H2 Digestion – summary of mark schemes
H.2.2
Explain the structural features of exocrine gland cells.
Mark Schemes
A.
B.
C.
D.
E.
H.2.7
secretory cells arranged in layer one cell thick;
cells contain secretory vesicles;
cells are grouped in acini;
surrounded by basement membrane;
cells adjacent to duct / lumen;
Explain why pepsin and trypsin are initially synthesized as inactive precursors and how they are subsequently activated.
Mark Schemes
A.
B.
C.
D.
E.
pepsin digests proteins;
pepsin could digest cells that secrete it;
pepsinogen is the inactive form of pepsin;
pepsinogen is activated by hydrochloric acid / HCl / pepsinogen is converted into pepsin (active form) by HCl;
different cells in the stomach wall secrete pepsinogen and HCl;