INDEPTH: Haemoglobin 3.2.7 Flashcards

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1
Q

What does affinity mean?

A

The attraction of the haem group to oxygen

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2
Q

what is the name for when oxygen is released from oxyhaemoglobin?

A

Dissociation

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3
Q

What is the structure of a haemoglobin molecule?

A

A complex protein worth for subunits.

Each subunit consists of a polypeptide chain and a haem group

The haem group contains a single iron ion (Fe2+)

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4
Q

How many oxygen molecules can a haemoglobin molecule hold?

A

4

Each haem group can hold one oxygen molecule

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5
Q

Where does association and dissociation of haemoglobin and oxygen occur?

A

Association

Where the pO2 is high, in the lungs
(high partial pressure of oxygen)

Dissociation

Where the pO2 is low, in the respiring tissues
(low partial pressure of oxygen)

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6
Q

What does the partial pressure of oxygen mean?

A

The concentration of oxygen

The relative pressure that it contributes to a mixture of gasses

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7
Q

Describe the s - shaped association curve of haemoglobin

A

At low partial pressures:

  • Haem groups are in the centre of the molecule so association with oxygen is harder
  • Low saturation of haemoglobin

At Medium partial pressures:

  • Oxygen molecule associates, causing conformational change
  • Oxygen can bind to the haem group easier
  • High saturation

At high partial pressures:
-Saturation levels curve off

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8
Q

How is fetal haemoglobin different from adult?

A

It has a higher affinity for oxygen

The association curve is to the left of the adult haemoglobin association curve.

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9
Q

Why does fetal haemoglobin need to have a higher association for oxygen than adult?

A

Because fetal needs to associate with oxygen in the placenta, where the partial pressure of oxygen is low.

The low PP enables oxygen to dissociate from the mothers blood, and then as fetal haem has a higher affinity it can then associate with that oxygen.

This further lowers the PP of the surrounding tissue cause more maternal oxygen to be released.

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10
Q

What the three different options for CO2 once produced via respiration?

A

1) 5% dissolved directly into the plasma
2) 10% is combined with haemoglobin to form carbaminohaemoglobin
3) 85% is transported in the form of hydrogencarbonate ions

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11
Q

How are hydrogen carbonate ions formed?

A

1) CO2 diffuses into the red blood cells, combines with water to form a weak carbonic acid
2) This acid then dissociates to release H+ ions and hydrogen carbonate ions
3) Hydrogen carbonate ions diffuse into the blood plasma

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12
Q

How is the charge within the red blood cells maintained once the hydrogencarbonate ions move out?

A

The Chloride Shift

Chloride ions diffuse into the red blood cell

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13
Q

How is the red blood cell prevented from becoming acidic when carbonic acid dissociates?

A

Carbonic acid releases H+ ions

Hydrogen ions are taken out of solution by associating with haemoglobin to produce haemoglobinic acid,

The Haemoglobin acts a buffer to maintain a constant pH

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14
Q

What enzyme catalyses the reaction between water and CO2?

A

Carbonic anhydrase

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15
Q

What is the name of the process by which more oxygen is delivered to the tissues releasing more CO2?

A

The Bohr effect

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16
Q

Describe the Bohr effect?

A

1) Carbon dioxide enters the red blood cells from carbonic acid, which dissociates to release H+ ions
2) H+ ions diffuse into the cytoplasm, making it more acidic
3) This causes the tertiary structure of haemoglobin to change, reducing haemoglobins affinity to oxygen
4) This results in oxygen dissociating from the haem, and in effect delivering more oxygen to where more respiration is occurring

17
Q

Which way does the bohr shift shift the haemoglobin association curve?

A

Right