7/30/2019 Hour 2-Gaseous Exchange Dah Edit

1/25

Powerpoint@lecture Slides Are Prepared By Biology Lecturer, KMPk

mailto:point@lecturemailto:point@lecture

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

2/25

7.1 Gaseous exchange and

control in mammals

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

3/25

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

4/25

4

1

dissolved

in blood

plasma

2

as Carbamino

haemoglobin

3

as bicarbonate

ions

(HCO3-)

CO2 transportation in blood

CO2is transported between respiring tissues and

the lungs in 3 different ways:

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

5/25

At the end of this topic, student should be

able to:

c. describe the oxygen dissociation curve

of haemoglobin

d. compare oxygen dissociation curve of

haemoglobin and myoglobin

e. explain Bohr effect due to partialpressure of carbon dioxide

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

6/25

6

Oxygen dissociation curves of

haemoglobin

The curve shows

the relative

amounts of oxygen

bound to

haemoglobin

exposed to

solutions withdifferent PO2

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

7/25

7

Oxygen dissociation curves

of haemoglobin

When the partial

pressure of oxygen

is high as in lungcapillaries,

haemoglobin has a

high affinity for

oxygen to form

oxyhaemoglobin

Campbell 9th edition, page 907

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

8/25

8

Oxygen dissociation curves

of haemoglobin

When the partial

pressure of

oxygen is low asin respiring

tissues, the

oxyhaemoglobin

dissociates and

oxygen is

liberated

Campbell 9th edition, page 907

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

9/25

9

Compose of a single

polypeptide chain with

an iron atom that can

bind to an O2

molecule

Have higher affinity

for oxygen thanhemoglobin

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

10/25

10

When O2 levels fall in

muscle cells, myoglobinwill contain O2 after the

hemoglobin supplies

have been exhausted

Function :

store O2in the muscle

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

11/25

11

its O2 dissociation

curve is displaced

well to the left of

hemoglobin

it only begins to

release O2 when

the partialpressure of O2 is

below 20 mm Hg

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

12/25

12

in this way, it acts as

a store of O2 in resting

muscle (only releasing

it when supplies of

HbO2 have been exhausted)

the myoglobin-oxygen

dissociation curve is

hyperbolic rather than

sigmoid

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

13/25

At low PO2levels,

maternal hemoglobin

gives up oxygen to

fetal hemoglobinacross the placenta

The curve is shift to

the left shows that

fetal hemoglobin has a

higher affinity for

oxygen than mother at

the same PO2.

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

14/25

E.g:

At 40mmHg, fetal

hemoglobin is

almost 90%

saturated while

maternalhemoglobin is only

75% saturated.

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

15/25

- The effect of pH on

hemoglobin's

affinity for oxygen

- This is the result of

H+ binding to

hemoglobin

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

16/25

Bohr Effect/shift

It is shown

graphically by a

shift of the

oxyhemoglobindissociation curve

to the right.

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

17/25

Partial pressure of O2

high in lung capillaries,

haemoglobin has a high

affinity for O2

to form

oxyhaemoglobin

Partial pressure of O2

low in respiring tissues,

oxyhaemoglobin

dissociates and O2

liberated

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

18/25

Partial pressure of CO2

increases, pH also

decreases (increase of

H+), haemoglobin has a

low affinity for O2

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

19/25

19

Increase in CO2pressure willshift the O2

dissociationcurve to the

right

This effectknown as

Bohr Shift

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

20/25

The red line on the

graph represents the

oxygen dissociation

curve at a normal pH(pH = 7.4).

BOHR EFFECT

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

21/25

BOHR EFFECT

The green line

represents the

curve in the blood

of exercising

tissues, shifted to

the right of the

normal curve.

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

22/25

The black line

represents the

curve in the bloodat the lungs,

shifted to the left

of the normal

curve.

BOHR EFFECT

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

23/25

Remember!!!

Higher PCO2= Higher [H+]

= Lower pH = Shift

oxygen dissociation

curve to the RIGHT

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

24/25

What is the Oxygen Dissociation Curves?

What does a right shift indicate?

What are the causes of a right shift? Why is the fetus haemoglobin curve shifted to the

left?

What is myoglobin?

7/30/2019 Hour 2-Gaseous Exchange Dah Edit

25/25

17.3 Gaseous exchange and

control in plants

17.2 Role of chemoreceptors in

controlling breathing