Haemoglobin Structure And Function

Question 1

What is haemoglobin made up of?

Answer 1

2 alpha and two beta chains

Question 2

How much of RBCs is comprised of a globular haemoprotein

Answer 2

1/3

Question 3

What is a haemoprotein?

Answer 3

A group of specialised proteins that contain haem as a tightly bound prosthetic group

Question 4

What is haem a complex of?

Answer 4

Protoporphyrin IX and ferrous iron Fe2+

Question 5

How is the iron held in the centre of the haem molecule?

Answer 5

Bonds to the 4 nitrogens of a porphyrin ring

Question 6

How much Hb is synthesised in the erythroblasts?

Answer 6

65%

Question 7

How much Hb is synthesised at the reticulocyte stage?

Answer 7

35%

Question 8

What is haemoglobin synthesis stimulated by?

Answer 8

Tissue hypoxia (lack of oxygen)

Question 9

How is Hb synthesis stimulated by tissue hypoxia?

Answer 9

Hypoxia causes the kidneys to increase EPO production which increases RBC and Hb production

Question 10

What does EPO Stand for?

Answer 10

Erythropoietin

Question 11

What molecule delivers iron to the reticulocyte?

Answer 11

Transferrin

Question 12

Where does synthesis of protoporphyrins take place?

Answer 12

In the mitochondria of RBC precursors

Question 13

What is synthesis of protoporphyrins mediated by?

Answer 13

EPO and vitamin B6

Question 14

Protoporphyrin + iron->

Answer 14

Haem

Question 15

What are the starting reactants in the synthesis of protoporphyrin?

Answer 15

Glycine + succinyl CoA

Question 16

What is the iron stored as if you don’t need it?

Answer 16

Ferritin

Question 17

Where does synthesis of globin happen?

Answer 17

In the ribosome and RER

Question 18

What does proper globin synthesis depend on?

Answer 18

Genes

Question 19

How many functional globin chains are there?

Answer 19

8

Question 20

What are the two clusters of globin called?

Answer 20

A and B

Question 21

What genes are in the B-cluster?

Answer 21

Beta, gamma, epsilon and delta

Question 22

Where are the B-cluster genes found?

Answer 22

On the short arm of chromosome 11

Question 23

What genes are in the A-cluster?

Answer 23

Alpha and zeta

Question 24

Where are the A-cluster genes found?

Answer 24

Short arm of chromosome 16

Question 25

What types of globulin are found in foetal Hb?

Answer 25

Alpha and gamma

Question 26

What types of globulin are found in adult Hb?

Answer 26

Alpha and beta

Question 27

What are the functions of haemoglobin?

Answer 27

- carry oxygen from the lungs to the tissues - remove CO2 - buffering action- maintains blood pH as it changes from oxyhaemoglobin to deoxyhaemoglobin

Question 28

How many oxygens can one Hb bind to?

Answer 28

Four

Question 29

How long does it take for Hb oxygenation?

Answer 29

Less than 0.1 seconds

Question 30

What happens (physically) to the Hb when it’s oxygenated?

Answer 30

2,3-DPG is pushed out and the beta chains move closer

Question 31

What does DPG stand for?

Answer 31

Disphosphateglycerate

Question 32

What does the amount of o2 bound to hb and released to tissues depend on?

Answer 32

pO2 pCO2 Affinity of hb for O2

Question 33

What does oxygen affinity determine?

Answer 33

The proportion of o2 released to the tissues or loaded onto the cells at a given pressure

Question 34

What is the Bohr effect?

Answer 34

Alterations in the blood pH shifted the oxygen dissociation curve

Question 35

What happens to the oxygen dissociation curve in acidic pHs?

Answer 35

The curve shifts to the right

Question 36

What happens when the oxygen dissociation curve shifts to the right?

Answer 36

Results in an enhanced capacity to release o2 where it is needed

Question 37

What does the normal position of the haemoglobin oxygen dissociation curve depend on?

Answer 37

2,3 DPG concentration Hydrogen ion conc (pH) CO2 in RBC Structure of Hb

Question 38

What are standard conditions for the Hb- O2 dissociation curve?

Answer 38

37 Celsius pH 7.4 BE =0

Question 39

What are the three mechanisms for CO2 transport?

Answer 39

Dissolution in the plasma Formation of carbonic acid Binding to form carbaminohaemoglobin

Question 40

What is oxyhaemoglobin made up of?

Answer 40

Hb and 02

Question 41

What is deoxyhaemoglobin made up of?

Answer 41

Hb - o2

Question 42

What is methemoglobin made up of?

Answer 42

Hb with Fe3+

Question 43

What is carbaminohaemoglobin made up of?

Answer 43

CO2 binds non-covalently to globin chain of Hb