OCR biology AS transportation of carbon dioxide

1. Carriage of CO2
LO: How is CO2 transported in the blood
and how does this affect the %
saturation of Hb with O2?
STARTERSTARTER 1. PPQs about fetal Hb v adult Hb.
2. Discuss with partner about how
you think CO2 is transported.

2. LEVEL
ALL: Recall the 3 ways CO2 is
transported in the blood.
C-D
MOST: Describe the role of Hb in
carrying CO2.
B-C
SOME: Describe and explain he
significance of the dissociation
curves of adult HbO at
different CO2 levels.
A-B

3. Question of the lesson!
How is CO2 carried
around in the blood?

4. Literacy
Today’s main keyword is…
Carbonic anhydrase
A sentence with this word in it would be…

5. CO2 Transport
• 5% dissolved directly in plasma (inefficent – diffusion from
tissue to tissue down gradient).
• 10% is combined directly to Hb (carbaminohaemoglobin).
It does not interfere with O2 transport as CO2 is carried by
the globin protein.
• 85% is transported in the form of hydrogencarbonate ions
(HCO3
-
)

6. Tissues Capillary

7. Carriage of CO2
• CO2 diffuses into RBC, combines with H2O to form
_______ acid (catalysed by ________
__________ – H2CO3).
• Carbonic Acid Dissociates to release ________
ion (H+
) and ______________________ ions
(HCO3
-
)
• HCO3
-
ions diffuse out of _____ into plasma.
• _________ shift occurs (Cl-
ions rush into RBC –
why?)
• H+
ions cause inc/dec pH from approx 7.6 to 7.2.
• H+
ions taken up by Hb to make haemoglobinic
acid (HHb), which prevents the pH decreasing
CO2 H2O
H2CO3
-
H+
HCO3
-
Cl-
HHb
Carbonic anhydraseCarbonic
hydrogen
Hydrogen carbonate
RBC
Chloride

8. Releasing O2
• H+ ions compete for space
on the Hb – what are they
competing with?
• When pCO2 is high, the H+
ions will displace O2 causing
it to release – is this a bad
thing?
• If more CO2 is
produced, a greater
release of O2 will
occur – useful in tissues
that have been respiring a

9. Questions
1. List the ways in which CO2 is transported in the
blood
2. Describe how carbon dioxide is converted to
hydrogen carbonate ions
3. Explain the need for a chloride shift
4. Explain how the presence of CO2 can reduce the
affinity of Hb for O2.
5. Describe how Hb can supply more oxygen to
actively respiring tissues than to those with a
lower respiration level.

10. Examiner tips
When asked how
carbon dioxide is
transported,
remember that there
are three ways. Also
remember that the
hydrogencarbonate
ions difuse back into
the plasma – so most
carbon is carried in
the plasma, not in the
red blood cells.

16. Poster work
• Produce an A3 poster to show how Oxygen and
carbon dioxide are transported by the blood.
• Explain how the blood carries oxygen and carbon
dioxide using diagrams to aid you.
• Include Graph sketches to show the % saturation of
oxygen for Carbon dioxide and oxygen carriage.
• Explain each graph clearly.
• Bullet point key facts given to aid revision of a
difficult topic.
• Colourful work will aid your memory of this topic
too.