Part 2 Carboyhdrates 09 27 2010 Carbohydrates Functions o Main source of energy for cells o Spare protein o Add bulk to foods o Provide energy fiber Sources grains fruits dairy products Simple carbohydrates Sugars o Molecule with 6 carbon atoms and oxygen and hydrogen Complex carbohydrates Starches and fiber o Sometimes called polysaccharides o Long chains of sugar units Common dietary carbohydrate sources Rice wheat maize potato apple oranges grapes cane beet honey corn syrup milk Poly stratch starch Di Maltose Sucrose Sucrose Lactose Mono Glucose Fructose Galactose Glucose Glucose Glucose Monosaccharides Six carbon molecules o Glucose the body s predominant fuel o Fructose fruit sugar o Galactose one of the two components of the milk sugar lactose Disaccharides Sucrose Lactose Maltose Polysaccharides Glycogen o A combination of glucose and fructose o A combination of glucose and galactose o A combination of glucose and glucose 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 Lower Cholesterol and Heart Risk A High fiber diet o Liver uses blood cholesterol to make bile gallbladder stores bile Intestine bile aids digestions binds to fiber A little cholesterol in bile reabsorbed into the blood or fiber and bile excreted in feces B Low fiber diet o Liver uses blood cholesterol to make bile Gallbladder stores bile Intestine bile aids digestion Much of the cholesterol in bile reabsorbed into the blood or little bile excreted How Carbohydrates in Food Becomes Glucose in the Body Fiber starch and sugars enter small intestine o Pancreatic amylase breaks down starch to disaccharides o Enzymes on intestine wall break down di to mono saccharides o Monosaccharides enter capillary go to liver o Liver converts galactose and fructose to glucose o 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 infection Undigested lactose becomes fuel for intestinal bacteria that in turn Infants and small children have the enzyme lactase so they can 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 in 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 three carbon fragments and energy The three 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 then enters the Krebs Cycle and electron transport chain which yields 32 ATP CO2 and water Glycogen Metabolism 1 3 of all glycogen is stored in the liver The other 2 3 is stored in muscles Each glycogen molecule 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 Carbohydrates in the Diet When there is an inadequate carbohydrate in the diet the body has two problems some glucose o Having no glucose the body turns to protein and fat to make o Without carbohydrate in the diet fat cannot be used correctly for energy and the body converts its fats into ketone bodies Ketosis results when an undesirable high concentration of ketone bodies accumulate in the blood Minimum amount set 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 B cells 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 does not work to foster glucose uptake by the cells o Occurs later in life Blood Glucose Values Normal 100 mg dL Prediabetes 100 125 mg dL Diabetes 125 mg dL Complications of Diabetes Blindness Kidney disease Heart disease Nerve damage Increased infections Amputations 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 high fructose corn syrup or corn sugar is just one of these added sugars used by food industry because 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 high fructose corn syrup is energy intensive Scaling back on consumption of high fructose corn syrup is good for you and good for the environment Lipids Functions of Lipids 09 27 2010 Natures way of condensing energy stores o Also insulates protects organs Source of calories 9kcal gram Flavor and tenderness of food Slows stomach emptying more satiating Source of essential fatty acids Types of Lipids Triglycerides Phospholipids Sterols Phospholipids Glycerol two fatty acids phosphorous Phosphorus part makes it soluble in water Fatty acids make it soluble in fat Therefore can serve as an emulsifier Key role is in cells 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
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