Take the NUMS Biology — Homeostasis, Support and Movement (Set 7): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer…
The first 5 questions of this test, with the correct answer and explanation.
Q1. A Paramecium from pond water is moved into a salt solution that is isotonic to its cytoplasm. What happens to the activity of its contractile vacuole?
- A. It slows or almost stops because little water enters by osmosis ✓
- B. It fills with salt and bursts because the cell is hypertonic
- C. It reverses and takes water in because the medium is isotonic
- D. It pumps out water faster because the salt stimulates it
Answer: A. It slows or almost stops because little water enters by osmosis
Explanation: In pond water water enters by osmosis and the contractile vacuole expels it. In an isotonic solution there is no net water entry, so the vacuole has little to expel and its rate falls.
Q2. A section of compact bone shows concentric rings of matrix around a central channel. Which statement about this structure is correct?
- A. The central canal holds red bone marrow, and osteocytes lie within the canal itself
- B. The central canal is filled with cartilage, and osteoclasts lie in lacunae between the rings
- C. The central canal carries only lymph, and osteoblasts lie in lacunae between the rings
- D. The central canal carries blood vessels and nerves, and osteocytes lie in lacunae between the rings ✓
Answer: D. The central canal carries blood vessels and nerves, and osteocytes lie in lacunae between the rings
Explanation: A Haversian canal contains blood vessels and nerves. Concentric lamellae of matrix surround it and osteocytes sit in lacunae between the lamellae.
Q3. A healthy adult filters 180 litres of fluid per day and passes 1.5 litres of urine. What percentage of the filtrate is reabsorbed?
- A. 99.9%
- B. 99.2% ✓
- C. 92.5%
- D. 98.5%
Answer: B. 99.2%
Explanation: Reabsorbed = 180 − 1.5 = 178.5 L; 178.5 ÷ 180 × 100 = 99.2%.
Q4. A patient passes large volumes of dilute urine. After an ADH injection, the urine remains dilute. What is the most likely defect?
- A. The loop of Henle is secreting too much glucose
- B. The posterior pituitary cannot make ADH
- C. The glomerulus cannot filter plasma
- D. Collecting duct cells do not respond to ADH ✓
Answer: D. Collecting duct cells do not respond to ADH
Explanation: If the hormone is supplied but the response is absent, the target (kidney tubule) is at fault, as in nephrogenic diabetes insipidus.
Q5. A person drinks one litre of pure water quickly. Which sequence is expected over the next hour?
- A. Plasma osmolarity rises, ADH release rises and small concentrated urine is made
- B. Plasma osmolarity falls, ADH release rises and small concentrated urine is made
- C. Plasma osmolarity falls, ADH release falls and large dilute urine is made ✓
- D. Plasma osmolarity rises, ADH release falls and large dilute urine is made
Answer: C. Plasma osmolarity falls, ADH release falls and large dilute urine is made
Explanation: Water dilutes the plasma; hypothalamic osmoreceptors reduce ADH, so the collecting duct becomes less permeable and dilute urine is excreted.
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Q6. After drinking a large amount of alcohol, a person passes large volumes of dilute urine and feels thirsty. Which change is mainly responsible?
- A. Alcohol stimulates ADH release, so more water is reabsorbed
- B. Alcohol raises aldosterone, so more sodium is excreted
- C. Alcohol blocks glomerular filtration, so less urine is made
- D. Alcohol inhibits ADH release, so less water is reabsorbed
Q7. A diuretic blocks Na⁺/K⁺/2Cl⁻ transport in the thick ascending limb of the loop of Henle. What happens to the urine?
- A. Small volumes of dilute urine, as the loop absorbs more water
- B. Small volumes of concentrated urine, as the medullary gradient grows
- C. Large volumes of dilute urine, as the medullary gradient is lost
- D. Large volumes of concentrated urine, as more urea is filtered
Q8. Kangaroo rats, which live in deserts, have a kidney medulla that is relatively thicker than that of humans. What is the adaptive advantage?
- A. Wider collecting ducts allow urine to flow out faster
- B. Longer loops of Henle give more concentrated urine
- C. More glomeruli allow urine to be filtered faster
- D. Shorter loops of Henle allow urine to be more dilute
Q9. In haemodialysis, the dialysis fluid contains glucose at the normal blood concentration but no urea. Why is glucose included?
- A. To increase blood glucose, while urea diffuses into blood
- B. To provide energy, while urea is converted to glucose
- C. To prevent loss of water, while urea is actively pumped out
- D. To stop net glucose loss from blood, while urea diffuses out
Q10. A urine sample from a patient contains protein and red blood cells but a normal glucose level. Which part of the nephron is most likely damaged?
- A. The proximal convoluted tubule
- B. The glomerular filtration barrier
- C. The loop of Henle
- D. The collecting duct
Q11. During the rising phase of a fever, a person feels cold and shivers even though the body temperature is already 38.5 °C. Which explanation is correct?
- A. The set point has fallen, so heat production is switched on fully
- B. Pyrogens have raised the hypothalamic set point above body temperature
- C. The hypothalamus is damaged, so it cannot sense body temperature
- D. Sweat glands are overactive, so the skin is cooled far too much
Q12. Why is heat stroke more likely on a hot, very humid day than on a hot, dry day at the same temperature?
- A. Humid air is hotter than dry air, so more heat enters
- B. Sweat evaporates poorly in humid air, so cooling is reduced
- C. Sweat glands stop working in humid air, so no sweat forms
- D. Blood vessels constrict in humid air, so skin heat rises
Q13. Which of the following is an example of positive feedback?
- A. ADH release raising blood volume and then reducing ADH release
- B. Insulin release lowering blood glucose and stopping its own release
- C. Oxytocin in labour increasing uterine contractions further
- D. Sweating lowering body temperature and so reducing sweating
Q14. A freshwater bony fish is compared with a marine bony fish. Which pair of statements is correct?
- A. Both make dilute urine and drink large amounts of seawater daily
- B. Freshwater fish drink water and excrete salt; marine fish make dilute urine
- C. Both make concentrated urine and absorb salts through the gills
- D. Freshwater fish make dilute urine; marine fish drink and excrete salt by gills
Q15. Bird embryos in shelled eggs excrete mainly uric acid. What is the main advantage?
- A. Uric acid is a gas, so it escapes through the shell
- B. Uric acid is insoluble and non-toxic, so it can be stored
- C. Ammonia is made in larger amounts, so it dissolves in albumen
- D. Uric acid is soluble and toxic, so it can be diluted in the egg
Q16. A muscle sarcomere is 2.4 µm long when relaxed and 1.8 µm long when contracted. The A band is 1.6 µm long. What are the I-band lengths relaxed and contracted? (I-band length in a sarcomere = sarcomere length − A band.)
- A. 0.4 µm relaxed and 0.1 µm contracted
- B. 0.8 µm relaxed and 0.2 µm contracted
- C. 0.8 µm relaxed and 0.8 µm contracted
- D. 1.6 µm relaxed and 0.2 µm contracted
Q17. Muscles of a dead body become stiff (rigor mortis). Which change explains this?
- A. Calcium is pumped back in, so troponin locks actin
- B. ATP is made in excess, so myosin heads stay bound to actin
- C. Lactic acid dissolves actin, so filaments become rigid
- D. ATP is lacking, so myosin heads cannot detach from actin
Q18. Isolated muscle fibres supplied with ATP fail to contract when calcium ions are removed using a chelating agent. What does this show?
- A. Calcium ions supply the energy that ATP cannot provide
- B. Calcium converts ATP into creatine phosphate in the fibre
- C. Calcium binds myosin heads to detach them from actin
- D. Calcium binding to troponin exposes myosin-binding sites on actin
Q19. During a 10-second sprint the ATP stored in muscle is used up within a few seconds. Which store restores ATP most rapidly?
- A. Fat droplets, which make ATP by lactic acid fermentation
- B. Creatine phosphate, which donates its phosphate to ADP
- C. Glycogen, which makes ATP by aerobic respiration alone
- D. Haemoglobin, which releases ATP that is bound to oxygen
Q20. One motor neuron supplies 1000 muscle fibres in a thigh muscle, but another supplies only 10 in a finger muscle. Which conclusion is correct?
- A. Finger muscles can make stronger contractions, as each motor unit is small
- B. Finger muscles can make finer movements, as each motor unit is small
- C. Both muscles give identical control, as all fibres contract fully
- D. Thigh muscles can make finer movements, as each motor unit is large
Q21. A muscle tissue has branched, striated, uninucleate cells joined by intercalated discs. It is:
- A. myoepithelial tissue
- B. cardiac muscle
- C. skeletal muscle
- D. smooth muscle
Q22. A child living with very little sunlight develops bowed legs, and blood tests show low calcium absorption. What is the most likely cause?
- A. Excess vitamin A, which reduces calcium absorption in bones
- B. Excess calcitonin, which increases calcium release from bones
- C. Vitamin D deficiency, which reduces calcium absorption from the gut
- D. Vitamin C deficiency, which reduces collagen cross-links in tendons
Q23. Rotating the head from side to side to say 'no' mainly uses which joint?
- A. The pivot joint between atlas and axis
- B. The ball-and-socket joint between atlas and axis
- C. The gliding joint between the lumbar vertebrae
- D. The hinge joint between skull and atlas
Q24. A forearm is modelled as a lever. The biceps attaches 4 cm from the elbow and a 3 kg weight is held 32 cm from the elbow. Ignoring the weight of the forearm, what force (in kg-weight) must the biceps exert to hold it?
- A. 24 kg-weight
- B. 3 kg-weight
- C. 96 kg-weight
- D. 12 kg-weight
Q25. Why do cartilage injuries heal more slowly than bone fractures?
- A. Cartilage is too hard, so cells cannot enter into it
- B. Cartilage contains no collagen, so it cannot be repaired
- C. Cartilage has no cells, so it cannot make new matrix
- D. Cartilage has no blood supply, so cells get little nutrition
Q26. Rheumatoid arthritis differs from osteoarthritis because rheumatoid arthritis is:
- A. a deposit of uric acid crystals in joints
- B. an autoimmune attack on the synovial membrane
- C. a wear and tear loss of articular cartilage
- D. a loss of bone mass in elderly women
Q27. The strings of celery stalk give flexible support to young growing stems. They are made of:
- A. sclerenchyma, dead cells with uniformly lignified walls
- B. collenchyma, living cells with unevenly thickened walls
- C. parenchyma, living cells with thin cellulose walls
- D. xylem vessels, dead cells with lignin deposits only
Q28. A tree trunk is cut and 25 annual rings are counted. The rings from years 8 to 10 are much wider than the rest. What is the best interpretation?
- A. The tree is about 8 years old and those years had very low rainfall
- B. The tree is about 50 years old and those years had very cold winters
- C. The tree is about 25 years old and those years were favourable
- D. The tree is about 25 years old and those years had no secondary growth
Q29. A person breathes very fast and deeply for several minutes in a panic. Blood CO₂ falls. Using CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻, what happens to blood pH?
- A. It stays fixed, because bicarbonate is a perfect buffer
- B. It rises, because the equilibrium shifts right and H⁺ falls
- C. It rises, because the equilibrium shifts left and H⁺ falls
- D. It falls, because the equilibrium shifts right and H⁺ rises
Q30. In a patient with metabolic acidosis the kidneys help to restore pH. Which response occurs in the tubule cells?
- A. More H⁺ is reabsorbed and more bicarbonate is secreted
- B. Less H⁺ is secreted and bicarbonate is excreted
- C. More H⁺ and more bicarbonate are both excreted
- D. More H⁺ is secreted and more bicarbonate is reabsorbed