Level 1 — RecognitionCell Theory & Microscopy

Cell Theory & Microscopy

⏱ 20 minutes30 marksprintable — key stays hidden on paper

Level 1: Recognition (MCQ, Matching, True/False with Justification)

Time limit: 20 minutes Total marks: 30

Section A — Multiple Choice (1 mark each) — 10 marks

Choose the single best answer.

Q1. Which scientist first observed and named "cells" while examining cork?

A) Antonie van Leeuwenhoek
B) Robert Hooke
C) Rudolf Virchow
D) Theodor Schwann

Q2. The statement "all cells arise from pre-existing cells" is credited to:

A) Schleiden
B) Hooke
C) Virchow
D) Leeuwenhoek

Q3. Which term describes the ability to distinguish two close points as separate?

A) Magnification
B) Resolution
C) Contrast
D) Staining

Q4. Which microscope can produce a 3-D image of a specimen's surface?

A) Light microscope
B) TEM
C) SEM
D) Wet mount

Q5. A structure measures $2\ \mu m$ . Expressed in nanometres this is:

A) $20\ nm$
B) $200\ nm$
C) $2000\ nm$
D) $0.002\ nm$

Q6. Antonie van Leeuwenhoek is best known for:

A) Proposing the cell theory
B) First observing living microorganisms ("animalcules")
C) Discovering that plants are made of cells
D) Stating cells come from cells

Q7. If an image is $50\ mm$ long and the actual object is $100\ \mu m$ , the magnification is:

A) $\times 5$
B) $\times 50$
C) $\times 500$
D) $\times 5000$

Q8. The main purpose of staining a specimen is to:

A) Increase magnification
B) Increase resolution of the lens
C) Improve contrast so structures are visible
D) Preserve the tissue permanently only

Q9. Which is a correct tenet of cell theory?

A) The cell is the basic unit of life
B) Cells contain only DNA
C) All cells have a nucleus
D) Cells cannot reproduce

Q10. Convert $0.5\ mm$ to micrometres:

A) $5\ \mu m$
B) $50\ \mu m$
C) $500\ \mu m$
D) $5000\ \mu m$

Section B — Matching (1 mark each) — 5 marks

Q11–Q15. Match each scientist (left) to their contribution (right). Write the letter.

Scientist		Contribution
Q11. Hooke		A) Concluded all animals are made of cells
Q12. Leeuwenhoek		B) First saw and named cells (cork)
Q13. Schleiden		C) Cells come from pre-existing cells
Q14. Schwann		D) First observed living single-celled organisms
Q15. Virchow		E) Concluded all plants are made of cells

Section C — True / False with Justification (3 marks each) — 15 marks

State True or False (1 mark) and give a one-line justification (2 marks).

Q16. A light microscope has higher resolution than a transmission electron microscope.

Q17. Magnification and resolution mean the same thing.

Q18. $1\ \mu m = 1000\ nm$ .

Q19. When preparing a wet mount, a coverslip is lowered at an angle to avoid trapping air bubbles.

Q20. Electron microscopes can be used to view living specimens.

Answer keyMark scheme & solutions

Section A

Q1 — B (1). Hooke examined cork (1665) and coined "cells" for the empty box-like spaces.
Q2 — C (1). Virchow (1855): omnis cellula e cellula.
Q3 — B (1). Resolution = minimum distance at which two points appear separate.
Q4 — C (1). SEM scans the surface giving a 3-D-appearing image.
Q5 — C (1). $2\ \mu m \times 1000 = 2000\ nm$ .
Q6 — B (1). Leeuwenhoek observed "animalcules" with single-lens microscopes.
Q7 — C (1). $M=\dfrac{\text{image}}{\text{actual}}=\dfrac{50\ mm}{0.1\ mm}=500$ .
Q8 — C (1). Stains bind structures, adding contrast; they do not change lens resolution/magnification.
Q9 — A (1). "Cell is the basic unit of life" is a core tenet; others are false (not all cells have a nucleus, etc.).
Q10 — C (1). $0.5\ mm \times 1000 = 500\ \mu m$ .

Section B

Q11 → B (1)
Q12 → D (1)
Q13 → E (1)
Q14 → A (1)
Q15 → C (1)

Section C

Q16 — False (1). Justification (2): The TEM has far higher resolution (~0.2 nm) than the light microscope (~200 nm) because electrons have a much shorter wavelength than light.

Q17 — False (1). Justification (2): Magnification = how many times larger the image appears; resolution = ability to distinguish two close points. Increasing magnification without resolution gives "empty magnification" (blurry).

Q18 — True (1). Justification (2): By definition $1\ \mu m = 10^{-6}\ m$ and $1\ nm = 10^{-9}\ m$ , so $1\ \mu m = 1000\ nm$ .

Q19 — True (1). Justification (2): Lowering the coverslip at ~45° with a mounted needle lets liquid spread and pushes air out, preventing bubbles that obscure the view.

Q20 — False (1). Justification (2): Specimens must be fixed/dehydrated and viewed in a vacuum, which kills living cells; electrons cannot pass through living hydrated tissue.

[
  {"claim":"Q5: 2 micrometres = 2000 nm","code":"um=2; nm=um*1000; result=(nm==2000)"},
  {"claim":"Q7: magnification = image/actual = 50mm/0.1mm = 500","code":"image_mm=50; actual_mm=0.1; M=image_mm/actual_mm; result=(M==500)"},
  {"claim":"Q10: 0.5 mm = 500 micrometres","code":"mm=0.5; um=mm*1000; result=(um==500)"},
  {"claim":"Q18: 1 micrometre = 1000 nm","code":"um_in_m=Rational(1,10**6); nm_in_m=Rational(1,10**9); result=(um_in_m/nm_in_m==1000)"}
]