Chapter 5 - Carbohydrates Flashcards
The carbohydrate family includes… (3 things)
Sugar, Starch, and Fiber
Carbohydrates are composed of…
Carbon, Hydrogen, and Oxygen
What is the main source of carbohydrates?
Plants, which produce glucose during photosynthesis
Monosaccharide
Class of single sugars that aren’t broken down during digestion. Considered a simple sugar.
(CH2O)6
Disaccharide
Class of sugars formed by the chemical bonding of 2 monosaccharides. Considered a simple sugar.
(CH2O)12
What is the chemical formula for glucose?
C6h12O6 → (CH2O)6
Polysaccharide
Class of complex carbohydrates containing many glucose units, from 10 to 1000 or more.
Hexose
A carbohydrate containing 6 carbons
Glucose (AKA Dextrose)
Most abundant monosaccharide.
Most of it in our diet is linked with other sugars.
Fructose (AKA Levulose)
Monosaccharide found in fruits, vegetables, and honey.
Fructose accounts for how much of the total energy intake in North Americans?
9-11%
Galactose
Monosaccharide found most abundantly as a part of the disaccharide lactose (milk sugar)
What are three common sugar alcohols?
Sorbitol, Mannitol, Xylitol
Sugar alcohols derive from…?
Monosaccharides
Pentose
Carbohydrate with 5 carbons.
ex: Ribose and Deoxyribose
Condensation Reaction
Chemical reaction in which 2 molecules bond to form a larger molecule by releasing water.
Works by taking a (OH) from one sugar and taking an (H) from the other.
What are two of the C-O-C bonds?
Alpha Bonds and Beta Bonds
Which bonds cannot be easily broken down by the digestive enzymes in the small intestine?
Beta Bonds
Maltose
Disaccharide containing 2 glucose molecules joined by an alpha bond. Produces enzymes that break down polysaccharides stored in the seeds to sugar.
Sucrose
Common table sugar composed of glucose and fructose linked by an alpha bond. Found naturally in plants and can be purified to various degrees.
Oligosaccharides
Complex carbohydrates containing 3 to 10 simple sugar units
Raffinose
Indigestible oligosaccharide composed of 3 monosaccharides (galactose-glucose-fructose)
Stachyose
Indigestible oligosaccharide composed of 4 monosaccharides (galactose-galactose-glucose-fructose)
Raffinose and Stachyose are found in what foods?
Onions, cabbage, broccoli, whole wheat, legumes
Raffinose and Stachyose pass into the large intestine where…
they’re metabolized by bacteria, which produced gas and other by-products
Starch
Complex carbohydrate made of multiple units of glucose attached together in a form the body can digest
Fiber
Complex carbohydrate in foods of plant origin that is made of multiple units of glucose attached together in a form that cannot be broken down by digestion in the stomach or small intestine
Amylose
Digestible straight-chain type of starch made of multiple glucose units
Amylopectin
Digestible branch-chain type of starch made of multiple glucose units
Both amylose and amylopectin are…
plant starches, found in 1:4 ratios
Amylose’s bonds are broken by…
amylase enzymes
Amylopectin’s bonds are broken by…
alpha-dextrinase enzymes in the intestine
Glycogen (AKA Animal Starch)
Carbohydrate made of multiple units of glucose with a highly branched structure; the storage form of glucose in humans; is synthesized and stored in the liver and muscles.
Glycogen is broken down by…
enzymes in the body cells where it is stored
How much glycogen is stored in the liver, and how much is stored in the muscles?
90g (360 kcal) is stored in the liver; 300g (1200 kcal) is stored in the muscles
Total Fiber
Dietary and functional fiber in food
Dietary Fiber
Fiber found naturally in food
Functional Fiber
Fiber added to food to provide health benefits
Fiber is composed mainly of… (5 things)
nonstarch polysaccharides: cellulose, hemicelluloses, pectins, gum, and mucilages
Lignins
Non-carbohydrate components of dietary fibers
Fibers are made of which bonds?
Beta bonds; this means fiber is digested in the large intestine
Insoluble Fibers
Fibers that aren’t easily dissolved in water or metabolized by bacteria in the large intestine; includes cellulose, some hemicelluloses, and lignins.
What are some of the benefits of insoluble fibers?
They decrease intestinal transit time, constipation, diverticular disease, and colon cancer
Soluble Fibers (AKA Viscous Fibers)
Fibers that dissolve in water and can be metabolized (fermented) by bacteria in the large intestine; include pectin, gums, and mucilages.
What are some of the benefits of soluble (viscous) fibers?
They lower the levels of cholesterol and glucose in blood and they delay gastric emptying
What kind of sweeteners provide energy?
Nutritive sweeteners
High fructose corn syrup has what percent of fructose?
55%, can range from 40-90%
What are the two types of nutritive sweeteners?
Sugars (lactose, maltose, glucose, sucrose, invert sugar, fructose) and Sugar Alcohols (sorbitol, mannitol, xylitol)
What are the eight types of nonnutritive sweeteners?
Tagatose (Naturlose) Cyclamate Aspartame (Equal) Acesulfame-K (Sunette) Saccharin (Sweet'N Low) Sucralose (Splenda) Neotame Stevia (Truvia)
Which nonnutritive was banned in the United States in 1970?
Cyclamate
Acceptable Daily Intake (ADI)
Estimate of the amount of sweetener that an individual can safely consume daily over a lifetime.
Expressed a mg/kg of body weight per day.
What is the ADI for saccharin?
5mg/kg of body weight per day
What is the ADI for aspartame?
50mg/kg of body weight per day
What is the ADI for neotame?
18mg/kg of body weight per day
What is the ADI for acesulfame-K?
15mg/kg of body weight per day
What is the ADI for sucralose?
5mg/kg of body weight per day
What is the ADI for stevia?
4mg/kg of body weight per day
The Dietary Guidelines suggest limiting the amount of added sugars in your diet to __% of your energy intake.
6%
What is the adequate intake (AI) for fiber?
14g/1000kcal
What is the Daily Value (DV) for fiber?
25g/2000kcal
What is the recommended daily allowance (RDA) for carbohydrates?
130g/day, or 45-60% of total energy intake
What is the main function of glucose?
To act as a source of energy for body cells
Gluconeogenesis
Synthesis of new glucose by metabolic pathways in the cell. Amino acids derived from protein usually provide the carbons for this glucose.
Insulin
Hormone produced by beta cells in the pancreas. Among other processes, insulin increases the movement of glucose from the blood stream into body cells, increases the synthesis of glycogen in the liver, and decreases the breakdown of fat (lipids)
Ketone
Produced in the liver during the breakdown of fat when carbohydrate intake is very low
Ketone Bodies
Incomplete breakdown products of fat, containing 3 or 4 carbons
Ketosis
Condition of having a high concentration of ketone bodies and related breakdown products in the blood stream and tissues
Diverticula
Pouches that have extruded through the exterior wall of the large intestine
Diverticulosis
Condition of having many diverticula in the large intestine. Asymptomatic.
Diverticulitis
Inflammation of the diverticula, caused by acids produced by bacterial metabolism inside the diverticula. Symptomatic.
What are 4 things that indigestible carbohydrates do?
They…
- Promote bowel health
- Reduce obesity risk
- Enhance blood glucose control
- Reduce cholesterol absorption
What role does the mouth play in carbohydrate digestion and absorption?
Some starch is broken down to polysaccharide and disaccharide units by salivary amylase
What role does the stomach play in carbohydrate digestion and absorption?
Salivary amylase is inactivated by the acidity in the stomach. No further digestion can occur here.
What role does the pancreas play in carbohydrate digestion and absorption?
Pancreatic amylase and dextrinase are secreted into the small intestine to break polysaccharides from starch into disaccharides
What role does the small intestine play in carbohydrate digestion and absorption?
Enzymes in the wall of the small intestine break the disaccharides down into monosaccharides
What role does the liver play in carbohydrate digestion and absorption?
The absorbed monosaccharidse are transported to the liver by the portal vein
What role does the large intestine play in carbohydrate digestion and absorption?
Some soluble fiber is metabolized into acids and gases by bacteria in the large intestine
What role does the rectum and anus play in carbohydrate digestion and absorption?
Insoluble fiber escapes digestion and is excreted in feces
Monosaccharides (except fructose) are absorbed by…
Active Absorption
Fructose is absorbed by…
Facilitated Diffusion
Primary Lactose Intolerance
Insufficiency of lactase enzyme that breaks down lactose
Secondary Lactose Intolerance
Occurs when conditions of the small intestine damage the cells that produce lactase
Hyperglycemia
High blood glucose, above 126mg/dl of blood on a fasting basis
Hypoglycemia
Low blood glucose, below 50mg/dl of blood
What is the typical range for blood glucose?
70 to 100mg/dl of blood when fasting
Fasting Blood Glucose
Measurement of glucose levels in the blood taken after an 8-12 hour or overnight period without any food or caloric beverages (a fast)
Type 1 Diabetes
Autoimmune disease causing failure of the pancreas to produce insulin and an inability to control blood glucose levels
Type 2 Diabetes
Progressive disease characterized by insulin resistance or loss of responsiveness of body cells to insulin, resulting in hyperglycemia
Glucagon
Pancreatic hormone secreted in response to a decrease in blood glucose, prompting the breakdown of glycogen in the liver and promoting gluconeogenesis
Metabolic Syndrome (formerly Syndrome X)
Condition characterized by poor blood glucose regulation, hypertension, increase blood lipids, and abdominal obesity; usually accompanied by a lack of physical activity
Reactive Hypoglycemia (AKA Postprandial Hypoglycemia)
Low blood glucose that may follow a meal high in simple sugars, with corresponding symptoms of irritability, headaches, nervousness, sweating, and confusion
Fasting Hypoglycemia
Low blood glucose occurring after 8 or more hours of fasting
Glycemic Index (GI)
Blood glucose response of a given food, compared with a standard (typically, glucose or white bread)
Glycemic Load (GL)
Amount of carbohydrate in a food multiplied by the glycemic index of that food. The result is then divided by 100.
