IB Biology HL B2.3 Cell Specialization Questions

Practise IB Biology HL B2.3 with evidence-led questions on stem-cell potency, differentiation, exchange surfaces and the structure–function adaptations of specialized cells.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Use insulin-mRNA or signalling-gradient evidence to explain embryonic cell differentiation.
  • Explain how stem cells self-renew and use potency to produce specialized tissues.
  • Classify totipotent, pluripotent and multipotent stem cells by developmental potential.
  • Interpret cell-size graphs to explain falling SA:V ratios and their effect on exchange.
  • Relate microvilli, transport proteins and mitochondria to intestinal or renal absorption.
  • Distinguish thin type I gas-exchange cells from type II surfactant-secreting pneumocytes.
  • Explain how surfactant lowers alveolar surface tension and prevents collapse.
  • Compare cardiac and skeletal muscle; link cardiac branching and gap junctions to impulse conduction.
  • Relate the sperm mid-piece’s mitochondria to ATP production for movement.
  • Label mature human egg diagrams with the nucleus, cytoplasm and surrounding structures.

Question 1

[Maximum number: 1]

Type I diabetes is a leading cause of death in advanced countries and is associated with various severe or fatal complications, including blindness, kidney failure, heart disease, stroke, neuropathy, and amputations. Embryonic stem cells are considered to be a powerful tool in the treatment of diabetes.

In a study, embryonic stem cells were grown in culture and tested for insulin mRNA. A drug was injected into two groups of healthy mice in order to simulate type I diabetes 15 days prior to the transplant of embryonic stem cells. The mice in the transplant group received embryonic stem cells that produce insulin mRNA. The control group did not receive the transplant. The graph shows the blood glucose concentration in both groups.

Figure for Question 1 — IB Biology HL

Describe the reason for testing for insulin mRNA in the embryonic stem cell cultures.

Question 2

[Maximum number: 3]

Outline reasons for the therapeutic use of stem cells.

Question 3

[Maximum number: 1]

State what change there has been in the cell surface area to volume ratio in red blood cell 1.

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