PART 2

• To understand how carbon dioxide influences haemoglobin (The Bohr Effect).

The Effect of CO2 – The Bohr Effect

In the presence of an increased concentration of carbon dioxide, the oxygen dissociation curve shifts to the right side of the graph paper!!!!

The Effect of CO2 – The Bohr Effect• More Carbon Dioxide combines with water in the blood to

form more Carbonic acid. • This lowers the pH of the blood (makes it more acidic) and

changes the oxygen dissociation curve- the curve shifts to the right. The results:

• This lowers the haemoglobin’s affinity for it’s oxygen.• So more oxygen is released more easily to the respiring tissue.• This is called the Bohr effect

ppO2

ppO2

Effect of Carbon dioxide

0

B Apartial pressure of oxygen

% saturation

of HbCO2 Partial pressure 3 kPa

CO2 Partial pressure 6kPa ( pH will be lower)

100

80

60

40

20

0

Bohr Shift

• By shifting the curve to the right, oxyhaemoglobin will give up more oxygen at a given partial pressure of oxygen

TASK:

1)Write out the flow chart in bold with arrows from the middle of p153 textbook into the space at the bottom of HB p5.

2)Read page 202 of the Heineman book

and Do Q 1-3

3)Read page 161 of the AS text book and do Q7

By the end of this lesson you should be able to:

• Describe the habitats of animals that have different types of haemoglobin

• Describe the oxygen dissociation curves of these animals

• Explain the advantages of having different types of haemoglobin

Lugworm

Left shifted curves (fig 4 p154)

Partial pressure of O2

% Saturation of Hb

Human Hb

Lugworm Hb

Lugworm Hb

• Can you suggest what conditions animals with this type of haemoglobin may be living in?

• How has shifting the curve to the left affected the partial pressure at which the Hb is fully saturated?

• TASK: Use the bottom of textbook p153 and top of p154 to help you to answer the questions in the box on HB p6.

HIGHLIGHT THESE SECTIONS AT THE TOP OF HB P6:

• Animals with haemoglobin with a left shifted curve will be found in habitats where there is very little oxygen (sometimes called anaerobic conditions)

• Their haemoglobin has an even higher affinity for oxygen than human haemoglobin.

• This means their haemoglobin takes up more oxygen molecules more readily and can become fully saturated even at very low concentrations of oxygen

Foetus

Foetal Haemoglobin

adult haemoglobin

100

80

60

40

20

partial pressure of oxygen

% saturation of Hb

foetal haemoglobin

Llama

Prairie dog

• Animals which live in extremely low oxygen concentrations of have a curve even further to the left.

• See p154 NT textbook fig 4, showing the oxygen dissociation curve for the Lugworm (The graph is similar for Blood Worms and Tubifex Worms that live in burrows in mud at the bottom of lakes).

MyoglobinAn extra Respiratory Pigment just found in the muscle cells of diving mammals only. Myoglobin has an extremely high

affinity for oxygen and acts as an oxygen store. The oxygen dissociation curve for myoglobin is a hyperbolic shape.

Seal

http://www.bbc.co.uk/news/science-environment-26743090

• Haemoglobin with a right shifted curve has

a lower affinity for oxygen.

• This means that (for a given partial pressure of oxygen) the haemoglobin will give up more oxygen more readily to the respiring muscle cells.

• This type of haemoglobin is found in very active animals with a high respiration rate eg in shrews, in mackerel fish.

RIGHT SHIFTED CURVESHIGHLIGHT THESE SECTIONS AT THE TOP OF HB P7:

Haemoglobin of very active animalshas a right shifted curve:

Mackerel

Species Partial pressure of oxygen at which haemoglobin is 50% saturated/kPa

Mackerel 2.1

Carp 0.4

Mammal Body mass/kg Partial pressure of oxygen at which haemoglobin is 50% saturated/kPa

Mouse 0.002 7.5

Rat 0.2 6.7

Sheep 49 4.8

Human 70 4.3

Horse 725 3.6

Elephant 3000 3.1

Mammal Body mass/kg Partial pressure of oxygen at which haemoglobin is 50% saturated/kPa

Mouse 0.002 7.5 Right Shift

Rat 0.2 6.7 Right Shift

Sheep 49 4.8 Right Shift

Human 70 4.3

Horse 725 3.6 Left Shift

Elephant 3000 3.1 Left Shift

MyoglobinAn extra Respiratory Pigment just found in the muscle cells of diving mammals only. Myoglobin has an extremely high

affinity for oxygen and acts as an oxygen store. The oxygen dissociation curve for myoglobin is a hyperbolic shape.

Seal

TASKS:

1. Do the summary task bottom of HB p7.

2. Circle the correct answer choices on the handout sheet called ‘Comparing Different Types of Respiratory Pigments’.

3. Answer Q1,2,3 from peach box on textbook p155.

4. Do the exam questions Q1,3,4 (sent via e-mail) and bring these with you to next lesson.

More Hb TASKS:

1. Read p152-155 AS book carefully.

2. Do the Green box questions Q1-12 on p154-155 and check your own answers with the first column on p250.

By the end of this lesson you should be able to:

• Describe the habitats of animals that have different types of haemoglobin

• Describe the oxygen dissociation curves of these animals

• Explain the advantages of having different types of haemoglobin