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Understanding Nutrition Chapter 4

Terms in this set (65)

carbohydrates
compounds composed of carbon, oxygen, and hydrogen arranged as monosaccharides or multiples of monosaccharides. Most carbohydrates have a ratio of one carbon molecule to one water molecule
sugars
simple carbohydrates composed of monosaccharides, disaccharides, or both.
monosaccharides
carbohydrates that generally form a single ring and are with six atoms of carbon (C6H12O6). The three monosaccharides are glucose, fructose, and galactose.
glucose
a monosaccharide, sometimes known as blood sugar in the body or dextrose in foods. (ose = carbohydrate)
fructose
a monosaccharide; sometimes known as fruit sugar or levulose. it is found abundantly in fruits, honey, and saps.
galactose
a monosaccharide; part of the disaccharide lactose
disaccharides
pairs of monosaccharides linked together. (glucose occurs in all three types; the second member of the pair is fructose, galactose, or another glucose)
condensation
a chemical reaction in which water is released as two molecules combine to form one larger product. This chemical reaction occurs to make a disaccharide, by linking two monosaccharides together. A hydroxyl (OH) group from one monosaccharide and a hydrogen atom (H) from the other combine to create a molecule of water. The two originally separated monosaccharides link together with a single oxygen (O).
hydrolysis
a chemical reaction in which one molecule is split into two molecules, with hydrogen (H) added to one and a hydroxyl group (OH) to the other from water (H2O). a chemical reaction that occurs commonly during digestion to break down disaccharides.
maltose
a disaccharide composed of two glucose units; sometimes known as malt sugar. This disaccharide produces when starch breaks down during carbohydrate digestion.
sucrose
a disaccharide composed of glucose and fructose; commonly known as table sugar, beet sugar, or cane sugar. This disaccharide occurs in many fruits and some vegetables and grains. It is sweetest of the disaccharides (because it contains fructose).
lactose
a disaccharide composed of glucose and galactose; commonly known as milk sugar. It is the principle carbohydrate of milk.
polysaccharides
compounds composed of many monosaccharides linked together. The three main types are glycogen, starches, and fibers.
glycogen
an animal polysaccharide composed of glucose; a storage form of glucose manufactured and stored in the liver and muscles. Glycogen is not a significant food source of carbohydrate and is not counted as a dietary carbohydrate in foods. It is only found in some meats (not plants). Glycogen performs an important role in the body (storing glucose for future use). Glycogen is made up of many glucose molecules linked in branched chains. When the hormonal message "release energy" arrives at a liver or muscle cell, enzymes respond by attacking the branches of glycogen, making glucose available.
starches
plant polysaccharides composed of many glucose molecules. Plants store glucose as starches. Found in wheat, rice, root crops, and legumes. When you eat a plant, your body hydrolyzes the starch to glucose and uses the glucose for its own energy purposes.
dietary fibers
in plant foods (vegetables, fruits, legumes, and grains), the nonstarch polysaccharides that are not digested by human digestive enzymes (because of the different bonds), although some are digested by GI tract bacteria.
soluble fibers
nonstarch polysaccharides that dissolve in water to form a gel. An example is pectin, from fruit, which is used to thicken jellies. These fibers are also fermentable in the colon and are commonly found in oats, barley, legumes, and citrus fruits. These fibers are associated with protecting against heart disease and diabetes by lowering cholesterol and glucose levels.
viscous
a gel-like consistency; created by soluble fibers
fermentable
used to describe fibers that can be broken down by bacteria in the GI tract.
insoluble fibers
nonstarch polysaccharides that do not dissolve in water. Examples include tough, fibers structures found in strings of celery and the skins of corn kernels. These fibers do not form gel (non-viscous), and are less readily fermented. Found mostly in whole grains (bran) and vegetables. These fibers promote bowel movements, alleviate constipation, and prevent diverticular disease.
functional fibers
fibers extracted from plants and added to foods or supplements, that have beneficial health effects. For example cellulose supplements used to alleviate constipation (not the cellulose added to cereal)... the ones added to cereal are just dietary fibers.
Total fiber
dietary fibers + functional fibers
resistant starches
starches that escape digestion and absorption in the small intestine of healthy people. They are considered dietary fibers (not functional fibers). Similar to insoluble fibers, these starches may support a healthy colon. Found in whole grains, legumes, just ripened bananas, cooked potatoes, cooked pasta, and cooked rice.
phytic acid (phytate)
a nonnutrient components of plant seeds. It occurs in the husk of grains, legumes, and seeds and is capable of binding minerals in insoluble complexes in the intestine, which the body excretes unused.
carbohydrate digestion
enzymes hydrolyze starch's long chains into shorter chains, the short chains to disaccharides, and the disaccharides to monosaccharides. Starts in mouth, ceases in stomach, and continues in small intestine. In the small intestine, carbohydrate digestion starts by when the enzymes from pancreatic amylase break down polysaccharides to shorter glucose chains and maltose. After this outer membranes of the intestinal cells have specific enzymes (maltase, sucrase, and lactase) to break down specific disaccharides into monosaccharides. In the large intestines, all that is left is fibers that will either be broken down by bacteria or leave the body.
amylase
an enzyme that hydrolyzes amylose (a form of starch). This enzyme is a carbohydrase that occurs in saliva
satiety
the feeling of fullness and satisfaction that occurs after a meal and inhibits eating until the next meal. This feeling especially occurs after consuming fibers because fibers delay gastric emptying.
maltase
an enzyme that hydrolyzes maltose
sucrase
an enzyme that hydrolyzes sucrose
lactase
an enzyme that hydrolyzes lactose
carbohydrate absorption
nutrient absorption of carbohydrates mostly occurs in the cells lining the small intestine. Glucose and galactose enter the cells lining the small intestines by active transport while fructose is absorbed through facilitated diffusion. As the blood from the small intestine circulates through the liver, cells take up fructose and galactose and convert them into compounds within the same metabolic pathways as glucose. While fructose and galactose are metabolized on the liver, glucose is sent out to the body's cells for energy.
lactose intolerance
a condition that results from the inability to digest the milk sugar lactose; characterized by gas, bloating, abdominal discomfort, and diarrhea. Basically the intestinal cells do not produce enough of the enzyme lactase to ensure that the disaccharide lactose is digested and absorbed efficiently. When the body fails to produce enough lactase, the lactose molecules remain in the intestine undigested, attracting water causing bloating. The undigested lactose becomes food for intestinal bacteria, which multiply and produce, irritating acid and gas.
lactase deficiency
a lack of the enzyme required to digest the disaccharide lactose into its component monosaccharides (glucose and galactose). May develop when the intestinal villi are damaged by disease, certain medicines, and malnutrition.
kefir
a fermented milk created by adding Lactobacillus acidophilus and other bacteria that break down lactose to glucose and galactose, producing a sweet, lactose free product.
storing glucose as glycogen
when blood glucose rises, the liver cells link excess glucose molecules by condensation reactions into long, branching chains of glycogen. When blood glucose falls, the liver cells break down glycogen by hydrolysis reactions into single molecules of glucose and release them into the bloodstream. This glucose becomes available to supply energy. The liver and muscle cells store glucose as glycogen and release glucose when needed.
using glucose for energy
a series of reactions break glucose into smaller compounds that yield energy when broken down completely to carbon dioxide and water.
gluconeogenesis
the making of glucose from a noncarbohydrate such as amino acids (from proteins) or glycerol. Occurs when we do not consume enough carbohydrates (which provide glucose).
protein-sparing action
the action of carbohydrate (and fat) in providing energy that allows protein to be used for other purposes.
ketone bodies
acidic compounds produced by the liver during the break down of fat when carbohydrate is not available. ketone bodies provide an alternative fuel source during starvation. ketone bodies are fat fragments that combine together and accumulate in the blood causing ketosis.
ketosis
an undesirably high concentration of ketone bodies in the blood and urine. Because ketone bodies are acidic, ketosis disturbs the body's normal acid-base balance.
acid-base balance
the equilibrium in the body between acid and base concentrations
using glucose to make fat
when glucose is extra, fat is created. The liver breaks down glucose into smaller molecules and puts them into the more permanent energy storage compound - fat. The fat then travels to fatty tissues of the body for storage.
glucose homeostasis
the body maintains blood glucose within its limits that permit the cells to nourish themselves. Blood glucose homeostasis is regulated by two hormones; insulin and glucagon
insulin
a hormone secreted by special cells in the pancreas in response to elevated blood glucose concentration. Insulin controls the transport of glucose from the bloodstream into the muscle and fat cells. The amount of insulin secreted corresponds with the rise in glucose. As the circulating insulin contacts the body's cells, receptors respond by ushering glucose from the blood into the cells. Most of the cells use the glucose for their own energy, while the liver and muscle tissues store glucose as glycogen for storage. Elevated blood glucose returns to normal levels as excess glucose is stored as glycogen and fat.
glucagon
a hormone secreted by special cells in the pancreas in response to low blood glucose concentration. Glucagon signals release of glucose from liver glycogen stores in order to raise blood glucose.
epinephrine
a hormone of the adrenal gland that modulates the stress response; formerly called adrenaline. When the body experiences steps, epinephrine acts quickly to ensure that all body cells have energy fuel in emergencies. Epinephrine works to release glucose from liver glycogen to the blood.
diabetes
metabolic disorder characterized by elevated blood glucose resulting from insufficient insulin, ineffective insulin, or both. The complete term is diabetes mellitus. When blood glucose levels are higher than normal, but below diagnosis of diabetes, the condition is called prediabetes.
type 1 diabetes
the less common type of diabetes in which the pancreas produces little or no insulin.
type 2 diabetes
the more common type of diabetes in which the cells fail to respond to insulin. Usually accompanies obesity and results from insulin resistance coupled with insufficient insulin secretion.
hypoglycemia
an abnormally low blood glucose concentration. It is usually a consequence of poorly managed diabetes; too much insulin, strenuous physical activity, inadequate food intake, or illness.
glycemic response
the extent to which a food raises the blood glucose concentration and elicits an insulin response. Glycemic response refers to how quickly glucose is absorbed after a person eats, how high blood glucose rises, and how quickly it returns to normal. Slow absorption, a modest rise in blood glucose, and a smooth return to normal are desirable.
glycemic index
a method of classifying foods according to their potential for raising blood glucose. Different foods elicit different glycemic responses.
dental caries
decay of teeth. Can occur from added sugars and from the breakdown of starches in the mouth. Bacteria in the mouth ferment the sugars and, in the process, produce an acid that erodes tooth enamel, causing tooth decay. The longer the food stays in the mouth, the more likely this is to happen (stickier foods stay longer and increase odds). It also depends on how often sugar is eaten (non sugary foods can help sugar from tooth surfaces... so sugary foods should be eaten with meals, not in between). Milk product help in preventing tooth decay by neutralizing acids, stimulating salivary flow, inhibiting bacterial activity, and remineralizing damaged enamel... (caries = rottenness)
factors contributing to dental caries
the bacteria that reside in dental plaque, the saliva that cleanses the mouth, the minerals that form the teeth, and the foods that remain after swallowing
dental plaque
a gummy mass of bacteria that grows in teeth and can lead to dental carries and gum disease.
artificial (nonnutritive) sweeteners
sugar substitutes that provide virtually no energy; sometimes called nonnutritive sweeteners (ex: stevia).
Acceptable Daily Intake (ADI)
the estimated amount of a sweetener that individuals can safely consume each day over the course of a lifetime without adverse effects.
sugar alcohols
sugar like compounds that can be derived from fruits or commercially produced from dextrose; also called polls. Examples include erythritol, isomalt, lactitol, Maltitol, mannitol, sorbitol, and xylitol. Often are in "sugar-free" or reduced kcalorie products. Sugar alcohols contain fewer kcalories than sugars. Because they yield energy, they are sometimes referred to as nutritive sweeteners. they have a low glycemic response because they are slower to enter blood stream compared to sugars. They can cause gas and diarrhea because some of the sugar alcohols might not be absorbed and have to be broken down by bacteria. They also do not contribute to dental caries (found often in gum and mints).
nutritive sweeteners
sweeteners that yield energy (unlike nonnutritive sweeteners), including both sugars and sugar alcohols.
describe how added sugars can contribute to health problems
sugars increase risk of dental caries, excessive intakes replace needed nutrients and fiber, and sugars contribute to obesity when energy intake exceeds needs.
health benefits of, and recommendations for, starches and fibers
a diet rich in starches and fibers supports efforts to control body weight and prevent heart disease, some cancer, diabetes, and GI disorders. Recommendations urge people to eat plenty of whole grains, vegetables, legumes, and fruits enough to provide 50% of the daily energy intake.
fiber's effect on heart disease
foods rich in soluble fibers (bran, oats, barley, a legumes) lower blood cholesterol by binding with bile acids in the GI tract and thereby increasing their excretion. Consequently, the liver must use its cholesterol to make new bile acids. In addition, the bacterial by-products of fiber fermentation in the colon also inhibit cholesterol synthesis in the liver (lowering blood cholesterol).
fiber's effect on diabetes
high fiber foods (whole grains) can prevent type 2 diabetes. When soluble fibers trap nutrients and delay their transit through the GI tract, glucose absorption is slowed, which helps to prevent glucose surge and rebound.
fiber's effect on GI health
fiber stimulates the GI tract so that they can retain their strength and resist bulging into pouches known as diverticula. Insoluble fibers such as cellulose (found in cereal brans, fruits, and vegetables)increase stool weight, ease passage, and reduce transit time.
Fiber's effect on cancers
fibers may help prevent colon cancer by diluting, binding, and rapidly removing potential cancer-causing agents from the colon. In addition, soluble fibers stimulate bacterial fermentation of resistant starch and fiber in the colon, a process that produces short-chain fatty acids that lower the pH. These small fat molecules activate cancer-killing enzymes and inhibit inflammation in the colon.
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