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CAIE IGCSE Biology 2.2 Size of specimens Question Bank

Practise using magnification, actual size and unit conversions with microscope images, scale bars and biological measurements.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • calculate magnification, image size or actual size from microscope diagrams and measurements
  • convert between mm and micrometres before comparing cells or using scale bars
  • extract values from figures and report calculated biological sizes with suitable units

Covered syllabus points

2.2.1—Magnification formula2.2.2—Magnification and size of biological2.2.3—mm and micrometre conversions

2.2 Size of specimens question 1

[Maximum number: 2]

Bacteria are useful in biotechnology and genetic engineering.
Fig. 6.1 shows a photomicrograph of a bacterium.

Fig. 6.1

Fig. 6.1

Question (a)

(a)

Write the formula that would be used to calculate the actual width of the bacterium.

[ 1 ]

Question (b)

(b)

The actual width of the bacterium is 0.0008 mm .
Convert this value to micrometres (μm)(\mu \mathrm{m}).
. μm\mu \mathrm{m}

[ 1 ]

2.2 Size of specimens question 2

[Maximum number: 1]

The diagram shows a magnified image of a human liver cell with a mitochondrion labelled. The actual size of the liver cell is 20μ m20 \mu \mathrm{~m}.

The image size of the liver cell is 40 mm and the image size of the mitochondrion is 4 mm .

Figure for Question 2.2 Size of specimens question 2 — CAIE IGCSE Biology

What is the actual size of the mitochondrion shown in the diagram?

A

0.002 mm0.002 \mathrm{~mm}

B

0.02 mm

C

0.2 mm0.2 \mathrm{~mm}

D

2 mm

2.2 Size of specimens question 3

[Maximum number: 1]

Pregnancy can occur after the fusion of a male gamete and a female gamete.

One of the functions of the placenta is to provide a barrier to toxins and pathogens.

A study was done on donated afterbirths. The afterbirth is a placenta with part of the umbilical cord attached.

The purpose of the study was to find the maximum size of particles that can pass through the placenta and enter the umbilical cord.

The researchers inserted beads with a diameter of 0.5μ m0.5 \mu \mathrm{~m} into blood vessels in the placenta. Three hours later they recorded the percentage of beads found in the blood in the placenta and in the umbilical cord.

They then repeated the tests using beads with diameters of 0.8μ m,2.4μ m,5.0μ m0.8 \mu \mathrm{~m}, 2.4 \mu \mathrm{~m}, 5.0 \mu \mathrm{~m} and 8.0μ m8.0 \mu \mathrm{~m}.

Their results are shown in Fig. 2.1.
percentage of beads found in the blood after 3 hours

Fig. 2.1

Fig. 2.1

Key:
□ umbilical cord
□ placenta

Convert the diameter of the 5.0μ m5.0 \mu \mathrm{~m} beads into millimetres (mm).
. mm

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