6.1 – Digestion

Discuss as a table What are the 4 major macromolecules? What are the polymers and monomers of each one?

Essential Idea: The structure of the wall of the small intestine allows it to move, digest and absorb food. 6.1 Digestion and Absorption Understandings: The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut   The pancreas secretes enzymes into the lumen of the small intestine Enzymes digest most macromolecules in food into monomers in the small intestine Villi increase the surface area of epithelium over which absorption is carried out Villi absorb monomers formed by digestion as well as mineral ions and vitamins Different methods of membrane transport are required to absorb different nutrients Applications: Processes occurring in the small intestine that result in the digestion of starch and transport of the products of digestion to the liver Use of dialysis tubing to model absorption of digested food in the intestine Skills: Produce an annotated diagram of the digestive system Identify tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph

Purpose of digestion A. Food is made of cells, and therefore macromolecules (carbs, lipids, proteins, nucleic acids) that your body needs to function

B. Macromolecules are too big to cross cell membranes C B. Macromolecules are too big to cross cell membranes C. Your digestive system breaks polymers down into monomers so that they can get into your cells

D. Your cells use the monomers to build macromolecules (this is called assimilation)

Poly/di/mono saccharides monosaccharides Amylase   Ingested form Break down into Enzymes Category Carbohydrates Poly/di/mono saccharides monosaccharides Amylase Lipids Triglycerides glycerol and fatty acids Lipase Proteins amino acids Protease/endopeptidase Nucleic Acids DNA/RNA nucleotides Endonuclease

4 steps Ingestion – eat Digestion – break down into smaller molecules Absorption – molecules move from digestive tract into blood and lymph Transport – circulatory system delivers molecules to cells

III. Structures of the Alimentary Canal A. Mouth – Chemical and mechanical digestion 1. Salivary glands – produce saliva which lubricates food for travel to stomach and contains enzymes to chemically digest carbohydrates a. Salivary amylase – Breaks starch/complex carbs down to maltose (a disaccharide of glucose)

B. Esophagus – move food to stomach 1 B. Esophagus – move food to stomach 1. Peristalsis – smooth muscle contractions https://www.youtube.com/watch?feature=endscreen&NR=1&v=o18UycWRsaA

Stomach – Chemical and mechanical digestion 1. Produces chyme – mixture of food, digestive enzymes, and stomach acid 2. Gastric juices – contain pepsin – an enzyme that breaks down proteins to amino acids a. Hydrochloric acid (HCl) – a cofactor required for pepsin to work – makes pH of stomach about 2

Small Intestine – Chemical digestion and nutrient absorption into the blood 3 parts – duodenum, jejunum, ileum Chemical digestion – mostly in duodenum and jejunum a. Trypsin to break down proteins, pancreatic amylase to break down carbs, pancreatic lipase to break down lipids to glycerol and fatty acids *These three enzymes are produced by the pancreas

Muscle Contractions – circular and longitudinal muscles alternate contractions in order to push food through the digestive tract

4. Absorption – starts in the jejunum, mostly in the ileum a 4. Absorption – starts in the jejunum, mostly in the ileum a. Monomers are absorbed from the lumen of the small intestine into the blood

ii. Monomers of carbs and proteins go to Villi – finger-like projections lining the small intestine, increase surface area i. Each one contains capillaries (blood vessels) and a lacteal (lymph vessels) ii. Monomers of carbs and proteins go to blood, subunits of lipids go to lymph iii. Blood goes from the intestines straight to the liver for detoxification https://www.youtube.com/watch?v=0oBNJTP49Mw&feature=related

Large Intestine – Water reabsorption (maintains water balance – diarrhea, constipation) 1. 3 parts – ascending, transverse, descending 2. Millions of e.coli in symbiotic relationship – they get food, shelter, and they produce vitamin K for us F. Rectum – stores waste until elimination Anus – elimination waste from the body

With a partner Discuss what you had for dinner last night, how it has moved through your digestive tract since then, and what has happened to that food at each major structure of the alimentary canal.

IV. Accessory organs and their functions A IV. Accessory organs and their functions A. Liver – produces bile (helps digest fats), detoxifies blood, creates glycogen for carbohydrate storage

B. Gall bladder – stores and concentrates bile

C. Pancreas 1. Exocrine function – products are released through a duct into the duodenum a. Produces digestive enzymes – pancreatic amylase, pancreatic lipase, trypsin b. Produces sodium bicarbonate to neutralize stomach acid in the small intestine *** All three accessory organs feed into the same duct into the duodenum***

2. Endocrine function – hormones released into the blood a. Produces hormones that regulate blood sugar - insulin (lowers blood sugar) and glucagon (raises blood sugar)

Review as a table What are hydrolysis and condensation reactions? What is their function and what does each type of reaction look like chemically?

V. Digestion is an enzyme-driven process A V. Digestion is an enzyme-driven process A. Digestive enzymes catalyze hydrolysis reactions – hold macromolecules in place and stress bonds until body heat causes them to break

Digestive Enzyme Location Produced Location Used Substrate Products Salivary amylase Salivary glands Mouth Complex Carbs (Polysaccharides) Maltose (Disaccharide) Pepsin Stomach Proteins Amino acids Trypsin Pancreas Small Intestine Pancreatic amylase Pancreatic lipase Lipids Glycerol and fatty acids

https://www.youtube.com/watch?v=_rucrIv-EUA Wrecking ball parody