Outline two important structural features of cell X.

Explain the role of bile in lipid digestion.

Explain why trypsin is initially synthesized as an inactive precursor and how it is activated.

microvilli/brush border to increase surface area;
enzymes (peptidases and disaccharase) bound to membranes (of microvilli) to complete hydrolysis/digestion;
tight junctions separate fluid of intestinal lumen from intercellular fluid/ impermeable barrier;
large number of mitochondria as high energy demand for active transport;
pinocytotic vesicles formed by endocytosis/uptake of fluid with products of digestion;

bile contains bile salts (and pigments);
bile salt molecules have both a hydrophilic and hydrophobic end;
reduces size of fat/lipid globules / emulsifies fats;
causes increase in total surface area so acted on more effectively by enzyme (lipase);

trypsin is protein-digesting enzyme/protease;
trypsinogen is inactive form produced by pancreas;
produced in inactive form to prevent it digesting cells of pancreas;
converted to active form trypsin in small intestine by enterokinase/ enteropeptidase;
enterokinase/enteropeptidase secreted by intestinal mucosa/wall of small intestine;

Several answers related to having protein channels which was not credited with a mark but most scored at least one.

Many good answers were seen but also a large number which did not refer to bile salts being present, so losing marks.

Again, some good scores but a large number of candidates lost marks because of imprecise answers such as not mentioning the pancreas as the trypsin source and often incorrectly saying it was activated by HCl in the stomach.