Introduction to Digestion

1. Introduction to Digestion We are what we eat!

2. What is involved in the process of Digestion? • How would you define digestion? • Here’s one definition: a process of breaking down food or macromolecules into smaller molecules for absorption • While watching the demo, try to figure out the four stages of digestion

3. The Four Stages of Digestion • What was the first stage that occurred in the demo? • Hint: without this stage, your system wouldn’t have any food to break down.... • Ingestion = the taking in of nutrients i.e. the act of eating and putting food into your mouth!

4. The Four Stages of Digestion • What happened next? • Hint: without this stage, our body can’t use the nutrients that we ingest.... 2. Digestion = the break down of food by mechanical and chemical processes into molecules small enough for cells of the body to absorb

5. The Four Stages of Digestion • And next? • Hint: without this stage, our tissues have no way of getting the broken down nutrients 3. Absorption = the transport of digested nutrients to the tissues of the body

6. The Four Stages of Digestion • And last? • Hint: without this stage, we can be in a lot of pain and discomfort.... 4. Egestion or elimination = the removal of undigested solid waste from the body

7. But wait – just what the heck are we digesting???? • Q: What is the hotdog? The muffin? The yogurt? • A: Different forms and combinations of macromolecules that we need to survive! • We break them down with the help of enzymes and through hydrolysis reactions

8. What are Macromolecules? • Macromolecules are very large organic molecules • They are made up of smaller molecules that are linked together • They are the nutrients and raw materials that are involved with all cellular functions • They provide the energyfor metabolism

9. What are Macromolecules? • Four categories of macromolecules: • Carbohydrates • Proteins • Fats (lipids) • Nucleic acids • These plus some minerals and vitamins are known as essential nutrients = a nutrient that cannot be made by the body, and must therefore be obtained from food

10. Carbohydrates • Contain carbon, hydrogen, and oxygen generally in the same ratio (C:2H:O) • Provide short-term and long-term energy storage for organisms • Monosaccarides = one sugar; consists of a molecule with 3 to 7 carbon atoms (e.g. Glucose or fructose) • Taste sweet

11. Carbohydrates • Dissacharides = a sugar made up of two monosaccaride molecules (e.g. Sucrose) • Polysaccarides = complex carbs, consist of many linked monosaccarides (e.g. Starch, cellulose, glycogen)

12. Proteins • Found in meats, milk products, eggs, vegetables, nuts and soy • Macromolecule made up of amino acids • Amino acids join together by peptide bonds and many joined together = polypeptide • Proteins are needed for cell growth and repair, and enzymes are proteins, as well as antibodies

13. Proteins

14. Fats or Lipids • Found in animal and fish products, nuts and seeds, avocado and dairy products • Fats are organic compounds that do not dissolve (insoluble) in water • Basic structure is a glycerol molecule and three fatty acid chains • Needed for nerve and musclefunction

15. Fats or Lipids

16. Nucleic Acids • Nucleic acids direct growth and development of all organisms using a chemical code • Our body can make them, but there are times when what we make is not enough, therefore we need to get them from what we eat • Two types of nucleic acid = • Ribonucleic acid (RNA) • Deoxyribonucleic acid (DNA)

17. Homework • Read up on Macromolecules in your text • Section 2.1 (pg 32) to the end of Section 2. 5 (pg. 47) • Answer the questions in the handout.