Biology option D in International Baccalaureate Diploma Programme

1. TRANSPORT OF
RESPIRATORY GASES

2. Shows the affinity of hemoglobin for oxygen
The degree to which O₂ binds to hemoglobin is
determined by the partial pressure of O₂ in the blood
OXYGEN DISSOCIATION CURVES

3. Hemoglobin saturated at
very high pO₂
At low pO₂ few heme bound to
oxygen. Hemoglobin does not
carry much oxygen
Easier for more oxygen to
be picked up

4. Carbon dioxide is carried in three forms in blood plasma
Dissolved as carbon dioxide
Reversibly converted to bicarbonate
(hydrogencarbonate) ions that are dissolved in plasma
Bound to plasma protein
CARBON DIOXIDE
TRANSPORT IN BLOOD

5. Majority is converted to more soluble and less toxic bicarbonate
(hydrogencarbonate) ion
Occurs in red blood cells
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3
-
Enzyme carbonic anhydrase
When cells release CO₂, bicarbonate ion and hydrogen ion are generated
pH of the blood become lower
In lungs, when CO₂ leaves the blood, the reaction is driven to the left and
converted back to CO₂ (exhale)
CO₂ → HCO₃⁻

6. Metabolism ↑, more CO₂ released into blood, pH of blood ↓
Low pH indicates high acidity in blood
High blood acidity shift the O₂ dissociation curve to the right
(Low affinity of hemoglobin for O₂)
Greater release of O₂ from hemoglobin
This ensures respiring tissues have enough O₂
In lungs, pCO₂ is lower, so saturation of hemoglobin can occur at lower pO₂
THE BOHR SHIFT

7. Hyperventilation that occurs in response to exercise
Chemoreceptors in medulla, aorta and carotid artery are able to detect
changes in concentration of CO₂ in blood
High level of CO₂ triggers an increase in ventilation rate for the body to
remove the CO₂ build-up
CO₂ diffuses into alveoli and ventilation expels the CO₂ from body
EFFECT OF CO₂ ON
VENTILATION RATE

8. Medulla
Oblongata(brainstem)
Intercostal nerve
Stimulate the
intercostal muscle in
the thorax
Phrenic nerve
Stimulate the
diaphragm
REGULATION OF
VENTILATION RATE
When lungs expand, stretch receptors in the walls of the chest and lungs send signals to
the respiratory center
This triggers a cessation of the signals leading to inspiration until the animal exhales
Then a new signal is sent

9. Blood CO₂ increase
pH of blood decrease
Chemoreceptors in carotid artery and aorta sends
signals to breathing center in medulla oblongata
Nerve impulse sent from medulla oblongata to
diaphragm and intercostal muscle
Ventilation rate increase
CHEMORECEPTORS AND
BLOOD PH

10. Allows the transfer of oxygen in the
placenta onto the fetal hemoglobin
Fetal hemoglobin has a higher affinity
for oxygen at all partial pressures
This ensures that oxygen is transferred
to the fetus from the maternal blood
across the placenta
DIFFERENCES IN OXYGEN AFFINITY
BETWEEN FETAL AND ADULT
HEMOGLOBIN

11. Analysis of dissociation curves for hemoglobin and
myoglobin
ANALYSIS OF
DISSOCIATION CURVES

13. INTERPRETING MICROGRAPHS
OF LUNG TISSUE
Identification of pneumocytes, capillary endothelium
cells and blood cells in light micrographs and electron
micrographs of lung tissue.

15. D.6 TRANSPORT OF RESPIRATORY GASES (AHL)
APPLICATION

16. pH of blood regulated to stay within the narrow range of 7.35-7.45
Blood pH falls below 7.35
Chemoreceptors send signal to respiratory centre to increase the rate of
ventilation
Hyperventilation withdraws CO2 from the blood driving the carbonic acid
rxn to the left. Hence, this action of withdrawing Hydrogen ions from
blood raising the pH
CO2+H2O=H2CO3=H++HCO3
-
In the kidney, H+ ions can be secreted into the urine bound to buffers to
raise the pH. Greater amounts of bicarbonate will be reabsorbed from the
tubules to neutralize the acid
If blood to basic, bicarbonate ions can be secreted into the distal
convoluted tubule of the kidney
Chemical buffers exist within the extracellular fluid and these can’t remove
the acids or bases, but can minimize effect.
REGULATION OF BLOOD PH

17.  High altitudes, amount of O2 decreased. Because
pressure decreased
 Volume of gases cover large area and spread further
 So partial pressure of O2 is reduced
 Decreases hemoglobin affinity for oxygen
 Results is less oxygen in body tissues used for
metabolism
 Can cause altitude sickness- fatigue, nausea, headaches
 Severe altitude sickness, loss of coordination, coma,
death
GAS EXCHANGE AT HIGH
ALTITUDES

18.  lung condition- alveoli become damaged and cannot efficiently carry out
gas exchange
 How? Fragile alveoli overinflate with trapped air and lose their elasticity
 So? Without elasticity, gas exchange becomes difficult between alveoli
and capillaries.
 Enhance by? Scar tissue will build up to cover up the damaged alveoli,
hence, alveoli will thicken, so gas exchange becomes more difficult
 Cause? Cigarette smoking and exposure to air pollutants , genetic defect
 Treatment? Cessation of smoking, avoiding air pollutants, use of
chemical therapies, delivery of low levels of oxygen directly to the lungs
EMPHYSEMA