Chapter 4 Flashcards
What are the functions of carbohydrates in the body?
Carbohydrates have six major functions within the body: Providing energy and regulation of blood glucose Sparing the use of proteins for energy Breakdown of fatty acids and preventing ketosis Biological recognition processes Flavor and Sweeteners Dietary fiber
What is the simplest unit of Carbohydrate and how they are made by plants?
Glucose The most abundant carbohydrate Produced by plants through photosynthesis Water, carbon dioxide, and energy from the sun are combined to produce glucose
Define simple and complex carbohydrates.
Simple carbohydrates Contain one or two molecules Monosaccharides contain only one molecule Glucose, fructose, galactose, ribose Disaccharides contain two molecules Lactose, maltose, sucrose Complex carbohydrates Long chains of glucose molecules Hundreds to thousands of molecules long Also called polysaccharides Starch, glycogen, most fibers
Identify the monosaccharides (there are 3), and disaccharides (there are 3), and what are the food sources of each?
Monosaccharides:
Glucose, Fructose, Galactose
Disaccharide:
Lactose=Glu+Gal
Maltose=Glu+Glu
Sucrose=Glu+Fru
What are the polysaccharides? Give examples of the different types.
Starch-glucose storage in plants, found in grains, legumes, and tubers
Glycogen-storage form of glucose in animals, stored in the liver and muscles
Fiber-forms the support structures leaves, stems, and plants
What is the storage form of carbohydrates in plants vs animals?
Animals:
Glycogen
Animals, including humans, store glucose as glycogen Stored in the liver and muscles Not found in food and therefore not a source of dietary carbohydrate
Plants:
Starch
Plants store glucose in the form of starch
We digest (break down) starch to glucose
Grains, legumes, and tubers are good sources of starch in our diet 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
Where are Carbohydrates stored in humans?
Stored in the liver and muscles
What is the preferred fuel for most body functions?
Red blood cells rely only on glucose for their energy supply
Brain needs glucose to function properly
Both carbohydrates and fats supply energy for daily activities
Glucose is especially important for energy during exercise
Describe digestion & absorption of carbohydrates: include each monosaccharide and the type of absorption.
Salivary amylase
Enzyme that begins carbohydrate digestion in the mouth Breaks carbohydrates down to maltose Disaccharides are not digested in the mouth
There is no digestion of carbohydrates in the stomach; stomach acid inactivates salivary amylase.
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
Additional enzymes in the small intestine digest disaccharides to monosaccharides.
These enzymes include maltase (breaks down maltose), sucrase (breaks down sucrose), and lactase (breaks down lactose).
Monosaccharides are absorbed into the cells lining the small intestine and then enter the bloodstream.
Fructose and galactose 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 and muscles. Once the storage capacity of the liver and muscles is reached, excess glucose is stored as fat.
Glucose is stored as glycogen in both liver and muscle. The glycogen stored in the liver maintains blood glucose between meals; muscle glycogen provides immediate energy to the muscle during exercise.
What happens to each monosaccharide after absorption?
x
Define/understand the differences for the Acceptable Macronutrient Distribution Range for carbohydrates, the RDA for carbohydrate, the Adequate Intake for fiber, and the recommended intake of added sugars.
Recommended Dietary Allowance (RDA) is 130 grams/day just to supply the brain with glucose. This does not include the amount of carbohydrate needed to support daily activities.
45-65% of daily calorie intake should be in the form of carbohydrates.
Added Sugars
Added sugar intake should be 25% or less of total kcals
Diets high in simple sugars:
Can cause dental problems such as cavities and gum disease
Are associated with increased levels of low-density lipoproteins (LDL, sometimes referred to as “bad cholesterol”) and triglycerides
Are associated with decreased levels of high-density lipoproteins (HDL, sometimes referred to as “good cholesterol”)
May contribute to obesity.
The Adequate Intake (AI) of fiber is 14 grams for every 1,000 kcal in the diet, approximately 25 grams/day for women and 38 grams/day for men.
Most Americans eat only half the recommended amount of fiber.
Increasing fluid intake as you increase you fiber intake is important to prevent constipation.
Food sources of fiber include whole grains, vegetables, fruits, nuts, and legumes.
Which hormone is released when your blood glucose levels fall too low?
Glucagon
Secreted by alpha cells of the pancreas Stimulates the breakdown of glycogen to glucose, which is then secreted to the bloodstream and transported to cells; raises blood glucose levels Stimulates gluconeogenesis – the production of new glucose from amino acids
Regulation of blood glucose by the hormone glucagon. When blood glucose levels are low, the pancreas secretes glucagon. Glucagon enters the cell, where it stimulates the breakdown of stored glycogen into glucose. This glucose is then released into the bloodstream.
Which hormone is released after a meal?
Insulin
Secreted by beta cells of the pancreas Helps cells take in glucose from the blood; lowers blood glucose levels Stimulates the liver and muscles to take up glucose and convert it to glycogen
Identify the energy source used when exercising at maximum intensity.
Glucose - not fat
What are ketones and when does our body make excesses of these?
Ketones-substances produced during the breadown of fat when carbohydrate intake is insufficient to meet energy needs. Ketones provide and alternative energy source for the brain when glucose levels are low.
What are the health benefits of complex carbohydrates? Include the benefits of fiber in your answer.
x
Identify risks of a diet low in fiber and health benefits of adequate intake
Fiber helps us stay healthy
May reduce the risk of colon cancer: binds cancer-causing substances and speeds elimination from colon Helps prevent hemorrhoids, constipation, and other intestinal problems: keeps stool soft and moist, gives GI tract muscles “something to push on” Reduces risk for diverticulosis, a condition that occurs when bulging pockets form in the wall of the colon May reduce the risk of heart disease: delays or blocks absorption of dietary cholesterol May enhance weight loss: causes a feeling of fullness May lower risk of type 2 diabetes: slows the release of glucose into the blood; improves regulation of insulin and blood glucose
Identify the most prevalent form of diabetes
Type 2 diabetes
Most people with diabetes have Type 2 diabetes Obesity is the most common trigger for a cascade of changes that eventually results in Type 2 diabetes Body cells are resistant or less responsive to insulin (known as insulin insensitivity or insulin resistance) Excess insulin is often produced to compensate for this resistance Eventually, excessive insulin production becomes insufficient to maintain normal blood glucose levels Hyperglycemia results because cells cannot take in the glucose from the blood Cause is unclear but genetics, obesity, and physical inactivity play a role Treated with diet, exercise, and possibly oral medications
Describe lactose intolerance.
is the inability to digest lactose, a sugar found in milk and to a lesser extent milk-derived dairy products. It is not a disorder as such, but a genetically-determined characteristic.
Lactose intolerant individuals have insufficient levels of lactase, an enzyme that catalyzes hydrolysis of lactose into glucose and galactose, in their digestive system. In most cases this causes symptoms which may include abdominal bloating and cramps, flatulence, diarrhea, nausea, borborygmi (rumbling stomach), or vomiting[1] after consuming significant amounts of lactose. Some studies have produced evidence that milk consumption by lactose intolerant individuals may be a significant cause of inflammatory bowel disease.[2][3]
Identify the potential health risks associated with diets high in simple sugars.
Added sugar intake should be 25% or less of total kcals
Diets high in simple sugars:
Can cause dental problems such as cavities and gum disease Are associated with increased levels of low-density lipoproteins (LDL, sometimes referred to as “bad cholesterol”) and triglycerides Are associated with decreased levels of high-density lipoproteins (HDL, sometimes referred to as “good cholesterol”) May contribute to obesity.
Describe type 1 and type 2 diabetes.
Three types:
Type 1 diabetes Type 2 diabetes Gestational diabetes (discussed in Chapter 14)
Type 1 diabetes
Accounts for 10% of all cases Body cannot produce enough insulin which causes hyperglycemia – high blood sugar (glucose) Requires insulin injections Cause is unknown, but may be an autoimmune disease
Type 2 diabetes
Most people with diabetes have Type 2 diabetes Obesity is the most common trigger for a cascade of changes that eventually results in Type 2 diabetes Body cells are resistant or less responsive to insulin (known as insulin insensitivity or insulin resistance) Excess insulin is often produced to compensate for this resistance Eventually, excessive insulin production becomes insufficient to maintain normal blood glucose levels Hyperglycemia results because cells cannot take in the glucose from the blood Cause is unclear but genetics, obesity, and physical inactivity play a role Treated with diet, exercise, and possibly oral medications
Define ketosis and describe the risks associated with a low carbohydrate diet.
Ketosis /kɨˈtoʊsɨs/ is a state of elevated levels of ketone bodies in the body.[1] It is almost always generalized throughout the body, with hyperketonemia, that is, an elevated level of ketone bodies in the blood. Ketone bodies are formed by ketogenesis when liver glycogen stores are depleted. The ketone bodies acetoacetate and β-hydroxybutyrate are used for energy.[2]
Name the alternative sweeteners.
Aspartame: Equal and NutraSweet; composed of two amino acids (phenylalanine and aspartic acid). People with the genetic disorder phyenylketonuria (PKU) cannot break down phenylalanine. The build-up of phenylalanine, in a person with PKU, causes brain damage so these individuals should not consume aspartame.
Sucralose: Splenda
Acesulfame-K: Sunette and Sweet One
Saccharin: Sweet n’ Low
If you would like to buy whole grain bread, what should you look for on the label?
Whole grain
Whole Wheat
What is dietary fiber?
refers to nutrients in the diet that are not digested by gastrointestinal enzymes.
Functional fiber?
consists of isolated, nondigestible carbohydrates that have beneficial physiologic effects in humans. Total fiber is the sum of dietary fiber and functional fiber.
Soluble fiber?
fiber dissolves in water. It is readily fermented in the colon into gases and physiologically active byproducts, and can be prebiotic and/or viscous. Soluble fibers tend to slow the movement of food through the system.
Insoluble fiber?
fiber does not dissolve in water. It can be metabolically inert and provide bulking or prebiotic, metabolically fermenting in the large intestine. Bulking fibers absorb water as they move through the digestive system, easing defecation.[1] Fermentable insoluble fibers mildly promote stool regularity, although not to the extent that bulking fibers do, but they can be readily fermented in the colon into gases and physiologically active byproducts. Insoluble fibers tend to accelerate the movement of food through the system.
What is the glycemic index?
A measure of food’s ability to raise blood glucose levels
Type of carbohydrate, way food is prepared, and its fat and fiber content affect how quickly body absorbs it and, therefore, its glycemic index
Combination of foods eaten affect how body absorbs food, so glycemic index of total meal is more important than individual foods
Glycemic load = grams of carbohydrate in food X glycemic index of food
Foods with a low glycemic load:
Cause low to moderate fluctuations in blood glucose
Are better for people with diabetes
Are generally higher in fiber
May reduce the risk of heart disease, colon cancer, and prostate cancer
Foods with a high glycemic load:
Cause sudden large increases in blood glucose and insulin
Where are carbohydrates digested?
Image
What is glucogon?
Glucagon
Secreted by alpha cells of the pancreas
Stimulates the breakdown of glycogen to glucose, which is then secreted to the bloodstream and transported to cells; raises blood glucose levels
Stimulates gluconeogenesis – the production of new glucose from amino acids
Regulation of blood glucose by the hormone glucagon. When blood glucose levels are low, the pancreas secretes glucagon. Glucagon enters the cell, where it stimulates the breakdown of stored glycogen into glucose. This glucose is then released into the bloodstream.
