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.

33 questions in this syllabus scope, with question parts counted together.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam analysis

SL · 2010–2025
Papers with this topic41 / 141in the analysed sample
Latest appearanceNovember 2025
Tagged question parts46
Paper types5

Most tested objectives

  1. B2.3.6—Surface area-to-volume ratios12 papers
  2. B2.3.1—Differentiation after fertilization8 papers
  3. B2.3.8 (HL)—Pneumocytes in alveoli8 papers
  4. B2.3.2—Properties of stem cells7 papers
  5. B2.3.4—Types of stem cells3 papers

Common question formats

  • Definition or recall
  • Graph interpretation
  • Process explanation
  • Diagram interpretation

Recent exam appearances

November 2025Paper 1A SL · TZ1Q10[ 1 ]
May 2025Paper 1A SL · TZ3Q11[ 1 ]
May 2025Paper 1A SL · TZ2Q10[ 1 ]

141 papers analysed · Tagging incomplete

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

Exam points

  • Explain how selective gene expression and suppression differentiate embryonic cells.
  • Relate signalling-chemical gradients in unspecialized cells to cell differentiation.

Question 1

[Maximum number: 1]

The micrograph shows two types of blood cell.

Figure for Question 1 — IB Biology SL

What determines the differences between the two types of cell?

A

Different number of mitotic cycles

B

Different expression of some genes

C

Reaction to oxygen of red blood cells

D

Reaction to antigens of white blood cells

Exam points

  • Explain how stem cells self-renew by repeated division while remaining undifferentiated.
  • Explain potency as the capacity to differentiate into mature specialized cell types.
  • Compare the broader differentiation potential of embryonic stem cells with that of most adult stem cells.

Question 1

[Maximum number: 1]

Stargardt's is an inherited disease caused by the mutation of a gene associated with vitamin A processing in the eye. It results in degeneration of receptor cells and loss of vision. For what reason are stem cells suitable to treat this disease?

A

They can be taken from the eye of an embryo and transplanted into a patient.

B

They can produce vitamin A in newborn babies.

C

They can develop into receptor cells and prevent blindness.

D

They can be removed from an embryo to detect early onset of the disease.

Exam points

  • Interpret treatment-response data to compare bone-marrow stem-cell release after isoprenaline and clenbuterol with the control.
  • Compare CXCL12 mRNA levels after isoprenaline and clenbuterol with the control.

Question 1

[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).

Figure for Question 1 — IB Biology SL
Figure for Question 1 — IB Biology SL

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

Figure for Question 1 — IB Biology SL

Exam points

  • Classify totipotent, pluripotent and multipotent stem cells using developmental stage and tissue source.
  • Order neuron, bone-marrow, umbilical and embryonic cells from least to greatest differentiation potential.

Question 1

[Maximum number: 1]

Which term describes very early-stage embryonic stem cells in a mouse?

A

Totipotent

B

Pluripotent

C

Multipotent

D

Unipotent

Exam points

  • Identify the egg cell as the largest by volume among egg, sperm, red and white blood cells.

Question 1

[Maximum number: 1]

The image shows part of a mammalian cell.

Figure for Question 1 — IB Biology SL

What is the specialized function of this mammalian cell?

A

Locomotion

B

Absorption

C

Reception of stimuli

D

Gas exchange

Exam points

  • Explain why a growing cell's surface area-to-volume ratio falls as volume outpaces surface area.
  • Relate cell surface area to exchange and volume to metabolic, waste or resource demand.
  • Interpret a cell-diameter graph or size-change table to compare surface area, volume and their ratio.

Question 1

[Maximum number: 1]

How would surface area, volume and surface area to volume ratio of a cell change as the cell becomes bigger, if the cell does not change shape?

Surface area

Volume

Surface area : volume

Increase

Increase

Increase

Increase

Increase

Decrease

Increase

Decrease

Decrease

Decrease

Increase

Increase