Digestion and absorption

• What is the function of bile salts?

  Emulsification. Bile salts break down bigger fat globules into tiny droplets called micelles which increases the surface area for lipase action.
• Digestion in Mammals?

  Carbohydrates digested by amylase and membrane-bound disaccharidases. Lipids digested by lipases including the action of bile salts. Proteins digested by endopeptidases, exopeptidases and membrane-bound dipeptidases.
• The action of the carrier protein X in Figure 1 is linked to a membrane-bound ATP hydrolase enzyme. Explain the function of this ATP hydrolase

  The Hydrolysis of ATP into ADP + Pi releases energy. This energy allows ions to move against the concentration gradient

  
• The movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum. Explain how

  A concentration gradient for the diffusion of sodium is maintained. Sodium moves into the cell by facilitated diffusion and brings glucose with it/ Sodium moves into the cell by co-transport bringing glucose with it.
• Roles of micelles 


  Make fatty acids more soluble in water, They carry fatty acids to the epithelial cell , Help maintain a high concentration of fatty acids compared to ileum cells, etc.
• What is the function of exopeptidases ?

  Exopeptidases hydrolyse peptide bonds in on the terminal amino acids (Trypsin - small intestine)
• What is the function of endopeptidases?

  Endopeptidases hydrolyse peptide bond in the central region of proteins ( Pepsin - Stomach)
• What is the function of dipeptidases?

  Dipeptidases break down peptide bonds between two amino acids (it breaks a dipeptide bond)
• What processes take place when molecules are absorbed into the ileum?

  Facilitated diffusion and the co-transport