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Health Science Paper 2, May/June 2008  
Questions: 1 2 3 4 5 Main
General Comments




Question 2

(a) Explain the digestion otfats and proteins.
(b) Trace the path of digested fats from the site of absorption to the heart.



This question was avoided by candidates. In part (a) few candidates that answered the question mixed up the digestion of fats with protein digestion. In part (b) candidates were unable to trace the path of digested fats from the site of absorption to the heart. Expected answers were as follows:

Fat digestion

- Bile is released by the liver into the duodenum;
- Creating an alkaline medium in the duodenum
- Where the bile emulsifies the fat/breaks large fat molecules into smaller molecules;
- Lipase, an enzyme is secreted by the pancreas into the duodenum;
- Where it converts fats into fatty acids and glycerol;
- Lipase produced by the ileum/intestinal juices work on the unconverted fats and changes
- it to fatty acids and glycerol.

Protein digestion

- The stomach wall secretes gastric juice, containing hydrochloric acid; pepsin and renin
- The hydrochloric acid creates a suitable medium for the action of pepsin; pepsin converts proteins to peptones; rennin co-agulates milk proteins; pepsin then converts the coagulated/insoluble proteins to peptones;
- The duodenum has an alkaline medium due to the presence of alkaline salts/bile;
- The pancreas secretes trypsin into the duodenum which converts peptones to peptides;
- The ileum secretes peptidase which changes peptides to amino acids.

The Path of Fats

- Fatty acids and glycerol diffuse into lacteals of the villi;
- Lacteals unite to form large lymph vessels;
- which reach the thoracic duct;
- the thoracic duct empties itself into the vena cava;
- which enters the heart through the right auricle.

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