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Powerpoint@lecture Slides Are Prepared By Biology Lecturer, KMPk

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7.1 Gaseous exchange and

control in mammals

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Describe the basic structure of

haemoglobin and its characteristics as

respiratory pigments. Explain the transport of carbon dioxide

by haemoglobin.

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Consist of four

polypeptide subunits;

two chain

two chain

held together by

hydrogen bond

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Structure of haemoglobin

Each peptide contains

a haem group, bind

with oxygen

Therefore, one

hemoglobin (Hb)

molecule binds

up to fouroxygen molecules

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Combines reversely with O2 to formoxyhaemoglobin in areas of high O2

concentration region

- releases O2in areas of low O2

concentration region

Hb + 4O2 Hb(O2)4

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1

dissolved in

blood plasma

2

as Carbamino-

Haemoglobin

3

as

bicarbonate

ions (HCO3-)

CO2 transportation in blood

CO2

is transported between respiring tissues and

the lungs in 3 different ways:

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Air inAir inLungLung

TissueTissueFluidFluid

RBCRBC

Plasma inPlasma inCapillaryCapillary

1.1. COCO22 diffusesdiffuses

through tissuethrough tissuecapillary wallcapillary wall

DissolvesDissolves

in plasmain plasma,,

AsAsHCOHCO

33-,-,

Bound toBound tohemoglobin.hemoglobin.

2.2. COCO22is carriedis carriedto the lungsto the lungs

3.3. COCO22diffusesdiffuses

through lungthrough lungca illary wallcapillary wall

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Only about 7% of the CO2 released by respiring cells

is transported/dissolved in blood plasma

In plasma,CO2

slowly combine with water to form

carbonic acid

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About 23% CO2

binds to amino

ends of the hemoglobin

polypeptide chain to form

carbaminohemoglobin

the amount of CO2 that is able

to combine with Hb depends onthe amount of O2 already being

carried by the Hb

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3. As

bicarbonate ion (HCO3

-)

About 70% is transported in the blood in the form

of bicarbonate ions (HCO3

-)

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3. As

bicarbonate ion (HCO3

-)

CO2

diffuses passively into

bloodstream and passes into the

erythrocytes.

- combines with water to form

carbonic acid H2CO

3(catalysed by

carbonic anhydrase)- then dissociates into H+ and

HCO3

-

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Accumulation of H+ will

lower the pH of its surrounding

H+

tend to displace O2 fromhaemoglobin and make less

affinity of haemoglobin for

oxygen

this is called the Bohr effect

3. As

bicarbonate ion (HCO3

-)

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Hb accepts H+ fromcarbonic acid forming

haemoglobinic acid (HHb)

Hb acts as a buffermolecule (to minimize

the change in blood pH)

3. As

bicarbonate ion (HCO3

-)

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this enables large

quantities of carbonic acidto be carried to the lungs

without any major

alteration in blood pH

3. As

bicarbonate ion (HCO3

-)

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most of bicarbonate ions

diffuse out into the plasma,

where it is carried in the

bloodstream to the lungschloride ions (Cl-) in the

plasma diffuse into

erythrocytes to replace

bicarbonate ions

3. As

bicarbonate ion (HCO3

-)

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This is to balance the

loss of bicarbonate ion,

and to maintain the

electrical balance betweenblood plasma and

erythrocyte

this is called chlorideshift

3. As

bicarbonate ion (HCO3-)

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1

dissolved in

blood plasma

2

as Carbamino-

Haemoglobin

3

as

bicarbonate

ions (HCO3-)

CO2 transportation in blood

CO2 is transported between respiring tissues and

the lungs in 3 different ways:

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17.1 Gaseous exchange and control in mammals

c) describe the oxygen dissociation curve of

haemoglobin

d) compare oxygen dissociation curve of

haemoglobin and myoglobin

c) explain Bohr effect due to partial pressure

of carbon dioxide