carbohydrates
DESCRIPTION
WK 3 LEC BIOCHEM: CHOTRANSCRIPT
CARBOHYDRATES
WEEK 3BIOCHEMISTRY
LECTURE
organic compounds composed of C, H & O
found primarily in plantsan 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
A.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. Disaccharidesyield two molecules of monosaccharides when hydrolyzedex. sucrose (glucose+fructose); lactose (glucose+galactose); maltose (glucose+glucose)
CLASSIFICATION
C. Polysaccharidesconsist 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 effectso nutrient displacement- occurs when whole foods,
which are minimally processed, are not eaten and are replaced by foods containing added sugar
o dental caries- related to eating concentrated sweets and sticky CHO; sugar supports bacterial growth leading to plaque and tooth decay
o 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
o 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 disorderpossible causes:o fasting, intestinal malabsorption of glucoseo 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 DMo a form of DM in which the pancreas
produces NO insulin at allo characterized by Beta cell destruction with
severe insulin deficiency, is caused by autoimmune destruction of pancreatic B cells
o age of onset: < 30 years old NOT risk related
DIABETES MELLITUS
TYPE 2 DMo a form of DM in which the pancreas produces
some insulin that is defective and unable to serve the complete needs of the body
o insulin resistance is the hallmark of this disorder, this means there’s a decreased response to insulin by target tissues
o age of onset: > 30 years oldo risk related: the risk increases with family history,
age, weight and caloric intake
DIABETES MELLITUS
o a fasting plasma glucose ≥ 126 mg/dlo symptoms of DM plus a random
plasma glucose ≥ 200 mg/dlo a plasma glucose level ≥ 200 mg/dl
after an oral dose of 75 grams of glucose (oral glucose tolerance test)
DIAGNOSTIC CRITERIA OF DM
opolydipsia, polyuria (glucosuria), polyphagia, weight loss
Gestational DM- a form of DM occurring after the 20th month of gestation
S/SX