- What is the Alimetary Canal?
- What is the lumen?
- What is the name of the entry of food into the alimentary canal?
- What is the definition of digestion ?
- What is mechanical digestion?
- What is chemical digestion?
- What is absorption?
- What is egestion ?
- The alimentary canal is the tube running from the mouth to the anus
- The middle of the alimentary canal is a lumen, which is technically still outside the body
- Digestion is the breakdown of polymers into monomers small enough to enter cells
- Primates chew their food and mammalian stomach churns it increasing the surface area (MECHANICAL)
- Large surface area allows better access for enzymes which catalyse the hydrolysis of polymers into their monomer subunits (CHEMICAL)
- Absorption is the movement of small molecules (water, inorganic ions, vitamins) + products of digestion from the lumen into cells in the wall of the canal, then into the bloodstream.
- Food which cannot be digested or absorbed. It passes through the canal and leaves from the anus as faeces by egestion.
How are proteins digested ?
1.Endopeptidases - break down bonds between amino acids in the interior of the molecule which produces smaller polypeptides e.g. pepsin and trypsin
2.Exopeptidases - break down smaller polypeptides. These break off the end of amino acids. There are two types:
- aminopeptidases - break down free amino acid group end
- carboxypeptidases - break down free carboxyl group end
Absorption in the small intestine.
Absorption occurs accross epithelial cells by facilitated diffusion and active transport, relying largely on Na+ cotransport.
Describe how the small intestine is adapted for the absorption of soluble food.
- Large surface area provided by villi/microvilli
- folds increase surface area
- Long; increasing time for absorption
- Thin epithelium gives a short diffusion pathway
- Capillary network absorbs amino acids/sugars; into blood
- Lacteal for absorption of digested fats
- Abundant mitochondria in epithelial cells supply energy for active transport
- Epithelial cells have carrier proteins for facilitated diffusion/active transport.