Chapter 4 Nutrients Lesson 1 - Carbohydrates


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Chapter 4 Nutrients Lesson 1 - Carbohydrates

  1. 1. Nutrients Chapter 4
  2. 2. Lesson objectives: <ul><li>Introduction to the need for food and the 7 classes of food </li></ul><ul><li>Carbohydrates (monosaccharides, disaccharides and polysaccharides) </li></ul><ul><li>New terms: condensation, polymerisation & hydrolysis </li></ul><ul><li>Structure and function of starch, glycogen and cellulose </li></ul><ul><li>Fats – structure and function </li></ul>
  3. 3. Need for food <ul><li>To provide energy for vital activities of body </li></ul><ul><li>To synthesize new protoplasm (for growth, repair, reproduction) </li></ul><ul><li>To maintain health (prevent deficiency diseases) </li></ul><ul><li>Movement (locomotion) </li></ul>
  4. 4. 7 classes of food
  5. 5. Activity: In pairs, identify the various ingredients and nutrients present in a burger
  6. 6. Ingredients Nutrients present Bread Carbohydrate, vitamins, fibre Carbohydrate, protein, vitamins, fibre, minerals, water Lettuce Carbohydrate, protein, vitamins, fibre, minerals, water Tomato Cheese Fats, proteins, vitamins, minerals (Ca 2+ ) Beef Proteins, fats, minerals
  7. 7. Nutrients in food (7 classes of food) <ul><li>Carbohydrates </li></ul><ul><li>Proteins </li></ul><ul><li>Fats </li></ul><ul><li>Vitamins </li></ul><ul><li>Dietary fibre </li></ul><ul><li>Water </li></ul><ul><li>Mineral salts </li></ul>Organic nutrients (obtained from living organisms; compounds of carbon) Inorganic nutrients
  8. 8. Question: <ul><li>Which class of food provides the most energy to the body? </li></ul><ul><li>Why is it than not advisable for people who want to lose weight to consume more carbohydrates in place of proteins or fats? </li></ul>
  9. 9. Carbohydrates
  10. 10. Carbohydrate Carbohydrates Monosaccharides Disaccharides Polysaccharides (simple sugars) (complex sugars) starch cellulose glycogen e.g. maltose, lactose, sucrose glucose, galactose, fructose
  11. 11. Carbohydrates <ul><li>Generalised formula: </li></ul><ul><li>C n H 2m O m </li></ul><ul><li>e.g. glucose n = 6, m = 6 </li></ul><ul><li>formula: C 6 H 12 O 6 </li></ul><ul><li> sucrose n = 12, m = 11 </li></ul><ul><li>formula: C 12 H 22 O 11 </li></ul>
  12. 12. Types of sugar Mono saccharides Di saccharides condensation condensation condensation
  13. 13. Condensation <ul><li>is a chemical reaction whereby 2 simple molecules are joined together to form a larger molecule with the removal of one molecule of water </li></ul>
  14. 14. Polymerisation <ul><li>Definition : </li></ul><ul><li>process of condensing many similar molecules to form a large molecule </li></ul>glucose
  15. 15. Hydrolysis <ul><li>A reaction whereby a water molecule is added to split up a complex molecule into its constituent units </li></ul>1. 2.
  16. 16. * Disaccharides & Monosaccharides maltase lactase sucrase maltose lactose sucrose glucose + fructose glucose + galactose glucose + glucose Monosaccharide Disaccharide
  17. 17. Summary: Carbohydrates Monosaccharides Disaccharides Polysaccharides (simple sugars) (complex sugars) starch cellulose glycogen e.g. maltose, lactose, sucrose glucose, galactose, fructose condensation polymerisation hydrolysis
  18. 18. Starch Glycogen Cellulose
  19. 19. Starch <ul><li>Most impt. source of carbohydrates in our food </li></ul><ul><li>Rich in vegetable foods (cereals, potatoes) </li></ul><ul><li>Not formed or stored by animals </li></ul><ul><li>Detected by iodine test </li></ul>
  20. 20. Starch Mixture of straight & branched chains linked by chemical bonds Hydrolysis by acids/enzymes break bonds -> releasing reducing sugars
  21. 21. Glycogen <ul><li>a.k.a “animal starch” </li></ul><ul><li>Formed when numerous glucose units condense to form highly branched chains of glucose units </li></ul><ul><li>Storage form of carbohydrate in animals & fungi </li></ul><ul><li>Animals: stored mainly in liver & muscles </li></ul>
  22. 22. Starch & Glycogen are suitable storage materials because… <ul><li>Insoluble in H 2 O (do not change osmotic pressure in cells) </li></ul><ul><li>Large molecules (unable to diffuse through cell membrane) </li></ul><ul><li>Can easily be hydrolysed to glucose when needed </li></ul><ul><li>Molecules have compact shape (occupy less space c.f. glucose molecules) </li></ul>
  23. 23. Using mneumonics <ul><li>In pairs, use mneumonics to memorise the points on why starch & glycogen are suitable as storage materials </li></ul>L I C E ompact shape arge molecule nsoluble asily hydrolysed
  24. 24. Cellulose <ul><li>Carbohydrate that forms greater part of cell walls of plants </li></ul><ul><li>Similar to starch (consists of glucose units linked together to form straight chains) </li></ul><ul><li>Differ in the way glucose units are linked between them </li></ul><ul><li>Inert (digestible by few organisms) -> forms bulk of undigested matter in Man </li></ul><ul><li>Fibre important to proper functioning of large intestine </li></ul>
  25. 25. Functions of carbohydrates <ul><li>As source of energy </li></ul><ul><li>To form supporting structures e.g. cellulose cell walls </li></ul><ul><li>*Converted to other organic compounds e.g. amino acids and fats </li></ul><ul><li>Formation of nucleic acids ( DNA ) </li></ul><ul><li>To synthesize lubricants </li></ul><ul><li>( mucus -> carbohydrate + protein ) </li></ul>