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WK 3 LEC BIOCHEM: CHO

WK 3 LEC BIOCHEM: CHO

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    Carbohydrates Carbohydrates Presentation Transcript

    • CARBOHYDRATES WEEK 3 BIOCHEMISTRY LECTURE
      • organic compounds composed of C, H & O
      • found primarily in plants
      • an excellent source of energy
      CARBOHYDRATES
      • the sugar GLUCOSE is the most important CHO
      • 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
      CARBOHYDRATES
      • Monosaccharides
      • building blocks of CHO
      • are CHO that cannot be hydrolyzed or broken into simpler CHO
      • composed of single CHO unit
      • ex. glucose, fructose, galactose
      CLASSIFICATION
      • B. Disaccharides
      • yield two molecules of monosaccharides when hydrolyzed
      • ex. sucrose (glucose+fructose); lactose (glucose+galactose); maltose (glucose+glucose )
      CLASSIFICATION
      • C. Polysaccharides
      • consist of many units of monosaccharides
      • ex. starch and fiber – food sources; glycogen--storage form in the liver and muscles
      CLASSIFICATION
      • provide energy, fiber and naturally occurring sweeteners
      • 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
      • ketones or ketone bodies—intermediate products of metabolism of fats
      • ketoacidosis—increase levels of ketones in the body that affects the pH balance of the body
      FUNCTIONS
      • the gastrointestinal tract has the role of digesting CHO into monosaccharides for easy absorption
      • digestion: mouth—salivary amylase/ptyalin (enzyme)
      • ex. starch------- dextrin, maltase
      • small intestine—brush border cells secrete enzymes(maltase,sucrase)
      • monosaccharides are then absorbed in the small intestine
      DIGESTION & ABSORPTION
      • Glycogenesis- the process of converting glucose to glycogen
      • Glycogenolysis- the process of converting glycogen back to glucose
      • Gluconeogenesis- the process of producing glucose from fats and proteins
      METABOLISM
      • blood glucose is a source of energy to all cells
      • glucose is essential for normal brain function and cell formation
      • N value= 70-120 mg/dl
      BLOOD GLUCOSE REGULATION
      • controlled by a sophisticated hormonal system:
      • INSULIN- lowers blood glucose level by glycogenesis
      • GLUCAGON- increases blood glucose level by glycogenolysis
      • SOMATOSTATIN- inhibits the functions of insulin & glucagon
      BLOOD GLUCOSE REGULATION
      • many meanings: simple CHO, sucrose, white table sugar
      • 3 issues: focus
      • sources: nutritive sweeteners: refined white sugar, brown sugar, dextrose, honey, sugar alcohols (sorbitol, mannitol)
      • consumption levels
      SUGAR- A Special Disaccharide
      • health effects
      • nutrient displacement- occurs when whole foods, which are minimally processed, are not eaten and are replaced by foods containing added sugar
      • dental caries- related to eating concentrated sweets and sticky CHO; sugar supports bacterial growth leading to plaque and tooth decay
      • obesity/DM
      SUGAR- A Special Disaccharide
      • other sweeteners
      • sugar alcohols or sugar replacers- are nutritive sweeteners because they provide 2 to 3 kcalories/gram
      SUGAR- A Special Disaccharide
      • 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
      • 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)
      SUGAR- A Special Disaccharide
      • Starch- the storage form of plant CHO
      • -food sources: grains, legumes, vegetables and fruits
      • 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
      • Primary Prevention: obesity, constipation, colon cancer
      COMPLEX CARBOHYDRATES/POLYSACCHARIDES
      • low blood glucose level
      • is not a disease but a symptom of an underlying disorder
      • possible causes:
      • fasting, intestinal malabsorption of glucose
      • anti-DM drugs, overproduction of insulin by the pancreas
      HYPOGLYCEMIA
      • is a disorder of CHO metabolism characterized by hyperglycemia caused by insulin that is either defective or deficient
      DIABETES MELLITUS
      • TYPE 1 DM
      • a form of DM in which the pancreas produces NO insulin at all
      • characterized by Beta cell destruction with severe insulin deficiency, is caused by autoimmune destruction of pancreatic B cells
      • age of onset: < 30 years old
      • NOT risk related
      DIABETES MELLITUS
      • TYPE 2 DM
      • a form of DM in which the pancreas produces some insulin that is defective and unable to serve the complete needs of the body
      • insulin resistance is the hallmark of this disorder, this means there’s a decreased response to insulin by target tissues
      • age of onset: > 30 years old
      • risk related: the risk increases with family history, age, weight and caloric intake
      DIABETES MELLITUS
      • a fasting plasma glucose ≥ 126 mg/dl
      • symptoms of DM plus a random plasma glucose ≥ 200 mg/dl
      • a plasma glucose level ≥ 200 mg/dl after an oral dose of 75 grams of glucose (oral glucose tolerance test)
      DIAGNOSTIC CRITERIA OF DM
      • polydipsia, polyuria (glucosuria), polyphagia, weight loss
      • Gestational DM- a form of DM occurring after the 20 th month of gestation
      S/SX