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A Handbook of Biology

ØXÝGËÑ-HÅËMØGLØBÏÑ DÏSSØÇÏÅTÏØÑ ÇÜRVË

It is a sigmoid curve obtained when percentage saturation of Hb with O2 is

plotted against the pO2. It is used to study the effect of factors like pCO2, H⁺

concentration and temperature, on binding of O2 with Hb.

Partial pressure of oxygen (mm Hg)

Percentage saturation of haemoglobin

with oxygen

20

0

20

40

40

60

60

80

80

100

100

Oxygen dissociation curve

ÇØ2 TRÅÑSPØRT

It is the transport of CO2 from tissues to lungs. In tissues, pCO2 is high and

pO2 is low. In lungs, pCO2 is low and pO2 is high. This favours CO2 transport

from tissues to lungs. It occurs in 3 ways:

As carbamino-haemoglobin In

tissues, 20-25% of CO2 binds to Hb

to form carbamino-haemoglobin.

In alveoli, CO2 dissociates from

carbamino-haemoglobin. [AIPMT

2010]

As carbonic acid In tissues,

7% of CO2 is dissolved in

plasma to form carbonic

acid and carried to lungs.

As bicarbonates About 70% of CO2

is transported by this method. [NEET

2014] RBCs and plasma contain

an enzyme, carbonic anhydrase. It

facilitates the following reactions:

Carbonic anhydrase

Carbonic anhydrase

2

2

2

3

3

CO

H O

H CO

HCO

H

-

+

¾¾¾¾¾¾¾¾¾¾®

¾¾¾¾¾¾¾¾¾¾®

+

+

←¾¾¾¾¾¾¾¾¾

¾

←¾¾¾¾¾¾¾¾¾

¾

In tissue, pCO2 is high, CO2 diffuses into blood and forms HCO^-

3 ^{and H+.}