D4 Chemical Digestion 2021 (PDF)

DIGESTION D4 Chemical digestion Learning Intentions for D4 Students will be able to discuss the accessory organs and their digestive functions. Students will be able to discuss, in detail, the chemical digestion that occurs in the small intestine including: The components of pancreatic...

DIGESTION D4 Chemical digestion Learning Intentions for D4 Students will be able to discuss the accessory organs and their digestive functions. Students will be able to discuss, in detail, the chemical digestion that occurs in the small intestine including: The components of pancreatic fluid and their functions The role of bile in lipid digestion The role of carbohydrases Students will be able to describe how all 4 macromolecules are broken down and absorbed into our bodies. Accessory Organs Pancreas, liver & gallbladder NOT physically part of the digestive tract (food does not pass through these structures!) Secrete substances to aid in chemical digestion  Accessory Organs Pancreas – delivers pancreatic fluid to duodenum; enzymes must be activated by secretions from small intestine. Pancreatic fluid contains: Proteases (trypsin & chymotrypsin) Pancreatic amylase Lipase Bicarbonate – neutralizes acid from stomach, chyme ends up with pH ~8 Nucleases  Accessory Organs Liver – largest internal organ; main digestive function is to produce and secrete bile. Bile – greenish-yellow fluid made of bile pigments and bile salts. Bile pigments – waste products from old RBCs (leave body in feces) Bile salts – assist lipase with fat digestion via emulsification. (Works like a detergent, breaking fat into small droplets & increasing surface area for lipases) NOTE: Emulsification is a physical process, not chemical! Gallbladder Stores bile between meals Fat-containing chyme will stimulate gallbladder to contract and send bile into duodenum Gastric Enzymes 1. Amylases – digest polysaccharides (e.g. salivary amylase); produced by salivary glands and pancreas 2. Carbohydrases – digest simple sugars (e.g. maltase, lactase, sucrase); produced by small intestine 3. Lipases – digest fats (e.g. pancreatic lipase); produced by pancreas 4. Proteases – digest larger polypeptides (e.g. pancreatic protease); produced by stomach and pancreas 5. Peptidases – digest peptides  into amino acids; produced by pancreas 6. Nucleases – digest nucleic acids  into nucleotides; produced by pancreas 7. Nucleosidases – digest nucleotides  into bases, sugars, phosphates; produced by small intestine Page 903 in Campbell KNOW THIS!! Chemical Digestion—where breakdown occurs REMEMBER THESE ENZYMES!! Digestion - Carbohydrates Beings in the mouth as salivary amylase starts to break down polysaccharides (starch) No digestion in stomach (salivary amylase denatured by low pH) Most digestion in small intestine Pancreatic amylase continues breakdown of polysaccharides into disaccharides Other carbohydrases (sucrase, maltase, lactase) hydrolyze diasaccharides into monosaccharides Carbohydrates Glucose is actively transported into cells of the intestinal wall to move into the bloodstream. Digestion - Proteins Pepsin in stomach begins hydrolysis of proteins to form smaller polypeptides Majority of protein digestion is in small intestine Proteases (trypsin & chymotrypsin) break polypeptides into shorter peptides Peptidases break short peptides into amino acids Proteins Amino acids are actively transported into the cells of the intestinal wall to move into the bloodstream. Digestion - Lipids Arrival of fats in duodenum stimulates secretion of bile, emulsifying fat droplets (emulsification is a physical process) Lipase hydrolyzes triglycerides into glycerol and fatty acids Lipids Glycerol and fatty acids diffuse into the cells of the intestinal wall where they are resynthesized into fats, coated with proteins, and move into lymph vessels for eventual transport into the bloodstream. Digestion/Absorption – Nucleic Acids Not considered a major nutrient In small intestine, nucleases break nucleic acids into nucleotides Nucleosidases break into sugars, nitrogen bases & phosphates Actively transported into intestinal epithelial cells and moved into bloodstream for use by cells Check Your Understanding: What? So What? Now What? I can describe the function of the accessory organs and their role in physical and chemical digestion I can demonstrate how the macromolecules are broken down and absorbed into our bodies. Did you know? Babies produce lipase in their salivary glands and stomach to speed up fat digestion from milk. If a whole protein is absorbed by cells in the intestine it can trigger an allergic reaction (e.g. people with allergies to fish, eggs, nuts) The average person passes 500 mL of intestinal gas each day… excuse you! Assignment/Videos https://www.youtube.com/watch?v=nM5kMSjBrmw Stations lab work time Chemical digestion chart (booklet) Begin digestion review