Biology · Form and function
B3.1 — Gas exchange
Biology · SL / HL · syllabus-mapped notes
B3.1.1
Gas exchange as a vital function in all organisms
Explain why gas exchange gets harder with size, as SA:V falls and diffusion distance rises.
B3.1.2
Properties of gas-exchange surfaces
State the four properties of a gas-exchange surface: permeable, large, moist and thin.
B3.1.3
Maintenance of concentration gradients at exchange surfaces in animals
Explain how capillary networks, blood flow and ventilation maintain concentration gradients.
B3.1.4
Adaptations of mammalian lungs for gas exchange
Explain four adaptations of mammalian lungs: surfactant, bronchioles, capillary beds, surface area.
B3.1.5
Ventilation of the lungs
Explain ventilation using the diaphragm, intercostal muscles, abdominal muscles and ribs.
B3.1.6
Measurement of lung volumes
Measure tidal volume, vital capacity, and the inspiratory and expiratory reserves.
B3.1.7
Adaptations for gas exchange in leaves
Explain six leaf adaptations for gas exchange, from waxy cuticle to veins.
B3.1.8
Distribution of tissues in a leaf
Draw and label a plan diagram of a transverse section of a dicotyledonous leaf.
B3.1.9
Transpiration as a consequence of gas exchange in a leaf
Explain transpiration as a consequence of gas exchange, and the factors affecting its rate.
B3.1.10
Stomatal density
Determine stomatal density from micrographs or leaf casts, using repeat counts.
B3.1.11
Adaptations of foetal and adult haemoglobin for the transport of oxygen
Explain cooperative binding and allosteric CO2 binding, and why foetal haemoglobin binds more strongly.
B3.1.12
Bohr shift
Explain how increased carbon dioxide increases oxygen dissociation, and why that helps active tissue.
B3.1.13
Oxygen dissociation curves as a means of representing the affinity of haemoglobin for oxygen at different oxygen concentrations
Explain the S-shape of the oxygen dissociation curve, and how to read a shifted curve.