NUMS — Medical & Dental Entry Test
Take the NUMS Biology — Cell Structure and Function (Set 2): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer review.…
What this test covers
The first 5 questions of this test, with the correct answer and explanation.
Q1. Which observation was most important in extending the cell theory to state that all cells arise from pre-existing cells?
Answer: A. Virchow's observation of cells dividing to form new cells
Explanation: Rudolf Virchow (1855) proposed 'omnis cellula e cellula', based on cell division, which became the third tenet of cell theory.
Q2. A cell measures 30 mm in a photomicrograph taken at a magnification of ×1500. What is its actual size?
Answer: D. 20 µm
Explanation: Actual size = image size ÷ magnification = 30 000 µm ÷ 1500 = 20 µm.
Q3. To study the three-dimensional surface of a pollen grain at high resolution, the most suitable instrument is a:
Answer: B. Scanning electron microscope
Explanation: The SEM scans a beam across a metal-coated surface and gives detailed 3-D surface images; the TEM shows internal sections.
Q4. A liver homogenate is centrifuged at increasing speeds. Which organelle will sediment first (at the lowest speed)?
Answer: A. Nuclei
Explanation: In differential centrifugation the largest, densest structures pellet first: nuclei, then mitochondria/lysosomes, then microsomes, then ribosomes.
Q5. Fish living in very cold water have cell membranes rich in unsaturated fatty acids. This adaptation:
Answer: C. Keeps the membrane fluid at low temperature
Explanation: Kinks at C=C double bonds stop phospholipid tails packing tightly, so the membrane stays fluid when cold.
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Q6. Which type of molecule crosses a pure phospholipid bilayer most easily by simple diffusion?
Q7. Water moves rapidly into kidney collecting-duct cells through specific membrane proteins. These channel proteins are called:
Q8. Potato cylinders are placed in sucrose solutions of different concentrations. They neither gain nor lose mass in 0.3 M sucrose. In 0.5 M sucrose the cylinders will:
Q9. Cell P has a water potential of −400 kPa and the adjacent cell Q has −700 kPa. Which statement is correct?
Q10. Cells lining the gut take in droplets of extracellular fluid in small vesicles. This non-specific uptake of liquid is called:
Q11. Cholesterol enters cells when LDL particles bind specific surface proteins clustered in coated pits. In familial hypercholesterolaemia these proteins are defective. The process affected is:
Q12. Muscle cells have a highly specialised smooth ER called the sarcoplasmic reticulum. Its main function is to:
Q13. Cells of the adrenal cortex and testes, which secrete steroid hormones, are rich in:
Q14. The face of the Golgi apparatus that receives vesicles from the ER is called the:
Q15. During metamorphosis, a tadpole's tail is gradually absorbed. The organelles most directly responsible for digesting the tail cells are:
Q16. Lysosomal enzymes work best at an acidic pH of about 5. This is an advantage because:
Q17. Peroxisomes in liver cells contain catalase. Its role is to:
Q18. Germinating castor seeds convert stored fat into sugar. The organelle containing the glyoxylate-cycle enzymes for this is the:
Q19. Mitochondria contain their own DNA and 70S ribosomes. In humans, mitochondrial DNA is inherited:
Q20. Cells of potato tubers store starch in colourless plastids called:
Q21. As a tomato ripens from green to red, its chloroplasts change into:
Q22. Freshwater protists such as Amoeba have contractile vacuoles. Their function is to:
Q23. Large molecules such as mRNA leave the nucleus through:
Q24. During which stage of the cell cycle are chromosomes most condensed and best seen for counting under a microscope?
Q25. An antibiotic binds 70S ribosomes and blocks protein synthesis in bacteria without killing human cells. Which side effect in human cells is still possible?
Q26. Which structure is present in both prokaryotic and eukaryotic cells?
Q27. Intermediate filaments, such as keratin filaments in skin cells, mainly function to:
Q28. In cross-section, the axoneme of a eukaryotic cilium shows microtubules arranged as:
Q29. People with a defect in the dynein arms of cilia often suffer from repeated chest infections and male infertility. The best explanation is that:
Q30. A cube-shaped cell of side 2 µm grows to a side of 4 µm. Its surface area to volume ratio changes from: