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9. Carbohydrates Chapter 16

9. Carbohydrates Chapter 16. CARBOHYDRATES. Contain C, H, O only C X H 2Y O Y = C X (H 2 O) Y i.e hydrates of carbon most common names end in '-----ose'. Carbohydrates General Structural Features. Usually 5/6 membered rings with C and one O

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9. Carbohydrates Chapter 16

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  1. 9. Carbohydrates Chapter 16

  2. CARBOHYDRATES Contain C, H, O only CXH2YOY = CX(H2O)Y i.e hydrates of carbon most common names end in '-----ose'

  3. CarbohydratesGeneral Structural Features Usually 5/6 membered rings with C and one O Many -OH groups  water soluble (simple ones )  easily broken down for energy (already partly 'oxidized')

  4. From Monosaccharides to Polysaccharides A monosaccharide is the smallest molecular unit of a carbohydrate. Glucose, the prototypical monosaccharide, is the most abundant organic molecule on earth. The root sacchar- comes from the Latin saccharum, "sugar".

  5. A disaccharide is a molecule formed from a combination of two monosaccharides, eg. sucrose A polysaccharide is a molecular chain (maybe branched) of hundreds / thousands of mono- saccharides, eg. cellulose

  6. Formula Carbohydrate Common Carbohydrates Monosaccharides, C6(H2O)6 Glucose (blood sugar, grape sugar, dextrose) C6H12O6 Fructose ( levulose ) C6H12O6 Galactose C6H12O6 Disaccharides, C12(H2O)11 Sucrose (table sugar,beet sugar, cane sugar) C12H22O11 Maltose (malt sugar) C12H22O11 Cellobiose C12H22O11 Lactose (milk sugar ) C12H22O11 Polysaccharides, Cx(H2O)y Starch Cellulose

  7. Glucose – a 2,3,4,5,6-pentahydroxy hexanal C6H12O6 – a(aldo)hexose open chain cyclic (6 mem. ring = pyran)

  8. Glucose – single then soluble

  9. Polysaccharides – the Glycosidic Linkage glycosidic linkage monosaccharides starch = 1,4 linkages = cellulose

  10. STARCHES Plant : Amylose -straight chain (~200 -D glucose units)  Amylopectin - branched every ~25 units (1000+ -D glucose units)  Dextrins -partial breakdown of amylopectin (food additives , paste , fabric finishes ) Animal :  Glycogen -branches every~12 units -short-term energy in body (liver & muscle).

  11. More Branching = Faster ‘Breakdown’ Amylopectin Glycogen

  12. Amylose Helical Structure • Left hand helix (partial)

  13. Iodine test for Starch • Helical structure of amylose holds the I3- ion; linear cellulose does not

  14. Carbohydrates The Most Common Energy Source H2O H2O H2O (starch) (glucose) Chemical Breakdown / Reaction = Digestion Complex  Dextrins  Simple  Mono-  acetate(2C) + CO2 + H2O + Energy NB. can be reversed, ie. glucose   glycogen O2

  15. Starch Breakdown / Digestion Complex Dextrins Small Mono-

  16. Energy Sources Instant Blood sugar(glucose): ~1g/L or 20Cal or ~30mins. Short Term Liver/Muscles(glycogen): ~325g or ~6 hrs. the more muscle, the more glycogen any excess is converted into fat Long Term Fat(adipose tissue): ~ 20kg or ~35 days

  17. Nutritional / Dietary Carbohydrates Starch - the digestible carbohydrate(for humans) Simple - mono-/disaccharides, eg. sugars Complex -seeds/roots of plants, eg. grains(pasta), corn, potatoes, rice Recommended - at least 55% of our Caloric intake (10% sugar & 45% complex) N A average - 20% sugar + 25% complex!

  18. Cellulose - indigestible carbohydrate for humans Soluble(pectins/gums) - fruits(apples), grain husks (oat bran) Insoluble(fiber/bulk/roughage) - potato skins, apple peels, celery, lettuce Recommended - ~30g/day NA average - ~15g/day

  19. What is Dextrose? Dextrose (Blood sugar) is the form of glucose that rotates the plane of polarized light in a clockwise direction.

  20. What is “invert sugar?” • Hydrolysisof (+)sucrose (table sugar) produces equal amounts of (+)glucose and (-) fructose (levulose). • But, fructose optical rotation is larger (negatively) than glucose rotation is positively. Hence, the resulting solution is levorotatory (-). • Thus, start with only (+) then get (-) after hydrolysis-so the net result of hydrolysis is inversion of the direction of the optical rotation • Honey is mostly invert sugar –ie an equal mixture of glucose and fructose

  21. Sucrose -> Glucose + Fructose (Invert) sucrose(+66) sucrase (invertase) D-glucose(+52) (dextrose) D-fructose(-92) (levulose) +

  22. Maltose – the basic unit of Starch (down) - linkage requires maltase (humans > yes)

  23. Cellobiose – the basic unit of Cellulose (up) - linkage requires cellobiase (humans > no)

  24. Why Dietary Fibre? It's Indigestible! Beneficial statistical correlations for colon cancer, obesity, diabetes, heart disease. Acts as a sponge for water and other substances Functions as a physical 'cleaner' Soluble - can help lower cholesterol levels reduces rate of glucose absorption Insoluble - fills you up eat less fat 'cleans' folds in intestinal walls no physical damage to intestinal walls adsorbs/removes many 'nasties'

  25. Cellulose is a major component of grass, leaves, wood, cotton(produced by photosynthesis). World Biomass Production = 1011 tons annually Present: Humans benefit indirectly by allowing ruminants(cows, sheep) to digest cellulose and convert it into protein which we eat. Human Exploitation of Cellulose

  26. Enzyme & Substrate: like a Lock & Key Enzymes are huge protein molecules with intricate but well-defined shapes. They are the catalysts that bring about all the chemical reactions in our bodies. For effective reactivity the molecule must fit into the convolutions of the shape of the enzyme. Much like a key must fit the tumblers of a lock.

  27. Lactose Intolerance Lactase is the enzyme that specifically breaks the -1,4- linkage of lactose to produce D-galactose and D-glucose. Infants have a highly active form but 70% of adults have some lactase deficiency. If lactose is not cleaved in small intestine it passes to the colon and 1) absorbs water or 2) is degraded by bacteria, resulting in cramps, diarrhea, etc.  About 10% of NA adults permanently lose their lactase compared to 3% of Danes and 97% of Thais.

  28. Lactose (milk sugar) – a disaccharide lactase + H2O D-galactose D-glucose 4-O-(-D-galactopyranosyl)-D-glucopyranose

  29. Solving the problem • Buy it!

  30. Sweetness Index SubstanceRelative Sweet Taste Lactose 0.16 Maltose 0.33 Glucose 0.74 Sucrose 1.00 Fructose 1.73 (NB. Glucose + Fructose = Honey or Invert Sugar) Aspartame 180 Saccharin 300

  31. Sucrose : lots of –OH’s: high water solubility -D-glucopyranosyl- -D-fructofuranoside

  32. Refined Sugar NA sugar consumption: ~1kg (1750) (annually/person) ~50 kg(1990) Per day: 50, 000/365= 136 grams per person/day world-wide production = >80 million tons (60% from cane; 40% from beets) Dangers:·dumps too much glucose into blood too quickly · all other nutrients(vitamins, minerals) are removed

  33. Everybody’s Comfort Food ! Wow !

  34. An Informative Label ?! …..Not Likely

  35. Refined Sugar in some Processed Foods Food% Sugar Jello ~83Coffeemate ~65 Shake’N Bake ~50 Salad Dressing~30 Ketchup ~29 Ice cream ~21 Peaches(in syrup) ~18 Peanut butter ~9 Coca Cola ~9

  36. Sugar in human blood • Blood sugar is glucose (dextrose) • It is the only fuel for the brain and the Central nervous system (CNS) and supplies the E for basal metabolism • For continuous supply, a concentration of 0.06 to 0.11 weight % is maintained

  37. Control of Blood Sugar (normal ~100mg/dL) Too Low (<75mg/dL) = hypoglycemia(fainting) Too High (>150mg/dL) = hyperglycemia/diabetes

  38. Urine test for diabetes • Above 0.16 weight % in blood , glucose seeps through the kidneys into the urine

  39. Diabetes Mellitus Type I (insulin dependent): ~10% of all diabetics (juvenile onset) Type II (non-insulin dependent; insulin receptors in cells have become inactivated by excess use of sugar): ~90% of all diabetics (formerly called adult onset but now found in 10-12 year olds!) NB. Diabetes is: 1) second only to trauma for leg amputation 2) leading cause of blindness in adults over 20 3) leading cause of kidney failure 4) almost triples risk of heart attack or stroke

  40. Type 1 Diabetes • Body produces virtually no insulin • Thus insulin needed for treatment • Absence of insulin causes uncontrolled lipolysis of fat and severe wasting of body tissues, eventually resulting in death

  41. Living with Type 2 Diabetes • Body makes too little insulin or its effect is resisted • In some cases insulin is needed • sometimes controlled with a reduced sugar diet • Loss of weight will cause an increase in the number of insulin receptors, hence improved condition

  42. Canadians Discover Insulin (1921) • Frederick Banting and his assistant Charles Best isolated insulin from the pancreas of dogs (canine insulin) and administered it to Type 1 patients • Nobel Prize awarded to Banting and McLeod for this work

  43. Structural Differences • Porcine & canine insulin are identical and have 50/51 amino acids in common with human insulin • Bovine insulin and human insulin have 48/51 amino acids in common • Thus porcine insulin most often used

  44. Source of Human Insulin • Patients who are allergic to these can now get cloned Insulin marketed as the Drug Humulin

  45. Synthesis of Human Insulin • Saran Narang (NRC Ottawa) 1930-2007 • Synthesised the proinsulin gene • Enabled mass production of Humulin • Via recombinant DNA • Insulin is a protein • 51 amino acids • DNA>RNA>protein

  46. Other molecules with sugar type structures

  47. Fake Fats •Simplesse - from egg white or milk proteins ·Emulsified starch - in Hellman’s light mayonaisse ·Emulsified protein - gelatin + water ·Olestra* ($200 million, by Proctor&Gamble) - may cause cramps/diarrhea(dehydration) reduces absorption of vit. A, D, E, K (fat- soluble vitamins) into body * not digested; available in USA since 1996; must carry warning label; not legal in Canada

  48. Olestra = Sucrose Octa Palmitate Not OH but OR (R = O=C-C16 (sat. = palmitate) NB. At least 6OHs esterified to be non-metabolized

  49. Olestra – Indigestible ! Olestra a Triglyceride

  50. Chitin (an exoskeleton polymer) (D)-glucosamine

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