Take the NUMS Biology — Homeostasis, Support and Movement (Set 1): 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 person drinks very little water on a hot day. Which change will occur in their kidneys?
- A. Aldosterone secretion stops and Na⁺ is lost
- B. Glomerular filtration of glucose increases
- C. ADH secretion stops and dilute urine is produced
- D. More ADH is released, collecting ducts become more permeable and concentrated urine forms ✓
Answer: D. More ADH is released, collecting ducts become more permeable and concentrated urine forms
Explanation: Dehydration raises plasma osmolarity; hypothalamic osmoreceptors trigger ADH release, inserting aquaporins into collecting ducts.
Q2. A patient with diabetes insipidus produces large volumes of dilute urine. The most likely cause is:
- A. Deficiency of ADH or failure of kidneys to respond to it ✓
- B. Damage to the Bowman's capsule only
- C. Excess insulin
- D. Excess aldosterone
Answer: A. Deficiency of ADH or failure of kidneys to respond to it
Explanation: Without ADH action collecting ducts stay impermeable to water, so water is not reabsorbed.
Q3. Glucose appears in the urine of an untreated diabetic patient because:
- A. ADH increases glucose excretion
- B. Glucose is secreted actively into the loop of Henle
- C. The glomerulus cannot filter glucose
- D. Blood glucose exceeds the renal threshold, saturating carriers in the proximal tubule ✓
Answer: D. Blood glucose exceeds the renal threshold, saturating carriers in the proximal tubule
Explanation: Glucose is normally fully reabsorbed by carriers in the PCT; when filtered load exceeds the transport maximum, excess spills into urine.
Q4. Which substance is normally present in the glomerular filtrate but absent from normal urine?
- A. Sodium ions
- B. Glucose ✓
- C. Urea
- D. Water
Answer: B. Glucose
Explanation: Glucose is filtered but completely reabsorbed in the PCT; urea, water and Na⁺ appear in urine in varying amounts.
Q5. Protein molecules such as albumin are normally absent from the glomerular filtrate because:
- A. They are converted into urea
- B. They are too large to pass through the filtration membrane ✓
- C. They are digested in the Bowman's capsule
- D. They are actively reabsorbed in the loop of Henle
Answer: B. They are too large to pass through the filtration membrane
Explanation: The basement membrane and podocyte slits act as a filter that holds back large plasma proteins and cells.
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Q6. The loop of Henle is longer in desert mammals such as the kangaroo rat. This adaptation allows them to:
- A. Excrete more water
- B. Create a steeper salt gradient in the medulla and produce highly concentrated urine
- C. Filter blood faster
- D. Reabsorb more glucose
Q7. Which part of the nephron is impermeable to water but actively pumps out Na⁺ and Cl⁻?
- A. Thick ascending limb of the loop of Henle
- B. Descending limb of the loop of Henle
- C. Proximal convoluted tubule
- D. Bowman's capsule
Q8. Low blood pressure in the afferent arteriole triggers the juxtaglomerular apparatus to release renin. The final effect of this pathway is:
- A. Inhibition of ADH release
- B. Dilation of all blood vessels
- C. Decreased Na⁺ reabsorption
- D. Increased aldosterone, Na⁺ reabsorption and rise in blood pressure
Q9. Mammals excrete nitrogen mainly as urea rather than ammonia because urea:
- A. Is more soluble and highly toxic
- B. Requires no energy to produce
- C. Is insoluble and excreted as a paste
- D. Is less toxic and can be stored in moderate concentrations needing less water
Q10. Birds and reptiles excrete uric acid. This is advantageous because uric acid:
- A. Is more toxic than ammonia
- B. Is produced without using energy
- C. Is insoluble and non-toxic, so it can be excreted with very little water
- D. Requires a lot of water for excretion
Q11. The ornithine (urea) cycle takes place in the:
- A. Liver
- B. Spleen
- C. Kidney
- D. Pancreas
Q12. Kidney stones most commonly consist of:
- A. Sodium chloride
- B. Calcium oxalate
- C. Bilirubin
- D. Glucose crystals
Q13. In hemodialysis, urea moves from the patient's blood into the dialysis fluid because:
- A. The membrane allows blood cells to pass
- B. Urea is pumped actively across the membrane
- C. The dialysis fluid contains no urea, so urea diffuses down its gradient across the membrane
- D. The dialysis fluid has a higher urea concentration
Q14. On a cold day, a person shivers and the skin appears pale. Pallor results from:
- A. Vasodilation of skin arterioles
- B. Increased sweating
- C. Increased blood flow to the skin
- D. Vasoconstriction of skin arterioles to reduce heat loss
Q15. The thermoregulatory centre in humans is located in the:
- A. Hypothalamus
- B. Cerebellum
- C. Pituitary gland
- D. Medulla oblongata
Q16. Brown adipose tissue in newborn babies generates heat because its mitochondria:
- A. Lack an electron transport chain
- B. Store glycogen instead of fat
- C. Carry out anaerobic respiration only
- D. Contain an uncoupling protein that lets protons bypass ATP synthase
Q17. Homeostasis is maintained mostly by negative feedback, which means that:
- A. No receptors are involved
- B. A change from the set point triggers responses that reverse the change
- C. A change triggers responses that increase the change further
- D. The set point keeps changing continuously
Q18. In a skeletal muscle sarcomere during contraction, which of the following shortens?
- A. The A-band
- B. The thick filaments
- C. The H-zone and I-band
- D. The thin filaments
Q19. Calcium ions trigger skeletal muscle contraction by binding to:
- A. ATP, splitting it
- B. Myosin heads directly
- C. The sarcolemma, causing depolarisation
- D. Troponin, which moves tropomyosin to expose myosin-binding sites on actin
Q20. Rigor mortis occurs after death because:
- A. Calcium is pumped back into the sarcoplasmic reticulum
- B. ATP is no longer available to detach myosin heads from actin
- C. Myosin cannot bind actin
- D. Actin filaments dissolve
Q21. A muscle receiving rapid repeated stimuli with no time to relax shows a sustained maximal contraction called:
- A. Muscle fatigue
- B. Tetanus
- C. Tonus
- D. Muscle twitch
Q22. Cardiac muscle differs from skeletal muscle in that it:
- A. Lacks striations
- B. Has branched cells joined by intercalated discs and is highly resistant to fatigue
- C. Is multinucleated with long unbranched fibres
- D. Is under voluntary control
Q23. When the biceps contracts to flex the elbow, the triceps relaxes. This arrangement is described as:
- A. Antagonistic muscles
- B. Synergistic muscles
- C. Tetanic muscles
- D. Tonic muscles
Q24. The hip joint allows movement in many planes, whereas the knee mainly allows flexion and extension. These joints are respectively:
- A. Hinge and pivot joints
- B. Ball-and-socket and hinge joints
- C. Pivot and saddle joints
- D. Gliding and ball-and-socket joints
Q25. Osteoporosis, common in post-menopausal women, is mainly due to:
- A. Deficiency of vitamin C only
- B. Inflammation of joint synovial membranes
- C. Loss of bone mass as bone resorption exceeds formation, linked to reduced oestrogen
- D. Excess deposition of uric acid in joints
Q26. A middle-aged man with high blood uric acid wakes with a hot, swollen and very painful big-toe joint. The underlying cause of his condition is:
- A. Deposition of uric acid crystals in joints
- B. Autoimmune destruction of synovial membrane
- C. Deficiency of vitamin D
- D. Wear of articular cartilage with age
Q27. Which statement correctly compares cartilage with bone?
- A. Cartilage contains Haversian canals
- B. Bone cells are called chondrocytes
- C. Cartilage has a matrix of calcium phosphate, bone has chondrin
- D. Cartilage has no blood vessels, while bone is well supplied with blood vessels
Q28. Rickets in children results from deficiency of:
- A. Iodine, causing goitre
- B. Iron, causing anaemia
- C. Vitamin D, leading to poor calcium absorption and soft bones
- D. Vitamin A, causing night blindness
Q29. Herbaceous (non-woody) plant stems remain upright mainly due to:
- A. Secondary xylem formation
- B. Deposition of lignin in all cells
- C. Turgor pressure of cells pressing against their cell walls
- D. Presence of bark
Q30. Sclerenchyma differs from collenchyma in that sclerenchyma cells:
- A. Are usually dead at maturity with thick lignified walls
- B. Are found only in young leaves
- C. Contain chloroplasts for photosynthesis
- D. Are living with unevenly thickened cellulose walls