Digestion and absorption

• Where is amylase produced?

  Pancreas, salivary glands and small intestine
• What is hydrolysis?


  Breaking bonds by adding water
• What is the importance of digestion?

  Hydrolyses large food molecules into smaller molecules

  Which can move across cell membrane

  And be absorbed into the blood
• Why are different enzymes needed to catalyse the breakdown of carbohydrates, proteins and lipids?

  Enzymes are proteins with specific tertiary structures

  Active site complementary to a specific substrate

  Only specific substrate will bind to active site and form E-S complex
• Where is maltase produced?

  (In the cell membrane of epithelial cells)

  Small intestine
• Where is maltase secreted?

  Small intestine

  (In the epithelial cells of the small intestine)
• Where is amylase secreted?

  Mouth and small intestine
• What are the roles of the glands in the digestive system?

  To produce digestive juices
• Name two types of glands in the digestive system

  Pancreatic glands

  Salivary glands
• What is the function of the small intestine in the digestive system?

  It is where some digestion occurs and the absorption of soluble food also occurs
• What is the function of the stomach in the digestive system?

  It is where digestion occurs.

  It produces hydrochloric acid
• What is the role of the liver in the digestive system?

  It produces bile
• What are enzymes?


  Biological catalysts with a specific shape active site
• Where is lipase produced?

  Pancreas and small intestine
• Where is lipase secreted?

  The small intestine
• Where is protease produced?

  Stomach, pancreas and small intestine
• Where is protease secreted?

  Stomach and small intestine
• What is the role of bile in the digestive system?

  Neutralises HCl (from stomach) to provide alkaline conditions in which small intestine enzymes work best

  It emulsified the fats into smaller fat droplets giving a larger surface area for lipase to act on
• Where is bile produced?

  Liver
• Where is bile stored?

  Gall bladder
• What are proteins hydrolysed to?

  Amino acids
• What is starch hydrolysed to?

  alpha glucose
• What is fat hydrolysed to?

  Fatty acids and glycerol

  Monoglycerides
• Why can starch not be absorbed as easily?

  It is a large, insoluble molecule
• What is starch first digested to?

  Maltose
• What is maltose digested to?

  alpha glucose
• Explain how starch is hydrolysed to maltose

  Amylase in the small intestine and mouth hydrolyses the glycosidic bonds
• Explain how maltose is hydrolysed to alpha glucose

  Maltase (membrane bound disaccharidase)

  Hydrolyses glycosidic bond in maltose to produce alpha glucose
• Which monosaccharides is sucrose hydrolysed to?

  Glucose

  Fructose
• Which monosaccharides is lactose hydrolysed to?

  Glucose

  Galactose
• Explain co transport of glucose and sodium ions


  Na+ actively transported out of epithelial cells into blood

  Establishes concentration gradient for Na+ into epithelial cells from lumen

  Na+ and glucose move by facilitated diffusion via co-transporter proteins into epithelial cell

  Glucose diffuses out of the cell into the blood by facilitated diffusion
• How is the small intestine adapted for digestion?

  The lining Is folded into villi which give a large surface area

  The epithelial cells have microvilli which increase the surface area even more
• Explain how dipeptides are hydrolysed to amino acids

  Dipeptidases in the cell surface membrane of epithelial cells

  Hydrolyse peptide bond between 2 amino acids
• Explain the steps in the digestion of a protein to a dipeptide

  Endopeptidases hydrolyse peptide bonds within the protein

  Exopeptidases hydrolyse peptide bonds at the ends of the protein
• What is the difference in the co-transport of amino acids and the co-transport of glucose?

  With glucose - Na+ are actively transported into the blood

  With amino acids- Na+ are actively transported into the ileumSee an expert-written answer!We have an expert-written solution to this problem!
• Describe how exopeptidases work

  Hydrolyse peptide bonds at the ends of the protein

  Remove single terminal amino acids from proteins
• Explain how amino acids are absorbed

  Na+ actively transported into the ileum from the epithelial cells

  Na+ and amino acids diffuse into cells via sodium-dependent transporter proteins
• Where does lipid digestion occur?

  The lumen of the small intestine
• Explain the role of bile in lipid digestion

  Bile salts emulsify lipids

  Provide a larger surface area for lipase
• Explain lipid digestion


  In the small intestine lipase hydrolyses ester bonds

  Produces monoglycerides, fatty acids and glycerol

  Monoglycerides and fatty acids form micelles with bile salts