Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Carbohydrates

What Are Carbohydrates? Carbohydrates One of the three macronutrients A primary energy source, especially for nerve cells Composed of carbon, hydrogen, oxygen Good sources include fruits and vegetables

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings What Are Carbohydrates? Glucose The most abundant carbohydrate Produced by plants through photosynthesis

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Photosynthesis C 6 H 12 O 6 6 CO 2 (gas) + 12 H 2 O(liquid) + photons→ C 6 H 12 O 6 (aqueous) + 6 O 2 (gas) + 6 H 2 O(liquid) Visuals unlimited

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings What Are Carbohydrates? Simple carbohydrates Contain one or two molecules Monosaccharides contain only one molecule Glucose, fructose, galactose Disaccharides contain two molecules Lactose, maltose, sucrose

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Monosaccharides

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Disaccharides

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings What Are Carbohydrates? Complex carbohydrates Long chains of glucose molecules Hundreds to thousands of molecules long Also called polysaccharides Starch, glycogen, most fibers

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Complex Carbohydrates

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Complex Carbohydrates Starch Plants store carbohydrates such as starch We break down starch to glucose Grains, legumes, and tubers are good sources of starch in our diet Amylopectin endosperm germ bran

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Whole Grains endosperm germ bran Bran= Roughage Fiber B-vitamins Trace minerals Phytochemicals Endosperm= Energy Carbohydrates Protein Germ= Nutrients B-vitamins Vitamin E Trace Minerals Phytochemicals Unsaturated lipids Ex: wheat, barley, oat grains

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Complex Carbohydrates Glycogen Animals store carbohydrates as glycogen Stored in the liver and muscles Not found in food and therefore not a source of dietary carbohydrate

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Complex Carbohydrates Fiber Dietary fiber is the non-digestible part of plants Grains, rice, seeds, legumes, fruits Functional fiber is carbohydrate extracted from plants and added to food Cellulose, guar gum, pectin, psyllium Total fiber = dietary + functional fiber

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Digestion of Carbohydrates Salivary amylase Enzyme that begins carbohydrate digestion in the mouth Breaks carbohydrates down to maltose  There is no digestion of carbohydrates in the stomach.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Digestion of Carbohydrates

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Digestion of Carbohydrates Most chemical digestion of carbohydrates occurs in the small intestine. Pancreatic amylase Enzyme produced in the pancreas and secreted into the small intestine Digests carbohydrates to maltose

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Digestion of Carbohydrates Additional enzymes in the small intestine digest disaccharides to monosaccharides: (1) maltase (2) sucrase (3) lactase Monosaccharides are absorbed into the cells lining the small intestine and then enter the bloodstream.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Digestion of Carbohydrates All monosaccharides are converted to glucose by the liver. Glucose circulating in the blood is our primary energy source. Excess glucose is converted to glycogen by the liver.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Storage of Glycogen

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Digestion of Carbohydrates We do not have the enzymes necessary to digest fiber. Bacteria in the large intestine can break down some fiber. For humans, most fiber remains undigested and is eliminated with feces.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Blood Glucose The level of glucose in the blood must be closely regulated. Two hormones, insulin and glucagon, control the level of glucose in the blood.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Blood Glucose: Insulin Insulin Produced by beta cells of the pancreas Helps cells take in glucose from the blood Stimulates the liver to take up glucose and convert it to glycogen

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Blood Glucose: Insulin

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Blood Glucose: Glucagon Glucagon Produced by alpha cells of the pancreas Stimulates the breakdown of glycogen to glucose to make glucose available to cells of the body Stimulates gluconeogenesis – the production of glucose from amino acids

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Blood Glucose: Glucagon

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Blood Glucose Glycemic index A food’s ability to raise blood glucose levels Foods with a low glycemic index: Are better for people with diabetes Are generally higher in fiber May reduce the risk of heart disease and colon cancer

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Glycemic index ClassificationGI rangeExamples Low GI55 or lessMost fruit and veggies (not potato), basmati rice, oats, all- bran Medium GI56-69Sucrose, Mars bar High GI70 or more Corn flakes, baked potato, jasmine rice, white bread, white rice

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Role of Carbohydrates Energy Each gram of carbohydrate = 4 kcal Red blood cells rely only on glucose for their energy supply Both carbohydrates and fats supply energy for daily activities Glucose is especially important for energy during exercise

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Role of Carbohydrates Energy Sufficient energy from carbohydrates prevents production of ketones as an alternate energy source Excessive ketones can result in high blood acidity and ketoacidosis High blood acidity damages body tissues

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Role of Carbohydrates Energy Insufficient carbohydrate intake causes the body to find an alternate source of glucose Often proteins are used for gluconeogenesis – the production of new glucose

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Role of Carbohydrates Fiber May reduce the risk of colon cancer May reduce the risk of heart disease May enhance weight loss Help prevents hemorrhoids, constipation, and diverticulosis

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings How Much Carbohydrate? Recommended Dietary Allowance (RDA) is 130 grams/day just to supply the brain with glucose % of daily calorie intake should be in the form of carbohydrates. Focus on foods high in fiber and low in added sugars.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Simple vs. Complex Carbs Diets high in simple sugars: Can cause dental problems such as cavities and gum disease Are associated with increased levels of “bad cholesterol” Are associated with decreased levels of “good cholesterol”

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Simple vs. Complex Carbs The Adequate Intake (AI) of fiber is 14 grams for every 1,000 kcal in the diet. Most Americans eat only half the recommended amounts of fiber. Whole grain foods are a more healthful choice than foods with added sugar.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Alternative Sweeteners Nutritive sweeteners Contain 4 kcal energy per gram Sucrose, fructose, honey, brown sugar, sugar alcohols Non-nutritive (alternative) sweeteners Provide little or no energy

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Alternative Sweeteners Acceptable Daily Intakes (ADI) have been established for: aspartame sucralose acesulfame-K No ADI has been set for saccharin but it has been removed from the list of cancer-causing agents.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Alternative Sweeteners

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Health Disorders Three health disorders related to carbohydrate metabolism are Diabetes Hypoglycemia Lactose intolerance

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Diabetes Inability to regulate blood glucose levels Three types: Type 1 diabetes Type 2 diabetes Gestational diabetes Untreated diabetes can cause nerve damage, kidney damage, blindness, and can be fatal

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Diabetes Type 1 diabetes Accounts for 10% of all cases Patients do not produce enough insulin Causes hyperglycemia – high blood sugar (glucose) Requires insulin injections May be an autoimmune disease

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Diabetes Type 2 diabetes Most diabetics have Type 2 diabetes Body cells are insensitive or unresponsive to insulin Excess insulin is often produced Causes hyperglycemia because cells cannot take in the glucose from the blood

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Diabetes Type 2 diabetes Cause is unclear but genetics, obesity, and physical inactivity play a role Treated with diet, exercise, and possibly oral medications Healthy lifestyle choices may prevent or delay onset of type 2 diabetes

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Hypoglycemia Low blood sugar (glucose) Reactive hypoglycemia results when too much insulin is produced after a meal Causes shakiness, sweating, anxiety Fasting hypoglycemia results when too much insulin is produced even when the patient has not eaten

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Lactose Intolerance Lactose intolerance Insufficient lactase production causes an inability to digest lactose found in dairy products Symptoms include intestinal gas, bloating, nausea, cramping, diarrhea Lactose intolerant people may need to find alternate sources of calcium

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Why are carbs so important? Neurons from entorhinal cortex (Limbic System) ©1998 Dr. Norberto Cysne Coimbra M.Sc., Ph.D., Laboratory of Neuroanatomy and Neuropsychobiology, Faculty of Medicine of Ribeirão Preto of the University of são Paulo; Neuroscience Art Galleries Brain cells require two times as much energy as other cells in your body! A lack of glucose affects your ability to think and remember.