Heme Metabolism

Question 0

Hemoglobin, cytochromes, peroxidases, and catalse are categorized as what?

Answer 0

Hemoproteins

Question 1

What has 4 linked pyrrole rings with a central Fe2+?

Answer 1

Porphyrin ring

Question 2

What two substrates form delta-aminolevulinate?

Answer 2

Glycine and succinyl CoA

Question 3

What is the enzyme that produces ALA?

Answer 3

ALA Synthase

Question 4

What is the coenzyme in the formation of ALA?

Answer 4

Pyridoxal phosphate

Question 5

What controls enzyme activity and transcription of delta-ALA gene?

Answer 5

The level of heme in the cell

Question 6

What is formed from two molecules of ALA being condensed?

Answer 6

Porphobilinogen

Question 7

What enzyme condenses two ALA molecules to form porphobilinogen?

Answer 7

ALA dehyrdatase

Question 8

What is ALA dehydratase inhibited by?

Answer 8

Lead

Question 9

How many molecules of glycine and succinyl CoA are required to produce 1 heme molecule?

Answer 9

8

Question 10

Heme is formed from what, by insertion of Fe2+

Answer 10

Protoporphyrin IX

Question 11

What enzyme inserts Fe2+ into protopophyrin forming heme?

Answer 11

Ferrochelatase

Question 12

Defective enzymes have been found for most steps in heme synthesis, creating conditions known as what?

Answer 12

Porphyrias

Question 13

What is the most common porphyrias?

Answer 13

Porphyria cutanea tarda

Question 14

Most porphyrias are photosensitive except which two?

Answer 14

ALA dehyrdatase prophyria and acute intermitten porphyria

Question 15

Heme synthesis requires what two types of reactions?

Answer 15

Decarboxylation and oxidation

Question 16

Where are RBCs destroyed?

Answer 16

Mostly in the spleen, somewhat in the liver

Question 17

Heme, in its first degradative step, is oxidized to what? (2)

Answer 17

Biliverdin and CO

Question 18

Biliverdin is reduced to what?

Answer 18

Bilirubin

Question 19

What transports bilirubin to the liver?

Answer 19

Serum albumin

Question 20

What happens to bilirubin in the liver?

Answer 20

It is conjugated to glucuronate and secreted into the bile

Question 21

Bilirubin diglucuronide is hydrolyzed to what? where does this happen?

Answer 21

Free bilirubin; intestines

Question 22

What converts bilirubin into urobilinogens and stercobilins?

Answer 22

Bacteria

Question 23

What happens to urobilinogens and stercobilins?

Answer 23

They are excreted into the urine and feces

Question 24

What does icterus mean?

Answer 24

Yellowing of the skin

Question 25

Accumulation of bilirubin in skin and mucous membranes is known as what?

Answer 25

Jaundice

Question 26

Accumulation of bilirubin in nerve tissue is known as what?

Answer 26

Kernicterus

Question 27

Which of the three types of jaundice comes from conditions that cause excessive levels of RBC destruction, overwhelming the heme degradation capacity?

Answer 27

Prehepatic (hemolytic)

Question 28

Which of the three types of jaundice comes from conditions of the liver that interfere with bilirubin uptake or conjugation enzyme (bilirubin glucuronyl transferase)?

Answer 28

Hepatic (hepatocellular)

Question 29

Which of the three types of jaundice comes from physical obstructions that prevent bile from reaching the intestinal tract?

Answer 29

Posthepatic (obstructive)

Question 30

What is the protein that is produced in the liver and carries two Fe3+ in the circulation?

Answer 30

Transferrin

Question 31

What is the protein that is produced in the liver, is used to store iron as a hydroxyphosphate, and binds over 2000 Fe3+'s

Answer 31

Ferritin

Question 32

What is formed with high iron uptakes; consists of granules of protein, polysaccharide and Fe3+?

Answer 32

Hemosiderin (associated with excess Fe)