Carbohydrates

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WK 3 LEC BIOCHEM: CHO

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Carbohydrates

  1. 1. CARBOHYDRATES WEEK 3 BIOCHEMISTRY LECTURE
  2. 2. <ul><li>organic compounds composed of C, H & O </li></ul><ul><li>found primarily in plants </li></ul><ul><li>an excellent source of energy </li></ul>CARBOHYDRATES
  3. 3. <ul><li>the sugar GLUCOSE is the most important CHO </li></ul><ul><li>it is as GLUCOSE that the bulk of dietary CHO is absorbed into the bloodstream and it is from GLUCOSE that all other CHO in the body are formed </li></ul>CARBOHYDRATES
  4. 4. <ul><li>Monosaccharides </li></ul><ul><li>building blocks of CHO </li></ul><ul><li>are CHO that cannot be hydrolyzed or broken into simpler CHO </li></ul><ul><li>composed of single CHO unit </li></ul><ul><li>ex. glucose, fructose, galactose </li></ul>CLASSIFICATION
  5. 5. <ul><li>B. Disaccharides </li></ul><ul><li>yield two molecules of monosaccharides when hydrolyzed </li></ul><ul><li>ex. sucrose (glucose+fructose); lactose (glucose+galactose); maltose (glucose+glucose ) </li></ul>CLASSIFICATION
  6. 6. <ul><li>C. Polysaccharides </li></ul><ul><li>consist of many units of monosaccharides </li></ul><ul><li>ex. starch and fiber – food sources; glycogen--storage form in the liver and muscles </li></ul>CLASSIFICATION
  7. 7. <ul><li>provide energy, fiber and naturally occurring sweeteners </li></ul><ul><li>protein-sparing effect—if enough CHO is provided to meet the energy need of the body, CHON can be spared or saved to use for specific protein functions </li></ul><ul><li>ketones or ketone bodies—intermediate products of metabolism of fats </li></ul><ul><li>ketoacidosis—increase levels of ketones in the body that affects the pH balance of the body </li></ul>FUNCTIONS
  8. 8. <ul><li>the gastrointestinal tract has the role of digesting CHO into monosaccharides for easy absorption </li></ul><ul><li>digestion: mouth—salivary amylase/ptyalin (enzyme) </li></ul><ul><li>ex. starch------- dextrin, maltase </li></ul><ul><li> small intestine—brush border cells secrete enzymes(maltase,sucrase) </li></ul><ul><li>monosaccharides are then absorbed in the small intestine </li></ul>DIGESTION & ABSORPTION
  9. 9. <ul><li>Glycogenesis- the process of converting glucose to glycogen </li></ul><ul><li>Glycogenolysis- the process of converting glycogen back to glucose </li></ul><ul><li>Gluconeogenesis- the process of producing glucose from fats and proteins </li></ul>METABOLISM
  10. 10. <ul><li>blood glucose is a source of energy to all cells </li></ul><ul><li>glucose is essential for normal brain function and cell formation </li></ul><ul><li>N value= 70-120 mg/dl </li></ul>BLOOD GLUCOSE REGULATION
  11. 11. <ul><li>controlled by a sophisticated hormonal system: </li></ul><ul><li>INSULIN- lowers blood glucose level by glycogenesis </li></ul><ul><li>GLUCAGON- increases blood glucose level by glycogenolysis </li></ul><ul><li>SOMATOSTATIN- inhibits the functions of insulin & glucagon </li></ul>BLOOD GLUCOSE REGULATION
  12. 12. <ul><li>many meanings: simple CHO, sucrose, white table sugar </li></ul><ul><li>3 issues: focus </li></ul><ul><li>sources: nutritive sweeteners: refined white sugar, brown sugar, dextrose, honey, sugar alcohols (sorbitol, mannitol) </li></ul><ul><li>consumption levels </li></ul>SUGAR- A Special Disaccharide
  13. 13. <ul><li>health effects </li></ul><ul><li>nutrient displacement- occurs when whole foods, which are minimally processed, are not eaten and are replaced by foods containing added sugar </li></ul><ul><li>dental caries- related to eating concentrated sweets and sticky CHO; sugar supports bacterial growth leading to plaque and tooth decay </li></ul><ul><li>obesity/DM </li></ul>SUGAR- A Special Disaccharide
  14. 14. <ul><li>other sweeteners </li></ul><ul><li>sugar alcohols or sugar replacers- are nutritive sweeteners because they provide 2 to 3 kcalories/gram </li></ul>SUGAR- A Special Disaccharide
  15. 15. <ul><li>alternative sweeteners or artificial sweeteners- non-nutritive sweeteners, provide no nutrients and few, if any, kcalories; main function is to replace naturally sweet kcaloric substances such as sugar or honey </li></ul><ul><li>ex. Aspartame(Nutrasweet/Equal) - formed by bonding of the amino acids phenylalanine and aspartic acid; 180 to 200 times sweeter than sucrose; contraindicated for persons with phenylketonuria(PKU) </li></ul>SUGAR- A Special Disaccharide
  16. 16. <ul><li>Starch- the storage form of plant CHO </li></ul><ul><li>-food sources: grains, legumes, vegetables and fruits </li></ul><ul><li>Fibers- consist of substances in plant foods including CHO and lignin that cannot be digested by humans; its texture provides bulk that thickens chyme and eases the work of the GIT muscles that regulate movement of the food mass </li></ul><ul><li>Primary Prevention: obesity, constipation, colon cancer </li></ul>COMPLEX CARBOHYDRATES/POLYSACCHARIDES
  17. 17. <ul><li>low blood glucose level </li></ul><ul><li>is not a disease but a symptom of an underlying disorder </li></ul><ul><li>possible causes: </li></ul><ul><li>fasting, intestinal malabsorption of glucose </li></ul><ul><li>anti-DM drugs, overproduction of insulin by the pancreas </li></ul>HYPOGLYCEMIA
  18. 18. <ul><li>is a disorder of CHO metabolism characterized by hyperglycemia caused by insulin that is either defective or deficient </li></ul>DIABETES MELLITUS
  19. 19. <ul><li>TYPE 1 DM </li></ul><ul><li>a form of DM in which the pancreas produces NO insulin at all </li></ul><ul><li>characterized by Beta cell destruction with severe insulin deficiency, is caused by autoimmune destruction of pancreatic B cells </li></ul><ul><li>age of onset: < 30 years old </li></ul><ul><li>NOT risk related </li></ul>DIABETES MELLITUS
  20. 20. <ul><li>TYPE 2 DM </li></ul><ul><li>a form of DM in which the pancreas produces some insulin that is defective and unable to serve the complete needs of the body </li></ul><ul><li>insulin resistance is the hallmark of this disorder, this means there’s a decreased response to insulin by target tissues </li></ul><ul><li>age of onset: > 30 years old </li></ul><ul><li>risk related: the risk increases with family history, age, weight and caloric intake </li></ul>DIABETES MELLITUS
  21. 21. <ul><li>a fasting plasma glucose ≥ 126 mg/dl </li></ul><ul><li>symptoms of DM plus a random plasma glucose ≥ 200 mg/dl </li></ul><ul><li>a plasma glucose level ≥ 200 mg/dl after an oral dose of 75 grams of glucose (oral glucose tolerance test) </li></ul>DIAGNOSTIC CRITERIA OF DM
  22. 22. <ul><li>polydipsia, polyuria (glucosuria), polyphagia, weight loss </li></ul><ul><li>Gestational DM- a form of DM occurring after the 20 th month of gestation </li></ul>S/SX

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