Porphyins, Heme, Bile

Question 1

Where are porphyrins found?

Answer 1

Myoglobin
Hemoglobin
Cytochrome C

Question 2

How is delta-aminolevalinate synthesized?

Answer 2

Succinyl-CoA + glycine

Question 3

What enzyme catalyzes synthesis of delta-aminolevalinate?

Answer 3

Aminolevulinic acid synthase (ALAS)

Question 4

What does ALAS need as a coenzyme?

Answer 4

Pyridoxal phosphate (PLP) vitamin B6

Question 5

How is porphobilinogen created?

Answer 5

2 aminolevalinate

Question 6

What enzyme catalyzes porphobilinogen synthesis?

Answer 6

Aminolevulinic acid dehydratase (ALAD)

Question 7

What can vitamin B6 deficiency cause?

Answer 7

Anemia

Question 8

What is protoporphyrin?

Answer 8

Heme B without Fe2+

Question 9

What are two isoforms of ALAS?

Answer 9

ALAS 1: all cells (x-linked)

ALAS 2: liver bone marrow

Question 10

What is hemin?

Answer 10

Heme with Fe3+ (oxidized form)

Question 11

What does increase hemin level indicate?

Answer 11

Too much heme A, B and C

Question 12

What does too much hemin cause?

Answer 12

Inhibition of ALAS enzyme

Question 13

What do heavy metals inhibit?

Answer 13

ALAD

Question 14

What does decreased ALAD cause?

Answer 14

Accumulation of ALA

Question 15

What is ALAD deficiency called?

Answer 15

Doss porphyria

ALAD porphyria

Question 16

What do you treat doss porphyria?

Answer 16

Prophylactic hemin to slow ALAS and decrease porphyrin accumulation

Question 17

What is heme broken down into?

Answer 17

Biliverdin + Fe3+

Question 18

How does bilirubin get transported in the blood?

Answer 18

Albumin

Question 19

Biliverdin is broken down to bilirubin by what?

Answer 19

Biliverdin reductase

Question 20

What happens to bilirubin in the liver?

Answer 20

It is glycosylated to bilirubin diglucoronide

Question 21

What is indirect and direct bilirubin?

Answer 21

Indirect (unconjugated): not glycosylated

Direct (conjugated): glycosylated

Question 22

What enzyme conjugates bilirubin to glucose?

Answer 22

Uridine diphosphogluconurate glucuronosyltransferase (UDP-Glucuronosyltransferase)

Question 23

What is Gilbert’s syndrome?

Answer 23

Decreased UDP-glucuronosyltransferase

Question 24

What does Gilbert’s syndrome cause?

Answer 24

Increased indirect and decreased direct bilirubin and increased bilirubin in the blood (jaundice)

Question 25

What does CO act as?

Answer 25

A vasodilator helping blood flow in tissue injury caused by heme oxidase

Question 26

What is the most important antioxidant in the body?

Answer 26

Bilirubin

Question 27

What is elevated in a liver deficiency or blocked bile duct?

Answer 27

Alkaline phosphatase (ALP)

Question 28

What are the two primary bile salts/acids?

Answer 28

Cholic acid

Chenodeoxycholic acid

Question 29

How are primary bile salts turned to secondary bile salts?

Answer 29

Removal of a hydroxyl group by bacteria

Question 30

How are secondary bile salts made more soluble?

Answer 30

Liver adds a taurine or glycine

Question 31

What activates transcription of HMG-CoA reductase?

Answer 31

SREBP

Question 32

When does HMG-CoA reductase get activated?

Answer 32

When cholesterol is low

Question 33

What inhibits transcription of 7alpha-hydroxylase gene when cholesterol is low?

Answer 33

SREBP

Question 34

Why does SREBP inhibit 7alpha-hydroxylase gene?

Answer 34

To not waste cholesterol on bile production

Question 35

What stimulates transcription of 7alpha-hydroxylase gene when cholesterol is too high?

Answer 35

Liver X receptor (lowers cholesterol by increasing bile acids)

Question 36

What inhibits transcription of the 7alpha-hydroxylase gene when bile acid levels are too high?

Answer 36

Farnesoid X receptor (bile acids are too high)

Question 37

Most important enzyme in classical pathway:

Answer 37

Cholesterol 7alpha-Hydroxylase

Question 38

Most important enzyme in acidic pathway:

Answer 38

Sterol 27-Hydroxylase