digestive enzymes

• what are digestive enzymes used to do?


  break down biological molecules in food
• What produce a variety of different digestive enzymes?

  Specialised cells in the digestive systems of mammals

  the enzymes are then released into the gut to mix with food
• what do enzymes only work with?

  specific substrates
• what are different enzymes needed to do?

  To catalyse the breakdown of different food molecules
• what are carbohydrates broken down by?

  Amylase and membrane-bound disaccharidases
• what is amylase?

  a digestive enzyme that catalyses the conversion of starch (polysaccharide) into the smaller sugar maltose (disaccharide)

  • This involves the HYDROLYSIS of the GLYCOSIDIC BONDS in starch
• what produces amylase?

  the salivary glands
• where is amylase released?

  into the mouth (by the salivary glands)
• which 2 places produce amylase?

  • salivary gland (release amylase into mouth)
  • pancreas (release amylase into small intestine)
• where is amylase that is produced into the pancrease released into|?

  the small intestine
• what are membrane-bound disaccharidases?

  enzymes that are attached to the cell membranes of epithelial cells lining the ileum
• what is the ileum?

  the final part of the small intestine
• what do membrane-bound disaccharidases do?

  help to break down disaccharides into monosaccharides

  • this involves the hydrolysis of glycosidic bonds
• give examples of disaccharides?

  maltose sucrose lactose
• give examples of monosaccharides?

  glucose fructose galactose
• What is the DISACCHARIDASE that breaks down maltose and what are the monosaccharide products from this?

  maltase

  glucose + glucose
• What is the DISACCHARIDASE that breaks down sucrose and what are the monosaccharide products from this?

  sucrase

  glucose + fructose
• What is the DISACCHARIDASE that breaks down lactose and what are the monosaccharide products from thid?

  lactase

  glucose + galactose
• How can monosaccharides be transported across the cell membranes of the ileum epithelial cells?

  via specific transporter proteins
• what are lipids broken down by?

  Lipase

  • with the help of bile salts
• what is a monoglyceride?

  a glycerol molecule with one fatty acid attached
• what do lipase enzymes do?

  catalyse the breakdown of lipids into monoglycerides and fatty acids

  • this involves the hydrolysis of the ester bonds in lipids
• where are lipases made?


  pancreas
• where do lipases work?

  in the small intestine
• what produces bile salts?

  liver
• what do bile salts do?

  emulsify lipids (they cause the lipids to form small droplets)
• what process are bile salts really important in?

  the process of lipid digestion
• why is it good that bile salts emulsify lipids?

  • Several small lipid droplets have a bigger surface area than a single large droplet (for the same vol of lipid)
• what does the formation of small droplets of lipids do?

  greatly increases the surface areaa of lipid that is available for lipases to work on
• what happens once the lipid has been broekn down?

  the monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles
• what are proteins broken down by?

  a combination of different proteases (or peptidases)
• what are proteases/peptidases?

  enzymes that catalyse the conversion of proteins into amino acids by hydrolysing the peptide bonds between amino acids
• What do endopeptidases do?

  act to hydrolyse peptide bonds WITHIN a protein
• give 2 examples of endopeptidases?


  trypsin and chymotrypsin

  • they are synthesised in the pancreas and secreted into the small intestine
• give another example of an endopeptidase?

  
  

  pepsin

  • it is released into the stomach by cells in the stomach lining
• what conditions does pepsin only work in?

  acidic conditions - provided by HCL in the stomach
• What are proteins broken down by?

  endopeptidases and exopeptidases
• what do exopeptidases do?

  act to hydrolyse peptide bonds at the ends of protein molecules

  • they remove SINGLE AMINO ACIDS from proteins
• what are dipeptidases ?


  exopeptidases that work specifically on dipeptides
• what do dipeptidases do?

  they act to separate the two amino acids that make up a dipeptide by hydrolysing the peptide bond between them