Digestion and abs: Practice Questions

• a.

  Endopeptidases act first in the stomach, then bile salts emulsify the protein for exopeptidase action in the ileum.

• b.

  Membrane-bound dipeptidases act first in the duodenum, followed by exopeptidases and endopeptidases in the ileum.

• c.

  Endopeptidases hydrolyse internal peptide bonds, followed by exopeptidases and then membrane-bound dipeptidases.

• d.

  Exopeptidases hydrolyse peptide bonds at the ends of the chain, followed by endopeptidases and then membrane-bound dipeptidases.

• a.

  The active transport of \(Na^{+}\) ions out of the cell by the sodium-potassium pump; glucose then leaves the cell via facilitated diffusion.

• b.

  The osmosis of water carrying \(Na^{+}\) ions out of the cell; glucose then enters the blood via a membrane-bound disaccharidase.

• c.

  The facilitated diffusion of \(Na^{+}\) ions into the cell; glucose then leaves the cell via active transport using ATP.

• d.

  The active transport of \(Na^{+}\) ions into the cell by the sodium-potassium pump; glucose then leaves the cell via simple diffusion.

• a.

  To emulsify large lipid droplets into smaller droplets, increasing the surface area for lipase action.

• b.

  To provide an acidic environment required for the optimal activity of pancreatic lipases.

• c.

  To decrease the surface area of lipid droplets to protect them from acidic gastric juices.

• d.

  To hydrolyse the ester bonds in triglycerides to produce fatty acids and glycerol.

• a.

  Micelles are large lipid droplets found in the lumen; chylomicrons are the smaller droplets formed after emulsification by bile salts.

• b.

  Micelles are formed within the epithelial cells and transport triglycerides to the Golgi apparatus to be packaged into chylomicrons.

• c.

  Micelles transport triglycerides directly into the blood; chylomicrons transport them into the lymphatic system through the cell-surface membrane.

• d.

  Micelles facilitate the movement of fatty acids and monoglycerides to the epithelial cell membrane; chylomicrons are formed inside the cell for transport into lacteals.

• a.

  Endopeptidases act as co-factors for exopeptidases, increasing the affinity of the active site for the peptide bond.

• b.

  Exopeptidases can only bind to the substrate once endopeptidases have removed the R-groups from the central amino acids.

• c.

  Endopeptidases hydrolyse internal peptide bonds, creating more terminal ends for exopeptidases to act upon.

• d.

  Endopeptidases lower the activation energy of exopeptidases by partially denaturing the tertiary structure of the protein.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.