This free quiz has 11 real AQA A-level Biology exam questions on mass transport in animals (27 marks, about 35 minutes). It marks itself: tick-box, diagram and calculation questions are marked for you, and for written answers you check your work against the real AQA mark scheme.
What the quiz covers (AQA 3.3.4.1)
calculating heart rate and cardiac output from ventricle volume data
which blood vessel carries blood at the lowest pressure
identifying the main blood vessels on a circulation diagram
how arterioles reduce blood flow, and how the aorta wall suits its function
using a pressure graph to explain blood flow during the cardiac cycle
why binding of one oxygen helps the next to bind, and the effect of carbon dioxide
the role of haemoglobin in loading, transporting and unloading oxygen (5 marks)
how tissue fluid is formed and returned to the circulation (5 marks)
How to use it
Write each written answer in full before you open the mark scheme, then tick only the points you really made. For the two calculations, write out each step on paper. Use precise terms such as partial pressure, hydrostatic pressure and water potential, and say where each process happens.
Where students lose marks (from AQA examiners’ reports and mark schemes)
Each point below is followed by wording that gained marks.
Cooperative binding. Many students wrote only that haemoglobin's “shape” changes so more oxygen binds, or just named “positive cooperativity”, which scored nothing. Only 11% gained both marks on one paper, and “active site” was rejected.
✔ Gains credit: binding of the first oxygen changes the tertiary or quaternary structure of haemoglobin, which uncovers another binding site (haem group) for oxygen.
Say where loading happens. The most common omission was not saying where oxygen is loaded and unloaded, and red blood cells were often not mentioned at all. Writing about oxygen “concentration” instead of partial pressure gained no credit.
✔ Gains credit: haemoglobin loads oxygen in the lungs at high partial pressure of oxygen, carries it as oxyhaemoglobin in red blood cells, and unloads it in respiring tissues at low partial pressure of oxygen.
Carbon dioxide and pH. A common misconception was that carbon dioxide binds to haemoglobin. Others linked the change to the rate of respiration rather than pH, didn't give the direction of the pH change, or contradicted themselves, e.g. “high affinity, so unloads oxygen easily”.
✔ Gains credit: more carbon dioxide lowers blood pH, which decreases haemoglobin's affinity for oxygen, so more oxygen is unloaded for aerobic respiration in the tissues.
Why valves open and close. Many students described when a valve opens or closes without explaining the cause, or explained only opening or only closing. Some seemed unsure of the difference between the atria and the aorta, and “S-L” or “A-V valve” wasn't accepted.
✔ Gains credit: a valve opens when the pressure behind it is higher than the pressure in front of it, and closes when the pressure in front is higher, e.g. an atrioventricular valve closes when pressure in the ventricle is higher than in the atrium.
Elastic recoil, not pumping. A common misconception was that muscle in the aorta wall pumps blood or acts as a second pump. Few students mentioned both stretch and recoil of the elastic tissue, and “contracts” or “relaxes” wasn't accepted for recoil.
✔ Gains credit: elastic tissue in the artery wall stretches and then recoils, which smooths blood flow and maintains blood pressure.
Arterioles control blood flow. The role of muscle in arteriole walls wasn't known by most students. Common wrong answers mentioned valves, or said that dilation of vessels reduces blood flow.
✔ Gains credit: smooth muscle in the arteriole wall contracts, constricting the lumen and reducing blood flow; when the muscle relaxes, the arteriole dilates and blood flow increases.
Water, not “tissue fluid”. Students often wrote that “tissue fluid”, “plasma” or even “blood” is forced out of capillaries, which was rejected. Others said water leaves by osmosis, or left osmosis out of its return.
✔ Gains credit: high hydrostatic pressure forces water and small molecules out of the capillary; plasma proteins remain and lower the water potential of the blood, so water moves back in by osmosis, and excess tissue fluid enters the lymph.
Keep practising
The other AQA 3.3 self-marking quizzes: Surface area to volume · Gas exchange · Digestion and absorption · Mass transport in plants
Topic 3.2 quizzes start with cell structure
The AQA topic index
weekly AQA group classes: Year 12 on Tuesdays at 5.15pm, Year 13 on Wednesdays or Thursdays at 6.30pm
Questions © AQA, from past A-level and AS Biology papers, with their mark schemes and examiners’ reports.