Digestion Notes

1. Function of Digestive System break down large molecules and absorption

proteins made up of C, H, O, N, sometimes S & P amino acids are building blocks peptide bond is bond between amino acids dipeptide is 2 amino acids bonded together enzyme speed up reactions (catalyze) they are proteins affected by temp. & pH

enzymes basic function of an enzyme is to increase the rate of a reaction. most enzymes act specifically with only one reactant (called a substrate) to produce products enzymes are regulated from a state of low activity to high activity and vice versa

Enzymes continued Individuality of a living cell is due in large part to the unique set of some3,000 enzymes that it is genetically programmed to produce. If even one enzyme is missing or defective, the results can be disastrous.

Steps of Enzymes The enzyme and the substrate are in the same area. 2. The enzyme grabs on to the substrate at a special area called the active site. The combination is called the enzyme/substrate complex.

Steps of Enzymes 3. A process called catalysis happens. Catalysis is when the substrate is changed. It could be broken down or combined with another molecule to make something new. 4. The enzyme releases the product. When the enzyme lets go, it returns to its original shape. It is then ready to work on another molecule of substrate.

2. Mouth 1. teeth - chew food incisors - cut canines - tear or shred molars - crush and grind 2. tongue - helps swallow the food 3. saliva - digest starches comes from salivary gland under tongue Amylase: group of enzymes breaking down starch

3. swallowing 1. epiglottis = covers the trachea (tube to lungs) 2. esophagus = muscular tube that connects mouth to stomach. food is pushed down by a force called peristalsis

4. stomach gastric juice is churned with the food 2. gastric juice is made of water, hydrochloric acid & pepsin 3. pepsin is an enzyme that breaks down proteins 4. mucus lines the stomach to protect from the acid 5. food is now called chyme; passes through the pyloric sphincter

5. small intestine 1. duodenum : first 25 cm, many enzymes enter to digest food 2. bile - breaks down fats is stored and released from the gallbladder 3. pancreatic juices – breaks down protein, fats and starch 4. lipase: enzyme that breaks down fat molecules into fatty acids and glycerol 5. amylase: enzyme that breaks down carbohydrates into disaccharides

6. villi multitudinous threadlike projections covering the surface of the mucous membrane lining the small intestine, serving as the sites of absorption of fluids and nutrients.

7. liver Detoxification of blood for sugars and amino acids produces bile pH 11 and sends it to the gallbladder stores glucose Breaks down RBC’s produces cholesterol and urea from protein metabolism

8. gallbladder stores bile (emulsifies fats), body can function without the gallbladder

9. pancreas 1. Secretes pancreatic juices (several different enzymes) into small intestine Trypsin -proteins, Lipase - fats Amylase - starch Lies behind the stomach

10. large intestines absorbs water 2. makes several vitamins like K & some B

11. rectum last part of alimentary canal 2. stores feces

12. stages of digestion 1. mechanical digestion = physical break down by teeth & stomach churning 2. chemical digestion: enzymes break apart individual molecules of food

13. digestive enzymes pepsin: breaks down proteins (stomach) amylase: breaks down carbohydrates (mouth & small intestines) 3. lipase= breaks down fat molecules (small intestines) Pancreatic juices = breaks down protein, fats, starches (small intestines) Trypsin = breaks down protein in small intestine

14. sites of digestion carbohydrates - broken down by saliva in mouth & small intestines proteins - broken down mostly in stomach & also in small intestines fats - broken down by bile & pancreatic juices in the small intestines