BIOL 233- Goals for Chapter 4 PDF

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Chapter 4 Define and Use: 

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Sugar o o o Starch o

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One of the two main types of carbohydrates in food are simple carbs (sugars) It is a source of a carbohydrates and energy Added to many nutrient rich foods to improve their flavor, texture, and appeal Starch is the major storage form of carbohydrate in plants; starch is composed of long chains of glucose molecules in a straight (amylase) or branching (amylopectin) arrangement Plants store energy as starch for use during growth and reproduction Rich sources of starch are:  Grains (Wheat, rice, corn, oats, millet, and barley)  Legumes (Peas, beans, and lentils)  Tubers (Potatoes, yams, and cassava) When starch is added to foods, it gives a moist, gelatinous texture to food Starch takes two main forms in plants:  Amylase is made up of long, unbranched chains of glucose molecules  Ex: Wheat flour contains a higher proportion of amylose  Amylopectin is made up of branched chains of glucose molecules  Ex: Cornstarch contains a higher proportion of amylopectin Though the body usually digests starch easily, there is a subgroup known as resistant starches which are not digested in the small intestine

Fiber o All types of plant foods contain dietary fiber o Dietary fiber consists of nondigestible carbohydrates and lignins that are intact and intrinsic in plants o They are polysaccharides, but aren’t digested in the human GI tract o Functional fibers are isolated, nondigestible carbs that have beneficial physiological effects o Fiber is NOT found in animal foods o Total fiber is the sum of dietary fiber and functional fiber and classified into two types:  Soluble fiber dissolves easily in water, and when it attracts water in the GI tract it becomes gel-like and slows digestion and absorption  Insoluble fibers do not dissolve in water, and these fibers add bulk to stool in the colon and decrease intestinal transit time of food through the GI tract Simple Carbohydrate o Simple carbs occur naturally as simple sugars in fruits, milk, and other foods o The two main types of sugars are:

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Monosaccharides, which consists of a single molecule Disaccharides, which consist of two sugar molecules chemically joined together Complex carbohydrate o Complex carbs are chains of more than two sugar molecules o Short carb chains can have as few as three monosaccharide molecules, but long chains, the polysaccharides, can contain hundreds or even thousands Glucose o The most abundant simple carbohydrate unit in nature, also referred to as dextrose o Plays a key role in both foods and the body o Glucose gives a mild sweet flavor to food, and is usually joined to other sugars to form disaccharides, starch, or dietary fiber o In the body, glucose supplies energy to cells, and the body regulates blood glucose levels (blood sugar) to ensure a constant fuel source for vital body functions o Only fuel used by the brain Fructose o (Levulose or fruit sugar), Fructose is the sweetest of all sugars and occurs naturally in fruits and vegetables o Normally added to foods in the form of high-fructose corn syrup and content of the sweetener is approximately 55% Sucrose o (table sugar); composed of one molecule of glucose and one molecule of fructose o Sucrose provides some of the natural sweetness of honey, maple syrup, fruits, and vegetables o When food labels lists sugar as an ingredient, it commonly refers to sucrose Lactose o Composed of one molecule of glucose and one molecule of galactose o (Milk sugar) Major sugar in milk and dairy products Glycogen o (Animal starch) Glycogen is the storage form of carb in living animals o It plays an important role in our bodies as a readily mobilized store of glucose o Skeletal muscle and the liver are the two major sites of glycogen storage o In muscle cells, glycogen provides a reservoir of glucose for strenuous muscular activity o Liver cells use glycogen to regulate blood glucose levels Pancreatic Amylase o Starch-digesting enzyme secreted by the pancreas Cellulose o Cellulose gives plant cell walls their strength and rigidity o Form the woody fibers that support tall trees and also forms the brittle shafts of hay and straw and the stringy threads in celery Insulin

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o Produced by beta cells in the pancreas, this polypeptide hormone stimulates the uptake of blood glucose into muscle and adipose cells, the synthesis of glycogen in the liver o Insulin acts like a key, “unlocking” the cells of the body and allowing glucose to enter and fuel them Glucagon o Produced by alpha cells in the pancreas, this polypeptide hormone promotes the breakdown of liver glycogen to glucose, increasing blood glucose o Glucagon is stimulated by low blood glucose levels and by growth hormone o It also stimulates gluconeogenesis, or the synthesis of glucose from protein Glycemic Index o Measure of the effect of food on blood glucose levels o The ratio of the blood glucose value after eating a particular food to the value after eating the same amount of white bread or glucose Diabetes mellitus o A disease where the bodies do not produce enough insulin (Type 1) or do not use insulin properly (Type 2) Nutritive Sweetener o Nutritive sweeteners are digestible carbs and so provide energy o They include mono and disaccharides, and sugar alcohols from either natural or refined sources Nonnutritive sweeteners o Many times sweeter than nutritive sweeteners are o Their energy contribution is minimal because of the small amounts used

Important to Know  Most plant foods (fruits, vegetables, grains, beans) provide energy mainly as carbohydrates  Most of the world’s calories consumed come from carbohydrates  The USDA recommends that 45-65% of calories be from carbohydrates  Plants make carbs from water, carbon dioxide and the energy in sunlight  Only PLANT foods contain fiber (mostly the indigestible plant cell wall carbohydrate cellulose) Describe the relationship between sugar consumption ad hyperactivity in children Research studies have not found a consistent link between sugar and hyperactivity Carbs actually have a calming effect by increasing production of the sleep-inducing chemical serotonin Describe where and how carbohydrate digestion and absorption takes place 1. Carbohydrate digestion begins in the mouth; the action of salivary amylase in the mouth begins to digest starch to shorter glucose chains

2. Stomach acids halts carbohydrate digestion; as soon as food reaches the stomach, stomach acid inactivates the amylase, and proteases destroy the enzyme 3. Carbohydrate digestion resumes in the small intestine, where monosaccharides are absorbed; in the small intestine, pancreatic amylase completes the digestion of starch to maltose. Specific enzymes digest disaccharides to monosaccharides, which are absorbed into the bloodstream 4. Monosaccharides enter intestinal cells through a variety of transport proteins and use a facilitated diffusion to leave the cells and enter the blood stream; once in the bloodstream, the monosaccharides travel to the liver via the portal vein. The liver can convert fructose and galactose to glucose. The liver may form glucose into glycogen, burn it for energy, or release it to the bloodstream for use in other parts of the body Identify in what form the body stores excess glucose  To store excess glucose, the body assembles it into the long, branched chains of glycogen  Glycogen can be broken down quickly, releasing glucose for energy as needed Explain why very low carbohydrate diets can be dangerous     

With very low carbohydrate diets, the liver cannot break down fat completely so instead it produces small compounds called ketone When ketone bodies are produced more quickly than the body can use them, ketone levels build up in the blood and can cause a condition known as ketosis Ketosis is usually caused by very low carbohydrate diets, starvation, uncontrolled diabetes mellitus, and chronic alcoholism As the concentration of ketone bodies increase, the blood becomes too acidic The body loses water as it excretes excess ketones in urine, and dehydration is a common consequence of ketosis

Explain why, and describe how, blood glucose levels are tightly regulated, including the specific roles of insulin and glucagon o The body regulates blood glucose levels to maintain an adequate supply for glucose for cells o If blood glucose levels are too low, a person becomes shaky and weak; and if it’s too high, a person becomes sluggish and confused and have difficulty breathing o If the blood glucose levels are too high, then insulin is released to stimulate cells to take up glucose from the blood, and insulin stimulates liver and muscle cells to store glucose and glycogen o If blood glucose levels are too low, glucagon is released to stimulate liver cells to break down glycogen to glucose, glucagon also stimulates liver cells to make glucose from amino acids Explain why whole wheat flour is better than “enriched” white flour 

Whole wheat compared to white flour naturally has the level of fiber found in wheat whereas in white flour, most of the fiber has been stripped away during processing

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Whole wheat flour has less calories but also has more iron, calcium, protein and other nutrients compared to white flour

Describe the major benefits of fiber consumption   

Fiber helps control blood glucose levels and prevents constipation Improve cholesterol levels by lowering LDL cholesterol Lowers risk for metabolic syndrome and other diseases

Describe the major risks of excess sugar consumption  Major factor in overweight and obesity  A high sugar intake also contributes to dental caries, or cavities; the bacteria in the mouth feed on sugars, producing acid that eats away tooth enamel and dental structure  Risk of heart disease increases  Risk for diabetes increases when overconsumption of sugar in beverages and foods increase Examples of Foods in each carb category  High-Fiber o Brown Rice, whole fruits instead of fruit juices, legumes, lentils, pinto, kidney and black beans  Complex carbohydrates o Sweet potatoes, squash, pumpkin, oats  Simple carbs o Mangoes, raisins, milk, yogurt  Nutritive sweetener o White sugar, brown sugar, honey, maple syrup, high fructose corn syrup  Nonnutritive sweetener o Saccharin, aspartame, and acesulfame K; diet sodas, juices, sugar-free gum Choosing Carbs wisely  Best types of carbs are unprocessed and “natural” state ones such as raw vegetables. Sunflower seeds, walnuts, beans, rice, and whole grains are another important source of good carbohydrates to seek for in a diet  The carbs to avoid are the highly processed convenience foods which can lead to weight gain, obesity, heart disease, high cholesterol and even cancer. Most baked goods, snacks, candies, cakes, white sugar, and corn syrup are common foods loaded with bad carbs which you should try to avoid...