Digestion and Absorption

• What is the definition of digestion?

  The hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membranes.
• Which enzyme is involved in carbohydrate digestion and where is it found?

  Amylase is found in the mouth.
• What enzymes are involved in carbohydrate digestion in the small intestine?

  Maltase, sucrase, and lactase are found in the membrane of the small intestine.
• What are the substrates and products of amylase?

  Amylase converts starch into smaller polysaccharides.
• What does maltase do in carbohydrate digestion?

  Maltase converts maltose into 2 x glucose.
• What is the role of sucrase in carbohydrate digestion?

  Sucrase converts sucrose into glucose and fructose.
• What does lactase do in carbohydrate digestion?

  Lactase converts lactose into glucose and galactose.
• Where are lipids digested?

  Lipids are digested in the small intestine.
• What must happen before lipids can be digested?

  Lipids must be emulsified by bile salts produced by the liver.
• What is the purpose of emulsification in lipid digestion?

  Emulsification breaks down large fat molecules into smaller, soluble molecules called micelles, increasing surface area.
• How are lipids digested?

  Lipase hydrolyses the ester bond between the monoglycerides and fatty acids.
• What are the enzymes involved in protein digestion?

  Endopeptidases, exopeptidases, and dipeptidases.
• What is the role of endopeptidases in protein digestion?

  Endopeptidases break between specific amino acids in the middle of a polypeptide.
• What do exopeptidases do in protein digestion?

  Exopeptidases break between specific amino acids at the end of a polypeptide.
• What is the function of dipeptidases in protein digestion?

  Dipeptidases break dipeptides into amino acids.
• How are certain molecules absorbed into the ileum despite a negative concentration gradient?

  They are absorbed through co-transport.
• Which molecules require co-transport for absorption?

  Amino acids and monosaccharides require co-transport.
• How are sodium ions involved in co-transport?

  Sodium ions (Na+) are actively transported out of the cell into the lumen, creating a diffusion gradient.
• Why do fatty acids and monoglycerides not require co-transport?

  They are nonpolar, allowing them to easily diffuse across the membrane of the epithelial cells.