Digestion IB SL Essay Question

a) Draw a diagram of the human digestive system. [4]

Mark Scheme; one mark for each correctly drawn & labelled part; (max 4)

• mouth,
• esophagus
• stomach
• small intestine
• large intestine
• liver & gall bladder
• pancreas

b) Describe the role of enzymes in the process of digestion of proteins, carbohydrates & lipids in humans. [6]

Mark scheme:

 marks awarded for

• the-enzyme name, of one amylase, protease & lipase.
• correct substrate & products
• correct place where enzymes are produced & act.
• a general comment about role of enzymes in chemical digestion.

eg   "Proteins are digested by protease enzymes (eg pepsin), in acid conditions in the stomach.  They become polypeptides / amino acids."  Scores 3 marks.

c) Explain how blood glucose concentration is controlled in humans. [8]

Mark Scheme

• explanation of homeostasis;
• the role of negative feedback
• involvement of the endocrine system (ie hormones)
• insulin hormone - lowers blood glucose
• glucagon - raises blood glucose
• pancreas islets/ ß-cells/alpha-cells produce these hormones
• liver & muscles convert glucose (with insulin);
• to glycogen
• and vice versa (with glucagon)