NHM 101 1nd Edition Lecture 10 Outline of Last Lecture I Carbohydrates Outline of Current Lecture II Carbohydrate Digestion and Absorption III Glucose in the Body IV Lipid Digestion and Absorption V Functions of Lipids Current Lecture Carbohydrate Digestion Mouth o Salivary enzyme Amylase hydrolyzes starch into smaller molecules shorter polysaccharides or maltose Stomach o No new enzymes are introduced to break down CHO o Salivary amylase diminishes as stomach acid and protein digestion enzymes break it down o Fiber may promote satiety feeling of fullness Small intestine o Pancreatic amylase continues breaking down polysaccharides o Final digestion takes place on outer membranes of intestinal cells Maltase breaks maltose into 2 glucose molecules Sucrase breaks sucrose into glucose and fructose Lactase breaks lactose into glucose and galactose o Mostly glucose molecules remain Large Intestine o Fibers remain and attract water o Bacteria in GI tract ferment some fibers mainly soluble Generates water and gas Fibers do contribute a small amount of energy for the colon 2kcal g Carbohydrate Absorption These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Primarily takes place in the Small Intestine o Active Transport Glucose and galactose o Facilitated diffusion Fructose o Fructose and galactose are metabolized by liver o Glucose sent to bodys cells for energy Lactose Intolerance Only about 30 of adults have enough Lactase Lactose Intolerance Symptoms o Lactose remains undigested in intestine and attracts water Causes bloating abdominal discomfort and diarrhea o Lactose also becomes a food for intestinal bacteria Bacteria multiply and produce irritating acid and gas Causes further abdominal discomfort and diarrhea Lactose Intolerance Causes o Lactase declines with age o Intestinal villi are damaged by disease medications prolonged diarrhea Total elimination of milk products is usually not necessary o Most can consume a small amount 6 grams of lactose Managing lactose intolerance o Experiment with milk products with a gradual increase o Consume milk products with other foods o Consume fermented milk products Kefir and yogurt o Cheese is often well tolerated o Use milk products treated with an enzyme that breaks down lactose Lactaid Glucose in the body Primary energy source for cells Glycogen Storage o Blood glucose rises after meal o Excess glucose molecules are combined by condensation to form glycogen o When blood glucose falls the liver cells break down glycogen by hydrolysis Single glucose molecules are released into blood stream o Muscle cells hold onto most of their glycogen to use during exercise o Body can only sore a small amount of glycogen What if we do not provide our body with adequate carbohydrates o Proteins can be used to make glucose but not easily Gluconeogenesis the making od new glucose Adequate dietary CHO is needed to prevent gluconeogenesis o Ketone bodies are formed when fat fragments combine Ketones provides fuel during starvation When production is higher than the use ketones accumulate in the blood Ketone bodies are acidic disturbing the acid base balance Body needs at least 50 100g of CHO per day o If too much Glucose to fat Liver will break down glucose and store as fat Blood Glucose Steady stream of blood moves past cells to deliver glucose Fast blood sugar between 70 99 mg dl Blood glucose is regulated by insulin and glucagon o Both secreted by the pancreas o Insulin Blood glucose rises insulin released glucose goes into cells blood glucose returns to normal o Glucagon Blood glucose falls between meals glucagon released signals liver to breakdown glycogen stores blood glucose returns to normal Diabetes Blood glucose remains above normal after meal due o inadequate or ineffective insulin Type 1 Diabetes o Pancreas does not produce any or enough insulin o Typically diagnosed in childhood Type 2 Diabetes o Cells do not respond to insulin o Typically occurs due to obesity Hypoglycemia o Rare in healthy people o Symptoms weakness rapid heartbeat sweating anxiety hunger o Replace refined CHO with fiber rich CHO and eat small frequent meals Glycemic Response Glycemic response extend to which food raises blood glucose and elicits an insulin response o Slow absorption or response o Fast absorption or response i e a crash Glycemic index a method to classify foods according to their potential to raise blood glucose o Compare 100g of food to 100g of a reference food typically glucose or white bread o Low legumes milk products o Moderate whole grains fruits o High processed foods bread carrots Lipid Digestion Challenge is to keep the lipids mixed vs separation o Lipids hydrophobic o Digestive enzymes are hydrophilic Mouth o Some hard fats melt Stomach o Muscles contract to propel contents toward pyloric sphincter o Lipid particles broken down by gastric lipase Small Intestine o When fat enters Cholecystokinin CCK is released which signals release of bile from the gallbladder Bile acts as an emulsifier so the enzymes can act on the fat Most fat digestion occurs in the small intestine o Pancreatic lipase and intestinal lipase Lipid Absorption Glycerol and short and medium chain fatty acids absorbed directly into bloodstream Monoglycerides and long chain fatty acids form micelles spherical complex o Transported by proteins called chylomicrons Lipid transport is made possible by a group of vehicles know as lipoproteins o Chylomicrons Largest of the lipoproteins Least dense Get smaller as triglycerides are removed from the cells o Very Low Density Lipoproteins VLDL Composed primarily of triglycerides Transport lipids to tissues Get smaller and more dense as triglycerides are removed and VLDL becomes LDL o Low Density Lipoproteins LDL Composed primarily of cholesterol with few triglycerides Transport lipids to tissues o High Density Lipoproteins HDL Composed primarily of protein Transport cholesterol from the cells to the liver o Health Implications High LDL is associated with a higher risk of heart disease and known as bad cholesterol High HDL appears to have a protective effect Functions of Lipids Part of every cell membrane Energy o Storage of triglycerides in adipose tissues is unlimited Insulation of body temperature Protection of vital organs In foods lipids function to o Give foods flavor and aroma o Transport fat soluble vitamins A D E K o Provide kcalories