Digestion and Absorption

• What is digestion?

  The process in which relatively large, insoluble biological molecules in food are hydrolysed into smaller, soluble molecules that can be absorbed across the cell membranes into the bloodstream and delivered to cells in the body
• The products of digestion are used to either provide cells with energy or to build other molecules for cell growth, repair and function.
• What is the use of the products of digestion?


  To provide cells with energy or to build other molecules for cell growth, repair and function
• Enzymes are specific to one substrate
• Enzymes are responsible for breaking down polymers into sections, and other enzymes may then need to break them down further into their monomers
• Epithelial cells have membrane bound enzymes and also carrier proteins for specific molecules to aid digestion.
• Where does digestion begin?


  In the mouth
• What is the function of teeth in digestion?


  Breaks down food into smaller pieces, this increases its surface area to volume ratio
• What is the tube connecting the mouth and the stomach called?

  The oesophagus
• The contractions of the smooth muscle in the wall of the oesophagus help move food down towards the stomach.
• Protein digestion begins in the stomach
• Carbohydrate digestion begins in the mouth
• How does the stomach aid the digestion of molecules?

  The glandular tissue produces enzymes and stomach acid, and the muscular tissue churns the food, mixing it with the enzymes and acid.
• How does stomach acid aid protein digestion?


  The acid helps to unravel proteins tertiary structure to enable enzyme activity, as well as lowering the pH, which is optimal for stomach enzymes to work. The lowered pH is also detrimental to any microorganisms present in the food
• What are the three sections of the small intestine?

  Duodenum, jejunum, ileum