10 03 2012 Carbohydrates Functions o Main source of energy for cells o Spare protein o Add bulk to foods o Provide fiber Sources o Grains fruits dairy products Simple carbohydrates sugars o Molecule with 6 carbon atoms oxygen and hydrogen Complex carbohydrates scratches fiber o Sometimes called polysaccharides many saccharides o Long chains of sugar units Monosaccharide s o Six carbon molecules Glucose the body s predominant fuel Fructose fruit sugar Galactose one of the two components of the milk sugar lactose Disaccharides o Sucrose a combination of glucose and fructose o Lactose a combination of glucose and galactose o Maltose a combination of glucose and glucose Polysaccharides o Glycogen Animal starch configured in long chains of glucose molecules The body s storage form of carbohydrates o Starch from plant sources o Fiber Plant material long chains of glucose molecules whose structure is resistant to enzymatic degradation Cellulose hemicellulose and pectin Lower cholesterol and heart risk o o high fiber diet lowers cholesterol o o How Carbohydrate in Food becomes Glucose in the Body o Fiber starch and sugars enter small intestine pancreatic amylase breaks down starch to o Enzymes di saccharides on intestine wall break down di to disaccharides mono saccharides o Monosaccharide s enter capillary go to liver o Liver converts galactose and fructose to glucose o Fiber travels through unchanged to colon Lactose Intolerance o Deficiency in the enzyme lactase Symptoms include nausea diarrhea and gas o Effects 80 of world population Can be induced in remainder of population by substrate induction o Undigested lactose become fuel for intestinal bacteria that in turn produce gas and irritants o Infants and small children have the enzyme lactase so they can digest mothers milk o During childhood lactase begins to disappear in many people o Some ethnic groups are more likely to develop lactose intolerance By adolescence it is gone in about 75 of African Americans Jews native Americans Mexicans and in 90 of Asians Regulation of Blood Glucose o After a meal blood glucose rises Promotes an increase in insulin release o Insulin promotes glycogen formation In liver and muscle o After a while glucose levels fall Promoting glucagon release o Glucagon stimulates glycogen conversion to glucose from liver Glucose Metabolism o Glucose enters the cell and is first divided into two 3 carbon fragments and energy o The 3 carbon fragments called pyruvate enter the mitochondria and are reduced to 2 carbon units called acetyl o This process is done anaerobically and yields CO2 as well as 2 coA units of ATP o The acetyl coA then enters the Krebs Cycle and electron transport chain which yields 32 ATP CO2 and water 1 3 of glycogen stored in liver o One third of all glycogen is stored in the liver o The other two thirds is stored in muscles o Each glycogen molecule has many branches that stick out o Glucagon stimulates the breakdown of liver glycogen to glucose which can then enter the bloodstream o Epinephrine stimulates the breakdown of muscle glycogen to glucose which can be used to produce ATP in the muscles Nutrient conversion to Fat o Excess carbohydrate intake is converted to fat in the liver after repleting glycogen stores and after restoring normal blood glucose o Excess protein and fat also can result in fat deposition o The liver releases these fatty acids into the blood o Fat cells adipocytes take up these fatty acids and store them Inadequate CHO in the diet o When there is inadequate carbohydrate in the diet the body had two problems make some glucose Having no glucose the body turns to protein and fat to Without carbohydrate in the diet fat can not be broke down completely for engery And the bosy conerts its fats in to ketone bodies o Ketosis results when an undesirable high concentration of ketone bodies accumulate in the blood o Minimum amount set by the DRI committee is 130 grams a day for an average sized person Diabetes o Type one IDDM Characterized by an immune response to pancreatic b cell Eventually the pancreas stops making insulin Often starts early in life o Type 2 NIDDM Characterized by insulin resistance the insulin is there but it doesn t work to foster glucose uptake by the cells Occurs later in life adult onset Blood Glucose Values o Normal 100 mg dL o Prediabetes 100 125 mg dL o Diabetes 125 mg dL Complications of diabetes o Blindness o Kidney disease o Heart disease o Nerve damage o Increased infections o Amputations of limbs Alternative Sweeteners o Naturally occurring sweeteners corn syrup high fructose molasses levulose fructose or fruit sugar honey sugar alcohols High Fructose Corn Syrup o Used by body like any other sugar o No evidence that it is preferentially stored as fat o Concern is the amount of added sugars in our diet HFCS or corn sugar is just one of these added sugars used by food industry b c it is expensive High Fructose Corn Syrup and the environment o Corn is grown as monoculture which depletes soil of nutrients requires higher amounts of pesticides and fertilizer o Processing corn into HFCS is energy intensive o Scaling back on consumption of HFCS is good for you and good for the environment Functions of Lipids Nature s way of condensing energy stores also insulates protects organs 10 03 2012 Source of carioles 9 calories gram Flavor and tenderness of food Slow stomach emptying more satiating Source of essential fatty acids Types of Lipids Phospholipids o Glycerol two fatty acids phosphorus Phosphorus part makes it soluble in water Fatty acids make it soluble in fat Therefore can serve as an emulsifier Key role in cell membrane o o o o o Sterols Large molecules consisting of interconnected rings of carbon atoms with side chains of carbon hydrogen and oxygen attached o Cholesterol Bile Is found in all animal cell membranes Is nonessential Forms plaques that cause atherosclerosis o Cholesterol serves as the raw material for Vitamin D Steroid hormones including the sex hormones Triglycerides main fat o Main form of fat in food o Made up of glycerol backbone and three fatty acids o Fatty acids classified by length of carbon atoms and location of double bonds organization of hydrogen around the double bonds o Saturated Fatty Acids A fatty acid carrying the maximum of hydrogen atoms A fatty acid with less than maximum hydrogen atoms Unsaturated Fatty Acids Monosaturated FA Polyunsaturated FA Trans Fatty Acids Fatty acids with unusual shapes Arise when
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