Nutrition in Man

Recap! Crossword puzzle!

Lesson Objectives By the end of the lesson, you should be able to: State the 3 parts of the small intestine. Describe the functions of the duodenum in terms of digestion by stating the enzymatic reaction that takes place. Explain the role of bile in the process of fats digestion in the small intestine.

Structure of the small intestine

Parts of Small Intestine Three parts: 1)Duodenum 2)Jejunum 3)Ileum

Structure 6 metres long!!!

Structure Lining of the walls the small intestine contains intestinal glands which secrete digestive enzymes

Structure Walls contain villi and microvilli, and single-cell epithelium, blood and lymph capillaries for absorption of digested food particles

Duodenum

Structure Receive pancreatic juice from pancreas via pancreatic duct. Receive intestinal juice from the intestinal gland Receive bile(produced from liver, stored in gall bladder and released via bile duct

bile intestinal juice pancreatic duct pancreatic juice bile duct All three fluids are alkaline Neutralise the acidic chyme Provide a suitable alkaline medium (~pH 8.5) for the action of the pancreatic and intestinal enzymes Small intestine (Duodenum)

Functions Secretion of Intestinal Juice Functions Intestinal juice contain digestive enzymes : maltase, protease (erepsin) and lipase

Intestine juice Functions – enzymes SubstrateEnzymeProduct MaltoseMaltaseGlucose PolypeptideProtease (erepsin) Amino acids FatsLipaseFatty acid +glycerol

Duodenum Pancreatic juice Function Pancreatic juice contain enzymes pancreatic amylase, pancreatic lipase and trypsin

Pancreatic juice SubstrateEnzymeProduct StarchAmylaseMaltose ProteinProtease (trysin) Polypeptide FatsLipaseFatty acid +glycerol

Bile Liver cells secrete bile Alkaline greenish-yellow liquid Has no enzymes so cannot digest food Aid in digestion of fats Bile stored temporarily in gall bladder When gall bladder contracts, bile flows into duodenum via bile duct

Simulate action of Bile Add a small amount of oil to a beaker of water Shake it Add liquid detergent to simulate bile. Observe!

In the small intestine, bile salts emulsify fats. big drop of fat Bile salts emulsify fats into tiny fat droplets. + bile salts

In the small intestine, bile salts emulsify fats. They lower the surface tension of the fats, that is, they reduce the attractive forces between the fat molecules. big drop of fat Bile salts emulsify fats into tiny fat droplets. + bile salts

In the small intestine, bile salts emulsify fats. They lower the surface tension of the fats, that is, they reduce the attractive forces between the fat molecules. This causes the fats to break into tiny fat droplets suspended in water, forming an emulsion. big drop of fat Bile salts emulsify fats into tiny fat droplets. + bile salts tiny fat droplets

In the small intestine, bile salts emulsify fats. They lower the surface tension of the fats, that is, they reduce the attractive forces between the fat molecules. This causes the fats to break into tiny fat droplets suspended in water, forming an emulsion. Note that this is just a physical break-up, but no chemical digestion of fat molecules has occurred. big drop of fat Bile salts emulsify fats into tiny fat droplets. + bile salts tiny fat droplets

Emulsification increases the surface area to volume ratio of the fats, speeding up their digestion by lipase. Bile salts emulsify fats into tiny fat droplets. tiny fat droplets

Emulsification increases the surface area to volume ratio of the fats, speeding up their digestion by lipase. + lipase Bile salts emulsify fats into tiny fat droplets. tiny fat droplets

Emulsification increases the surface area to volume ratio of the fats, speeding up their digestion by lipase. Emulsified fats are digested by lipases to fatty acids and glycerol. + lipase Bile salts emulsify fats into tiny fat droplets. tiny fat droplets

Emulsification increases the surface area to volume ratio of the fats, speeding up their digestion by lipase. Emulsified fats are digested by lipases to fatty acids and glycerol. fatty acids and glycerol + lipase Bile salts emulsify fats into tiny fat droplets. tiny fat droplets

Summary

Small intestine SubstrateEnzyme Product/ Substrate EnzymeProduct Starch Pancreatic amylase MaltoseMaltaseGlucose Carbohydrate digestion

Small intestine Fat digestion Bile emulsifies fats and breaks them up into minute fat globules Enlarges surface area of fats Speed up digestion End products are fatty acids and glycerol SubstrateEnzymeProduct FatsLipase Fatty acids and Glycerol

Small intestine Protein digestion Some digested in the stomach Undigested proteins enter small intestine Converted to polypeptides by protease (trypsin) SubstrateEnzyme Product/ Substrate EnzymeProduct Proteins Protease (Trypsin) Polypeptides Protease (Erepsin) Amino acids

Small intestine Region of digestion SecretionSourceEnzymeAction Small intestine BileLiver-Emulsifies fat Pancreatic juice PancreasAmylase Protease (Trypsin) Lipase Starch  maltose Proteins  polypeptides Fats  fatty acids and glycerol Intestinal juice Intestinal glands Maltase Protease (Erepsin) Lipase Maltose  glucose Polypeptides  amino acids Fats  fatty acids and glycerol

Muddiest Point Any Question?