← Biology syllabus

EnglandBiology

Module 3: Exchange and transport

5 dot points across 5 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How is each blood vessel adapted to its job, and how is tissue fluid formed and returned?

3.1.2 Transport in animals: the structure and functions of arteries, arterioles, capillaries, venules and veins; the formation of tissue fluid from plasma at the arterial end of a capillary bed and its return at the venous end and via the lymphatic system, explained in terms of hydrostatic and oncotic (osmotic) pressure.
A focused answer to the OCR H420 3.1.2 dot point on blood vessels and tissue fluid. Covers the structure and function of arteries, arterioles, capillaries, venules and veins, and how hydrostatic and oncotic pressure form tissue fluid at the arterial end and return it at the venous end and via the lymph.
12 min answer →

Why do large organisms need specialised exchange surfaces, and how are mammalian, fish and insect gas-exchange systems adapted?

3.1.1 Exchange surfaces: the need for specialised exchange surfaces as size and metabolic rate increase and surface-area-to-volume ratio falls; the features of an efficient exchange surface; the structure and function of the mammalian gas-exchange system, the counter-current system in fish gills, and the tracheal system of insects.
A focused answer to the OCR H420 3.1.1 dot point on exchange surfaces and gas exchange. Covers why surface-area-to-volume ratio drives the need for exchange surfaces, the features of an efficient surface, the mammalian lung, the fish counter-current system and the insect tracheal system.
12 min answer →

How does the structure of the mammalian heart produce a coordinated cardiac cycle, and how is each beat controlled?

3.1.2 Transport in animals: the structure of the mammalian heart and the events of the cardiac cycle (atrial systole, ventricular systole and diastole), the pressure and volume changes that open and close the valves, and the myogenic control of heart rate by the SAN, AVN, bundle of His and Purkyne tissue, including the interpretation of electrocardiograms (ECGs).
A focused answer to the OCR H420 3.1.2 dot point on the mammalian heart. Covers the heart's structure, the three stages of the cardiac cycle, how pressure changes open and close the valves, myogenic control by the SAN, AVN, bundle of His and Purkyne tissue, and how to read an ECG.
13 min answer →

How does haemoglobin load oxygen in the lungs and unload it in respiring tissues, and how is carbon dioxide carried?

3.1.2 Transport in animals: the role of haemoglobin in transporting oxygen, the oxygen dissociation curve and cooperative binding, the Bohr effect, the higher oxygen affinity of fetal haemoglobin, and the transport of carbon dioxide including the formation of hydrogencarbonate ions and the chloride shift.
A focused answer to the OCR H420 3.1.2 dot point on oxygen transport. Covers haemoglobin and cooperative binding, the sigmoidal oxygen dissociation curve, loading and unloading, the Bohr effect, fetal haemoglobin, and carbon dioxide transport as hydrogencarbonate with the chloride shift.
13 min answer →

How does water move up a plant in the xylem, how is sugar moved in the phloem, and how do xerophytes limit water loss?

3.1.3 Transport in plants: the structure and function of xylem and phloem; the cohesion-tension theory of water transport in the xylem and the factors affecting transpiration; the mass flow hypothesis of translocation in the phloem from source to sink; and the adaptations of xerophytes for reducing water loss.
A focused answer to the OCR H420 3.1.3 dot point on transport in plants. Covers xylem and phloem structure, the cohesion-tension theory of transpiration, the factors affecting transpiration rate, the mass flow hypothesis of translocation, and xerophyte adaptations.
13 min answer →