heme metabolism

Question 1

what is the structure of heme?

Answer 1

• porphyrin ring

- central Fe++

Question 2

what makes up porphyrin ring?

Answer 2

4 linked pyrrole rings

Question 3

what is the function of heme

Answer 3

component of hemoproteins:
hemoglobin
myoglobin
peroxidases
catalase
cytocromes

Question 4

what amino acid is used in the first step in heme synthesis?

Answer 4

glycine

Question 5

what is the first step in heme synthesis?

Answer 5

glycine + succinyl CoA -> ? aminoleuvulinate synthase

? - ALA

Question 6

what is the coenxyme for ?-ALA: amino levulinate synthase?

Answer 6

pyridoxal phosphate PLP

remember B6 is used in amino acid synthesis…proteins

Question 7

what controls the ?-ALA enzymatic activity?

Answer 7

the level of HEME in the cell already.

Question 8

2 molecules of ?-ALA condense to form what?

Answer 8

porphobilinogen

Question 9

what is signifigant about the enzyme that combines the 2 ?-ALA molecules into porphobilinogen?

Answer 9

Inhibited by lead

Second step in heme synthesis is inhibited by led.

Question 10

how much glycine and succinyl CoA is required to produce 1 heme molecule?

Answer 10

8 molecules of glycine

8 molecules of succinyl CoA

Question 11

what does ferrochelates do?

Answer 11

sticks Fe2++ in the middle of heme

Question 12

what disease will a defective enzyme in heme synthysis cause?

Answer 12

porphyrias

Question 13

most common porphyrias cause what?

Answer 13

photosensitivity

Question 14

Where are RBC’s destroyed, major site and minor site?

Answer 14

Major = splene
Minor = liver

Question 15

What are produced in hemolytic anemias?

Answer 15

• free heme

- hemoglobin

Question 16

What carries free heme in the blood?

Answer 16

hemopoxins

Question 17

What carries free hemoglobin in the blood?

Answer 17

haptoglobulin

Question 18

What is heme oxidized into during the first degradative step?

Answer 18

• biliverdin and carbon monoxide

Question 19

what is biliverdin reduced to?

Answer 19

bilirubin

Question 20

how does biliverdin, that gets reduced in the blood get to the liver?

Answer 20

• Serum albumin

- this is of course if the heme was produced in spleen

Question 21

what is bilirubin conjugated to in the liver?

What type of reaction?

Answer 21

Glucuronate, —- PHase II

—–bilirubin digluconuronide

Question 22

what is the first step after bilirubin is conjugated with glucuronate?

Answer 22

its secreted in the bile

Question 23

What is the conjugated bilirubin, bilirubin diglucuronide hyroxylized to in the intestines?

Answer 23

Hydroxylized into free bilirubin

Question 24

what two things does bacterial flora convert free bilirubin into? How?

Answer 24

Deconjugation:

• urobilinogens
• stercobilins

Question 25

How are urobilinoges excreated?

Answer 25

• feces

- urin if is further altered to urobilins

Question 26

How are stercobilins excreted?

Answer 26

feces - brown

Question 27

What is jaundice?

Answer 27

accumulation of bilirubin in skin and mucus membranes

Question 28

What are three causes of jaundice?

Answer 28

• prehepatic - excessive RCB destruct
• hepatic - Liver problems with conjucation/uptake
• posthepatic - bile duct obstruction

Question 29

What transports Fe into circulation?

Answer 29

transferrin - a protein

Question 30

What is used to store liver, where, as what?

Answer 30

Ferritin is used to store Fe in liver as a hydroxyphosphate

- binds many Fe

Question 31

What is formed during and iron accumulation disease?

Answer 31

hemosiderin - protein aggragates with iron

-granules of protein, polysaccharide and Fe?

Question 32

is Iron actively excreated form body?

Answer 32

no, some is lost in bile.