Liver and Friends Flashcards
1
Q
What is another name for vitamin A?
A
retinol
2
Q
Where is vitamin A/ retinol stored and what is it stored as?
A
stored in stellate cells as retinyl ester
3
Q
How is vitamin A made active?
A
retinyl ester activated to retinol by lecithin retinol acyltransferase (LRA)
4
Q
What is the function of retinol?
A
helps maintain healthy teeth, skeletal and soft tissue, mucus membranes, and skin
5
Q
What is another name for vitamin D?
A
cholecalciferol
6
Q
How is vitamin D found in food?
A
found in food as ergocalciferol
7
Q
Where is ergocalciferol metabolised?
A
liver
8
Q
What is vitamin E a collective term for?
A
vitamin E is a family of 8 fat soluble compounds
9
Q
What is the main function of vitamin E?
A
antioxidant
10
Q
Where is vitamin E stored?
A
either liver or adipose tissue
11
Q
What are the forms of vitamin K and where are they found?
A
two forms acquired from plant or meat sources
phylloquinone = green leafy vegetables menaquinones= animal sources
12
Q
What us another name for vitamin B12?
A
cobalamin
13
Q
How much vitamin B12 is stored in the body?
A
2-5mg
14
Q
Where is vitamin B12 stored?
A
liver
15
Q
Which vitamins are fat/ water soluble
A
ADEK= fat soluble B12= water soluble
16
Q
What is the distribution of iron in the body?
A
50% haemoglobin
25% haem-containing proteins
25% liver ferritin
17
Q
How is iron stored?
A
iron is bound to transferrin after being absorbed by duodenal epithelial cells
most of stored iron is in the Kupffer cells of liver as ferritin
18
Q
Where is iron absorbed?
A
duodenum
19
Q
What organ maintains blood glucose levels?
A
liver
20
Q
What is excess glucose stored as?
A
glycogen
21
Q
How much glycogen do different muscles store?
A
liver stores 100mg
skeletal muscles stored 300g
22
Q
What stimulates formation/ breakdown of glycogen?
A
formation: insulin release
breakdown: glucagon release
23
Q
What are xenobiotics?
A
a foreign chemical substance not normally found or produced in the body which cannot be used for energy requirements
24
Q
What are microsomes?
A
fragments of endoplasmic reticulum with attached ribosomes that contain microsomal enzymes
25
Define lipophilic
able to pass through plasma membranes
26
What happens in phase 1 reactions?
make drugs more hydrophilic to be excreted by kidneys
introduce/ expose hydroxyl (OH) and other polar groups
carried out via oxidation, reduction and hydrolysis
facilitated by microsomal enzymes
27
What are some properties of pharmacologically active compounds?
lipophilic
non-ionised at pH 7.4
bound to plasma proteins to be transported
28
What enzymes carry out phase 2 reactions?
most are done by non-microsomal enzymes except glucuronidation which is done by microsomal enzymes (UGT)
29
What is UGT?
microsomal enzymes- uridine diphosphate glucuronosyltransferase
30
What us UDPGA?
urine diphosphate- glucaronic acid
31
What are the 3 types of protein?
plasma proteins
clotting factors
complement proteins
32
What is the most common plasma protein and its function?
albumin
maintains osmotic pressure
binding + transporting large/ hydrophobic molecules
33
What is vitamin K essential for?
synthesis of clotting factors 10,9,7,2
34
What are two phase 2 reactions?
conjugation
| glucuronidation
35
What occurs in conjugation reactions?
attachment of substituent groups
inactive products
catalysed by transferases
increases hydrophilicity
36
What occurs in glucuronidation reactions?
adding glnucaronic acid groups
increases hydrophilicity
done by glucoronosyltransferase
UDPGA is an essential coenzymes for glucuronidation reactions
37
What are phase 1 and phase 2 reactions concerning?
drug metabolism
38
What is the function of the glucose-alanine cycle?
muscle protein being degraded to provide more glucose to generate additional ATP for muscle contraction when stores are low
39
What is ALT and what is it's clinical significance?
alanine aminotransferase
it's concentration in serum is used to measure liver health
40
Describe the steps of the urea cycle.
1. ammonia and carbon dioxide added to ornithine
2. another ammonia is added to citrulline to make arginine
3. arginine is cleaved by arginase into urea and ornithine and the cycle goes round again
41
What is the only compound generated in the urea cycle?
urea
42
What are high levels of ammonia associated with?
neurotoxicity
43
Where are the enzymes for the urea cycle found?
all found in hepatocytes
44
Where is body fat stored?
mostly in adipocytes
| some stored in hepatocytes
45
What forms are fats stored in and in what distribution?
triglycerides- 78%
protein- 21%
carbohydrates- 1%
46
Where are LDLs formed?
plasma
47
Where are HDLs formed?
liver
48
Where are VLDLs formed?
hepatocytes
49
What is the function of LDLs?
main cholesterol carrier- carries cholesterol to all cells in body
essential for cell membrane and steroid hormone production
50
What is the function of HDLs?
removes excess cholesterol from blood and tissues delivering it to the liver to be secreted into bile
51
What is the function of VLDLs?
deliver triglycerides from liver to adipocytes
52
What happens if there is a high density of LDLs?
high levels of LDL will be taken up by cell via endocytosis and deposition will increase risk for heart attack
53
What are the types of lipoproteins?
LDL- low density lipoproteins
HDL- high density lipoproteins
VLDL- very low density lipoproteins
54
What is the general function of lipoproteins?
lipid metabolism
55
What 2 enzymes are involved in hepatic metabolism of lipids and what do each do?
lipoprotein lipase:
-hydrolyses triglycerides in lipoproteins into 2 free fatty acids and 1 monoglyceride
hepatic lipase:
- found in liver and adrenal glands
- converts IDL (intermediate density lipoprotein) into LDL thereby packaging it with more triglycerides to be released into the body
56
What are the main functions of the gallbladder?
1. production and concentration of bile
| 2. bilirubin and enterohepatic secretion of bile salts
57
What is the function of bile?
to emulsify fats
58
Where is bile produced?
liver hepatocytes
59
What stimulated secretion of bile
cholecystokinin (CCK)
60
What causes release of CCK?
released in response to increased fatty acid concentration in duodenum
61
How is bile concentrated?
concentrated in the gallbladder by absorption of NaCl and H2O
62
What are the constituents of bile?
```
bile salts
lecithin (a phospholipid)
carbonate ions (HCO3-)
cholesterol
bile pigments (e.g. bilirubin)
```
63
Describe the duct system between the liver, gallbladder and pancreas.
right and left hepatic duct merge to form common hepatic duct
cystic duct (from gallbladder) joins common hepatic duct to form common bile duct
pancreatic duct merges with common bile duct at the ampulla of vater where secretions enter the duodenum, flow controlled by sphincter of odd
64
What percentage of bile salts are recycled?
95%
65
Describe process of enterohepatic circulation.
- bile salts enter intestinal tract via bile
- reabsorbed via Na+ coupled transporters
- majority of reabsorption in terminal ileum, some in jejunum
- returned to liver via hepatic portal vein (HPV) to be used again in bile
- 5% of bile salts lost to faeces
66
What is enterohepatic circulation?
the movement of bile acid molecules from the liver to the small intestine and back to the liver
67
How are new bile salts made?
new bile salts synthesised by liver from cholesterol
68
How are old erythrocytes broken down?
liver- by kupffer cells (a type of macrophages)
| spleen- by macrophages
69
What colour is bilirubin?
yellow
70
Describe the full process of bilirubin metabolism.
1. RBCs ingested by macrophages/ kupffer cells
2. haemoglobin broken down into haem and globin
3. globing broken down into amino acids (used to make new RBCs in bone marrow)
4. haem further broken down into biliverdin and Fe2+ and CO. This is catalysed by haem oxygenase (HO)
5. biliverdin is reduced by biliverdin reductase to make unconjugated bilirubin
6. unconjugated bilirubin is bound to albumin and transported to liver
7. undergoes glucuronidation to make conjugated bilirubin, catalysed by UDP glucuronyl transferase
8. conjugated bilirubin is now soluble and dissolved in bile
9. excreted into duodenum with rest of bile
10. intestinal bacteria in terminal ileum reduce conjugated bilirubin into urobilinogen
11. urobilinogen is lipid-soluble so 10% is reabsorbed into blood, bound to albumin, transported to liver, oxidised to urobilin
12. urobilin is recycled into bile or transported to kidneys and excreted in urine- responsible for yellow colour of urine
13. remaining 90% of urobilinogen is oxidised by a different intestinal bacteria into stercobilin
14. stercobilin is excreted in faeces (responsible for brown colour)
71
What does unconjugated bilirubin need to be removed?
it is toxic
72
What colour is biliverdin?
green
73
What is the predominant pigment in haemoglobin?
bilirubin
74
What are the types of jaundice?
1. Pre-hepatic- excessive RBC breakdown, leads to overwhelming of liver to deal with bilirubin. Unconjugated bilirubin in bloodstream.
2. Hepatic/ intrahepatic- dysfunction of hepatic cells. Both conjugated and unconjugated bilirubin in blood.
3. Post-hepatic/ obstructive- obstruction of biliary drainage.
75
What are the 2 broad functions of the pancreas?
exocrine
| endocrine
76
What are the exocrine secretions of the pancreas?
bicarbonate
digestive enzymes
zymogens
77
What is the function of pancreatic bicarbonate?
protects duodenum from gastric acid
| buffers chyme to a suitable pH
78
How is bicarbonate secreted from the pancreas?
- secretion stimulated by secretin
- pancreatic duct cells secrete HCO3- into duct lumen via Cl-/HCO3- exchanges
- HCO3- for this comes from dissociation of carbonic acid
- Cl- is recycled back into lumen via CFTR channel
79
What is a CFTR channel?
cystic fibrosis transmembrane conductance regulator
80
What stimulated release of pancreatic enzymes into the duodenum?
CCK
81
What active enzymes does the pancreas secrete? What do each of them do?
alpha amylase- converts starch to maltose
| lipase- converts triglycerides into monoglyceride + fatty acids
82
What does the pancreas secrete zymogens?
protects the pancreas from auto digestion
83
What activates pancreatic zymogens?
enterokinase in intestinal epithelial cells
84
What are 2 examples of pancreatic zymogens and what do they become after activation?
trypsinogen --> trypsin
| chymotrypsinogen --> chymotrypsin
85
What is the most common pancreatic exocrine inhibitor? What else does this substance inhibit?
somatostatin
gastric acid secretion
86
Where is somatostatin made?
D cells in islets of langerhans
87
What are the phases of gastric juice secretion and what occurs in each stage?
1. cephalic phase
- sensory experience: seeing and chewing food
- parasympathetic vagus nerve stimulation to acinar cells
- produce digestive enzymes
2. gastric phase
- prescience of food in stomach causes further parasympathetic vagus nerve stimulation to acing cells\- produces digestive enzymes
3. intestinal phase
- duodenum responds to arriving chyme and moderates gastric activity through hormones and nervous reflexes
