Take the NUMS Biology — Homeostasis, Support and Movement (Set 5): 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 healthy adult filters about 180 litres of filtrate per day and passes 1.8 litres of urine per day. What percentage of the filtrate is reabsorbed?
- A. 90%
- B. 99.9%
- C. 99% ✓
- D. 98.2%
Answer: C. 99%
Explanation: Reabsorbed volume = 180 − 1.8 = 178.2 L, which is 178.2 ÷ 180 = 99%.
Q2. A patient with uncontrolled diabetes mellitus passes glucose in the urine. Which explanation is correct?
- A. The glomerulus is damaged, so glucose is filtered but protein is retained
- B. Insulin blocks reabsorption, so glucose is lost with the sodium in the loop
- C. Glucose is not filtered, so it is lost by active secretion in the tubule
- D. Blood glucose exceeds the transporters' capacity, so some stays in the filtrate ✓
Answer: D. Blood glucose exceeds the transporters' capacity, so some stays in the filtrate
Explanation: Glucose is freely filtered and normally all reabsorbed in the proximal tubule by saturable carriers; when blood glucose exceeds the renal threshold, the carriers are saturated and glucose appears in the urine.
Q3. A patient passes 15 litres of very dilute urine per day, and the urine stays dilute after 12 hours without water. After an injection of ADH the urine becomes concentrated. What is the most likely cause?
- A. Failure of the pancreas to release insulin (diabetes mellitus)
- B. Failure of the collecting duct to respond to ADH (nephrogenic type)
- C. Failure of the pituitary to release ADH (cranial diabetes insipidus) ✓
- D. Failure of the adrenal cortex to release aldosterone
Answer: C. Failure of the pituitary to release ADH (cranial diabetes insipidus)
Explanation: Since the kidney responds to injected ADH, its collecting ducts work; the lack is of hormone from the posterior pituitary.
Q4. A person with adrenal cortex failure (Addison's disease) has low blood sodium, high blood potassium and low blood pressure. Which hormone is deficient and what is the tubular effect?
- A. Aldosterone, so Na⁺ reabsorption in the distal regions falls ✓
- B. Aldosterone, so Na⁺ reabsorption in the proximal tubule rises
- C. ADH, so water reabsorption in the collecting duct falls
- D. Adrenaline, so Na⁺ secretion in the distal regions falls
Answer: A. Aldosterone, so Na⁺ reabsorption in the distal regions falls
Explanation: Aldosterone increases Na⁺ reabsorption (and K⁺ secretion) in the distal tubule and collecting duct; water follows, maintaining blood volume and pressure.
Q5. Furosemide blocks the Na⁺–K⁺–2Cl⁻ transporter in the thick ascending limb of the loop of Henle. Which effect on urine is expected?
- A. Large volume, dilute, because the medullary gradient is weakened ✓
- B. Small volume, dilute, because the water is reabsorbed in the cortex
- C. Large volume, concentrated, because the medullary gradient is stronger
- D. Small volume, concentrated, because the ADH release is stimulated
Answer: A. Large volume, dilute, because the medullary gradient is weakened
Explanation: Active salt pumping out of the ascending limb creates the high osmolarity in the medulla. If blocked, the gradient needed to draw water out of the collecting duct is lost, so more dilute urine is made.
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Q6. Desert rodents produce very concentrated urine, whereas a beaver does not. Which kidney feature is most responsible for this difference?
- A. More numerous glomeruli with much larger capsules
- B. Relatively short loops of Henle that remain in the cortex
- C. A thicker proximal tubule with more microvilli
- D. Relatively long loops of Henle reaching deep into the medulla
Q7. Birds and reptiles excrete uric acid, whereas mammals excrete urea. Which advantage does uric acid give an embryo developing in a shelled egg?
- A. It is cheap to make and needs less ATP than ammonia
- B. It is insoluble and non-toxic, so it can be stored with little water
- C. It is highly soluble, so it can be diluted in the egg white
- D. It is volatile and toxic, so it can escape through the shell
Q8. Dialysis fluid for a kidney patient contains normal plasma concentrations of glucose and sodium but no urea. Why is this composition used?
- A. Urea diffuses out of blood, while glucose and sodium are not lost
- B. Urea is actively pumped out, while glucose is actively pumped in
- C. Urea diffuses into blood, while glucose and sodium are lost
- D. Urea is filtered out, while proteins are filtered in
Q9. A patient with nephrotic syndrome passes foamy urine rich in albumin and has swollen ankles. Which pair of statements explains both findings?
- A. Damaged filtration barrier lets protein out, and plasma oncotic pressure falls
- B. Damaged collecting duct lets protein out, and blood volume rises
- C. Damaged proximal tubule lets protein out, and plasma oncotic pressure rises
- D. Damaged filtration barrier lets protein out, and plasma hydrostatic pressure falls
Q10. Urine tests on three patients give: P — glucose positive, ketones positive, large volume; Q — protein positive, no glucose; R — no glucose, no protein, high specific gravity after fasting. Which conclusion is best?
- A. Q probably has diabetes mellitus, and R probably has diabetes insipidus
- B. P probably has diabetes insipidus, and R probably has glomerular damage
- C. P probably has glomerular damage, and Q probably has diabetes mellitus
- D. P probably has diabetes mellitus, and Q probably has glomerular damage
Q11. A patient with an infection has a body temperature of 39 °C, feels very cold and shivers although his skin temperature is normal. Which statement explains this?
- A. Pyrogens reset the hypothalamic set point downward, so heat gain is promoted
- B. Pyrogens stimulate sweating through the sympathetic nerves, so heat loss is promoted
- C. Pyrogens damage the thermoreceptors in the skin, so heat loss is promoted
- D. Pyrogens reset the hypothalamic set point upward, so heat gain is promoted
Q12. In the limbs of a wading bird standing in cold water, arteries run alongside veins. How does this arrangement help to conserve heat?
- A. Veins release more heat to the water because blood flows more quickly
- B. Arterial blood stops flowing so the veins remain warmer than the water
- C. Warm venous blood passes heat to the cooler arterial blood going to the feet
- D. Warm arterial blood passes heat to the cooler venous blood returning to the body
Q13. The oxygen consumption of two animals is measured as the surrounding temperature falls from 30 °C to 10 °C. Animal X's consumption rises, while Animal Y's falls. Which interpretation is correct?
- A. X is an ectotherm raising its metabolism, and Y is an endotherm slowing down
- B. X is an endotherm raising its metabolism, and Y is an ectotherm slowing down
- C. X is an endotherm slowing its metabolism, and Y is an ectotherm raising it
- D. X and Y are both ectotherms but of different body sizes
Q14. Post-menopausal women are at greater risk of osteoporosis than men of the same age. Which factor is mainly responsible?
- A. Rising parathyroid hormone levels, so the calcium is deposited in bones
- B. Rising oestrogen levels, so bone formation outpaces bone resorption
- C. Falling calcitonin levels, so osteoblasts become more active
- D. Falling oestrogen levels, so bone resorption outpaces bone formation
Q15. A child from a family that keeps indoors has bowed legs, and X-rays show poorly mineralised bone. Which deficiency is most probable?
- A. Vitamin C, which reduces collagen cross-linking
- B. Vitamin D, which reduces calcium absorption
- C. Vitamin K, which reduces the calcium uptake
- D. Vitamin A, which reduces the osteoclast activity
Q16. When you shake your head to say 'no', which joint is mainly involved?
- A. Ball-and-socket joint between the atlas and the axis
- B. Pivot joint between the atlas and the axis
- C. Hinge joint between the skull and the atlas
- D. Gliding joint between the axis and the third vertebra
Q17. A relaxed sarcomere is 2.4 μm long and the A band is 1.6 μm. When the muscle contracts, the sarcomere shortens to 1.8 μm. What is the total length of the I band (both halves) in the contracted sarcomere?
- A. 0.2 μm
- B. 0.8 μm
- C. 0.6 μm
- D. 0.4 μm
Q18. A few hours after death a body becomes rigid. Which explanation is correct?
- A. ATP is plentiful, so myosin heads detach and reattach rapidly
- B. ATP is lacking, so myosin heads stay attached to actin
- C. Troponin is lacking, so actin filaments fuse with each other
- D. Ca²⁺ is lacking, so myosin heads stay detached from actin
Q19. Curare is applied to a muscle-nerve preparation. Stimulating the nerve produces action potentials in the axon, but the muscle does not contract. Directly stimulating the muscle works normally. What is the site of curare action?
- A. Acetylcholine receptors at the motor end plate
- B. Acetylcholinesterase in the synaptic cleft
- C. Voltage-gated Na⁺ channels in the motor axon
- D. Troponin on the actin filaments in the muscle
Q20. A mutation prevents troponin from binding Ca²⁺. Motor nerve impulses and Ca²⁺ release from the sarcoplasmic reticulum are normal, yet the muscle fibre does not contract. Why?
- A. Tropomyosin keeps the myosin-binding sites on actin covered
- B. The motor end plate is not depolarised by acetylcholine
- C. Actin and myosin are no longer present in the sarcomere
- D. Myosin cannot hydrolyse ATP in the cross-bridge cycle
Q21. A marathon runner's leg muscle is rich in myoglobin and mitochondria and fatigues slowly. Which fibre type does it chiefly contain?
- A. Cardiac fibres with intercalated discs
- B. Fast-twitch (type II) white fibres
- C. Slow-twitch (type I) red fibres
- D. Fast-twitch fibres with glycolytic metabolism
Q22. Skeletal muscle can be put into sustained tetanus by rapid stimulation, but cardiac muscle cannot. The most important reason is that cardiac muscle has
- A. a lack of calcium ions for the contraction in each beat
- B. a lack of sarcomeres so that contraction cannot summate
- C. a short refractory period that ends before the contraction starts
- D. a long refractory period that lasts nearly as long as the contraction
Q23. A tissue sample shows striated cells with branching, one central nucleus per cell, and dark-staining bands between the cells. Which type of muscle is it?
- A. Smooth muscle
- B. Cardiac muscle
- C. Voluntary muscle
- D. Skeletal muscle
Q24. Cells at the corners of a young celery stem are alive, elongated and unevenly thickened with cellulose, helping to support growing parts. They are
- A. parenchyma cells
- B. collenchyma cells
- C. xylem vessels
- D. sclerenchyma fibres
Q25. A cross-section of a tree trunk shows 30 growth rings, with one very narrow ring in the middle. What is the most reasonable interpretation?
- A. Tree is about 30 years old, and one year was unfavourable for growth
- B. Tree is about 30 years old, and one year was favourable for growth
- C. Tree is about 15 years old, and one year was favourable for growth
- D. Tree is about 60 years old, and one year was unfavourable for growth
Q26. Healing of damaged articular cartilage is very slow compared with bone healing. Which explanation is correct?
- A. Cartilage has no blood supply, so nutrients and cells arrive slowly
- B. Cartilage has a rich blood supply, so it heals very slowly
- C. Cartilage has no cells, so there is no matrix repair
- D. Cartilage has no collagen, so repair fibres cannot form
Q27. A man wakes at night with intense pain and swelling in his big toe after a meal rich in red meat. Joint fluid shows needle-shaped crystals. Which condition is likely?
- A. Gout, from sodium urate crystals
- B. Rickets, from calcium phosphate crystals
- C. Osteoarthritis, from worn cartilage
- D. Rheumatoid arthritis, from synovial autoimmunity
Q28. A salmon migrates from the sea into a freshwater river. Which pattern of osmoregulation is expected after the move?
- A. It stops drinking, produces concentrated urine and takes up salts through the gills
- B. It keeps drinking, produces dilute urine and excretes salts through the gills
- C. It keeps drinking, produces concentrated urine and takes up salts through the gills
- D. It stops drinking, produces dilute urine and takes up salts through the gills
Q29. After a salty meal, blood osmolarity rises. Which sequence correctly lists the response?
- A. Osmoreceptors in the hypothalamus → posterior pituitary releases ADH → more water reabsorbed
- B. Osmoreceptors in the hypothalamus → posterior pituitary releases ADH → less water reabsorbed
- C. Osmoreceptors in the kidney → anterior pituitary releases ADH → more water reabsorbed
- D. Osmoreceptors in the hypothalamus → adrenal cortex releases ADH → more water reabsorbed
Q30. A man loses a lot of blood in an accident and his blood pressure falls. Which hormonal sequence helps restore pressure?
- A. Kidney releases aldosterone → renin forms → angiotensin II is released
- B. Liver releases renin → angiotensin II forms → ADH is released
- C. Kidney releases renin → angiotensin II forms → aldosterone is released
- D. Adrenal releases renin → aldosterone forms → angiotensin II is released