Neco Model Questions Vol1 2025 Biology Question 1

Practice practical question 1 from the 2025 Neco Model Questions Vol1 Biology examination. This question covers Cell Structure .

Neco Model Questions Vol1 2025 Biology Practical
Topic: Cell Structure
Question 1 NECO_MODEL_QUESTIONS_VOL1 • 2025 • BIOLOGY • practical

A prepared slide of an onion (Allium cepa) epidermal peel is examined under a light microscope using a 40× objective and a 10× ocular lens. The ocular micrometer has been calibrated so that one division equals 0.01 mm. The slide contains several rectangular cells with clearly visible cell walls, nucleus and a large central vacuole. Answer the following:

Question Parts

( a )
Identify and label the following structures on the diagram of the observed cell: cell wall, cell membrane, nucleus, nucleolus, vacuole and cytoplasm.
( b )
Measure the longest diameter of five different cells using the ocular micrometer. The recorded readings (in divisions) are: 12, 13, 11, 14, 12. (i) Convert each reading to millimetres. (ii) Calculate the mean cell diameter. (iii) Assuming each cell is approximately spherical, compute the average surface area (SA) and volume (V) of a cell. Use SA = 4πr² and V = 4/3 πr³, where r is the radius in millimetres. Take π = 3.14. (iv) Determine the average surface‑area‑to‑volume ratio (SA:V) and comment on its biological significance for diffusion.
( c )
Explain why a high surface‑area‑to‑volume ratio is advantageous for plant epidermal cells that are involved in gas exchange.
( d )
Identify two possible sources of error in the measurement of cell diameter and suggest a method to minimise each error.

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This is Neco Model Questions Vol1 2025 Biology Question 1. It is one of the practical questions from the 2025 Neco Model Questions Vol1 Biology examination.

The question covers Cell Structure .

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