Chapter 2 Carbohydrates
Terms in this set (120)
The process by which plants that contain chlorophyll are able to manufacture carbohydrate by combining carbon dioxide and water; sunlight is used as energy, and chlorophyll is a catalyst.
Provide practical energy (calorie) sources because of their availability, relatively low cost, and storage capacity.
Structure vary from simple to complex to provide both quick and extended energy for the body.
What is a carbohydrate composed of?
Carbon (C), hydrogen (H), and Oxygen (O).
The chemical name for sugar molecules; may occur as single molecules in monosaccharides, two molecules in disaccharides, or multiple molecules in polysaccharides.
Sugars with a simple structure of one or two single-sugar (saccharide) units; a monosaccharide is composed of one sugar unit, and a disaccharide is composed of two sugar units.
Large complex molecules of carbohydrates composed of many sugar units (polysaccharides); the complex forms of dietary carbohydrates are starch and dietary fiber.
Building blocks for all carbohydrates, require no digestion. Classified as simple carbohydrates; glucose (dextrose), fructose, galactose
Sources of monosaccharides
Corn syrup (commonly used in processed foods), fruits, honey, lactose (milk, milk products)
Pairs of monosaccharides which must be changed to simple sugars by hydrolysis before absorption. Simple carbohydrates; sucrose, lactose, and maltose.
Sources of disaccharides
Table sugar (sugar cane, sugar beets), milk, milk products, molasses, starch digestion, sweetener in food products
Large, complex compounds of many saccharide units in long chains; thus they are complex carbohydrates. Starch and glycogen
Sources of polysaccharides
Grains and grain products (cereal, bread, crackers, baked goods), rice, corn, bulgur, legumes, potatoes and other vegetables, storage form of carbohydrates in animal tissue (not a dietary source)
What is the most significant polysaccharide in human nutrition?
Starch. It is composed of many coiled and branching chains in a treelike structure. Each of the multiple branching chains is composed of 24 to 30 units of glucose, which are gradually released during digestion to supply a steady source of energy over time.
Carbohydrates provide energy. How many calories are in each gram of CHO?
What is the protein-sparing action of carbohydrates?
When an adequate supply (50-100g/day) of CHO are ingested, they allow the available protein to build and repair body tissue.
How does carbohydrates function as normal fat metabolism
CHO provide energy - if not available, then fat oxidation occurs, producing ketones.
Carbohydrates provide fiber, which forms
Soft, bulky stool
Glycogen is stored in
The liver and muscles for use as needed. A half day's supply of carbohydrates is stored in this form of glycogen.
Humans lack the necessary enzymes to digest dietary fiber. These polysaccharides do not have direct energy value like other carbs.
Found in grains, vegetables, and fruits. Recommended intake is 20-35 g/day. Lowers blood glucose levels; may prevent some colon cancers; and helps prevent constipation, hemorrhoids, and diverticular disease by softening stool.
does not readily dissolve in water (cellulose, hemicellulose, lignins)
partially dissolves in water (gums, pectins, some hemicellulose, mucilages)
Principal sources of carbohydrates are plant foods:
Cereal grains, vegetables, fruits, nuts, sugars
What is the only substantial animal source?
Basic single sugar in human metabolism, which is the form of sugar circulating in the blood.
What is the primary fuel for cells?
Glucose, a moderately sweet sugar, usually is not found as such in the diet, except in corn syrup or processed food items. Where does the body's supply of glucose mainly come from?
Digestion of starch
Why is glucose also called dextrose?
To denote the structure of the molecule (six carbons)
What only uses glucose as fuel?
Central nervous system, red blood cells, and brain use
Also called levulose or fruit sugars. Primarily found in fruits (from which it gets its name) and in honey.
Which of the simple sugars (monosaccharides) is the sweetest?
Can honey be a sugar substitute?
No, it is a sugar itself; therefore, it cannot be considered a substitute.
What does the amount of fructose in fruits depend on?
The degree of ripeness; as a fruit ripens, some of its stored starch turns to sugar.
How are high-fructose corn syrups manufactured?
By changing the glucose in cornstarch into fructose.
High-fructose corn syrups are heavily used in
Processed food products, canned and frozen fruits, and soft drinks.
High-fructose corn syrup are inexpensive sweeteners, and contribute to increased sugar intake in the United States. The per-capital consumption increased from zero in 1967 to
A height of 19.7 teaspoons per day in 1999 and was most recently estimated to be down to 14.4 tsp per day.
Not usually found as a free monosaccharide in the diet; it is a product of lactose (milk sugar) digestion.
Glucose + Fructose=
Glucose + Galactose=
Glucose + Glucose=
Common table sugar. It's two single-sugar units are glucose and fructose. Used in the form of granulated, powdered, brown sugar, and in molasses
By-product of sugar production
Sugar cane, sugar beets, maple syrup, candy, jams, and jellies
When people speak of sugar in their diets, which are they usually referring to?
Sugar in milk, which is formed in mammary glands.
Glucose and galactose are the two single-sugar units.
Only common sugar that's isn't found in plants.
Less soluble and less sweet than sucrose.
Remains in the intestine longer than other sugars, and it encourages the growth of certain useful bacteria.
Cow's milk contains....
Human milk contains....
Lactose promotes the absorption of
Calcium and phosphorus. The presence of all three nutrients in milk is advantageous for absorption.
A complex carbohydrate found in animal tissue that is composed of many glucose units linked together.
What is lactase?
The enzyme required for the digestion of lactose.
Caused by insufficient lactase. S/S are bloating, abdominal cramps, and diarrhea after drinking milk or consuming a milk-based food such as processed cheese.
Not usually found as such in food form; it is derived within the body from the intermediate digestive breakdown of starch.
Synthetically derived maltose is used in various processed foods.
Starch is made up entirely of glucose units. What happens during the breakdown of starch?
Many disaccharide units of maltose are released.
What are the important polysaccharides in human nutrition?
Where are starches found?
Grains, legumes, and other vegetables and in some fruits in small amounts.
Break down of starch
More complex in structure than simple sugars, so they break down more slowly and supply energy over a longer period of time.
The Dietary Reference Intakes recommend how much of total kilocalories to be consumed from carbohydrates? (With a greater portion coming from complex carbohydrates)
Used for food products such as flours, breads, or cereals that are produced from unrefined grain.
Retain the outer bran layers, the inner germ, and the endosperm and thus the nutrients found within. For example, dietary fiber, vitamins, and minerals.
Are refined grain products to which some (but not all) vitamins and minerals that were removed during the refining process - for example, riboflavin, niacin, thiamin, folate, and iron - have been added back to some extent.
Those that have nutrients added to them that would not naturally occur in that food regardless of how it was processed. (Calcium-fortified orange juice)
Recommended daily intake of fiber for women and men aged 19 to 50 years old is
25 and 38 g/day
Recommended daily intake of fiber for men and women aged 50 and over is
21 and 30 g/day
Average fiber intake for women and men in United States is
15.5 and 18.7 g/day... remarkably lower than recommended fiber intake and contribute to health problems.
Sudden increases in fiber intake can result in
Uncomfortable gas, bloating, and constipation. Fiber should be gradually increased, along with water intake, to an appropriate amount for the individual.
Scientists are confident that consuming a well-balanced diet high in whole grains, fruits, and vegetables providing ample fiber imparts health benefits, such as:
-Lowers blood cholesterol levels
-Promotes normal bowel function and prevents constipation
-Increases satiety, which helps the prevention of obesity
-Protects against disorders of the small and large intestines
-Slows glucose absorption, thereby reducing blood glucose spikes and insulin secretion.
Cereals, grains, potatoes, beans, and yams
Chief component of cell walls in plants. Holds water. Remains undigested in the GI tract and provides bulk to a diet.
Bulk helps move the food mass through the intestine.
Stems, leaves of vegetables, coverings of seeds and grains (found in whole grains).
In the cell wall of plants, phosphorus is stored in the form of phytic acid; this compound is undigested in humans because
of the lack of a necessary enzyme, Phytase. Phytic acid is a strong chelator of important minerals.
A ligand that binds to a metal to form a metal complex
Only noncarbohydrate type of dietary fiber.
Large compound that forms the woody parts in certain plants.
Binds the cellulose fibers in plants, which gives added strength and stiffness to plant cell walls.
Although it is an insoluble fiber, it also combines with bile acids and cholesterol in the human intestine to prevent their absorption.
Broccoli stems, fruits with edible seeds, such as strawberries and flaxseeds
Function of Lignin:
antioxidant; bind bile acids, thus decreasing serum cholesterol level.
absorb water and swell to a larger bulk, thus slowing the emptying of the food mass from the stomach, binding bile acids in the intestine, and preventing spastic colon pressure by providing bulk for normal for normal muscle action.
can also provide fermentation material on which colon bacteria can work.
Hemicellulose, pectins, gums, mucilages, and algal substances are
Nutritive sweeteners that provide 2 or 3 kcal/g
Sweeteners that contribute to total calorie intake (like sugar alcohols) are considered
Sugar substitutes that do not have a notable caloric value
Non-nutritive sweeteners or alternative sweeteners
Sugar alcohols includes
Sorbitol, mannitol, and xylitol; which are the alcohol forms of sucrose, mannose, and xylose.
What is the most well-known sugar alcohol?
Sorbitol. Widely used as sucrose substitute in various foods, candies, chewing gum, and beverages.
Sugar alcohols are absorbed in
Small intestines, like glucose. Sugar alcohols are absorbed more slowly and do not increase the blood sugar level as rapidly as glucose.
What is used in products that are intended for individuals who cannot tolerate high blood sugar level? (For example, those with diabetes)
Using sugar alcohol to replace sugar can lower risk of dental caries because
Oral bacteria cannot use the alcohol for fuel.
Downside of using excessive amounts of sugar alcohols in food products is
Slowed digestion may result in osmotic diarrhea
In ripe berries of the Sorbus aucuparia tree, naturally in small quantities in various berries, cherries, plums, and pears contains
How much glycogen do healthy, well-nourished adults store in the liver?
Approximately 100g, which is about 8% of the liver mass weight.
On average, how much glycogen can be stored in the skeletal muscle?
300-400 g, which is about 1% to 2% of the muscle mass weight
Glycogen in the liver is primarily used to
Maintain blood glucose level
Constant carb intake and reserves are necessary for the proper functioning of the central nervous system. The brain has no stored supply of glucose; therefore, it is especially dependent on
a minute-to-minute supply of glucose from the blood. Sustained and profound shock from low blood sugar may cause brain damage and can result in coma or death.
Carbohydrates as basic fuel supply:
energy for physical activities and all work of body cells
Carbohydrates as reserve fuel supply:
Provided by glycogen; maintains normal blood glucose level
proteins and fats
What is the vital emergency fuel for heart muscle?
excess added sugar in the diet. Examples are sweets, desserts, candy, soda.
The digestion of carbohydrate foods, starches, and sugars begin in the
Digestion in the mouth is accomplished by
muscle actions that mechanically break the food mass into smaller particles & chemical processes in which specific enzymes break down the nutrients into still smaller usable metabolic products.
Chewing of food, which is called ____________________, breaks food into fine particles and mixes it with saliva.
the proteins produced in the body that digest or change nutrients in specific chemical reactions without being changed themselves during the process; thus their action is that of a catalyst; digestive enzymes in GI secretions act on food substances to break them down into simpler compounds
When you see -ase at the end of a word, think
Salivary amylase, also known as Ptyalin:
enzyme secreted by the parotid glands, which lie under each ear at the back of the jaw.
acts on starch to begin its breakdown into dextrin and disaccharides.
Do monosaccharides require further digestion?
No, monosaccharides do not require further digestion; thus they travel unchanged to the stomach and small intestines for absorption. Absorbed directly into the blood stream.
Stomach (peristalsis continues mechanical digestion):
Gastric secretions include hydrochloric acid, which inhibits the action of salivary amylase.
Before the food completely mixes with the acidic stomach secretions, up to 20% to 30% of the starch may have been changed to maltose.
Muscle action continues to mix the food mass and then moves the food tot he lower part of the stomach.
The food becomes thick and creamy chyme, ready for its controlled emptying through the pyloric valve and into the duodenum.
Ph level in the stomach is
Peristalsis continues to help with digestion in the small intestine by mixing and moving chyme along the organ. The chemical digestion of carbohydrate is completed in the small intestine by specific enzymes from both the pancreas and the intestines.
Ph level in the small intestine
fructose and galactose are carried to the liver and changed to
the cells that are located on the microvilli within the lining of the intestinal tracts; the microvilli are in hair-like projections that protrude from the mucosal cells that help to increase surface area for the digestion and absorption of nutrients.
an entrance or gateway; for example, the portal blood circulation designates the entry of blood vessels from the intestines into the liver; it carries nutrients for liver metabolism, and it drains into the body's main systemic circulation to deliver metabolic products to body cells.
Enzymes from the brush border of the intestinal tract contain three disaccharidases:
sucrase, lactase, and maltase.
These specific enzymes act on their respective disaccharides to render the monosaccharides -- glucose, galactose, and fructose -- ready for absorption directly directly into the portal blood circulation.
Lactose tolerance affects ___________________ of adults worldwide, with a much higher prevalence in certain countries and ethnic groups.
What ethnicities have higher rated of lactose intolerance? (compared to Americans with European descent)
African Americans, Asian Americans, Hispanic Americans, and Native Americans.
How many carbohydrates are recommended for a 2000 kcal/day diet?
225 to 325 g
The 2015-2020 Guidelines advise individuals to do the following with regard to carbohydrate-rich foods:
-Consume at least half of all grains as whole grain. Increase whole-grain intake by replacing refined grains with whole grains.
-Increase vegetables and whole fruit intake. Eat a variety of vegetables from all subgroups -- dark-green, red, and orange vegetables, legumes (beans and peas), and starchy vegetables
-Chose more nutrient-dense foods and less foods and beverages with added sugar.
-Reduce the intake of calories from added sugars to less than 10% of total calories in the diet.
Islets of Langerhans in pancreas
secrete insulin. Impaired or absent insulin secretion results in high blood glucose level. Low blood glucose level of <70 mg/dL may occur with too much insulin or insufficient food intake.
is the hormone that controls glucose metabolism
Insulin and glucose
travel together, they have a bond together for the body to use the energy.
where insulin is at. At the beginning of Type 1, 80% of beta cells have been destroyed. During Type 2, beta cells are still present, they just are not working properly.
adipose tissue excreted in urine can damage kidneys, especially small vessels in other cells can also be damaged.
Diabetes 3 Ps
Normal blood glucose level
Excessive carb intake may lead to
obesity, dental caries, and digestive disturbances