OCR A 5.1.1–5.1.2 · 21 written questions · 43 marks · about 50 minutes · marked as you go
This free quiz has 21 written exam questions on homeostasis and excretion, all taken from OCR A Level Biology A papers (A level, 2017 to 2024, plus OCR practice or sample papers). Short answers mark themselves. For longer answers you write your answer, then tick off the OCR mark-scheme points you made, so you see exactly where the marks are. This quiz covers cell signalling, negative and positive feedback, temperature control in ectotherms and endotherms, excretion and the liver, kidney structure and the nephron, ADH and water balance, kidney failure and urine testing.
What the quiz covers (OCR A spec 5.1.1–5.1.2)
Cell signalling and feedback (5.1.1(b)(c)): identifying signalling molecules in a response pathway, what happens when the thermoregulatory set point rises, and how positive feedback can speed up hypothermia.
Temperature control (5.1.1(d)): defining an endotherm, advantages and disadvantages of being an ectotherm, comparing naked mole rats with other mammals, and the roles of peripheral and hypothalamic temperature receptors.
Excretion (5.1.2(a)): why bilirubin processing counts as excretion and where lost body mass actually goes.
The liver (5.1.2(b)(i)(ii)): the liver's blood supply and bile, and describing damaged liver tissue from micrographs.
The kidney and nephron (5.1.2(c)): naming regions of a kidney section, identifying a region from a photomicrograph, matching nephron regions to functions, the loop of Henle, the distal convoluted tubule and albumin in urine.
Water balance and kidney failure (5.1.2(d)(e)): nephrogenic diabetes insipidus and aquaporins, and using eGFR data to tell pregnancy from kidney failure.
Medical diagnosis (5.1.2(f)): banned drugs detected in urine and other diagnostic urine tests.
How to use it
Write every answer in full, as you would in the exam: the mark for each question is shown, so you know how much to write. When you self-mark, only tick a point if your answer clearly makes it, then read the examiner's tip under each question. Your progress is saved on your device, so you can do it in two sittings, and at the end you can retry just the questions where you dropped marks.
Prefer multiple choice? Try the 21-question Homeostasis and Excretion multiple choice quiz first.
Open the Homeostasis and Excretion quiz in a new tab (easier on a phone)
Where students lose marks (from OCR examiners' reports and mark schemes)
Each point below is followed by wording that gained marks.
Name the ions in the loop: Writing 'salt', 'solutes' or just 'ions' for what leaves the loop of Henle, or naming the wrong ions such as K⁺ or Ca²⁺.
✔ Gains credit: Na⁺ and Cl⁻ ions are actively transported out of the upper part of the ascending limb.
Say which limb you mean: Describing ion and water movements in the loop of Henle without saying whether it is the descending or ascending limb, or how each substance moves.
✔ Gains credit: The ascending limb is impermeable to water; water leaves the descending limb by osmosis.
Fever helps fight pathogens: Answering a question about a raised thermoregulatory set point only in terms of enzyme activity, without linking the higher temperature to the response to infection.
✔ Gains credit: The raised set point causes a fever, and the higher body temperature helps to kill pathogens and speeds up the immune response.
Less metabolism, less heat: Saying hypothermia continues because of positive feedback without explaining why, or suggesting responses like sweating in a mammal that is getting colder.
✔ Gains credit: Lower temperature reduces kinetic energy and enzyme activity, so the metabolic rate falls and less heat is released, so the temperature drops further.
eGFR is about ultrafiltration: Explaining high blood electrolytes in kidney failure as a problem with reabsorption, when GFR measures filtration at the glomerulus.
✔ Gains credit: A low eGFR means less ultrafiltration, so electrolytes such as Na⁺ and K⁺ stay high in the blood.
Compare eGFR with a healthy value: Comparing one patient's eGFR with another patient's instead of with the healthy reference value given in the question.
✔ Gains credit: Patient B's eGFR is much lower than the value expected in a healthy person of that age.
Stored fat, not dietary fat: Saying weight loss happens because fat from the diet is broken down, without saying it is stored body fat that is respired.
✔ Gains credit: Stored body fat is respired aerobically to carbon dioxide and water, and the carbon dioxide is excreted (exhaled).
Hypothalamus, not medulla oblongata: Thinking temperature receptors send impulses to the medulla oblongata to regulate body temperature.
✔ Gains credit: Receptors in the hypothalamus detect the temperature of the blood (core body temperature), and the hypothalamus is the thermoregulatory centre.
Keep practising
Try the Homeostasis and Excretion multiple choice quiz, the Transport in Animals multiple choice quiz, the Classification and Evolution written quiz or the Neuronal Communication written quiz, or browse all our OCR A Level Biology quizzes. Our OCR A masterclasses (Year 12 on Wednesdays at 5.15pm, Year 13 on Tuesdays at 6.30pm) work through real exam questions on one topic each week.
Questions, mark schemes and examiners' report extracts © OCR.