Exchange and mass transport

Surface area to volume ratio

c   The relationship between the size or structure of an organism and its surface area to volume ratio.

c   Changes to body shape and the development of systems as adaptations that facilitate exchange as this ratio reduces.

Gas exchange

c   Adaptations of gas exchange surfaces, shown by insect tracheal systems.

c   Structural and functional compromises between gas exchange and the limitation of water loss shown by terrestrial insects.

c   Adaptations of gas exchange surfaces, shown by fish gills.

c   Required practical 5: Dissection of animal or plant respiratory system or mass transport system or of an organ within such a system

c   The gross structure of the human gas exchange system.

c   Ventilation and the exchange of gases in the lungs. 

c   The mechanism of breathing.

c   The essential features of the alveolar epithelium as a gas exchange surface.

c   Lung diseases and the risk factors associated with them.

c   Adaptations of gas exchange surfaces in leaves of dicotyledonous plants (mesophyll and stomata).

c   Structural and functional compromises between gas exchange and the limitation of water loss shown by xerophytic plants.

Digestion and absorption

c   The purpose of digestion.

c   Digestion in mammals of:

• carbohydrates by amylases and disaccharidases
• lipids by lipase
• proteins by endopeptidases, exopeptidases and dipeptidases.

c   The role of bile salts.

c   Co-transport mechanisms and the role of micelles in the absorption of the products of digestion by cells lining the ileum.

Mass transport in animals

c   The general pattern of blood circulation in a mammal.

c   The quaternary structure of haemoglobins.

c   The role of haemoglobin in the loading, transport and unloading of oxygen.

c   The cooperative nature of oxygen binding, with the binding of the first oxygen molecule making the binding of subsequent oxygen molecules easier.

c   The effects of carbon dioxide concentration on oxygen dissociation (Bohr effect).

c   Many animals are adapted to their environment by possessing different types of haemoglobin with different oxygen transport properties.

c   The gross structure of the human heart.

c   Required practical 5: Dissection of animal or plant respiratory system or mass transport system or of an organ within such a system

c   Pressure and volume changes and associated valve movements during the cardiac cycle that maintain a unidirectional flow of blood.

c   The structure of arteries, arterioles and veins in relation to their function.

c   The structure of capillaries and the importance of capillary beds as exchange surfaces. 

c   The formation of tissue fluid and its return to the circulatory system

c   Cardiovascular disease (CVD) and associated risk factors.

Mass transport in plants

c   Xylem as the tissue that transports water in the stem and leaves of plants. 

c   The cohesion-tension theory of water transport in the xylem.

c   The use of a potometer to measure transpiration

c   Phloem as the tissue that transports organic substances in plants.

c   The mass flow hypothesis for the mechanism of translocation.

c   Investigating transport in plants using tracers and ringing experiments.