Haemoglobin synthesis

Question 1

Which of the stages of haemoglobin synthesis take place in the mitochondria?

Answer 1

Porphyrin ring formation
Iron insertion into Protoporphyrin IX

Question 2

What is the rate limiting step in haemaglobin synthesis?

Answer 2

ALA synthase is the enzyme responisble for the rate limiting step
ALA binds to porphyrin ring, which binds iron to form heme (core comp on hemoglobin)

Question 3

What are the basic constituents required to make Haemaglobin?

Answer 3

1. Heme group
2. Globin chains
3. Amino acids
4. Vitamin B6,9 &12

Question 4

Briefly describe how iron is absorbed and circulated

Answer 4

Iron is absorbed in the small intestine via DMT1 and ferroportin
It’s transported in the blood by transferin to tissues like the bone marrow

Question 5

What is the function of transferrin?

Answer 5

To transport iron to tissues and cells for use/ storage
Prevents free iron build up in the bloodstream

Question 6

Give the difference between the function of transferrin and ferroportin

Answer 6

Transferin- blood protein, transports Fe3+ to cells via t5ranferrin tramnsporters
Ferroportin- membrane transporter, exports Fe2+ from cells into the bloodstream, regulated by hepcidin

Question 7

What is hepcidin and describe it’s function?

Answer 7

A hormone produced inthe liver that regualtes Iron homeostasis
Function- decreases iron absorption in the intestine
Reduces iron release from macrophages and liver cells into the blood

Question 8

What is the Embeden-Meyerhof pathway?

Answer 8

Glycolysis- breakdown of glucose into pyruvate producing ATP and NADH

Question 9

Describe the structure of Hb with ref to all 4 levels of protein structure

Answer 9

Primary- Sequence of amino acids in 2 alpha and 2 beta chains
Secondary- Folding into alpha helices and B-turns
Tertiary- chains gain globular 3D structure wiht a heme group and oxygen binding
Quaternary- tetramer of 4 subunits with cooperative oxygen binding

Question 10

How are globin chains synthesised?

Answer 10

Gene transcription- genes are transcribed into mRNA in the nucleus
Translation- translated into polypeptide chains on ribosomes in the cytoplasm
Post- translat mods- polypetides fold into tertiary structure, heme group is encorporated into the globin chain

Question 11

How do fetal and adult Hb’s differ?

Answer 11

They have 2 gamma chains instead of beta chains
Fetal Hb has a higher affinity for oxygen

Question 12

How do RBC’s produce ATP if they can’t use O2?

Answer 12

They rely of anaerobic glycolysis
Glucose is converted to pyruvate generating 2 ATP

Question 13

List the embryonic haemaglobins?

Answer 13

Hb Gower-1: 2 zeta and 2 epsilon chains
Hb Gower-2: 2 alpjha and 2 epsilon chains
Hb portland: 2 zeta and 2 gamma chains

Question 14

List the fetal haemoglobins

Answer 14

HbF- 2 alpha and 2 gamma chains
Hb portland- 2 zeta and 2 gamma chains

Question 15

List the adult haemoglobins

Answer 15

HbA- 2 alpha and 2 beta chains
HbA2- 2 alpha and 2 delta chains
HbF- 2 alpha and 2 gamma chains