatostatin
decreases gastric motility via vagal reflex
increases blood flow

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19
Q

Site of production of somatostatin

A

produced by delta cells in the pancreas and stomach

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20
Q

what stimulates somatostatin release

A

triggered by CCK , ACh

increased blood glucose and amino acids (after eating)

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21
Q

what are the overall effects of somatostatin release

A

inhibitory effects
decreases acid production
decreases motility
decreases blood flow

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22
Q

motilin release

A

released every 90 minutes

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23
Q

what inhibits motilin release?

A

food in the stomach

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24
Q

Site of motilin release

A

mucosa of upper GI

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25
Q

what are the overall effects of motilin release

A

migrating motor complex (rumbling) which clears foreign bodies from GI tract

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26
Q

importance of migrating motor complex

A

clears foreign bodies from GI tract

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27
Q

Site of gastric inhibitory peptide release

A

k cells in the duodenum and jejunum

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28
Q

what stimulates gastric inhibitory peptide release

A

presence of food in the upper small intestine

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29
Q

what are the overall effects of gastric inhibitory peptide release

A

inhibits gastric secretions and motility

induces insulin secretion

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30
Q

Site of serotonin release

A

enterochromaffin cells

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31
Q

what stimulates serotonin release

A

vomitting

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32
Q

what is the role of antiemetics

A

antiemetics block 5-HT3 (serotonin receptor) on sensory afferent fibres (ondansetron)

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33
Q

what is the serotonin receptor

A

5-HT3

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34
Q

g cells in antrum of the stomach produce…

A

gastrin

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35
Q

why can gastrin and CCK bind to the same receptors

A

gastrin and CCK are structurally related peptides that share the same C terminal

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36
Q

what hormone binds with CCK2 and increases acid production and mucosa thickening

A

gastrin

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37
Q 
what hormone(s) do the following action:
increased splanchnic blood flow
A

gastrin
CCK
secretin

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38
Q

what hormone does the following action:

stimulates mucosa proliferation

A

gastrin

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39
Q

what hormone causes the release of histamine

A

gastrin

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40
Q

what hormone does the following action:

increased growth of stomach mucosa

A

gastrin

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41
Q 
what hormone(s) or substance(s) do the following action:
increase gastric acid secretions
A

gastrin

histamine

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42
Q

what hormone does the following action:

inhibit acid secretion

A

secretin
CCK
GIP

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43
Q

what hormones do the following action:

decreases motility

A 
secretin
GIP (no effect on intestinal motility)
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44
Q

what hormone does the following action:

decreases blood flow

A

somatostatin

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45
Q

what hormones do the following action:

increase motility

A

gastrin
CCK
motilin

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46
Q

what hormones cause insulin release in the GI tract

A

gastrin
CCK
secretin
GIP

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47
Q

the binding of hormones to CCK1 and CCK2 induce different effects. what are the effects per receptor

A

bind to CCK1 to inhibit acid secretion

bind to CCK2 to increase acid secretion

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48
Q

I cells in the upper tract produce…

A

CCK

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49
Q

S cells in the duodenum produce

A

secretin

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50
Q

delta cells in the pancreas produce

A

somatostatin

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51
Q

mucosa cells in the upper GI tract release…

A

motilin

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52
Q

k cells in the duodenum and jejunum produce

A

GIP - gastric inhibitory peptide

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53
Q

enterochromaffin cells release

A

serotonin

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54
Q

enterochromaffin-like cells release

A

histamine

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55
Q

Ondansetron

A

anti-emetic

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56
Q

what hormones induce pancreatic secretions

A

gastrin
CCK
secretin
GIP

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57
Q

which hormones are triggered by acid release

A

CCK
secretin
motilin

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58
Q

which hormone is triggered by carbohydrate release

A

GIP

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59
Q

which hormone is triggered by fat release

A

CCK
secretin
GIP
motilin

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60
Q

which hormone is triggered by protein release

A

gastrin
CCK
GIP

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61
Q

which hormones have a nervous stimuli

A

gastrin

motilin

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62
Q

which hormones are stimulated by distension

A

gastrin

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63
Q

what releases GIT peptides?

A

enteroendocrine cells distributed throughout mucosa (NOT IN GLANDS)

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64
Q

major site for GI peptide release

A

duodenum

jejunum

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65
Q

what are the conditionally essential amino acids

A

arginine
glutamine
tyrosine

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66
Q

what is a conditionally essential amino acid

A

aa that cannot be synthesised in sufficient quantities during growth and recovery

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67
Q

macrominerals intake value per day and examples

A

Ca and P

100mg/day

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68
Q

microminerals intake value per day and examples

A

Fe and Zn

< 100mg/day

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69
Q

how is a micromineral deficiency altered?

A

reversible by ingestion

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70
Q

BMR value

A

24kcal/day

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71
Q

what factors cause an increase in BMR

A

increased in males, children, hyperthyroidism and fever

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72
Q

what factors cause a decrease in BMR

A

decreased in females, hypothyroidism and in starvation

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73
Q

DIT

A

diet induced thermogenesis
thermic effect of food
10% of BMR

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74
Q

10% of BMR

A

DIT

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75
Q

thermic effect of food

A

DIT

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76
Q

Estimated average requirement

A

intake at which inadequacy is 50%

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77
Q

Recommended Dietary Allowance

A

intake at which risk is 2-3%

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78
Q

Adequate intake

A

range of healthy intake

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79
Q

upper limit

A

excessive amounts above this lead to excessive risk

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80
Q

intake at which inadequacy is 50%

A

Estimated average requirement

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81
Q

intake at which risk is 2-3%

A

Recommended Dietary Allowance

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82
Q

range of healthy intake

A

Adequate intake

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83
Q

excessive amounts above this lead to excessive risk

A

upper limit

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84
Q

total parenteral nutrition

A

IV –> H2O, glucose, AA, vitamins, salts

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85
Q

what is secondary malnutrition. give examples

A

this is a condition that prevents proper digestion/ absorption (loss of appetite, fever, infection, diarrhea, parasites)

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86
Q

what is micronutrient malnutrition

A

deficiency or too much of a vitamin/mineral

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87
Q

what is protein energy metabolism. give examples

A

underconsumption of calories or protein
marasmus - calorie deficiency
kwashiorkor - protein deficiency

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88
Q

marasmus

A

calorie deficiency

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89
Q

kwashiorkor

A

protein deficiency

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90
Q

calorie deficiency

A

marasmus

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91
Q

protein deficiency

A

kwashiorkor

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92
Q

dysphagia

A

difficulty swallowing

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93
Q

difficulty swallowing

A

dysphagia

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94
Q

name the salivary glands and describe their secretions

A

parotid - watery, serous, contains amylase
sublingual - mucous
submandibular - mixed serous and mucous, mucin, amylose

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95
Q

what gland(s) produce(s) mucous secretions?

A

sublingual

** submandibular - mixed

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96
Q

mucin

A

glycoprotein that maintains homeostasis of epithelia

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97
Q

contents of saliva

A 
mucins
alpha amylase 
lingual lipase
Ig A
lysozymes
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98
Q

compare saliva to ECF

A

saliva
less Na Cl
more K HCO3-

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99
Q

saliva production per day

A

1 L

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100
Q

compare and contrast the sympathetic and parasympathetic innervation of the salivary glands

A

both increase secretion
sympathetics constrict the vessels –> less blood flow –> less secretions
** they both allow for secretion but the parasympathetics allow for more

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101
Q

Xerostomia

A

dry mouth induced by stress

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102
Q

what are the layers of gut tube

A

lamina - mucosa - submucosa - meissner’s plexus - inner circular muscle - auerbach’s plexus - outer longitudinal muscle - serosa

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103
Q

submucosal plexus

A

meissner’s plexus

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104
Q

myenteric plexus

A

meissner’s plexus

auerbach’s plexus

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105
Q

muscularis externa

A

inner circular muscle

outer longitudinal muscle

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106
Q

where do the afferents of the intrinsic regulation of the gut go to

A

both the CNS for ANS regulation

Intramural plexus for intrinsic regulation

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107
Q

explain the phases of swallowing

A 
oral phase (voluntary)
Pharyngeal phase (reflex) - soft palate rises, epiglottis covers larynx, relaxation of the UES, constriction of the superior pharyngeal constrictor
esophageal phase (reflex) - primary peristaltic waves move food down and secondary waves clear the esophagus
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108
Q

name of reflex in swallowing

A

vagovagal reflex

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109
Q

nerves involved in pharyngeal phase of swallowing

A

CN V, VII, IX, X XII

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110
Q

nerves involved in secretion of saliva

A

CN VII, IX

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111
Q

describe the structure of the esophagus

A

divided into thirds
first - striated muscle
middle - striated and smooth muscle
last - smooth muscle

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112
Q

LES description, innervation and activity

A

physiological sphincter
always active
maintained by parasympathetics of X
vagal cholinergic activity

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113
Q

action of LES

A

relaxes ahead of peristalsis due to vagal stimulation through the release of VIP and NO

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114
Q

what is the effect of ACh, VIP and NO on the LES

A

active - contracts - ACh

inactive - relaxes - VIP and NO (INHIBITS CONTRACTION)

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115
Q

explain the process of vomiting

A

afferent X –> medulla (vomiting centre) –> V, VII, IX, X, XII efferents

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116
Q

where does the stimuli of vomiting enter the medulla and give examples of stimuli

A

enter medulla through the chemoreceptor trigger zone (bypassing the BBB)
eg. drugs, opioids, anesthesia

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117
Q

Muller’s Manoeuvre

A

forced inspiration against a closed glottis

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118
Q

Intrinsic control of the GI tract is done by the…

A

Enteric NS

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119
Q

How many neuron types are in the ENS and what are they?

A 
3
sensory (from mucosa) --> interneurons- --> motor neurons (control motility and secretions of smooth muscle and endo/exocrine cells)
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120
Q

function of motor neurons of the ENS

A

control motility and secretions of smooth muscle and endo/exocrine cells

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121
Q

plexuses of the ENS and their fxns

A

meissner’s plexus - secretion of mucosa

auerbach’s plexus - motor function of smooth muscle

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122
Q

what do excitatory fibres of the ENS release?

A

ACh

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123
Q

what do inhibitory fibres of the ENS release?

A

VIP and NO

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124
Q

Extrinsic control of the GI tract is done by the…

A

ANS

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125
Q

describe the sympathetic and parasympathetic innervation in the ANS

A

symp - arise from prevertebral ganglion –> releases noradrenaline
parasympathetics - arise from vagus nerve (upper GI) and the pelvic nerve (lower GI) - release Ach

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126
Q

what triggers the waves of smooth muscle contraction

A

cells of cajal

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127
Q

where are the cells of cajal located

A

between the circular and longitudinal muscles

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128
Q

describe the waves of smooth muscle contraction

A

initied cycles of EPSPs that do not reach the threshold of the AP
occurs along length of GI tract
fastest - duodenum
slowest - colon

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129
Q

regions of the stomach

A

secretory - fundus, body, antrum
motility - orad (proximal), caudad (distal)
the pacemaker region is divided in the 2 part

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130
Q

receptive relaxation

A

it is the vagovagal reflex of the lower esophagus and proximal stomach (orad) when swallowing
this reflex allows for an increase in volume without increasing pressure

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131
Q

Mixing in the stomach

A

controlled by mechanical stimuli
stomach distention –> gastric release
Ach release by vagus
gastrin is inhibited by secretin

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132
Q

describe the gastric phases

A

1) Cephalic
triggered by sight, smell or thought of food
release of gastrin, mucus, HCl and pepsinogen
stimulated by vagovagal and GRP (gastric releasing peptide)
2) gastric
stretch or distension of the stomach leads to an increase in the release of gastrin
stimulates mixing and emptying as well as HCO3- buffering
3) intestinal
release of CCK and secretin as receptors of the duodenum activate
amino acids entering stimulate the release of gastrin§

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133
Q

gastric glands and what they produce

A

1) surface epithelial cells - secrete thick mucus with mucin and HCO3- ; lubricates and protects against lower pH and enzymes
2) pyloric glands - located in antrum; g cells release gastrin; d cells release somatostatin (endocrine and paracrine)
3) oxyntic/ parietal cells secrete Hcl and intrinsic factor for B12 absorption
4) peptic or chief cells - secrete pepsinogen
5) enterochromaffin-like cells - secrete histamine (paracrine secretion)
6) mucous neck cells - thin mucus

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134
Q

what inhibits gastrin release

A

low pH through negative feedback

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135
Q

relationship of acid secretion and blood flow

A

acid secretion is proportional blood flow

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136
Q

process of acid secretion by oxyntic/ parietal cells

A

1) carbonic anhydrase : CO2 + H2O –> H2CO3 –> HCO3- + H+
2) Cl-/HCO3- exchanger releases HCO3- into the blood and Cl- into the stomach lumen
3) H+/K+ ATPase brings K+ into the cell and releases H+ into lumen –> H+ + Cl- –> HCl

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137
Q

what stimulates acid secretion

A

histamine

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138
Q

what inhibits acid secretion

A

somatostatin and PGE2

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139
Q

in acid secretion, Histamine uses a _____ receptor with the second messenger ____ which boosts _____ activity.

A

GPCR
cAMP
H+/K+ ATPase

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140
Q

Inhibitors such as somatostatin and PGE2 work by…

A

inhibiting the cyclisation of cAMP

H+/K+ ATPase stops working and there is no release of H+ into the lumen

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141
Q

in acid secretion, Ach and gastrin uses _____ which boosts _____ activity.

A

PLA and IP3

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142
Q

which pathway in acid secretion of the oxyntic cell is not inhibited by somatostatin and PGE2?

A

Ach and gastrin

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143
Q

CO2 + H2O –> H2CO3 enzyme

A

carbonic anhydrase

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144
Q

Cl-/HCO3- exchanger releases HCO3- into the _____ and Cl- into the _____.

A

blood

stomach lumen

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145
Q

H+/K+ ATPase brings __ into the cell and releases __ into lumen

A

K+

H+

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146
Q

too much acid secretion can cause —-

A

gastritis or inflammation of gastric mucosa

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147
Q

gastritis or inflammation of gastric mucosa caused by…

A

too much acid secretion

too little mucus secretion

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148
Q

_(bacteria)__ causes infiltration of leukocytes causing inflammation and increases acid secretion

A

helicobacter pylori

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149
Q

what do anti inflammatory medications act on inthe acid secretion pathway. example of drug

A

eg aspirin, ibuprofen

decreases the prostaglandins and increase acid secretion

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150
Q

structural adaptations of the stomach

A
  • tight junctions
  • lack of villi
    only lipid soluble substances and alcohol are absorbed here
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151
Q

composition of exocrine secretions of pancreas

A

1) aqueous component - mainly Na+ and HCO3- secreted by ductal epithelial cells
2) enzymatic component - mainly inactive precursors secreted by acinar cells

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152
Q

what pancreatic secretions are stimulated by the cephalic and gastric phases

A

vagal Ach stimulates both Acinar and ductal secretions

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153
Q

what hormones are involved in the intestinal phase and what is their action

A

1) secretin - stimulated by acid in duodenum and stimulates ductal cells to secrete HCO3- to buffer acids and Na+
2) CCK - stimulated by fat and AA in duodenum and stimulates acinar cells indirectly through vagal afferents

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154
Q

aqueous component of pancreatic secretions

A

mainly Na+ and HCO3- secreted by ductal epithelial cells

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155
Q

what do ductal epithelial cells secrete

A

Na+ and HCO3-

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156
Q

enzymatic component of pancreatic secretions

A

mainly inactive precursors secreted by acinar cells

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157
Q

what do acinar cells secrete

A

inactive precursors

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158
Q

what hormone stimulates ductal epithelial cells

A

secretin in the intestinal phase

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159
Q

what hormone stimulates acinar cells

A

CCK in the intestinal phase

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160
Q

bile is secreted by ….

A

hepatocytes

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161
Q

bile is stored in the…

A

gall bladder

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162
Q

bile is composed of

A

bilirubin, cholesterol, bile salts, other fats

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163
Q

how does CCK affect the gallbladder

A

CCK acts on CCK1 to constrict the gallbladder and secrete bile through the sphincter of oddi

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164
Q

brunner’s gland

A

located in the early duodenum and secrete mucus and HCO3- to protect af=against acidic secretion.

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165
Q

what stimulates the brunner’s gland

A

distention and PNS

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166
Q

regulation of food intake is done by the …

A

hypothalamus

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167
Q

inhibitory pathway of regulation of food intake

A

POMC (pro-opiomelanocortin pathway)
POMC containing neurons release alpha melanocyte-stimulating hormone (alpha MSH) which stimulates metabolism
the vagus nerve (X) or PNS induces satiety –> inhibits feeding

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168
Q

stimulatory pathway of regulation of food intake

A

orexigenic pathway involves neuropeptide Y which stimulates food intake and inhibits metabolism –> induces hunger

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169
Q

insulin site of production

A

beta cells of the pancreas

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170
Q

how does insulin affect the regulation of food intake?

A

induces feeling of satiety following a meal

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171
Q

orexigenic pathway

A

inhibits metabolism –> induces hunger

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172
Q

POMC (pro-opiomelanocortin pathway)

A

induces satiety –> inhibits feeding

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173
Q

inhibitory pathway of regulation of food intake -POMC containing neurons release _______ which stimulates metabolism

A

alpha melanocyte-stimulating hormone (alpha MSH)

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174
Q

stimulatory pathway of regulation of food intake -

orexigenic pathway involves ____ which stimulates food ____ and inhibits metabolism –> induces hunger

A

neuropeptide Y

intake

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175
Q

where is leptin released

A

from adipocytes

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176
Q

how does leptin affect the regulation of food intake?

A

stimulates the POMC and inhibits the NPY pathway –> induces satiety

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177
Q

what hormone inhibits the stimulatory pathway of regulation of food intake

A

leptin

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178
Q

how do gastric stimuli affect the regulation of food intake?

A

distention of stomach inhibits feeding –> satiety
CCK stimulates insulin release –> satiety
peptide YY released by enteroendocrine cells and inhibit NPY pathway –> satiety

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179
Q

how do dopaminergic neurons affect the regulation of food intake?

A

from the ventral tegmental areas of the midbrain

stimulates food intake through the reward pathway –> induces hunger

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180
Q

where do dopaminergic neurons come from?

A

from the ventral tegmental areas of the midbrain

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181
Q

enzymes and their enzymatic reactions in the digestion of proteins

A

endopeptidases (serine-protease mechanism):
trypsinogen –> trypsin (by enteropeptidase)
chymotrypsinogen –> chymotrypsin (by trypsin)
proelastase –> elastase (by trypsin)
pepsin - cleaves at N-terminal of hydrophobic AA

carboxypeptidase (metallo protease Zn2+ mechanism):
procarboxypeptidase –> carboxypeptidase (by trypsin)–> 1 of the 2 products below
1. A-C terminus of hydrophobic AAs
2. B-C terminus of basic AAs

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182
Q

trypsinogen –> trypsin (by … )

A

enteropeptidase

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183
Q

chymotrypsinogen –> chymotrypsin (by … )

A

trypsin

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184
Q

proelastase –> elastase (by …)

A

trypsin

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185
Q

carboxypeptidase (metallo protease Zn2+ mechanism):

procarboxypeptidase –> carboxypeptidase (by …)

A

trypsin

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186
Q

products of breakdown of carboxypeptidase

A
  1. A-C terminus of hydrophobic AAs

2. B-C terminus of basic AAs

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187
Q

products of protein digestion

A

tri and tetra peptides which are later cleaved by peptidases
amino acids

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188
Q

where does carbohydrate digestion occur and what is the major enzyme involved

A

mouth and intestine by salivary amylase and pancreatic amylase

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189
Q

enzymes involved in carbohydrate breakdown and their enzymatic reactions where applicable.

A

brush border enzymes of the intestine then complete digestion of disaccharides and oligosaccharides.
disaccharidases - sucrase (sucrose –> glucose) , lactase (glucose and galactose), trehalase (glucose and glucose)
oligosaccharides - glucoamylase and maltase (glucose and glucose) which digests maltose and maltotriose

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190
Q

where are brush border enzymes found

A

small intestine

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191
Q

disaccharidases

A

sucrase (sucrose –> glucose) , lactase (glucose and galactose), trehalase (glucose and glucose)

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192
Q

oligosaccharides

A

glucoamylase and maltase (glucose and glucose) which digests maltose and maltotriose

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193
Q

products of carbohydrate digestion

A 
glucose 
fructose
galactose
maltose
maltotriose 
alpha limit dextrins
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194
Q

villi of the small intestine are covered with ______ cells

A

columnar epithelial

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195
Q

most chyme is absorbed before getting to what area of the GI tract

A

jejunum

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196
Q

explain the absorption of proteins

A

absorption of peptides is much faster than amino acids

1) Na/H+ exchanger maintains H+ gradient which allows peptides to enter by cotransport
2) once inside, peptides are metabolised into free AAs. they enter the blood by facilitated diffusion
3) glutamate and aspartate are utilised as energy –> not transported

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197
Q

absorption of proteins -

_____ maintains H+ gradient which allows peptides to enter by ___

A

Na/H+ exchanger

cotransport

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198
Q

absorption of proteins -

absorption of ____ is much faster than ____

A

peptides

amino acids

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199
Q

absorption of proteins - once inside, peptides are metabolised into ____ . they enter the blood by ____

A

free AAs

facilitated diffusion

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200
Q

absorption of proteins -

______ are utilised as energy –> not transported

A

glutamate and aspartate

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201
Q

explain the absorption of monosaccharides

A

occurs either by passive diffusion (very very slow) or facilitated diffusion

APICAL
1) SGLT1 -
cotransport of glucose along with 2Na+
maintained by na/k ATPase pump (secondary active transport)
2) GLUT5 -
facilitated diffusion of fructose into the enterocyte

BASAL
1) GLUT2 -
facilitated diffusion of fructose, glucose, and galactose across basal membrane into blood (one way transport)
2) GLUT1 -
2-way transport of glucose (facilitated) across basal membrane

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202
Q

site of protein digestion

A

stomach (pH2) and intestines

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203
Q

action of SGLT1

A

cotransport of glucose along with 2Na+

maintained by na/k ATPase pump (secondary active transport)

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204
Q

action of GLUT5

A

facilitated diffusion of fructose into the enterocyte

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205
Q

action of GLUT2

A

facilitated diffusion of fructose, glucose, and galactose across basal membrane into blood (one way transport)

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206
Q

action of GLUT1

A

2-way transport of glucose (facilitated) across basal membrane

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207
Q

mechanism of transport by SGLT1

A

secondary active transport

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208
Q

mechanism of transport by GLUT proteins

A

facilitated diffusion

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209
Q

what transport proteins involved in the absorption of monosaccharides are found on the apical border?

A

SGLT1

GLUT5

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210
Q

what transport proteins involved in the absorption of monosaccharides are found on the basal membrane?

A

GLUT2

GLUT1

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211
Q

what is the site of lipid digestion and what enzymes are involved

A

starts in the mouth with lingual lipase and continues into the stomach (gastric lipase) and the small intestine (bile emulsification and pancreatic enzymes)

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212
Q

action of lingual lipase and gastric lipase

A

they are both acid-stable and work in the stomach

they act on triglycerides with short-medium fatty acid chains (<12)

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213
Q

how do bile salts affect lipid digestion

A

emulsification of lipids by bile salts increases SA for enzymes to work effectively

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214
Q

what substance emulsifies lipids

A

bile salts

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215
Q

explain the breakdown of lipids by pancreatic enzymes

A

pancreatic enzymes are hormonally controlled
1) pancreatic lipase - binds to lipid droplets only in the presence of pancreatic colipase
2) cholesterol esterase - hydrolyses cholesterol esters into cholesterol FAs
3) phospholipase A2 -
activated by trypsin; digests phospholipids –> lysophospholipids by removing 1 FA
4) lysophospholipase - removes the remaining FA at C1, leaving glyceryl phosphoryl

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216
Q

action of pancreatic lipase

A

binds to lipid droplets only in the presence of pancreatic colipase

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217
Q

action of cholesterol esterase

A

hydrolyses cholesterol esters into cholesterol FAs

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218
Q

action of phospholipase A2

A

activated by trypsin; digests phospholipids –> lysophospholipids by removing 1 FA

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219
Q

action of lysophospholipase

A

removes the remaining FA at C1, leaving glyceryl phosphoryl

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220
Q

what enzyme binds to lipid droplets only in the presence of pancreatic colipase

A

pancreatic lipase

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221
Q

what enzyme hydrolyses cholesterol esters into cholesterol FAs

A

cholesterol esterase

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222
Q

what enzyme is activated by trypsin; digests phospholipids –> lysophospholipids by removing 1 FA

A

phospholipase A2

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223
Q

what enzyme removes the remaining FA at C1, leaving glyceryl phosphoryl

A

lysophospholipase

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224
Q

what are the primary products of lipid digestion

A

fatty acids
cholesterol
2-monoacylglycerol

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225
Q

explain the process of lipid absorption

A

1) the products of lipid digestion (fatty acids, cholesterol, 2-monoacylglycerol) are combined with bile salts and phospholipids to form mixed micelles which have a hydrophobic surface
2) the brush border of enterocytes have a water layer through which the micelle cells can pass and are then absorbed into the enterocyte
* short and medium chain FA do not require micelles for absorption)
3) FAs and monoglycerides are transported into the ER to re-synthesize TGs
4) TGs are then grouped with cholesterol, phospholipids, vitamins and apolipoprotein B48 to form chylomicrons and are then excreted into the lymph.

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226
Q

formation of a mixed micelle

A

the products of lipid digestion (fatty acids, cholesterol, 2-monoacylglycerol) are combined with bile salts and phospholipids to form mixed micelles which have a hydrophobic surface

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227
Q

formation of a chylomicron

A

TGs are then grouped with cholesterol, phospholipids, vitamins and apolipoprotein B48 to form chylomicrons and are then excreted into the lymph.

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228
Q

digestion of iron

A

iron can be divided into heme and non-heme (food) iron.

both are digested by proteases in the stomach and intestine aided by HCl and vitamin C in order to release the iron.

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229
Q

in the stomach most non-heme iron is ____.

A

Fe3+

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230
Q

site of digestion of iron

A

stomach and small intestine

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231
Q

enzyme involved in digestion of iron

A

proteases (aided by HCl and vitamin C for iron release)

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232
Q

Explain the absorption of iren

A

1) HEME IRON
heme is absorbed entirely by the HCP1 (heme carrier protein) and Fe2+ is released from heme by heme-oxidase
2) NON-HEME IRON
Fe3+ (from stomach) is reduced by reductase D cyt B (duodenal cytochrome B) into Fe2+ and is then transported into the enterocyte via the DMT1 (divalent metal transporter)
3) Fe2+ from both the heme and non-heme iron in the enterocyte, are either stored as ferritin (protein) or converted back into Fe3+ by Hephestin where it binds to transferrin for transport around the body. it leave the basolateral membrane via FPN (ferroportin)
4) transferrin-bound iron (Fe3+) is carried to stores and bone marrow where it is absorbed via receptor-mediated endocytosis
5) A CURL (compartment of uncoupling of receptor and ligand) is then formed which releases Fe3+ from transferrin where it is stored as ferritin. Apotransferrin (transferrin without Fe3+) is recycled at the cell surface)

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233
Q

describe the breakdown of heme iron

A

heme absorbed by HCP1

Fe2+ is released from heme by heme-oxidase

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234
Q

what enzyme releases Fe2+ from heme iron

A

heme-oxidase

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235
Q

what protein absorbs heme iron

A

HCP1

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236
Q

describe the breakdown of non-heme iron

A

Fe3+ is broken down by reductaseD cytB –> Fe2+

transported into the enterocyte via DMT1

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237
Q

what transporter allows for the entry of Fe2+ from the stomach into the enterocyte

A

DMT1

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238
Q

what enzyme is responsible for the breakdown of Fe3+ in the stomach

A

reductase D cyt B

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239
Q

discuss the what happens to Fe2+ as it moves into the enterocyte

A

either stored as ferritin

converted back to fe3+ by hephestin which then binds to transferrin and leaves the basolateral membrane via ferroportin

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240
Q

what enzyme converts Fe2+ into Fe3+ in the enterocyte

A

Hephestin

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241
Q

what can Fe2+ be stored as

A

ferritin

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242
Q

to leave the enterocyte, Fe3+ must bind to what transport protein?

A

transferrin

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243
Q

what receptor does Fe3+ use to exit the basolateral membrane?

A

ferroportin

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244
Q

transferrin-bound iron (Fe3+) is carried to stores and bone marrow where it is absorbed via _____

A

receptor-mediated endocytosis

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245
Q

what is the function of the formation of a CURL

A

releases Fe3+ from transferrin where it is stored as ferritin

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246
Q

what is ferritin

A

protein containing ferric oxide hydroxide crystals (FcOOH)

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247
Q

what hinders the absorption of iron

A 
tanins
oxalate
phytate
inorganic phosphates
antacids
248
Q

deficiency of iron

A

anemia

249
Q

hepcidin

A

peptide hormone secreted by liver to regulate the entry of iron into circulation
it regulates iron absorption, plasma iron concentration and iron distribution.

250
Q

peptide hormone secreted by liver to regulate the entry of iron into circulation
it regulates iron absorption, plasma iron concentration and iron distribution.

A

hepcidin

251
Q

what receptor does hepcidin act on?

A

ferroportin

252
Q

significance of increased hepcidin levels

A

during infection and inflammation to restrict iron access to pathogens

253
Q

when iron levels drop, storage iron is mobilized first and then haemoglobin synthesis is impaired which leads to …

A

microcytic hypochromic anemia

254
Q

microcytic hypochromic anemia

A

when iron levels drop, storage iron is mobilized first and then haemoglobin synthesis is impaired

255
Q

hemosiderosis

A

accumulation of ferritin and hemosiderin which leads to free radical generation

256
Q

progression of hemosiderosis

A

organ damage - hemochromatosis

257
Q

accumulation of ferritin and hemosiderin which leads to free radical generation

A

hemosiderosis

258
Q

hemochromatosis

A

organ damage by progression of hemosiderosis

259
Q

precursors of heme

A

glycine and succinyl coA

260
Q

what determines the half life of a protein

A

N terminus residues

261
Q

degradation of a protein is done by…

A

ubiquitination (proteasomal system) or the lysosomal system

262
Q

n terminus of rapidly degraded proteins

A 
PEST
proline 
glutamine
serine
threonine
263
Q

what happens to amino acids in the body - protein turnover

A

Not stored. reused or broken down by the removal of NH3 group
NH3 goes to the urea cycle and the carbon skeleton is broken down to water and CO2

264
Q

main organs involved in amino acid level regulation and what processes occur in the organs

A

muscles (aa generation)

liver (gluconeogenesis, utilization and excretion)

265
Q

function of Glucose - Alanine Cycle

A

regulates the aa level

266
Q

Glucose - Alanine Cycle

A 
(in liver)
Alanine-->pyruvate + NH2
NH2--> urea 
Pyruvate --> glucose (transported to muscles)
glucose --> pyruvate 
pyruvate  lactate 
pyruvate  alanine (aaalpha keto acid)
(transported to liver)
267
Q

how is alanine synthesized

A

from glucose by the transamination from an amino acid into and alpha keto acid in the muscle.

268
Q

what does the liver convert alanine to

A

glucose via pyruvate through gluconeogenesis

269
Q

what reaction occurs with the following:

pyruvate alanine

A

aaalpha keto acid

270
Q

what class of aa yield TCA intermediates

A

glucogenic

271
Q

the breakdown of what class of aa yields acetoacetate or acetyl coA. give an example

A

ketogenic

leucine and lysine (all essential)

272
Q

examples of aa which are both ketogenic and glucogenic

A

isoleucine
phenylalanine
tryptophan
(essential)

tyrosine (nonessential)

273
Q

what aa can be made from phenylalanine

A

tyrosine

274
Q

what aa can be made from

glycine

A

serine

275
Q

what aa can be made from

serine

A

glycine

276
Q

serine can be further broken to what intermediate in the glycolysis pathway

A

pyruvate

277
Q

what reaction occurs with the following:
alaninepyruvate
what enzyme is used?

A

alpha ketoglutarate glutamate

alanine aminotransferase

278
Q

describe transamination and oxidative deamination

A

transamination is the transfer of the amino group from an amino acid to an alpha ketoglutarate to form glutamate and an alpha keto acid. vitamin B is used as a coenzyme. the enzyme involved is known as a transaminase.

oxidative deamination is the conversion of glutamate to alpha ketoglutarate by the removal of the NH4+ group .

279
Q

how is glutamine made from glutamate

A

by the addition of a NH3 group
glutamate –> glutamine
NH3 +ATP –> ADP + Pi

280
Q

how is glutamate made from glutamine

A

removal of a NH3 group
glutamine –> glutamate
H2O –> NH3

281
Q

transamination of alanine

A

alanine pyruvate
Alpha ketoglutarate glutamate
enzyme - alanine aminotransferase

282
Q

transamination of aspartate

A

aspartate oxaloacetate
Alpha ketoglutarate glutamate
enzyme - aspartate aminotransferase

283
Q

what reaction is catalysed by glutamate dehydrogenase

A

Glutamate –> Alpha ketoglutarate
NAD+ –> NADH
NH3 removed

Alpha ketoglutarate –> glutamate
NADPH –> NAD+
NH3 added

284
Q

describe oxidative and reductive amination

A

reductive - amino group added to the Alpha ketoglutarate and NADPH oxidized to NAD+ to form glutamate

oxidative - amino group is removed from glutamate and NAD+ is reduced to NADH to form Alpha ketoglutarate

285
Q

significance of the pathway catalysed by glutamate dehydrogenase

A

synthesis of amino acids§

286
Q

how are amino acids synthesized?

A

reductive amination followed by transamination

287
Q

how are amino acids disposed

A

transamination followed by oxidative deamination

288
Q

when the amino group is removed from an aa, they can be degraded into …

A

1) intermediate of TCA (glucogenic)

2) acetoacetate/ acetyl CoA (ketogenic)

289
Q

Urea Cycle

A

1) transamination (goes to liver) - amino group removed from aa and added to the alpha ketoglutarate to form glutamate
2) transamination 2 (goes to liver) - aspartate aminotransferase transfers an amino group from glutamate
3) oxidative deamination (in liver) - glutamate is oxidised by glutamate dehydrogenase into Alpha ketoglutarate, releasing NH3
4) NH3 combines with CO2 to form Carbamoyl phosphate using 2ATP
5) carbamoyl phosphate combines with ornithine to form citrulline
6) citrulline combines with aspartate to form argininosuccinate using 1ATP
7) argininosuccinate is then broken down into fumarate and arginine where fumarate can join the TCA cycle to form oxaloacetate with malate.
8) arginine is then hydrated (+ H2O) releasing urea with 2NH4 molecules and hence leaving with ornithine

290
Q

total energy used in urea cycle

A

3
2 for NH3 to combine with CO2
1 for citrulline to combine with aspartate to form argininosuccinate

291
Q

how many NH4 molecules are formed from 1 urea cycle and what molecules do they arise from

A

2
1st - glutamate
2nd - aspartate

292
Q

end product of the urea cycle

A

2 NH4 molecules

293
Q

aspartate is added to what step in the urea cycle and what molecule does it leave as

A

citrulline –> argininosuccinate

fumarate

294
Q

what enzyme catalyses the following reaction:

NH3 combines with CO2 to form Carbamoyl phosphate using 2ATP

A

carbamoyl phosphate synthetase 1

295
Q

what enzyme catalyses the following reaction:

carbamoyl phosphate combines with ornithine to form citrulline

A

ornithine transcarbamylase (OTC)

296
Q

what enzyme catalyses the following reaction:

citrulline combines with aspartate to form argininosuccinate using 1ATP

A

argininosuccinate synthase

297
Q

what enzyme catalyses the following reaction:

argininosuccinate is then broken down into fumarate and arginine

A

argininosuccinate lyase

298
Q

what enzyme catalyses the following reaction:

arginine is then hydrated (+ H2O) releasing urea with 2NH4 molecules and hence leaving with ornithine

A

arginase

299
Q

which molecules involved in the urea cycle are found in the mitochondrial matrix

A

ornithine

citrulline

300
Q

what is the significance of the formation of glutamate and aspartate

A

safely transport NH3 into the liver

301
Q

what occurs if free ammonia levels exceed the capacity of the urea cycle

A

plasma levels begin to rise causing toxicity to the CNS.

302
Q

cause of hyperammonemia

A

acquired - liver disease such as OTC deficiency

inherited - x linked

303
Q

liver disease such as OTC deficiency is a cause of

A

acquired hyperammonemia

304
Q

explain the body’s response to being in the fed state

A 
inc insulin
anabolism 
liver increases the production of glycogen, proteins, VLDL
adipose cells make triglycerides
muscle - makes protein
305
Q

explain the body’s response to being in the fasting state

A

increased glucagon
catabolism
liver - gluconeogenesis, glycogenolysis, Beta oxidation of fatty acids
adipose - lipolysis
muscle - uses FAs and ketone bodies as fuel
brain - uses glucose and ketone bodies

306
Q

ketone bodies are a product of _____

they are transported to tissues to be converted to ______.

A

Beta oxidation of fatty acids

acetyl coA

307
Q

where does gluconeogenesis occur

A

90% liver

10% kidney

308
Q

liver can support blood glucose levels for how long?

A

10-18 hours

309
Q

substrates for gluconeogenesis

A

lactate
glycerol
amino acids

310
Q

gluconeogenesis reaction

A

1) pyruvate carboxylase: pyruvate –> oxaloacetate (cofactor - biotin)
2) PEP carboxykinase: oxaloacetate –> PEP
3) Fructose-1,6-bisphosphatase: fructose-1,6-bisphosphate –> glucose-6-phosphate
4) glucose-6-phosphatase: glucose-6-phosphate –> glucose (glucose-6-phosphate translocase)

311
Q

what enzyme catalyses the following reaction:

pyruvate –> oxaloacetate

A

pyruvate carboxylase

cofactor - biotin

312
Q

what enzyme catalyses the following reaction:

oxaloacetate –> PEP

A

PEP carboxykinase

313
Q

what enzyme catalyses the following reaction:

fructose-1,6-bisphosphate –> glucose-6-phosphate

A

Fructose-1,6-bisphosphatase

314
Q

what enzyme catalyses the following reaction:

glucose-6-phosphate –> glucose

A

glucose-6-phosphatase

glucose-6-phosphate translocase

315
Q

bonds in glycogen

A

alpha 1,4 and alpha 1,6 glycosidic bonds

316
Q

where is glycogen stored? function?

A

liver to maintain blood glucose and muscle as fuel release

317
Q

explain glycogen synthesis

A

Glycogen synthase adds glucose units to non-reducing ends of an existing glycogen molecule. If there is not glycogen present, glycogenin acts as in new primer to accept glucose units to form in new chain.

318
Q

Building block of glycogen

A

UDP glucose

319
Q

Describe the structure of glycogenin and its importance in binding with glucose.

A

Glycogenin has a last residue of tyrosine which joins OH for binding

320
Q

Function of glycogenin

A

Remains attached to the growing chain and serves as a primer

321
Q

What are the branches of glycogen from by

A

Branching enzyme - amylo alpha(1,4)–>alpha(1,6) transglucosidase

322
Q

Glycogen synthesis

A

G-6-P UTP + G-1-P (phosphoglucomutase) [isomerisation]
UTP + G-1-P –> UDP glucose + PPi
(UDP glucose pyrophosphorylase)
[dephosphorylation]
UDP glucose –> glycogenin-G-G-G
(glycogen synthase) glycogenin is incorporated at this step and UDP is removed

323
Q

What are the branches of glycogen removed by

A

debranching enzyme

324
Q

TGs are resynthesized by what enzyme and from what

A

acyl coA and 2-monoacylglycerol

enzyme - acyl coA synthase

325
Q

acyl coA is made up of

A

FA + coA

326
Q

when fat is in the lymph, where does it enter the blood stream

A

thoracic duct

327
Q

glycogen phosphorylase

A

cleaves alpha 1-4 glycosidic bonds succeeding at the non-reducing ends, releasing them as glucose-1-phosphate
this enzyme stops at 4 residues before each branch, leaving a structure called limit dextrin which is removed by a debranching enzyme

328
Q

glycogen break down

A

1) glycogen phosphorylase: cleaves alpha 1-4 glycosidic bonds succeeding at the non-reducing ends, releasing them as glucose-1-phosphate
2) this enzyme stops at 4 residues before each branch, leaving a structure called limit dextrin which is removed by a debranching enzyme
3) G-1-P is then converted to G-6-P by phosphoglucomutase (same enzyme used in glycogen synthesis)
4) in the liver, G-6-P is changed into glucose by glucose-6-phosphorylase as it enters the blood

329
Q

glycogen breakdown - glycogen phosphorylase stops at 4 residues before each branch, leaving a structure called _____ which is removed by a _____

A

limit dextrin

debranching enzyme

330
Q

phosphoglucomutase

A

G-1-P is then converted to G-6-P

331
Q

G-6-P is changed into glucose by

A

glucose-6-phosphorylase

332
Q

G-1-P is then converted to G-6-P by

A

phosphoglucomutase

333
Q

glycogen phosphorylase cleaves ____ and releases them as _____

A

alpha 1-4 glycosidic bonds

glucose-1-phosphate

334
Q

regulation of glycogen

A

glycogen synthase and glycogen phosphorylase respond to:
1. allosteric regulation -
G-6-P allosterically activates glycogen synthase and inhibits glycogen phosphorylase
in the muscle, Ca2+ and AMP activate glycogen phosphorylase as they indicate the need for energy
2. hormonal regulation -
glucose synthase is activated when it is unphosphorylated
glucose phosphorylase is active when it is phosphorylated
glycogen (non - fed) and adrenaline (need for energy) activate cAMP dependant PKA which promotes phosphorylation
–> promotes glycogen phosphorylase –> increases glycogen breakdown –> increases glucose
–> inhibits glycogen synthase

335
Q

adipose tissue lipase

A

hormone sensitive enzyme that is responsible for breakdown of fat –> active when phosphorylated (activated by glucagon and adrenaline)

336
Q

hormone sensitive enzyme that is responsible for breakdown of fat

A

adipose tissue lipase

337
Q

activation of adipose tissue lipase

A

active when phosphorylated (activated by glucagon and adrenaline)

338
Q

allosteric regulation of glycogen

A

G-6-P allosterically activates glycogen synthase and inhibits glycogen phosphorylase
in the muscle, Ca2+ and AMP activate glycogen phosphorylase as they indicate the need for energy

339
Q

G-6-P allosterically activates ____ and inhibits _____

A

glycogen synthase

glycogen phosphorylase

340
Q

in the muscle, ____ activate glycogen phosphorylase

A

Ca2+ and AMP

341
Q

hormonal regulation of glycogen

A

glucose synthase is activated when it is unphosphorylated
glucose phosphorylase is active when it is phosphorylated
glycogen (non - fed) and adrenaline (need for energy) activate cAMP dependant PKA which promotes phosphorylation
–> promotes glycogen phosphorylase –> increases glycogen breakdown –> increases glucose
–> inhibits glycogen synthase

342
Q

hormonal regulation of glycogen - _____ is activated when it is unphosphorylated

A

glucose synthase

343
Q

hormonal regulation of glycogen - _____ is active when it is phosphorylated

A

glucose phosphorylase

344
Q

hormonal regulation of glycogen. - glucose synthase is activated when it is ______

A

unphosphorylated

345
Q

hormonal regulation of glycogen - glucose phosphorylase is active when it is _____

A

phosphorylated

346
Q

hormonal regulation of glycogen - ______ activate cAMP dependant PKA which promotes phosphorylation

A

glycogen (non - fed) and adrenaline (need for energy)

347
Q

hormonal regulation of glycogen -

glycogen (non - fed) and adrenaline (need for energy) activate _____ which promotes ______

A

cAMP dependant PKA

phosphorylation

348
Q

comment on the promotion and inhibition of hormones in the hormonal regulation of glycogen

A
  • -> promotes glycogen phosphorylase –> increases glycogen breakdown –> increases glucose
  • -> inhibits glycogen synthase
349
Q

GSDs

A

glycogen storage disorders

abnormal synthesis or breakdown of glycogen

350
Q

GSD1

A

von gierke’s disease - G-6- phosphatase deficiency
inability to produce glucose by gluconeogenesis
inability to maintain glucose levels (hypoglycemia)

351
Q

inability to produce glucose by gluconeogenesis

inability to maintain glucose levels (hypoglycemia)

A

von gierke’s disease - G-6- phosphatase deficiency

GSD1

352
Q

von gierke’s disease

A

G-6- phosphatase deficiency
GSD1
inability to produce glucose by gluconeogenesis
inability to maintain glucose levels (hypoglycemia)

353
Q

GSD V

A

McArdle Disease
muscle glycogen phosphorylase deficiency
muscle cannot breakdown glycogen
muscle fatigue

354
Q

McArdle Disease

A

GSD V
muscle glycogen phosphorylase deficiency
muscle cannot breakdown glycogen
muscle fatigue

355
Q

muscle glycogen phosphorylase deficiency
muscle cannot breakdown glycogen
muscle fatigue

A

McArdle Disease

GSD V

356
Q

G-6- phosphatase deficiency

A

von gierke’s disease

GSD1

357
Q

muscle glycogen phosphorylase deficiency

A

McArdle Disease

GSD V

358
Q

conversion of aa in lipid absorption

A

apolipoprotein b48

359
Q

conversion of monoacylglycerol in lipid absorption

A

TG by acyl coA synthase

360
Q

conversion of cholesterol in lipid absorption

A

cholesterol ester

361
Q

path of components in lipid absorption

A

apolipoprotein b48, TG, cholesterol ester, fat soluble vitamins, phospholipids —> chylomicron —> lymphatics —> thoracic duct

362
Q

where are Lipoprotein lipases found

A

most tissue except for brain and liver

363
Q

the adipose LPL os attached to _________ on the surface of the capillary epithelium

A

heparan sulphate glycoproteins

364
Q

what occurs when chylomicrons bind to LPL

A

hydrolyse TGs directly

365
Q

the binding of ___ and ____ hydrolyse TGs directly

A

chylomicrons and LPL

366
Q

after a meal, where do the fatty acids involved in TG synthesis come from

A

chylomicrons

367
Q

what does adipose tissue release

A

unesterified FA

free FA

368
Q

where does TG synthesis occur

A

adipose but also in liver and ammary glands

369
Q

FAs participate in TG synthesis in the form of ____ and ___ as G-3-P (biproduct of glycolysis)
what enzyme is uses?
** this is the rate limiting step

A

thioesters
glycerol
enzyme - glycerol phosphate-acyltransferase

370
Q

glycerol phosphate-acyltransferase

A

used in the synthesis of TG

371
Q

what stimulates TG synthesis

A

insulin which:
increase glycolysis –> increase G-3-P
increased LPL activity
induces glycerol phosphate-acyltransferase

372
Q

TG breakdown is catalysed by ____ and occurs by the stepwise removal of _____

A

lipase

each of the 3FA

373
Q

rate limiting step of TG breakdown

A

first cleavage

374
Q

how is lipase activated in TG breakdown

A

similar to glycogen breakdown, lipase is activated through phosphorylation by PKA as well as SNS innervation
adrenaline and glucagon also stimulates it

375
Q

what induces lipid breakdown

A

glucocorticoids, GH, TH

376
Q

Beta oxidation

A

this is a 2 step process which occurs in all cell types that have a mitochondria

  1. transport - shorter FAs can enter the mitochondrial membrane by passive diffusion whilst long chain FA require carriers eg. carnitine shuttle (CPT1 and CPT2)
    a. FAs are converted into their coA thioesters –> FA coA which then crosses the outer membrane
    b. CPT1 on the outer membrane replace the coA with carnitine –> FA carnitine goes through the inner membrane with translocase
    c. CPT2 on the inner membrane removes carnitive and adds back acetyl coA –> FAcoA. carnitine is then sent back into the intermembrane space through a translocase again
  2. beta oxidation
    cyclic reaction where 2Cs –> 1 NADH and 1 FADH2 –> 5ATP
    acetyl coA is not a substance for gluconeogenesis but stimulates pyruvate carboxylase ( pyruvate –> oxaloacetate)
    goal - generate ATP/energy from FA oxidation
377
Q

what cell type can beta oxidation not occur

A

RBC (not with mitochondria)

378
Q

transport of long chain FA

A

a. FAs are converted into their coA thioesters –> FA coA which then crosses the outer membrane
b. CPT1 on the outer membrane replace the coA with carnitine –> FA carnitine goes through the inner membrane with translocase
c. CPT2 on the inner membrane removes carnitive and adds back acetyl coA –> FAcoA. carnitine is then sent back into the intermembrane space through a translocase again

379
Q

what provides FAs for ketone production and in what form are they released?

A

adipose tissue

released as thioesters

380
Q

what transporters are found on the outer membrane of the mitochondria?

A

CPT1

381
Q

what transporters are found on the inner membrane of the mitochondria?

A

CPT2

translocase

382
Q

beta oxidation

cyclic reaction

A

removal of 2Cs (from FA coA) –> 1 NADH and 1 FADH2 –> 5ATP
acetyl coA is not a substance for gluconeogenesis but stimulates pyruvate carboxylase ( pyruvate –> oxaloacetate)
goal - generate ATP/energy from FA oxidation

383
Q

what enzyme involved in gluconeogenesis is stimulated by acetyl coA. what does it do?

A

pyruvate carboxylase ( pyruvate –> oxaloacetate)

384
Q

regulation of beta oxidation

A

malonyl coA is the first intermediate in FA synthesis and inhibits CPT1 –> FA synthesis and beta oxidation cannot occur at the same time
beta oxidation is dependant on the supply of free FA –> proportional to activity of adipose tissue

385
Q

what does CPT1 do

A

replace the coA with carnitine –> FA carnitine

386
Q

what does CPT2 do

A

removes carnitive and adds back acetyl coA –> FAcoA.

387
Q

FA synthesis and beta oxidation cannot occur at the same time. why?

A

malonyl coA is the first intermediate in FA synthesis and inhibits CPT1

388
Q

malonyl coA

A

first intermediate in FA synthesis and inhibits CPT1

FA synthesis and beta oxidation cannot occur at the same time.

389
Q

what enzyme inhibits CPT1?

A

malonyl coA

390
Q

beta oxidation is dependant on the _______ which is proportional to ______

A

supply of free FA

activity of adipose tissue

391
Q

ketogenesis - acetoacetate and beta hydroxybutyrate

A

ketone bodies, namely acetoacetate and beta hydroxybutyrate, are formed from acetyl coA in the liver mitochondrial cells ONLY.
They can also join the TCA cycle via acetyl coA

392
Q

ketone bodies

A

acetoacetate
beta hydroxybutyrate
acetone

393
Q

ketogenesis - acetone

A

formed by spontaneous decarboxylation of acetoacetate

394
Q

acetone is formed from the decarboxylation of

A

acetoacetate

395
Q

decarboxylation of acetoacetate forms

A

acetone

396
Q

the ketogenesis of acetone is a what type of rxn

A

decarboxylation

397
Q

acetyl coA can contribute to

A

TCA cycle
ketone bodies
oxaloacetate

398
Q

importance of ketone bodies

A

ketone bodies are important as they are transported to the heart, adrenal glands and renal cortex to be reconverted back to acetyl coA to be used in the TCA cycle. this represents the main energy source for these organs

399
Q

use of brown adipose

characterised by

A 
heat metabolism (instead of ATP) 
it is characterised by good blood supply, mitochondria and cytochromes but low ATP synthase
400
Q

MCADD

A

deficiency of medium chain acyl coA dehydrogenase which represents the first rate limiting step of beta oxidation.
it leads to the intolerance to fasting, impaired ketogenesis and hypoglycemia.

401
Q

deficiency of medium chain acyl coA dehydrogenase

A

MCADD

leads to the intolerance to fasting, impaired ketogenesis and hypoglycemia.

402
Q

circulating levels of ketone bodies are normally very low but increases during

A

fasting, diabetes, when fat breakdown is more than carb breakdown

403
Q

electrical impedance uses

A

higher resistance of fat that water to take measurements

404
Q

most accurate way to measure body fat

A

dual z-ray absorption

405
Q

relationship of BMI and mortality

A

v or J shaped relationship curve but waist circumference is a better tool

406
Q

metabolically healthy obese individuals have

A

normotension
normal lipid profile
normal liver function
low visceral/ ectopic fat

407
Q

what is visceral/ectopic fat

A

dangerous kind of fat since it is hormonally active

408
Q

obesity paradox

A

obese patients are more likely to suffer a heart attack but less likely to die from it

409
Q

____ is a better indication to mortality than ____

A

fitness

weight

410
Q

when fitness is involved, ___________ has no effect on mortality

A

BMI

pattern of exercise

411
Q

for people with high muscle mass or for adolescents, BMI should be measured by

A

kg/m^3 instead of kg/m^2

412
Q

eating hormones

A
  1. ghrelin - produced in the stomach - triggers desire to eat by binding to the secretagogue
    receptor in the arcuate nucleus in the brain, associated with dopamine response pathway
  2. leptin - produced by adipose tissue - triggers satiety. increases POMC secretion
    receptor also in arcuate nucleus in the brain
413
Q

ghrelin produced by

A

stomach

414
Q

ghrelin

A

triggers desire to eat by binding to the secretagogue

receptor in the arcuate nucleus in the brain, associated with dopamine response pathway

415
Q

ghrelin bind to

A

secretagogue

receptor in the arcuate nucleus in the brain

416
Q

leptin produced by

A

adipose tissue

417
Q

leptin

A

triggers satiety. increases POMC secretion

receptor also in arcuate nucleus in the brain

418
Q

leptin receptor

A

receptor also in arcuate nucleus in the brain

419
Q

POMC secretion is increased by

A

leptin

420
Q

enzyme that triggers desire to eat

A

ghrelin

421
Q

enzyme that triggers satiety

A

leptin

422
Q

weight loss in people with obesity causes changes in

A

appetite hormones (leptin and ghrelin) that can increase hunger for up to 1 year

423
Q

_____ is used in patients who failed to lose weight through dietary eg. ____

A

pharmacotherapy

orlistat

424
Q

liposuction reduces ______ not _____. comment on its efficiency.

A

subcutaneous fat
visceral fat
therefore has no benefit

425
Q

Bariatric surgery

A

reduces the consumption and absorption of food

426
Q

reduces the consumption and absorption of food

A

Bariatric surgery

427
Q

Bariatric surgery is recommended for

A

people with a BMI above 40
hyperlipidemia
hypertension
diabetes

428
Q

stages of weight complications

A

0 - no complications - if overweight - lifestyle therapy, if obese - pharmacotherapy and weight loss medication
1 - mild/ moderate complications - weight loss medication
2 - severe complications - bariatric surgery

429
Q

kwashiorkor

A

inadequate protein intake - edema, peeling skin, pigmented hair

430
Q

malnutrition is graded on a

A

graded on a z-scale
wasting is -2 to -3 based on weight/height
stunting is -2 to -3 based on height

431
Q

treating malnutrtion

A

phase 1 -
rehydration - resomal (reduced Na and increased K)
feeding - RTUF (ready to use therapeutic food) with high energy or

F-75 = 75 kcal/day if the child cannot tolerate RUTF

phase 2 -
rehabilitation - switched to F-100 - slowly increase to 150-220 kcal/day until wt/ht z scale is greater than -1
also include vitamin supplements
switch to RUTF asap

432
Q

cachexia

A

loss of muscle with/ without loss of fat

433
Q

loss of muscle with/ without loss of fat

A

cachexia

434
Q

refeeding syndrome

A

when someone with severe anorexia suddenly starts eating normally

435
Q

when someone with severe anorexia suddenly starts eating normally

A

refeeding syndrome

436
Q

fluoxetine

A

serotonin reuptake inhibitor to reduce binge eating

437
Q

serotonin reuptake inhibitor to reduce binge eating

A

fluoxetine

438
Q

effect of glucocorticoids and progesterone

A

stimulate appetite

439
Q

treatment of cancer cachexia

A

thalidomide

440
Q

thalidomide

A

treatment of cancer cachexia

441
Q

what stimulates appetite

A

effect of glucocorticoids and progesterone

ghrelin

442
Q

structure function of the zones of the liver

A

perivenous -
O2 poor region around the central hepatic vein
glutamine synthase

periportal -
O2 rich region around the portal vein
urea cycle takes place here.

443
Q

perivenous zone

A

O2 poor region around the central hepatic vein

glutamine synthase

444
Q

in what zone is glutamine synthase found

A

perivenous zone

445
Q

what is the O2 poor region of the liver

A

perivenous zone

446
Q

periportal zone

A

O2 rich region around the portal vein

urea cycle takes place here.

447
Q

in what zone does the urea cycle take place

A

periportal zone

448
Q

what is the O2 rich region of the liver

A

periportal zone

449
Q

main vessel in the periportal zone

A

portal vein

450
Q

main vessel in the perivenous zone

A

central hepatic vein

451
Q

explain blood flow in the zones of the liver

A

periportal zone –> midzone –> perivenous zone

452
Q

biosynthetic function of the liver

A

FATS

  1. TG - converts excess carbs and proteins into FA and TGs for adipose tissue
  2. cholesterol and phospholipids - some packaged into lipoproteins and exported to the rest of the body. others are secreted in bile
  3. lipoproteins - most synthesised in the liver

CARBOHYDRATES
Glucose from gluconeogenesis

PROTEINS made by the liver

  1. non-essential aas
  2. plasma proteins (albumin)
  3. clotting factors (fibrinogen)
  4. acute phase proteins (alpha and beta globulins)
    * * structural proteins and enzymes are exported proteins
OTHERS
ketone bodies
bile acids 
urea
nucleotide precursors (purine and pyrimidine)
453
Q

biosynthetic function of the liver - FATS

A
  1. TG - converts excess carbs and proteins into FA and TGs for adipose tissue
  2. cholesterol and phospholipids - some packaged into lipoproteins and exported to the rest of the body. others are secreted in bile
  3. lipoproteins - most synthesised in the liver
454
Q

cholesterol and phospholipids are packed into

A

lipoproteins

455
Q

what fat is most synthesised in the liver

A

lipoproteins

456
Q

biosynthetic function of the liver - CARBOHYDRATES

A

Glucose from gluconeogenesis

457
Q

biosynthetic function of the liver - proteins

A
  1. non-essential aas
  2. plasma proteins (albumin)
  3. clotting factors (fibrinogen)
  4. acute phase proteins (alpha and beta globulins)
    * * structural proteins and enzymes are exported proteins
458
Q

biosynthetic function of the liver - OTHERS

A

ketone bodies
bile acids
urea
nucleotide precursors (purine and pyrimidine)

459
Q

where is albumin synthesised

A

albumin is only synthesised in the liver by hepatic cells

it is regulated by stress

460
Q

what regulates albumin synthesis

A

stress

461
Q

albumin synthesis

A
  1. synthesised as pre proalbumin with aa extension at the N- terminal
  2. aa extension inserted into the ER membrane
  3. majority of extension cleaves in lumen leaving proalbumin
  4. proalbumin exported to golgi where extension is removed –> albumin
  5. albumin excreted directly –> not stored
462
Q

comment of the production and storage of albumin

A

only produced when needed
not stored (based on plasma concentration of colloid in hepatic interstitium)
**applies to periods without stress

463
Q

trace the path of albumin when it leaves

A

passes directly into the hepatic sinusoids until reaching the space of disse (parasinusoidal space) and enters the lymphatic system where it finally ends back into circulation at the thoracic duct

464
Q

albumin synthesis - synthesised as ___ with aa extension at the ____

A

pre proalbumin

N- terminal

465
Q

albumin synthesis -

aa extension inserted into the _____

A

ER membrane

466
Q

albumin synthesis -

majority of extension cleaves in lumen leaving _____

A

proalbumin

467
Q

albumin synthesis -

proalbumin exported to ____ where extension is removed and ____ is produced

A

golgi

albumin

468
Q

path of albumin when it leaves-
passes directly into the _______ until reaching the ______ and enters the _______ where it finally ends back into circulation at the _____

A

hepatic sinusoids
space of disse (parasinusoidal space)
lymphatic system
thoracic duct

469
Q

what do alpha and beta globulins indicate

A

they are acute phase proteins that indicate disease or malnutrition of the acute phase response

470
Q

what are alpha and beta globulins cleared by

A

asia glycoproteins on the surface of the hepatocyte

471
Q

asia glycoproteins

A

clears alpha and beta globulins

472
Q

where are asia glycoproteins found

A

surface of the hepatocyte

473
Q

describe the structure of haem

A

ferrous iron surrounded by a porphyrin ring

474
Q

where is Hb synthesised?

A

bone marrow

475
Q

where is heme synthesized?

A

liver

476
Q

myoglobin is synthesised by

A

muscle

477
Q

cytochrome p450 and catalase are synthesised by the

A

liver

478
Q

how many enzymes are involved in heme synthesis and where are they found

A

8
4 in mitochondria
4 in cytosol

479
Q

heme synthesis

A
  1. succinyl coA + glycine –> ALA (ALA synthase - mitochondria)
    **RLS
    inhibited by non-protein bound heme (free heme) by negative feedback. heme also stimulates globin synthesis to ensure low levels of free heme. (protein-bound heme does not inhibit ALA synthase)
  2. 2ALA –> PBG (ALA dehydrogenase - cytoplasm)
    *this enzyme has sulphurdural group which is inhibited by heavy metal (Pb2+)
    ALA is transported into the cytoplasm
  3. 4PBG –> hydroxymethylbilane (PBG deaminase and UP-cosynthase)
    hydroxymethylbilane –> UP1 (UP synthase 1)
    UP1 –> UP3
    * enzymes in cytoplasm
  4. decarboxylation of UP3 –> 5CO2H (UP decarboxylase)
    this allows for the transfer back into the mitochondria.
  5. decarboxylation into the mitochondria involves changing the side groups
    acetate –> methyl
    propionate –> vinyl
  6. chelation (insertion) of iron forms the free heme which inhibits ALA synthase
480
Q

production of ALA

A

succinyl coA + glycine –> ALA (ALA synthase - mitochondria)
**RLS
inhibited by non-protein bound heme (free heme) by negative feedback. heme also stimulates globin synthesis to ensure low levels of free heme. (protein-bound heme does not inhibit ALA synthase)

481
Q

what enzyme produces ALA

A

ALA synthase

482
Q

where is ALA synthase found

A

mitochondria

483
Q

inhibitors of ALA production

A

inhibited by non-protein bound heme (free heme) by negative feedback

484
Q

what does heme stimulate to ensure low levels of free heme

A

globin synthesis

485
Q

what is the importance of gloin synthesis by heme

A

to ensure low levels of free heme

486
Q

_____ heme does not inhibit ALA synthase

A

protein-bound

487
Q

2ALA –> ____
what is the enzyme involved
where does this take place

A

PBG
ALA dehydrogenase
cytoplasm

488
Q

explain the inhibition of ALA dehydrogenase

A

*this enzyme has sulphurdural group which is inhibited by heavy metal (Pb2+)

489
Q

in heme synthesis, heavy metals inhibit …

A

ALA dehydrogenase

490
Q

in heme synthesis, after the formation of PBG, where is ALA transported

A

into the cytoplasm

491
Q

4PBG –> ______
what enzyme is involved
where does this take place

A

hydroxymethylbilane
PBG deaminase and UP-cosynthase
cytoplasm

492
Q

____ –> hydroxymethylbilane

A

4PBG

493
Q

hydroxymethylbilane –> _____
enzyme involved
location

A

UP1
UP synthase 1
cytoplasm

494
Q

_____ –> UP1

A

hydroxymethylbilane

495
Q

UP1 –> ____

A

UP3

496
Q

____ –> UP3

A

UP1

497
Q

____ –> PBG

A

2ALA

498
Q

UP3 –> ____
what type of reaction is this
enzyme involved?
importance of step?

A

5CO2H
decarboxylation
UP decarboxylase
allows for the transfer back into the mitochondria.

499
Q

heme synthesis - decarboxylation into the mitochondria involves

A

changing the side groups
acetate –> methyl
propionate –> vinyl

500
Q

decarboxylation into the mitochondria involves changing the side groups
____ –> methyl

A

acetate

501
Q

decarboxylation into the mitochondria involves changing the side groups
acetate –> ____

A

methyl

502
Q

decarboxylation into the mitochondria involves changing the side groups
____ –> vinyl

A

propionate

503
Q

decarboxylation into the mitochondria involves changing the side groups
propionate –> ____

A

vinyl

504
Q

____ of iron forms the free heme which inhibits _____

A

chelation (insertion)

ALA synthase

505
Q

what inhibits ALA synthase

A

chelation (insertion) of iron forms the free heme which inhibits ALA synthase

506
Q

porphyrias

A

defects of heme synthesis leading to decreased synthesis (complete loss = death)
this can lead to toxic intermediates
no heme = no feedback = increase in toxic intermediate

507
Q

porphyrias

A

defects of heme synthesis leading to decreased synthesis (complete loss = death)
this can lead to toxic intermediates
no heme = no feedback = increase in toxic intermediate

508
Q

AIP - acute intermittent porphyrias

A

acute intermittent porphyrias is a defect in UP synthase 1 and hence there is no conversion of PBG to UP1

509
Q

defects of heme synthesis leading to decreased synthesis

A

porphyrias

510
Q

defect in UP synthase 1 and hence there is no conversion of PBG to UP1

A

AIP - acute intermittent porphyrias

511
Q

a defect of what enzyme prevents conversion of PBG to UP1

name of illness

A

UP synthase 1

AIP - acute intermittent porphyrias

512
Q

danger of porphyrias

A

this can lead to toxic intermediates

no heme = no feedback = increase in toxic intermediate

513
Q

ALA and PBG accumulation treatment

A

inhibit ALA synthase to prevent building up of PBG

514
Q

Regulation of heme synthesis

A
  1. negative feedback of free heme on ALA synthase
  2. heavy metals inhibit ALA dehydratase and chelation of iron
  3. Iron overload affects UP1–>UP3 (flipping of side chains)
515
Q

cutaneous manifestations of porphyrias

A

deficiency in UP decarboxylase which causes the accumulation of porphyrins and porphyrinogens which are photosensitive –> cause cellular damage when exposed to light

516
Q

deficiency in UP decarboxylase which causes the accumulation of

A

porphyrins and porphyrinogens which are photosensitive –> cause cellular damage when exposed to light

517
Q

what step of heme synthesis utilizes UP decarboxylase

A

decarboxylation of UP3 –> 5CO2H (UP decarboxylase)

this allows for the transfer back into the mitochondria.

518
Q

negative feedback of free heme on _____

A

ALA synthase

519
Q

heavy metals inhibit

A

ALA dehydratase and chelation of iron

520
Q

Iron overload affects UP1–>UP3 (flipping of side chains)

A

UP1–>UP3 (flipping of side chains)

521
Q

metabolism is involved with transforming lipophilic –> ____ for excretion

A

hydrophilic

522
Q

what are the phases of drug metabolism

A

phase 1 involves the transformation of a drug into a more polar metabolite in preparation for phase. 2
oxidation (cyt P450), reduction or hydrolysis.

phase 2 involves the combination of glucuronic acid, sulfate, acetic acids or aa with a functional group that may not be from phase 1

523
Q

phase 1 involves the transformation of a drug into a more ______ in preparation for phase. 2
the processes involved are _____________________

A

polar metabolite

oxidation (cyt P450), reduction or hydrolysis.

524
Q

phase 2 involves the combination of ________ with a ______ that may not be from phase 1

A

glucuronic acid, sulfate, acetic acids or aa

Functional group

525
Q

where is the oxidation of metabolites done

A

cytoplasm

526
Q

phase 1

A
  1. oxidation hydroxylation - addition of an OH group eg. lidocaine
  2. oxidation dehy
527
Q

phase 1

A
  1. oxidation hydroxylation - addition of an OH group eg. lidocaine
  2. oxidation dehydrogenation- removal of H eg. metabolism of ethanol
    step 1 - oxidation in ER
    ethanol –> acetaldehyde [NAD+ –> NADH] (alcohol dehydrogenase)
    step 2 - oxidation in the mitochondria
    acetaldehyde –> acetate [NAD+ –> NADH] (aldehyde dehydrogenase)
    **note the treatment of alcohol abuse
  3. oxidation dealkylation - replaces alkyl group with an aldehyde or OH
  4. reduction - removal of O or addition of H or e-
    eg. R-NO2 –> R-NH2
5. hydrolysis - addition of H2O (normally to an ester) 
uses esterases
eg. R-O-C - CH3 --> R-OH
              II
             O
528
Q

treatment of alcohol abuse

A

disulfiram (stored in adipose tissue)

inhibits oxidation of acetaldehyde into acetate by competing with NAD+ cofactor for binding on ALDH –> hangover

529
Q

oxidation hydroxylation

A

addition of an OH group eg. lidocaine

530
Q

oxidation dehydrogenation

A

removal of H eg. metabolism of ethanol
step 1 - oxidation in ER
ethanol –> acetaldehyde [NAD+ –> NADH] (alcohol dehydrogenase)
step 2 - oxidation in the mitochondria
acetaldehyde –> acetate [NAD+ –> NADH] (aldehyde dehydrogenase)

531
Q

oxidation dehydrogenation-

where does step 1 occur

A

ER

532
Q

oxidation dehydrogenation-

where does step 2 occur

A

mitochondria

533
Q

oxidation dehydrogenation- step 1
ethanol –> acetaldehyde
what is the accompanying equation
what enzyme is used

A

oxidation in ER
[NAD+ –> NADH]
(alcohol dehydrogenase)

534
Q

oxidation dehydrogenation- step 1

ethanol –> ____

A

acetaldehyde

535
Q

oxidation dehydrogenation- step 2
acetaldehyde –> _____
what is the enzyme used

A

acetate

aldehyde dehydrogenase

536
Q

where is disulfiram found

A

(stored in adipose tissue)

537
Q

purpose and action of disulfiram

A

treatment of alcohol

inhibits oxidation of acetaldehyde into acetate by competing with NAD+ cofactor for binding on ALDH –> hangover

538
Q

inhibits oxidation of acetaldehyde into acetate by competing with NAD+ cofactor for binding on ALDH

A

disulfiram

539
Q

phase 1 reactions

what process replaces alkyl group with an aldehyde or OH

A

oxidation dealkylation

540
Q

removal of O or addition of H or e-

A

reduction

541
Q

addition of H2O (normally to an ester)

A

hydrolysis

542
Q

phase 2

A
  1. glucuronic acid
    acts on drugs with OH, COOH and NH3
    replaces H with GA by Glucuronyl transferase
    R-OH –> R-O-GA [UDP-GA–>UDP]
  2. sulphate conjugation
    acts on aromatic compounds with OH and NH2
    comes between the O and H of OH and replaces the NH2
    conjugates with GA conjugation (paracetamol)
    R-O-H –> R-OSO3H
    (PAPS and sulfurtransferase)
  3. glycine conjugation
    acts COOH groups, replaces OH with glycine
  4. glutathione conjugation
    acts on epoxides, halides or electrophilic compounds
    replaces H with SG and =O has H added –> =SOH
543
Q

glucuronic acid

acts on drugs with

A

OH, COOH and NH3

544
Q

glucuronic acid
acts on drugs with OH, COOH and NH3
replaces __ with __ by _________

A

H
GA
Glucuronyl transferase

545
Q

sulphate conjugation

acts on

A

aromatic compounds with OH and NH2

546
Q

sulphate conjugation
acts on aromatic compounds with OH and NH2
comes between ______ and replaces the ____
conjugates with _______ (paracetamol)
what enzymes are used?

A

the O and H of OH
NH2
GA conjugation

enzymes - (PAPS and sulfurtransferase)

547
Q

glycine conjugation
acts on ________
replaces ___ with ______

A

COOH groups
OH
glycine

548
Q

glutathione conjugation
acts on _________
replaces __ with ___ and =O has H added –> =SOH

A

epoxides, halides or electrophilic compounds
H
SG

549
Q

metabolism of aspirin

A

phase 1 - esterases –> hydrolysis

phase 2 -
low doses - glycine conjugation (glycine transferase)
high doses - glucuronic conjugation (since first pathway is saturated)
top doses - urinary excretion (since both pathways saturated)

550
Q

what phase 1 reaction uses esterases

A

hydrolysis

551
Q

conjugation of drug with COOH groups

A

glucuronic acid

glycine conjugation

552
Q

conjugation of

aromatic compounds with OH and NH2

A

sulphate conjugation

553
Q

conjugation of

OH, COOH and NH3

A

glucuronic acid

554
Q

conjugation of

epoxides, halides or electrophilic compounds

A

glutathione conjugation

555
Q

metabolism of aspirin

low doses

A

glycine conjugation (glycine transferase)

556
Q

metabolism of aspirin

high doses

A

glucuronic conjugation (since first pathway is saturated)

557
Q

metabolism of aspirin

top doses

A

urinary excretion (since both pathways saturated)

558
Q

metabolism of paracetamol

A

phase 1 - oxidation dehydrogenase (only for glutamine pathway, making it lipophilic)

phase 2 -
main pathway - glucuronic conjugation (GA transferases)
major pathway - sulfate conjugation (PAPS and Sulfotransferase)
**the 2 above do not need first pass metabolism (skips phase)
minor pathway - glutathione conjugation (glutathione transferases)

559
Q

phase 1 reaction of aspirin

A

hydrolysis - esterases

560
Q

high doses of paracetamol build up causes

A

building up of electrophilic intermediate of glutathione pathway called NAPQI which at high concentrations can attack the liver
n - acetyl cysteine relieves this problem by stimulating glutathione production

561
Q

NAPQI

A

intermediate of glutathione pathway

562
Q

excess NAPQI

A

at high concentrations can attack the liver

563
Q

relief of high doses of paracetamol build up

A

n - acetyl cysteine

564
Q

how does n - acetyl cysteine relieve high doses of paracetamol build up

A

stimulating glutathione production

565
Q

what stimulates glutathione production

A

n - acetyl cysteine

566
Q

phase 1 of the paracetamol metabolization accompanies which pathway of phase 2

A

minor pathway - glutathione conjugation (glutathione transferases)

567
Q

metabolism of paracetamol - main pathway

A

glucuronic conjugation (GA transferases)

568
Q

metabolism of paracetamol

major pathway

A

sulfate conjugation (PAPS and Sulfotransferase)

569
Q

metabolism of paracetamol

minor pathway

A

glutathione conjugation (glutathione transferases)

570
Q

prodrugs

A

important since it requires this biotransformation to become active

571
Q

specific drug delivery

sulfasalazine

A

sulfasalazine –> 5-ASA for ulcerative colitis. this drug acts on the colon but cannot reach it without being absorbed
sulfasalazine can then reach the colon where azo reductases cleave the N-(triple bond)-N bond, releasing 5-ASA

572
Q

specific drug delivery

morphine

A

diamorphine –> morphine
diamorphine has 2 acetylated OH groups compared to morphine, making it hydrophobic –> can cross BBB where esterases can then cleave the acetylation revealing OH groups

573
Q

specific drug delivery
sulfasalazine
sulfasalazine –> _____ for ulcerative colitis. this drug acts on the ____ but cannot reach it without being absorbed
sulfasalazine can then reach the colon where ______ cleave the _____ bond, releasing 5-ASA

A

5-ASA
colon
azo reductases
N-(triple bond)-N

574
Q

specific drug delivery
diamorphine
diamorphine –> _____
diamorphine has 2 acetylated OH groups compared to morphine, making it hydrophobic –> can cross BBB where _____ can then cleave the acetylation revealing OH groups

A

morphine

esterases

575
Q

explain the improved physicochemical properties of

enalaprilat

A

enalapril –> enalaprilat (esterases)
enalaprilat is a poorly absorbed ACE inhibitor due to its polarity. The ethalester on enalapril is hydrophobic –> easily absorbed

576
Q

prolonged drug release - haloperidol

A

haloperidol decanoate –> haloperidol (esterases)
haloperidol is used to treat psychotic disorders (non-compliance).
haloperidol decanoate has a long ester –> when injected, the slow conversion rate allows effects to last 1 month

577
Q

bile stored in the liver is more ___ whereas bile stored in the gallbladder is more ____ and has more solid materials such as ________

A

diluted
concentrated
cholesterol, phospholipids, mobile salts

578
Q

functions of bile

A
  1. excretory
    releases bile pigments, cholesterol, bile acids, salts, drugs and particulate matter removed from blood by kupffer cells in the liver
  2. digestive
    bile is rich is bicarbonate which neutralises gastric acid.
    bile salts emulsify fats into small droplets
579
Q

excretory
releases bile pigments, cholesterol, bile acids, salts, drugs and particulate matter removed from blood by ______ in the liver

A

kupffer cells

580
Q

formation of bile salts

A
  1. cholesterol breaks down into cholic acid and chemosensory cholic acid
  2. acids are conjugated with glycine and taurine
  3. conjugated bile acid - na+ or k+ makes it a bile salt
  4. in the gut, bacterial alpha dehydroxylase
    converts conjugated cholic acid into deoxycholic acid
    converts conjugated chenodeoxycholic acid into lithocholic
    ** these are known as secondary bile salts and can be absorbed back into liver again and process restarts.
581
Q

bile is rich is bicarbonate which

A

neutralises gastric acid.

582
Q

formation of bile salts -

cholesterol breaks down into

A

cholic acid and chemosensory cholic acid

583
Q

formation of bile salts -

acids are conjugated with

A

glycine and taurine

584
Q

conjugated bile acid - _____ makes it a bile salt

A

na+ or k+

585
Q

in the gut, bacterial alpha dehydroxylase :
converts conjugated cholic acid into ____
converts conjugated chenodeoxycholic acid into _____

A

deoxycholic acid

lithocholic

586
Q

what is bilirubin

A

natural degradation of heme of erythrocytes after being phagocytosed in the spleen, liver or bone marrow

587
Q

degradation of RBC and bilirubin

A

RBC –> Hemoglobin –> globin –> aa
Hb –> heme –> bilirubin –> excreted
heme –> fe2+

588
Q

handling of free Hb

A
  1. scavenge and recycle iron -
    haptoglobin is complexed with Hb and metabolized in the liver and spleen forming an iron-globin complex and bilirubin to prevent loss of iron in urine.
  2. prevent major iron losses -
    hemopexin binds to free forming heme - hemopexin incomplete and taken up by the liver and stored as ferritin
  3. methemalbumin - complex of oxidized heme and albumin
589
Q

handling of free Hb
scavenge and recycle iron -
_____ is complexed with Hb and metabolized in the liver and spleen forming an ____________ to prevent loss of iron in urine.

A

haptoglobin

iron-globin complex and bilirubin

590
Q

handling of free Hb
prevent major iron losses -
_____ binds to free forming ________ in complex and taken up by the liver and stored as _____

A

hemopexin
heme - hemopexin
ferritin

591
Q

handling of free Hb

methemalbumin - complex of

A

oxidized heme and albumin

592
Q

bruises

A

RED –> purple = hemoglobin
yellow –> GREEN = biliverdin
YELLOW –> purple = bilirubin

593
Q

metabolism of bilirubin

A

RBC –> Hemoglobin –> globin –> aa
Hb –> heme –> biliverdin –> unconjugated bilirubin

  1. unconjugated bilirubin transported in bloodstream bound to albumin
  2. liver takes up bilirubin by carrier-mediated endocytosis and binds to cytoplasmic proteins (glutathione transferase and protein Y) making it water soluble –> cannot leave back into blood
  3. conjugated bilirubin secreted into biliary tree by active transport through multi drug resistant like protein. RLS
  4. 3 possibilities
    a) some fat soluble bilirubin have to be reabsorbed, but most is oxidised into urobilinogens by flora.
    b) colourless urobilinogens metabolised into brown stercobilin and excreted in faeces.
    c) some reabsorbed urobilinogen are oxidized to yellow urobilin and excreted as urine
594
Q

jaundice

A

yellow discoloration of the skin and sclera caused by hyperbilirubinemia ie. double the upper limit of 17 mmol/L

595
Q

unconjugated bilirubin transported in bloodstream bound to

A

albumin

596
Q

liver takes up bilirubin by _______ and binds to cytoplasmic proteins (_______) making it water soluble –> cannot leave back into blood

A

carrier-mediated endocytosis

glutathione transferase and protein Y

597
Q

conjugated bilirubin secreted into biliary tree by _____ through multi drug resistant like protein. RLS

A

active transport

598
Q

some fat soluble bilirubin have to be reabsorbed, but most is oxidised into _____ by ____.

colourless urobilinogens metabolised into brown _____ and excreted in faeces.

some reabsorbed urobilinogen are oxidized to ____ and excreted as urine

A

urobilinogens
flora

stercobilin

yellow urobilin

599
Q

yellow discoloration of the skin and sclera

A

jaundice

600
Q

types of jaundice

A
  1. pre-hepatic
    breakdown of RBC excess uptake –> hemolytic jaundice
    this can be due to hemolytic diseases, sickle cell anemia or leakage outside vessels
    this creates excess bilirubin circulating in blood.
    conjugated bilirubin in normal amounts since liver is still functional
    no urine bilirubin
    increase unconjugated bilirubin in the blood
  2. intrahepatic
    bilirubin cannot be taken up, conjugated and/or excreted because hepatocytes are damaged –> hepatocellular jaundice
    usually accompanied by excess AST and ACT (markers or liver function)
    increase conjugated bilirubin
    increased ALT or AST
    has urine bilirubin (abnormal)
3.posthepatic 
obstructed biliary flow - conjugated bilirubin regurgitation back into systemic circulation --> obstructive jaundice 
patients have pale stools (no stercobilin) and dark urine (excess conjugated bilirubin)
increase conjugated bilirubin 
increase ALP 
has urine bilirubin (dark)
no stercobilin
no urine urobilinogen
601
Q

Newborn jaundice

A

unconjugated hyperbilirubinemia (prehepatic) is caused by immature/ impaired uptake of the lover
this is due to enzymes of the liver only start to work after birth
therefore it usually resolves itself
treatment - phototherapy or phenobarbitone

602
Q

phototherapy

A

converts bilirubin to a water soluble non toxic form

603
Q

phenobarbitone

A

usually given to the mother prior to labour to induce UDP glucuronyl transferase

604
Q

gilbert’s syndrome

A

prehepatic
mild unconjugated hyperbilirubinemia
correlated with fasting or illness caused by reduced activity of UDP glucuronyl transferase
treated by phenobarbitone

605
Q

crigler syndrome

A

*mutation

606
Q

dubin johnson and rotor’s syndrome

A

conjugated hyperbilirubinemia
impaired biliary secretion
transport defect between liver and biliary tree (RLS) at. the multidrug resistant like protein

607
Q

pre-hepatic
breakdown of RBC excess uptake –> _____
this can be due to hemolytic diseases, sickle cell anemia or leakage outside vessels
this creates excess ____ circulating in blood.
conjugated bilirubin in normal amounts since liver is still functional
no ____
increase _____ in the blood

A

hemolytic jaundice
bilirubin
no urine bilirubin
unconjugated bilirubin

608
Q

intrahepatic
bilirubin cannot be taken up, conjugated and/or excreted because hepatocytes are damaged –> ____
usually accompanied by excess ___ (markers or liver function)
increase ____
increased ____
has ____ (abnormal)

A

hepatocellular jaundice
AST and ACT

conjugated bilirubin
ALT or AST
urine bilirubin

609
Q 
posthepatic 
\_\_\_\_biliary flow - conjugated bilirubin regurgitation back into systemic circulation --> \_\_\_\_ 
patients have pale stools (no stercobilin) and dark urine (excess conjugated bilirubin)
increase \_\_\_ 
increase \_\_\_ 
has urine bilirubin (dark)
no \_\_\_\_
no \_\_\_\_\_\_
A

obstructed biliary flow
obstructive jaundice

conjugated bilirubin
ALP

stercobilin
urine urobilinogen

610
Q

differential diagnosis of jaundice

conjugated bilirubin

A

pre - present
intra - increased
post - increased

611
Q

differential diagnosis of jaundice

ALT or AST

A

pre - normal
intra - increased
post - normal

612
Q

differential diagnosis of jaundice

ALP

A

pre - normal
intra - normal
post - inc

613
Q

differential diagnosis of jaundice

urine bilirubin

A

pre - absent
intra - present
post - present

614
Q

differential diagnosis of jaundice

urine urobilinogen

A

pre - present
intra - present
post - absent

615
Q

what type of jaundice is:
breakdown of RBC excess uptake –> hemolytic jaundice
this can be due to hemolytic diseases

A

prehepatic

616
Q

what type of jaundice is:

bilirubin cannot be taken up, conjugated and/or excreted because hepatocytes are damaged –> hepatocellular jaundice

A

intrahepatic

617
Q

what type of jaundice is:

obstructed biliary flow - conjugated bilirubin regurgitation back into systemic circulation –> obstructive jaundice

A

post hepatic

Finals (17 decks)

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