DP Biology (first assessment 2025)

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Question 23M.2.HL.TZ1.8

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Date May 2023 Marks available [Maximum mark: 15] Reference code 23M.2.HL.TZ1.8
Level HL Paper 2 Time zone TZ1
Command term Describe, Explain, Outline Question number 8 Adapted from N/A
8.
[Maximum mark: 15]
23M.2.HL.TZ1.8

Fluids inside unicellular and multicellular organisms allow materials to be moved.

(a)

Explain how vesicles are used by cells to move materials.

[5]

Markscheme
  1. fluidity of membranes allows vesicles to bud off membranes/fuse with membranes;
  2. materials taken into cells by endocytosis/vesicle formation;
  3. Paramecium takes in food / phagocytes engulf pathogens / another example;
  4. materials released from cells by exocytosis/by vesicle fusing with plasma membrane;
  5. neurotransmitter released at synapses / protein secretion / secretion from gland cell / another example;
  6. movement/transport of materials (inside vesicles) within cells/through the cytoplasm/between organelles/from an organelle to the (plasma)membrane/from the (plasma) membrane to an organelle;
  7. movement of proteins from the rough ER to the Golgi / another example;
(b)

Describe the transport of carbon compounds such as sucrose and amino acids in phloem.

[7]

Markscheme
  1. transport/translocation in (phloem) sieve tubes;
  2. flow of sap through pores in end walls/sieve plates;
  3. sugar/amino acids are transported dissolved in water/sap;
  4. loaded into phloem (companion cells/sieve tubes) by active transport;
  5. protons pumped out and sucrose then enters by cotransport;
  6. high solute concentration created in phloem/sieve tube;
  7. water enters (sieve tube) by osmosis;
  8. hydrostatic pressure in sieve tube increases;
  9. unloading from sieve tubes in sink/in roots;
  10. water leaves by osmosis lowering the hydrostatic pressure;
  11. sap movement (in phloem) from higher to lower pressure;
  12. movement from source/leaves to sink/roots;
(c)

Outline how food is moved from the stomach to the large intestine.

[3]

Markscheme
  1. by muscles (contracting);
  2. peristalsis/waves of muscle contraction followed by relaxation;
  3. longitudinal muscle pushes food along the intestine when it contracts;
  4. circular muscle constricts the intestine to ensure movement only onwards/not back to stomach;
  5. movement (from stomach to large intestine) via the small intestine/duodenum/ileum;

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