Gallstones

Question 1

Types of gallstones (1,2(a,b))

Answer 1

Cholesterol stones

Pigment stones - brown and black

Question 2

Formation of black pigment stones

Answer 2

Excess unconjugated bilirubin
Form in gallbladder
Not associated with bacteria

Question 3

Formation of cholesterol stones

Answer 3

Excess cholesterol (synthesised to make bile salts)
Yellow
Nucleating agents, cholesterol and calcium responsible for stones

Question 4

Formation of brown pigment stones

Answer 4

Form in gallbladder and duct
Contain bacteria (which deconjugates bile)
Unconjugated bile form stones

Question 5

Nucleating agents

Answer 5

Proteins
Calcium
biliary mucus

Question 6

Amino acids conjugated to bile acids

Answer 6

Glycine and taurine

Ratio 3:1

Question 7

Bile salts compared to bile acids?

Answer 7

Conjugated with glycine or taurine

Salts better detergent agents than bile acids

Question 8

Main bile acids

Answer 8

Cholic acid

Chenodeoxycholic acid

Question 9

Main bile salts

Answer 9

Glycocholic acid (glycine and cholic acid)
Taurochenodeoxycholic acid (taurine and chenodeoxycholic acid)

Question 10

Secondary bile acids

Answer 10

Formed by bacteria 
Deoxycholic acid (cholic acid is primary)
Lithocholic acid (chenodeoxycholic acid is primary)

Question 11

Enzymes for lipid digestion

Answer 11

Colipase
Lipase
Phospholipase
Cholesterol esterase

Question 12

How are triglycerides digested

Answer 12

Colipase binds TG on surface of emulsion droplet
Lipase can bind, hydrolizes ester bonds
monoglyceride and fatty acid are released

Question 13

How are phospholipids digested?

Answer 13

Phospholipase A2 binds phospholipids (lecithin)

Produce lysolecithin and fatty acids

Question 14

What does bile do?

Answer 14

Bile micelles solubilize multilamellar vesicles

Bile acids are amphipathic

Question 15

Multilamellar vesicles?

Answer 15

Lipolytic products (FA, MG etc) aggregate after action of lipases

Question 16

Amount of bile secreted from liver per day?

Answer 16

15-30g

Question 17

Amount of bile synthesis by liver per day

Answer 17

0.5g

Question 18

Amount of bile excreted each day?

Answer 18

0,5g

Question 19

Bilirubin synthesis?

Answer 19

Heme –> oxidised by heme oxygenase (oxidised twice)
–> Biliverdin (green pigment) –> biliverdin reductase –>
Bilrubin (red-orange pigment)

Bilirubin and derivatives = bile pigments

Question 20

Bilirubin transport?

Answer 20

Bind covalently to albumin in blood

Bilirubin not v soluble

Question 21

Drugs associated with bilirubin?

Answer 21

Sulfonamides and salicylates
Displace bilirubin from albumin
Bilirubin can enter CNS…possible damage

Question 22

Bilirubin excretion in liver?

Answer 22

Bilirubin enters hepatocyte
Bilirubin gluconyltransferase adds 2x glucoronate
Forms bilirubin diglucoronide - more soluble
Active transport –>into bile

Question 23

Bilirubin excretion after bile?

Answer 23

Intestine - flora hydrolyse bilirubin diglucoronide into urobilinogen –> urobilin or stercobilin

Question 24

Stercobilin?

Answer 24

Urobilinogen oxidised by flora, most into stercobilin, exreted in the faeces…gives it colour i.e. Brown

Question 25

Urobilin?

Answer 25

Some urobilinogen is reabsorbed from the gut and converted into urobilin in kidneys…gives urine colour