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This lecture covers the different forms of carbohydrates, their digestion, absorption, and metabolism, and the regulation of carbohydrate metabolism. It also explores the foods where each form of carbohydrate is found.

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Suggestions for course- your input please

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  1. Suggestions for course- your input please Please use only your CBU emails when communicating with me. Please check your CBU emails frequently including for messages from me.

  2. Lecture 3a- 22 January 2019 Most of this lecture derived from Chapter 4 of Gropper, Chapter 4,7 of Rolfes et al(Understanding Normal and Clinical Nutrition(Nutrition 2104/2108 text) Insel et al.(Nutrition) and page 96 of Smolin and Grosvenor (Nutrition-Science and Applications)

  3. TODAY’S LECTURE Carbohydrate metabolism and regulation

  4. Outline of lectures 3a and 3b Carbohydrates   -forms                         -monosaccharides                         -disaccharides                         -oligosaccharides                         -polysaccharides                         -fibre-next week

  5. Outline of lectures 3a and 3b Carbohydrates -foods where each is found                         -monosaccharides                         -disaccharides                         -oligosaccharides                         -polysaccharides

  6. Outline of lectures 3a and 3b -definitions                         -monosaccharides                         -disaccharides                         -oligosaccharides                         -polysaccharides

  7. Outline of lecture 3a and 3b -digestion                         -monosaccharides                         -disaccharides                         -oligosaccharides                         -polysaccharides

  8. Outline of lectures 3a and 3b -absorption, transport and distribution                         -monosaccharides                         -disaccharides                         -oligosaccharides                         -polysaccharides                         -glucose transporters

  9. Outline of lectures 3a and 3b -metabolism                         -glycogenesis                         -glycogenolysis                         -glycolysis                         -nicotinamide adenine dinucleotide                         -hexose monophosphate shunt                         -Krebs cycle                         -gluconeogenesis                         -regulation                                 -allosteric                                 -hormonal                                 -changes in equilibrium -rate limiting enzymes

  10. More detailed comments-lecture 3a Carbohydrates     -forms         -simple carbohydrates   -monosaccharides -glucose, fructose, galactose -disaccharides -maltose(glucose and glucose), -sucrose(glucose and fructose), -lactose(glucose and galactose)

  11. Carbohydrates  -forms -complex carbohydrates                   -oligosaccharides-three to ten saccharide units(some texts define as 2-10 units)-eg breakdown of starch  digestion                   -polysaccharides-more than 10 saccharides units-eg starch, glycogen

  12. Examples of foods where each is found      -monosaccharides-            -glucose-rare in foods as monosaccharide (except mother's milk and sports drinks)  but is found in foods as disaccharides and starch             -fructose-fruits and honey            -galactose-seldom occurs free in nature             

  13. Examples of foods where each is found      -disaccharides -maltose- part of starch                          - minor component of few foods            -sucrose-fruits, vegetables and grain                          -sugar cane- gives rise to table sugar                          -sugar beets-give rise to table sugar            -lactose-dairy products (eg milk)

  14. Examples of foods where each is found       -oligosaccharides- eg raffinose and stachyose are found inbeans and other legumes       -polysaccharides -glycogen-(storage carbohydrate in animal muscle and liver) -most of this is lost when meat is slaughtered                   -starch-(storage carbohydrate in plants)- potatoes

  15. Definitions       carbohydrate A compound or molecule that is composed of carbon, oxygen and hydrogen in the ratio of 1C:2H:1O carbo = carbon hydrate = H20

  16. Definitions        -monosaccharides-single carbohydrate units;        -contain 3-7 carbons(trioses, tetraoses, pentoses, hexoses, heptoses)        -disaccharides-two saccharide units       -oligosaccharides-3-10 saccharide units       -polysaccharides-more that 10 saccharide units

  17. Digestion -monosaccharides-pass untouched into small intestinal capillaries -disaccharides -maltose- untouched until maltase in small intestine -maltase produces two glucoses          -sucrose-untouched until sucrase in small intestine                        -sucrase produces glucose and fructose

  18. Digestion -disaccharides  -lactose-untouched until lactase in small intestine            -lactase produces glucose and galactose -oligosaccharides-undigested in stomach or small intestine-must be digested by colon bacteria which produce abdominal discomfort and flatulence and short chain fatty acids (acetic, proprionic and butyric acids)

  19. Digestion -polysaccharides -starch digestion mildly in mouth-salivary amylase (alpha-amylase), minimally in stomach via hydrochloric acid and mostly by pancreatic amylase in small intestine          -maltose units ultimately produced followed by maltase digestion

  20. Digestion -polysaccharides -resistant starch-common in legumes, raw potatoes and unripe bananas                            -resistant to starch digestion as above due individual inefficiency in digesting starches (class discussion) and physical properties of food

  21. Digestion -polysaccharides -resistant starch bacteria in colon ferment resistant starches and produce gas and short chain fatty acids (acetic, proprionic and butyric acids)

  22. Absorption, transport and distribution -monosaccharides-pass untouched into small intestinal capillaries                   -glucose and galactose enter by active transport and both go to liver                                    -fructose enters by facilitated diffusion and goes to liver                                    -glucose goes to liver(some glycogen produced and other metabolic pathways)

  23. Absorption, transport and distribution      -monosaccharides-    -fructose and galactose converted to glucose in liver                     -glucose also goes to directly to other tissues eg voluntary muscle(some glycogen produced and other metabolic pathways are followed)

  24. Absorption, transport and distribution oligosaccharides-undigested in stomach or small intestine-must be digested by colon bacteria which produce short chain fatty acids, abdominal discomfort and flatulence

  25. Absorption, transport and distribution -polysaccharides-starch digestion mildy in mouth-salivary amylase (alpha-amylase), minimally in stomach via hydrochloric acid and mostly by pancreatic amylase in small intestine                                -maltose units ultimately producing glucose which is handled as above

  26. Absorption, transport and distribution -glucose transporters-proteins required to get glucose into cells -table 4.2 Gropper

  27. -metabolism   -glycogenesis                   -conversion of glucose to glycogen(storage form of carbohydrate in humans)                   -occurs in liver and muscle (cytoplast)                   -glucose converted to glycogen precursors                   -most of glycogen arises from gluconeogenic precursors rather than glucose directly -figure 4.11 Gropper

  28. -metabolism         -glycogenolysis                -conversion of glycogen to glucose (usable form of carbohydrate in humans for energy and anabolism) Note:The end of the molecule containing a free carbon number one on glucose is called a reducing end. The other ends are all called non-reducing ends.                 -occurs in cytoplast                 -figure 4.12 Gropper                -regulation-figure 4.13 Gropper

  29. -metabolism

  30. -metabolism -glycolysis                -catabolism of glucose to yield energy and products for anabolism(e.g. gluconeogenesis-see below)                -anaerobic                -occurs in cytoplast                -figure 4.14 Gropper

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