L22- Types of Hb

Question 1

how many different types of Hb

Answer 1

3

Question 2

name the types of Hb

Answer 2

HbA
HbA2
HbF

Question 3

HbA

Answer 3

major adult Hb
- Composed of:
o 2 alpha chains
o 2 B chains

Question 4

HbA2

Answer 4

minor adult Hb
- Composed of:
o 2 a chains
o 2 𝛿 chains

Question 5

HbF

Answer 5

the normal faetal Hb
- Composed of:
o 2 alpha (a) chains
o 2 gamma (Y) chains

Question 6

features of HbF

Answer 6

o Has a greater affinity for oxygen than HbA so ensures oxygen transfer from maternal ciruclation to fetus RBCs through placenta
o Has a lower affinity for BPG

Question 7

HbA1C

Answer 7

(glycosylation of HbA)- has glucose residues attached to B-globin chains

• used to monitor diabetes

Question 8

expression of different alpha and beta globing genes is

Answer 8

regulated during development

i.e. alpha chains exist during foetal development, but beta chains only start being expressed near the end of pregnancy

Question 9

where are alpha-globin -like genes located

Answer 9

chromosome 16

Question 10

where are beta- globin- like genes located

Answer 10

chromosome 11

Question 11

haemoglobin are formed by

Answer 11

combination of alpha globing like genes and B-globin like chains

Question 12

structure of Hb

Answer 12

4 polypeptide chains

• quaternary
• 2 x alpha
• 2 x beta

Question 13

important of foetal Hb

Answer 13

• HbF is the major Hb in foetal blood

- Higher binding affinity for oxygen than HbA which allows transfer of oxygen to foetal blood supply from the mother

Question 14

sickle cell anaemia is causes by

Answer 14

mutation of glutamate to valine in Beta globin

Question 15

mutation of glutamate to valine in Beta globin causes

Answer 15

HbS- Hb sickle

Question 16

valine causes

Answer 16

sticky hydrophobic pockets to form- allows deoxygenated HbS to polymerase

Question 17

HbS polymerisation caused by hydrophobic pockets formed by valine

Answer 17

• tetrameric Hb stick together forming chains

- long chains of Hb cause the sickle shape

Question 18

dangers of sickle cell (2)

Answer 18

• Sickle cells are more prone to lyse (anaemia)

- More rigid (block microvasculature)

Question 19

thalassaemia

Answer 19

Group of genetic disorders where there is an imbalance between the number of alpha and Beta globin chains

Question 20

B- thalassaemia

Answer 20

• Decreased or absent B-globin chain production
• Alpha chains unable to form stable tetramers
• Symptoms appear after birth

Question 21

If you lose 1 B-globin copy on chromsosmes 11

Answer 21

Minor

Question 22

If you lose both B-globin copy on chromsosmes 11- Major

Answer 22

major

Question 23

alpha-thalassaemia

Answer 23

• Decreased or absent alpha-globin chain production
• Several diff levels of severity due to multiple copies of the alpha chain present
• B-chains can form stable tetramers with increased affinity for oxygen
• Onset before birth

Question 24

adults haemoglobin has

Answer 24

4 haem-containing subunits, 2alpha and 2 B chains of which can bind a molecule of O2

Question 25

Haemoglobin can exists in 2 interchangeable states:

Answer 25

o Low affinity T state (high affinity)

o High affinity R state (low affinity)

Question 26

Binding of oxygen to one subunit of haemoglobin causes

Answer 26

conformational changes which promotes the R state

Question 27

Sigmoidal binding curve for oxygen binding to haemoglobin is physiologically important as it

Answer 27

allows for efficient oxygen binding and delivery

Question 28

Oxygen binding to haemoglobin is dependent

Answer 28

on [CO2, H+ and BPG]

o These effectors work by stabilising the T state

Question 29

what inhibit Hb

Answer 29

CO