Haemoglobin Structure & Function Flashcards Preview

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Flashcards in Haemoglobin Structure & Function Deck (25)
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1
Q

When does globin synthesis begin?

A

Globin synthesis starts from the third week of gestation (prenatal) in the yolk sac

2
Q

What does a decrease in O2 affinity cause?

A

Causes oxygen release

3
Q

What is the result of high oxygen affinity?

A

Increased O2 affinity
=> Hb has highr O2 affinity
=> binds more strongly

4
Q

What does a normal Hb curve depened on

A

[2,3-DPG]
[H+] (pH)
CO2 in RBC
Hb structure

5
Q

How are different forms of Hb formed?

A

Various types of globin combine with haem to form the different haemoglobin
8 functional globin chains arrange in 2 clusters (A and B)

6
Q

Describe the Bohr effect on oxyhaemoglobin curves

A
  1. An increase in CO2 production by tissues
  2. CO2 released into blood
  3. Dissociation curve shifts to right
  4. Release of O2 from Hb diffuses into tissues
    - lower O2 affinity = unloaded readily
7
Q

Describe the structure of Hb

A
  • Globin chains have 4 polypeptide subunits (tetramers)
  • 2 α globin chains
  • 2 β globin chains
    Each globin chain contains its own haem
8
Q

What does a Bohr curve shifted to the right indicate?

A

Shift right = low affinity for O2
e.g.
Anemia, acedosis
despite less RBCs, they act more efficiently to deliver o2 to their target tissues

9
Q

Outline the steps of O2 binding and unloading

A
  1. β chains slide over each other
  2. When oxygenated the globin chains move closer
  3. Deoxygenated globin chains pulled apart for 2,3-DPG -
    decreasing affinity
10
Q

Outline the significance of Globin?

A

In polyribosomes

  • depends on genes
  • precise order of amino acids in globin chains determines the function of Hb
11
Q

What are the factors determining how much O2 binds to Hb?

A
  • PO2
  • PCO2
  • Hb affinity for O2
12
Q

What is oxygen affinity?

A

Ease with which haemoglobin binds and releases oxygen

Determines proportion of O2 released to tissues or loaded onto cells at a given oxygen pressure

13
Q

What is indicated by a Bohr curve shifted to the left?

A

Left shift = high O2 affinity
e.g.
Presence of abnormal Hb, alkalosis
Hb less readily unloads O2 to tissues, binds strongly

14
Q

What is the consequence of mutations on haemoglobin?

A

Deletions/mutations may lead to

  • abnormal globin synthesis (sickle cell)
  • Reduced rate of globin synthesis (thalassemia)
15
Q

What is the relationship between 2,3-DPG and Oxygen delivery?

A

Increased 2,3-DPG causes more oxygen delivery to tissues

This is the body’s main response to hypoxia

16
Q

What are the functions of Hb?

A

Carry O2 from lungs to tissues

  • Remove CO2
  • Buffer (maintains blood pH as it changes from oxyhaemoglobin to deoxyhaemoglobin
17
Q

How is Haem synthesised?

A

In mitochondria
1. Iron supplied to reticulocyte by transferrin enzyme
2. Protoporphyrins (RBC precursors) synthesised (via EPO
and Vit. B12 regulation)
3. Protoporphyrin + Iron => Haem

18
Q

How is CO2 transported in the body?

A

There are 3 mechanisms for CO2 transport

  1. Dissolution in plasma
  2. Formation of Carbonic acid
  3. Binding to carbaminohaemoglobin
19
Q

What is 2,3-DPG?

A

2,3-diphosphoglycerate is a metabolite formed in red blood cells
controls the movement of oxygen from RBCs to tissues

20
Q

How is Hb production regulated?

A

Regulation stimulated by hypoxia

Causes kidneys to produce more EPO, increasing RBC and Hb production

21
Q

How does Hb transport oxygen?

A

1 Hb can bind to 4 oxygen in <0.01s
When oxygenated 2,3-DPG pushed out
β chains move closer together

22
Q

How is Oxygen unloaded to tissues?

A

β chains pulled apart
2,3-DPG can enter between chains
results in lower O2 affinity

(this is responsible for the sigmoidal shape of oxygen dissociation curves)

23
Q

What is the normal [Hb] in blood?

A

Adult male: 13.5-16.5g/dl

Adult femaile: 12.5-15.0g/dl

24
Q

Which red cell precursors does Hb synthesis occur in?

A

65% in erythroblasts

35% in reticulocytes

25
Q

How are the components of Haemoglobin synthesised in accordance to one another to produce sufficient Hb?

A

Haem and globin synthesis occur separately in developing red cell precursors
Synthesis rates are carefully coordinated to ensure optimal efficiency of Hb assembly