Understanding the Digestive Process: From Ingestion to Nutrient Absorption

1. TOPIC 6.1 Digestion

2. Series of events in order: • Ingestion- eat the food • Digestion- series of chemical rxs to convert food to smaller molecules • Absorption- small molecules are absorbed through the cells of your digestive system into blood or lymphatic vessels • Transport- circulatory system delivers the small molecular nutrients to body cells

3. DIGESTION • process of making food absorbable • it must be changed into simpler chemical compounds • nutrients can't be used by the body until they are absorbed into the cells & tissues • They can't be absorbed unless they are small & soluble

4. Before & After Digestion Molecular Form Ingested Form After Digestion • Protein • Triglycerides • poly, di and monosaccharides • DNA and RNA • Amino acids • Glycerol and fatty acids • Monosaccharides • Nucleotides

5. HYDROLYSIS • Breaking food into smallest components • ex. albumin in egg whites • contain amino acid serine • needed in pancreas to produce insulin

6. Organs of the Digestive System • You can think of the digestive system as two sets of structures • First set called the alimentary canal: • consists of organs that food passes through directly • it’s a one-way tube with two openings

7. The Second Set • accessory organs outside of but connected to the alimentary canal • these organs produce digestive enzymes • Liver, pancreas, gall bladder, salivary glands, etc.

8. Enzyme-catalysedrxs • Increase rate of rx at lower T° (37°C) • Lower energy of activation • Amylase in salivary glands of mouth • Pepsin (a protease) in stomach cells • Lipase in pancreas cells

10. Be able to draw and label!!!!!!!!!!

11. ALIMENTARY CANAL

12. Mouth- amylase (in saliva) • mechanical digestion of all food (teeth chewing & grinding) • chemical digestion of carbohydrates begins • esophagus- passageway to stomach • smooth muscle- peristalsis

13. Stomach • Gastric Juices: • Pepsin – protease enzyme • HCl – creates optimium pH for pepsin to be active & helps degrade and breakdown food • Mucus – lines and protects stomach from HCl • mechanical digestion of food (churning of stomach walls)

14. Small Intestines • 1st portion called duodenum • Accessory organs secrete juices: • Bile – produced in liver, stored in gall bladder (emulsifies fats) • Trypsin (protease), lipase, amylase and bicarbonate from pancreas • absorption: small soluble nutrients (sugars, amino acids, fatty acids)

15. Villi of Small Intestines -greatly increase surface area for absorption Contain capillaries and lacteals (small vessel of the lymph system) lacteal Small molecules taken into capillaries, except fatty acids which are absorbed into lacteals

16. Inside the Villi • inside are two types of vessels, capillaries & lacteal • the capillaries web around the lacteal • protein & carbohydrates (amino acids & simple sugars) are absorbed by capillaries • lipids (fatty acids & glycerol) are absorbed in the lacteal

17. Circulatory System delivers absorbed molecules to body cells • Nutrient molecules used by cells: • For energy (e.g. glucose) • For buiding larger molecules (e.g. amino acids) • Assimilation= the process of bringing nutrients to a body cell and using it to build larger molecules

18. Two Questions for You: 1. A single sandwich is likely to contain carbohydrates, lipids and proteins. From a biochemical viewpoint, what will happen to each type of molecule on digestion?

19. 2. You ingest a glucose molecule in the starch of a breakfast cereal. State as many specific locations as you can for this single glucose molecule from the time it is in your mouth to the time it enters a muscle cell of your right forearm.