Chapter 4: Carbohydrates Basic steps in blood glucose regulation, including the role of insulin and glucagon Diabetes is characterized by a persistent high blood glucose concentration Diet and physical activity is helpful Insulin: a hormone produced in the pancreas; among other processes, insulin increases the synthesis of glycogen in the liver and the movement of glucose from the bloodstream into body cells The main medication employed Glucagon: a hormone made by the pancreas that stimulates the breakdown of glycogen in the liver into glucose; this ends up increasing blood glucose Keeps the blood glucose from falling too low Opposite effect of insulin Simple carbohydrates/ simple sugars Monosaccharides: once absorbed into the small intestine and delivered to the liver, much of the fructose and galactose is converted to glucose Glucose: a six-carbon monosaccharide that usually exists in a ring form Comes from the break down of starches and sucrose/table sugar Also known as dextrose Important source of energy Sugars and other carbs are converted to glucose in the liver Fructose: a six-carbon monosaccharide that usually exists in a ring form Also known as fruit sugar Fructose is absorbed by the small intestine and then transported to the liver when it is metabolized Converted to glucose and sometimes fat Galactose: a six-carbon monosaccharide that usually exists in a ring form Closely related to glucose Rarely found in nature by itself, usually bonded to glucose to form lactose After absorbed into the body, galactose goes to the liver where it is transformed to glucose or further metabolized into glycogen Disaccharides: when digested, these yield their component monosaccharides Sucrose= glucose+ fructose Table sugar Maltose= glucose+ glucose Produced in the digestion of food Fermentation: the conversion of carbohydrates to alcohol, acids, and carbon dioxide without the use of oxygen Lactose= glucose+ galactose Milk sugar Complex Carbohydrates Polysaccharides: carbohydrates containing many glucose units, from 10 to 1000 or more Starch: a carbohydrate made up of multiple units of glucose attached together in a form that can be digested by the body Amylose: a digestible straight-chain type of starch composed of glucose units Amylopectin: a digestible branched-chain type of starch composed of glucose units Fiber: substance that are found in plant foods that are not digested by the processes that take place in the stomach or small intestine Adds bulk to feces Cellulose, hemicellulose, pectin, gum, mucilage, and non-carbohydrate lignin Not broken down by human digestive enzymes Soluble fiber is fermented by bacteria in the large intestine Glycogen: a carbohydrate made of multiple units of glucose with a highly branched structure Also know as animal starch Glycogen is the storage form of glucose in humans and is synthesized (and stored) in the liver and muscles Why are some foods that are high on carbohydrates, such as cookies and nonfat milk, not considered to be concentrated sources of carbohydrates? They are diluted by fats or proteins Describe digestion of the various types of carbohydrates in the body Digestion of carbs: Mouth Salivary amylase Breaks down starch to shorter saccharides Digestion of carbs through the mouth?prolonged chewing Digestion of carbs: stomach Acidic environment, no further starch digestion Digestion of carbs: small intestine Pancreas releases enzymes Pancreatic amylase breaks starch into glucose Absorptive cells release enzymes Maltase: Maltose glucose + glucose Lactase: Lactose glucose + galactose Sucrase: Sucrose glucose + fructose Monosaccharides are absorbed and transported by the portal vein to the liver Describe why some people are unable to tolerate high intakes of milk Their bodies do not properly produce lactase which is an enzyme that breaks down lactose What are the important roles that fiber plays in the diet? Adds mass to feces (which eases the ?eliminating? process) Control blood glucose in diabetic people Lowers blood cholesterol Adds mass to meals What, if any, are the proven ill effects of sugar in the diet? Dental problems, obesity, hyper activity Why do we need carbohydrates in the diet? Supplies energy (glucose) Red blood cells, brain, central nervous system Protein sparing: spares/prevents protein from breaking down to provide energy needs Prevents ketosis (incomplete breakdown of fats) Summarize current carbohydrate intake recommendations RDA is 130 g/day for adults Typical American diet is 180-330 g/day Food & Nutrition Board suggests 45%-65% of total calories should be carbohydrates List three alternatives to simple sugars for adding sweetness to the diet Nutritive sweeteners (provide calories) Brown sugar, maple syrup, turbinado sugar (raw sugar), honey Alternative sweeteners (no calories & much sweeter) Sweet N? Low (saccharin), Acesulfame, neotame, Aspartame (equal)
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