Label the diagram to show the structure that is involved in digestion of proteins in acid conditions (using the letter A).
 

Label the diagram to show the structure where most absorption of water to prevent dehydration occurs (using the letter B).

 

Label the diagram to show the structure where most absorption of nutrients occurs (using the letter C).

 

Explain how the structure of veins is adapted to their function.
 

Cells defend the body against pathogens. Outline how some of these cells ingest pathogens in the blood and in body tissues.

Award [1] for each of the following correctly labelled.

stomach (labelled A)

Award [1] for each of the following correctly labelled.

large intestine (labelled B)

Award [1] for each of the following correctly labelled.

small intestine / ileum (labelled C)

valves to avoid backflow;
thin wall allows them to be pressed flat by muscles to move/carry blood under low pressure;
wide lumen (for a given blood vessel diameter) for slow flowing blood;

attraction to foreign protein/pathogen / chemotaxis;
membrane invaginates / engulfs foreign matter / phagocytosis/endocytosis;
formation of vacuole/vesicle;
(phagocytes) can squeeze out of walls of capillaries;
Accept clearly annotated diagrams.

Candidates knew the role and location of the stomach.

Marks were lost when candidates mixed up the identity and role of the small and large intestine (A.S. 6.1.4, 6.1.5). 

Marks were lost when candidates mixed up the identity and role of the small and large intestine (A.S. 6.1.4, 6.1.5). 

This was similar to past exam questions about structure and function of veins (A.S. 6.2.5). An easy mark, gained by most candidates, was that valves in veins prevent backflow of blood. Thin walls allowing muscle pressure to move blood or wide lumens to accommodate slow moving blood were cited less often. There was also glaring confusion with capillaries such as “veins have thin walls for diffusion of oxygen molecules” or “veins have walls of one cell thickness so exchanges can occur.”

This question required an outline of how some cells can ingest pathogens in the blood and in body tissues (A.S. 6.3.4). “Outline” meant only a brief account or summary, with or without a diagram. Quite a few candidates scored the maximum of two marks. They knew that phagocytes can detect/recognize/identify foreign protein or pathogens which can then be engulfed through phagocytosis. Unfortunately, more than a few candidates thought that antibodies engulf pathogens.