10 10 2012 Carbohydrates 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 starches fiber o Sometimes called polysaccharides o Long chains of sugar units Monosaccharides Six carbon molecules Glucose the body s predominant fuel Fructose fruit sugar Galactose one of the two components of the milk sugar lactose Disaccharides Sucrose a combination of glucose and fructose Lactose a combination of glucose and galactose Maltose a combination of glucose and glucose Polysaccharides Glycogen o Animal starch configured in long chains of glucose molecules o The body s storage form of carbohydrate Starch from plant sources Fiber o Plant material long chains of glucose molecules whose structure is resistant to enzymatic degradation o Cellulose hemicellulose and pectin Common dietary carbohydrate sources Rice wheat maize potato apple orange grapes cane beet honey corn syrup milk How carbohydrate in food becomes glucose in the body Fiber starch and sugars enter small intestine o Pancreatic amylase breaks down starch to disaccharides Enzymes disaccharidases on intestine wall break down di to mono saccharides Monosaccharides enter capillary go to liver Liver converts galactose and fructose to glucose Fiber travels through unchanged to colon Lactose intolerance Deficiency in the enzyme lactase o Symptoms include nausea diarrhea and gas Effects 80 of world population o Can be induced in remainder of population by substrate Undigested lactose becomes fuel for intestinal bacteria that in turn Infants and small children have the enzyme lactase so they can induction produce gas and irritants digest mothers milk During childhood lactase begins to disappear in many people 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 90 of Asians Regulation of blood glucose After a meal blood glucose rises o Promotes an increase in insulin release Insulin promotes glycogen formation o In liver and muscle After a while glucose levels fall o Promoting glucagon release Glucagon stimulates glycogen conversion to glucose from liver Glucose metabolism Glucose enters the cell and is first divided into two 3 carbon fragments and energy The 3 carbon fragments called pyruvate enter the mitochondria and are reduced to 2 carbon units called acetyl coA This process is done anaerobically and yields CO2 as well as 2 units of ATP The acetyl coA enter the Krebs Cycle and electron transport chain which yields 32 ATP CO2 and water Glycogen Metabolism the other 2 3 is stored in muscles 1 3 of all glycogen is stored in the liver each glycogen has many branches that stick out glucagon stimulates the breakdown of liver glycogen to glucose which can then enter the bloodstream epinephrine stimulates the breakdown of muscle glycogen to glucose which can be used to produce ATP in the muscles Nutrient Conversion to Fat Excess carbohydrate intake is converted to fat in the liver o After repleting glycogen stores o And after restoring normal blood glucose Excess protein and fat also can result in fat deposition The liver releases these fatty acids into the blood Fat cells adipocytes take up these fatty acids and store them Inadequate CHO in the diet problems When there is inadequate carbohydrates in the diet the body has 2 o Having no glucose the body turns to protein and fat to make o Without carbs in the diet fat cannot be broken down completely for energy and the body converts its fats into some glucose ketone bodies Ketosis results when an undesirable high concentration of ketone bodies accumulate in the blood Minimum amount sent by the DRI committee is 130 grams a day for an average sized person Diabetes Type 1 IDDM o Characterized by an immune response to pancreatic beta cell o Eventually the pancreas stops making insulin o Often starts early in life Type 2 NIDDM o Characterized by insulin resistance the insulin is there but it doesn t work to foster glucose uptake by the cells o Occurs later in life adult onset Blood glucose values Normal 100 mg dL Prediabetes 100 125 mg dL Diabetes 125 mg dL Complication of diabetes Blindness Kidney disease Heart disease Nerve damage Increased infections Amputation of limbs Alternative sweeteners Naturally occurring sweeteners o Corn syrup high fructose o Molasses o Levulose fructose or fruit sugar o Honey o Sugar alcohols High fructose corn syrup Used by body like any other sugar No evidence that it is preferentially stored as fat 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 inexpensive High fructose corn syrup and the environment Corn is grown as monoculture which depletes soil of nutrients requires higher amounts of pesticides and fertilizer Processing corn into HFCS is energy intensive Scaling back on consumption of HFCS is good for you and good for the environment Lipids Functions of Lipids 10 10 2012 Natures way of condensing energy stores also insulates protects organs Source of calories 9 calories gram Flavor and tenderness of food Slow stomach emptying more satiating Source of essential fatty acids Types of lipids Triglycerides Phospholipids Sterols Phospholipids Glycerol 2 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 is in cell membranes Sterols Large molecules consisting of interconnected rings of carbon atoms with side chains of carbon hydrogen and oxygen attached Cholesterol o Found in all animal cell membranes o Nonessential o Forms plaques that cause atherosclerosis o Cholesterol serves as the raw material for Bile Vitamin D Steroid hormones including the sex hormones Triglycerides Main form of fat in food Made up of glycerol backbone and three fatty acids Fatty acids classified by length of carbon atoms and location of double bonds organization of hydrogen around the double bonds Saturated fatty acid Unsaturated fatty acid A fatty acid carrying the maximum of hydrogen atoms A fatty acid with less than maximum hydrogen atoms Monounsaturated fatty acid Polyunsaturated fatty acid Trans fatty acids Fatty acids with unusual shapes Arise when polyunsaturated oils are hydrogenated o Advantage control
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