Activity 4: Digestion of Proteins and Lipids PDF

Activity 4: From food to nutrients Page 22-23 T. Mohammad Alsen 1- The digestion of proteins: Proteins, made up of amino acids , are organic materials that are digested by proteases. A protein 1- The digestion of proteins: The digestion of proteins...

Activity 4: From food to nutrients Page 22-23 T. Mohammad Alsen 1- The digestion of proteins: Proteins, made up of amino acids , are organic materials that are digested by proteases. A protein 1- The digestion of proteins: The digestion of proteins doesn’t take place in mouth, since saliva doesn’t contain any protease. Knowing that proteases are specific enzymes for the digestion of proteins, such as pepsin and trypsin. 1- The digestion of proteins: The digestion of proteins starts in the stomach by the pepsin, which is a protease found in gastric juice. Pepsin catalyzes the digestion of proteins into peptides. 1- The digestion of proteins: Trypsin, present in the pancreatic juice of the small intestine, catalyzes the chemical digestion of proteins or peptides into amino acids. 1- The digestion of proteins: The intestinal juice also helps the digestion of peptides into amino acids. 1- The digestion of proteins: Digestive tract Digestive juice / Enzyme Substrate Product Mouth Saliva / Salivary amylase No protein digestion ----- Esophagus No digestive juice secretion ---- Stomach Gastric juice Proteins Peptides Small intestine Pancreatic juice Proteins or peptides Amino acids 1- The digestion of proteins: Document (a):p.22 Explain the obtained results. The pancreatic extract (juice) contains a protease called trypsin that catalyzes the digestion of the proteins of the coagulated egg white into amino acids leading to its disappearance. The obtained amino acids give blue color with biuret test.  1- The digestion of proteins: Document (b):p.22 Draw a diagram showing the complete molecular simplification of proteins.  1- The digestion of proteins: Document (b):p.22 What does the complete digestion of proteins give? Amino acids 2- The digestion of lipids: Lipids, made up of fatty acids and glycerol, are organic materials that are digested by lipases. 2- The digestion of lipids: The digestion of lipids starts and ends in the small intestine by the action of bile, pancreatic, and intestinal juices. 2- The digestion of lipids: In the small intestine, bile, pancreatic and intestinal juices are secreted, where the pancreatic and intestinal juices contain lipases that are specific enzymes for the digestion of lipids, while, bile doesn’t contain a lipase. 2- The digestion of lipids: Bile, deprived of any enzymes, is a fluid released by the liver and stored in the gallbladder. 2- The digestion of lipids: The role of bile: 1- The bile renders the chemical medium basic, so when it mixed with the chyme (of the stomach) the pH increases from pH = 2 to pH = 8.4. Food in Food in stomach Bile small intestine pH = 2 pH = 8.4 pH= 8.4 2- The digestion of lipids: The role of bile: 2- The bile emulsifies the lipids to help the action of lipase. 2- The digestion of lipids: The role of bile: 1- The bile renders the chemical medium basic. How? By changing the chemical medium of the food coming from the stomach from pH = 2 to pH = 8.4 ana basic in the small intestine. 2- The bile favors the emulsification of lipids. How? The lipase is soluble in water phase. When we add bile, the lipid become dispersed in water and then the lipase become able to catalyze the digestion of lipids easily. Dccument (c): Dccument (d):  Dccument (d): 1.1- Analyze the obtained results. After 180 minutes, the level of oil decreases from 100% to 0%, while the quantity of fatty acids increases from 0% to 100%.  Dccument (d): 1.2- What con you conclude? Hence, the oil is digested into fatty acids by lipase(present in the pancreatic juice). Name another product obtained from the lipid digestion. Glycerol Dccument (e): The digestion process: Mechanical digestion involves physically breaking down food substances into smaller particles, by teeth and muscles, to more efficiently undergo chemical digestion. The role of mechanical digestion is to facilitate (help) the chemical digestion. The mechanical digestion: Digestive organ Mechanical digestion Mouth Mastication Esophagus Peristaltic movement Stomach Churning Small intestine Churning and peristaltic movement The digestion process: Mechanical digestion Chemical digestion No need for enzymes Needs enzymes By teeth or muscles or bile By juices contianing enzymes The identity stays the same The identity is changed E.g.: Big proteins to small pieces of Pr E.g.: Proteins to Amino acids From big to small size From big to small size but with different identity  The mechanical digestion: The mechanical digestion helps/ accelerates/ facilitates the chemical digestion. The starch digestion: The starch, made up of high number of rings of sugars, is a polysaccharide. The starch digestion: The starch is digested chemically by an enzyme called amylase to give maltose. There are two types of amylases: salivary amylase and pancreatic amylase. The starch digestion: Then, maltose is digested into glucose by the action of maltase present in the intestinal juice. The starch digestion: Salivary amylase salvia Or Intestinal juice Pancreatic amylase Pancreaitc juice  The starch digestion: - Starch is identified by iodine test that gives dark blue color with iodine solution. - Maltose and glucose are both reducing sugars that are identified by fehling test to a brick red precipitate. Note that fehling test can’t distinguish maltose from glucose.  The starch digestion: Tube A Tube B Content at the beginning - Distilled water - Maltase (intestinal juice) - Maltose - Distilled water - Bile - Maltose - Bile Content at the end - Distilled water - Maltase - Maltose - Distilled water - Bile - Glucose - Bile We can’t detect by using fehling test the tube in which digestion takes place at the end of the experiment, since both glucose and maltose are reducing sugars and give brick red precipitate with fehling test.