This free quiz has 12 real AQA A-level Biology exam questions on homeostasis and blood glucose (25 marks, about 35 minutes). It marks itself: the tick-box questions are marked for you, and for written answers you check your work against the real AQA mark scheme.
What the quiz covers (AQA 3.6.4.1–3.6.4.2)
the term for keeping a stable internal environment
how insulin and glucagon act on their target cells
why a high blood glucose concentration dehydrates body cells
using a diagram of blood pH control to outline the principles of negative feedback
why the link between insulin and osteocalcin is positive feedback
the role of glucagon in gluconeogenesis, and two ways the drug metformin lowers blood glucose
type I and type II diabetes, including why weight loss treats only type II and how less PI3K activity can cause it
producing a calibration curve for creatinine with a colorimeter (4 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. Use the exact terms examiners look for: water potential and osmosis rather than concentration and diffusion, receptors or cells rather than “the body”, and volume rather than amount. Learn glycogenesis, glycogenolysis and gluconeogenesis as three separate words, because near misses such as “glucogenesis” score nothing.
Where students lose marks (from AQA examiners’ reports and mark schemes)
Each point below is followed by wording that gained marks.
Water potential, not concentration. Some students wrote “diffusion” instead of osmosis, or referred only to “a concentration gradient”. Less successful answers focused on glucose moving or being converted to glycogen rather than on water.
✔ Gains credit: a high blood glucose concentration lowers the water potential of the blood, so body cells lose water by osmosis.
Negative feedback principles. Most students said the variable returns to the norm, but fewer explained how this is achieved, and less successful answers left out how the change is detected.
✔ Gains credit: a change from the norm is detected by receptors, and the response returns the variable to the norm or set point; separate mechanisms for an increase and a decrease give greater control.
Positive feedback means “more”. Many students just restated that one substance stimulates the other, or wrote “further” production, which could be at the same rate. Rote-learnt definitions with no link to the information given were not credited, and 55% scored zero on one such question.
✔ Gains credit: positive feedback means each change causes more of the other, so the deviation from normal gets greater.
Exercise, CO₂ and pH. Students often left out respiration, and a significant number said anaerobic respiration produces lactate and carbon dioxide. Others said more carbon dioxide raises blood pH, or left out chemoreceptors and ventilation.
✔ Gains credit: more respiration produces more carbon dioxide (anaerobic respiration produces lactate), which lowers blood pH and stimulates chemoreceptors, increasing the rate of ventilation.
Channel proteins in the membrane. Many thought insulin opens existing channels, and some said insulin binds to an “active site” or to cells without mentioning receptors. Answers that mentioned vesicles or channel proteins without the cell-surface membrane lost the mark, and active transport was rejected.
✔ Gains credit: insulin binds to receptors, and vesicles carrying glucose channel proteins fuse with the cell-surface membrane, so more glucose enters the cell by diffusion.
Receptors, not “the body”. It was common to see “the body is less sensitive to insulin”, or insulin “resistance” or “immunity” not linked to cells or receptors. “Lifestyle” was not credited, and some said only that the pancreas is not damaged.
✔ Gains credit: people with type II diabetes still produce insulin, but their cells or receptors are less sensitive to it, and type II is linked to weight, diet and lack of exercise.
Volume, not amount. Using “amount” rather than “volume” for solutions was a common theme, and many answers just said “read values” from the colorimeter. A few wrote calorimeter, and some drew a tangent to the calibration curve.
✔ Gains credit: make a dilution series with distilled water, add a known volume of the detecting solution to each, measure absorbance with a colorimeter, plot absorbance against concentration, then read off the unknown concentration from its absorbance.
Keep practising
The other AQA 3.6 self-marking quizzes: Stimuli and receptors · Nervous coordination · Muscle contraction · Kidney
Next, topic 3.7: the inheritance quiz
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.