DP Biology (first assessment 2025)

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Question EXEX.2.HL.TZ0.3

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Date Example questions Example questions Marks available [Maximum mark: 6] Reference code EXEX.2.HL.TZ0.3
Level HL Paper 2 Time zone TZ0
Command term Compare and contrast, Outline, State Question number 3 Adapted from N/A
3.
[Maximum mark: 6]
EXEX.2.HL.TZ0.3

Stem cells can differentiate into other cell types.

(a)

Outline how stem cells develop into specialized cells during development of the embryo.

[2]

Markscheme
  1. (by a process called) cell differentiation;
  2. different genes are expressed/ switched on;
  3. different concentrations of signaling molecules/ molecules determine position of cells in embryo;
(b)

Cardiac muscle cells and striated muscle fibres are highly specialized to produce movement. Compare and contrast the structure of both types of muscle cells.

[3]

Markscheme
  1. both contain myofibrils
    OR
    both have light and dark bands/ are striated;

  2. cardiac muscle cells are branched whereas striated muscle cells unbranched
    OR
    cardiac muscle cells Y shaped whereas striated muscle cells are elongated
    OR
    cardiac muscle cells are connected to other cardiac muscle cells but skeletal muscle cells are not;

  3. cardiac muscle cells are shorter than striated muscle cells;

  4. cardiac muscle cells have one nucleus but striated muscle cells have many nuclei/ are multinucleated;
(c)

State a development in electron microscopy that has improved the study of cell ultrastructure.

[1]

Markscheme

freeze-fracture/cryogenic electron microscopy/fluorescent stains/ immunofluorescence;

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