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IB Biology SL B2.3 Cell Specialization Questions

Practise IB Biology SL B2.3 cell specialization through selective gene expression, stem-cell potency, surface area-to-volume ratio and adapted cells.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Explain cell differentiation through selective gene expression and signals such as morphogen gradients.
  • Interpret CXCL12 and drug-response data to infer signals that mobilize adult bone-marrow stem cells.
  • Explain stem-cell self-renewal and how potency supports tissue repair or replacement.
  • Classify totipotent, pluripotent and multipotent cells by developmental potential and source.
  • Compare relative sizes of egg, sperm and blood cells as evidence of specialization.
  • Infer a specialized cell’s function from its size and structural features in a diagram.
  • Explain why a growing cell’s SA:V ratio falls, limiting exchange as metabolic demand rises.
  • Interpret cell-size graphs and data to compare SA:V ratios or infer exchange efficiency.

Covered syllabus points

B2.3.1—Differentiation after fertilizationB2.3.2—Properties of stem cellsB2.3.3—Stem cell niches in adult humansB2.3.4—Types of stem cellsB2.3.5—Cell size as specializationB2.3.6—Surface area-to-volume ratios

Question 1

[Maximum number: 1]

What results from an unspecialized cell experiencing gradients of signalling chemicals?

A

Cell differentiation

B

Meiosis

C

Saltatory conduction

D

DNA replication

Question 2

[Maximum number: 3]

Outline reasons for the therapeutic use of stem cells.

Question 3

[Maximum number: 3]

Stem cells in the bone marrow can be forced into blood vessels in a process called mobilization. Mobilization of stem cells from the bone marrow into the blood vessels represents the basis for modern bone marrow transplantation procedures.

To test the effect of light on the mobilization of stem cells, mice were subjected to a simulated "jet lag" by advancing the light-dark cycle by 12 hours. This was done by subjecting mice to a 24-hour light period before the results shown in the graph were recorded. The results were compared to the stem cells in control mice under normal conditions of 12 hours of light (□) and 12 hours of darkness (dark box).

Graph key: diamonds joined by a solid line represent Control; triangles joined by a dashed line represent Jet lag.
Time-series graph of stem cells per millilitre of mouse blood over 2–38 hours, comparing control and jet-lag conditions. Two strips below show light as white and darkness as black for the corresponding schedules.

Compare the effect of isoprenaline and clenbuterol with the normal release of stem cells and the production of mRNA for CXCL12.

Opposing horizontal bars for control, isoprenaline and clenbuterol treatments. Bars left of zero show CXCL12 mRNA as a percentage of control; hatched bars right of zero show stem cells released.

Question 4

[Maximum number: 1]

Which is a description of stem cells?

A

Hair follicle stem cells are pluripotent.

B

Stem cells in bone marrow are multipotent.

C

Very early embryo stem cells are pluripotent.

D

Late embryo stem cells are totipotent.

Question 5

[Maximum number: 1]

Which specialized cell has the largest volume?

A

Egg cell

B

Sperm cell

C

Red blood cell

D

White blood cell

Question 6

[Maximum number: 2]

The following shows an electron micrograph of a liver cell.

Figure for Question 6 — IB Biology SL

Outline the significance of the relationship between the surface area and volume of a cell.

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