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Flashcards in Heme Metabolism Deck (21)
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1

What is the general structure of the heme ring?

It is made of 4 pyrrole groups and an iron atom

2

What is the 1st step of heme synthesis?

Succinyl CoA + Glycine -> ALA

3

What is the rate limiting step of heme synthesis?

The 1st step to generate ALA

4

What is the enzyme catalyzing the 1st step of heme synthesis?

ALA Synthase

5

What is the 2nd step of heme synthesis?

2 ALA -> Porphobilinogen

6

What is the difference between porphyrinogens and porphyrins?

Porphyrinogens have no double bonds at the bridging carbons and are colorless.

Porphyrins have double bonds at the bridging carbons and have colors and are highly fluorescent.

7

What can happen to porphrinogens upon light exposure?

They can be converted into porphyrins via non-enzymatic oxidation

8

What is ALA synthase regulated by?

Heme will inhibit the action of ALA synthase

9

What is the mechanism of disease in acute intermittent porphyria?

It is caused by a deficiency of porphobilinogen deaminase.

This results in ALA build up which is toxic to neurons. The lack of heme formation will also shut off the negative feedback and exacerbate the disease as well.

10

What is the mechanism of disease in variegate porphyria?

Deficiency of protoporhyrinogen oxidase.

This causes a build up of porphyrinogen intermediates which can be converted into porphyrins via light and will damage the skin as a result.

11

What are the products of hemoglobin metabolism?

-Heme
-Globin

12

What does heme from hemoglobin eventually degrade to?

Bilirubin
Fe (reused)

13

What does globin from hemoglobin eventually degrade to?

Free amino acids

14

What breaks down the cyclic structure of heme?

Heme oxygenase

15

What is unconjugated bilirubin?

It is also known as indirect bilirubin and it is insoluble.

It complexes with albumin in the blood to be carried to the liver

16

What is conjugated bilirubin?

It is also known as direct bilirubin and it is soluble.

It is secreted through the bile and travels through the intestine where most of it is eventually recycled.

17

What are some of the causes of jaundice?

-Hemolysis
-Biliary Obstruction
-Hepatitis/Cirrhosis
-Neonatal Jaundice

18

What is the main bilirubin in hemolytic jaundice?

Unconjugated

19

What is the main bilirubin in biliary obstruction?

Conjugated

20

What is the main bilirubin in cirrhotic jaundice?

Mixed

21

What is the main bilirubin in neonatal jaundice?

Unconjugated

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