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Chapter 4
Carbohydrates
Key Terms
1.
acesulfame K: An artificial sweetener that is 200 times sweeter than common table sugar
(sucrose). Because it is not digested and absorbed by the body, it contributes no calories to
the diet and yields no energy when consumed.
2.
total fiber: The sum of dietary fiber and functional fiber.
3.
glycemic index: A measure of the effect of a food on blood glucose levels.
4.
pectins: Dietary fibers that are found in fruits.
5.
husk: The inedible covering of grain; also known as the chaff.
6.
endosperm: The middle portion of a grain kernel, high in starch to provide food for the
growing plant embryo.
7.
germ: The innermost part of a grain that can grow into a new plant. It is rich in protein,
oils, vitamins, and minerals.
8.
complex carbohydrates: Chains of more than two monosaccharides. May be
oligosaccharides or polysaccharides.
9.
functional fiber: Isolated nondigestible carbohydrates, including some manufactured
carbohydrates, that have beneficial effects in humans.
10.
alpha bonds: Chemical bonds linking monosaccharides, which can be broken by human
intestinal enzymes, releasing the individual monosaccharides. Starch, maltose, and sucrose
contain these.
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11.
epinephrine: A hormone released in response to stress or sudden danger, it raises blood
glucose levels to ready the body for “fight or flight.” Also called adrenaline.
12.
fructose: A common monosaccharide naturally present in honey and many fruits. Also
called levulose or fruit sugar.
13.
dietary fiber: Carbohydrates and lignin that are naturally in plants and are nondigestible;
that is, they are not digested and absorbed in the human small intestine.
14.
aspartame: An artificial sweetener composed of two amino acids. It is 200 times sweeter
than sucrose and sold by the trade name NutraSweet.
15.
lignins: Dietary fibers that are not a carbohydrate.
16.
trehalose: A disaccharide of two glucose molecules, but with a linkage different from
maltose. Used as a food additive and sweetener.
17.
ketosis: Abnormally high concentration of ketone bodies in body tissues and fluids.
18.
neotame: An artificial sweetener similar to aspartame, but one that is sweeter and does not
require a warning label for people with phenylketonuria.
19.
nutritive sweeteners: Substances that make foods sweet and can be absorbed and yield
energy in the body.
20.
dental caries: Destruction of the enamel surface of teeth caused by acids that are created
when bacteria break down sugars in the mouth.
21.
galactose: A monosaccharide that has a structure similar to glucose; usually joined with
other monosaccharides.
22.
pentoses: Sugar molecules containing five carbon atoms.
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23.
glucose: A common monosaccharide that is a component of disaccharides (sucrose, lactose,
and maltose) and various complex carbohydrates; present in the blood and also known as
dextrose.
24.
resistant starch: Starch that is not digested.
25.
lactose: A disaccharide composed of glucose and galactose; also called milk sugar.
26.
pancreatic amylase: Starch-digesting enzyme secreted by the pancreas.
27.
maltose: A disaccharide composed of two glucose molecules; sometimes called malt sugar.
It seldom occurs naturally in foods but is formed whenever long molecules of starch break
down.
28.
sucralose: An artificial sweetener made from sucrose. It is non-nutritive and about 600
times sweeter than sugar.
29.
starch: The major storage form of carbohydrate in plants; it is composed of long chains of
glucose molecules in a straight (amylose) or branching (amylopectin) arrangement.
30.
saccharin: An artificial sweetener that tastes about 300 to 700 times sweeter than sucrose.
Fill-in-the-Blank
1.
Hemicelluloses are a group of large polysaccharides in dietary fiber that are fermented
more easily than cellulose.
2.
Beta-glucans are branched polysaccharide chains of glucose found in barley and oats.
They help to lower blood cholesterol levels.
3.
A chronic disease in which uptake of blood glucose by body cells is impaired, resulting in
high glucose levels in the blood and urine, is diabetes mellitus.
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4.
Sugars composed of a single sugar molecule (a monosaccharide) or two joined sugar
molecules (a disaccharide) are simple carbohydrates.
5.
Dietary fibers that contain galactose and other monosaccharides, and are found between
plant cell walls, are gums.
6.
The layers of protective coating around the grain kernel that are rich in dietary fiber and
nutrients are called the bran.
7.
D-Tagatose
is an artificial sweetener derived from lactose that has the same sweetness as
sucrose with only half the calories.
8.
Beta bonds are chemical bonds linking monosaccharides, which sometimes cannot be
broken by human intestinal enzymes. Lactose contains digestible ones, and cellulose
contains nondigestible ones.
9.
A branched-chain polysaccharide in food composed of glucose units is amylopectin.
10.
Produced by the pancreas, glucagon promotes the breakdown of liver glycogen to glucose,
and so increases blood glucose levels.
11.
Disaccharides are carbohydrates composed of two monosaccharide units chemically
linked. They include sucrose (common table sugar), lactose (milk sugar), and maltose.
12.
The dried husk of the psyllium seed is psyllium.
13.
Monosaccharides are single sugar units. The common kinds are glucose, fructose, and
galactose.
14.
Glycogen is a very large, highly branched polysaccharide composed of multiple glucose
units. Sometimes called animal starch, it is the primary storage form of glucose in animals.
15.
Molecules formed from fat when cells do not have enough available carbohydrate to break
down fat completely are called ketone bodies.
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16.
Chitin is a long-chain structural polysaccharide of slightly modified glucose. Found in the
hard exterior skeletons of insects, crustaceans, and other invertebrates, it also occurs in the
cell walls of fungi. A polysaccharide derived from this is chitosan.
17.
Phenylketonuria (PKU) is an inherited disorder in which the enzyme that metabolizes
phenylalanine is missing.
18.
Substances that impart sweetness to foods but supply little or no energy to the body are
called non-nutritive sweeteners.
19.
Short carbohydrate chains composed of 3 to 10 sugar molecules are oligosaccharides.
20.
Produced by the pancreas, insulin stimulates the uptake of blood glucose into cells, the
formation of glycogen in the liver, and various other processes.
21.
Mucilages are gel-forming dietary fibers containing galactose, mannose, and other
monosaccharides; they are found in seaweed.
22.
Sucrose, also known as table sugar, is a disaccharide composed of glucose and fructose.
23.
Stevioside is a dietary supplement, not approved for use as a sweetener, that is extracted
and refined from Stevia rebaudiana leaves.
24.
Dihydrochalcones (DHCs) is a nonnutritive sweetner derived from bioflavonoids of citrus
fruits. It is approximately 300 to 2,000 times sweeter than sucrose.
25.
Thaumatin is a mixture of sweet-tasting proteins from a West African fruit, approximately
2,000 times sweeter than sucrose.
26.
Sugar alcohols are compounds formed from monosaccharides and are commonly used as
nutritive sweeteners; they are also called polyols.
27.
Long carbohydrate chains composed of more than 10 sugar molecules are called
polysaccharides. They can be straight or branched.
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28.
Refined sweeteners are substances composed of monosaccharides and disaccharides that
have been extracted and processed from other foods.
Fill-in-the-Blank Summaries
What Are Carbohydrates?
Carbohydrates are organic compounds that contain carbon, oxygen, and hydrogen. The two main
types of sugars are monosaccharides and disaccharides. Glucose, galactose, and fructose
are the three most common monosaccharides. Disaccharides are created when two
monosaccharides are joined. Glucose is the most abundant simple carbohydrate unit in
nature. It makes up at least one of the two sugar molecules in every disaccharide.
Fructose, also known as levulose, tastes the sweetest of all sugars. Galactose is usually
chemically bonded to glucose to form lactose.
When a food label lists sugar as an ingredient, the term refers to sucrose. Human milk tastes
sweeter than cow’s milk because it has a higher concentration of lactose. When digestive
enzymes break down starch in the mouth, a sweet taste is sensed. This sweet taste can be
attributed to maltose.
Complex Carbohydrates
Oligosaccharides are short carbohydrate chains of 3 to 10 sugar molecules. Long carbohydrate
chains are known as polysaccharides, and are composed of more than 10 sugar molecules.
Starches are polysaccharides. There are two main forms of starch in plants. Amylose is
made of long, straight chains of glucose molecules; amylopectin is made of branched
chains of glucose molecules.
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In human cells, glycogen can be broken down rapidly into single glucose molecules. The
skeletal muscles and the liver are the two main sites of glycogen storage. The liver uses
glycogen to regulate blood glucose levels.
There are many types of dietary fiber. The pectin in fruit gives fruit its body; when it breaks
down, fruit becomes mushy.
Cellulose gives plant cell walls their strength and rigidity. This type of fiber is nondigestible by
humans and a component of dietary fiber.
Short Answer
1.
Fiber is a necessary part of a healthy diet. The Adequate Intake (AI) value for total fiber is
38 grams per day for men aged 19 to 50 years, and 25 grams per day for women in the
same age-group. Name 10 foods that would help you meet your daily requirement of fiber.
Answers may include any of the following: apples, bananas, berries, cranberries,
grapefruit, mango, oranges, pears, asparagus, broccoli, Brussels sprouts, carrots, green
peppers, red cabbage, spinach, sprouts, almonds, peanuts, pecans, sesame seeds, sunflower
seeds, walnuts, most legumes, brown rice, oat bran, oatmeal, wheat-bran cereals, wholewheat breads.
2.
Where does most carbohydrate digestion occur?
Most carbohydrate digestion occurs in the small intestine.
3.
Using the Dietary Values as a reference, would consuming 200 grams of carbohydrates a
day within a 2,000 Kcalorie diet meet estimated needs for carbohydrates?
No, 300 grams of carbohydrates per day in a 2,000 Kcalorie diet are needed to meet 100
percent DV.
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4.
How many Kcalories of carbohydrates are provided in a food that contains 20 grams of
total carbohydrate?
20 grams of carbohydrate  4 Kcalories per gram = 80 Kcalories of carbohydrate
5.
What is responsible for causing the slightly sweet taste produced when you chew a slice
of fresh bread?
The starch in the bread breaking down into the sugar maltose
6.
Which carbohydrate source provides a reservoir of glucose for strenuous muscular
activity, and where is this carbohydrate source stored in the body?
Glycogen provides the glucose; this is stored in the muscle cells.
7.
What is “carbohydrate-loading” and how can it benefit marathon running and other
endurance events?
Carbohydrate-loading is a process which involves both carbohydrate intake and exercise
training in an attempt to increase the amount of carbohydrate stored in the muscles, and
made available during endurance events. This practice emphasizes eating highcarbohydrate meals and tapering off rigorous training in an attempt to increase the
amount of stored glycogen in the muscles by 20–40 percent above normal.
8.
Describe why a person with lactose maldigestion (or intolerance) experiences pain after
drinking or eating milk or dairy products.
People with an insufficient supply of the enzyme lactase are not able to break the beta
bonds in lactose, which then remains undigested until bacteria in the colon can attack it,
resulting in stomach pain.
9.
What is the primary fuel for most cells in the body? This is also the preferred fuel for the
brain, red blood cells, nervous system, fetus, and placenta.
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Glucose
10.
If inadequate carbohydrates are consumed in the diet, where does the body get its energy
source to maintain blood glucose levels and supply glucose to the brain?
The body makes its own glucose from protein and from the breakdown of fat.
11.
What does the pancreas secrete when blood glucose rises? When blood glucose falls?
Insulin; glucagon
12.
Eating a high-fiber diet is associated with decreased risk of certain chronic diseases.
Name four of them.
Obesity, diabetes mellitus, cardiovascular disease, gastrointestinal disorders
Labeling
Identify the various components necessary for a plant to make carbohydrates.
Energy, 6 carbon dioxide molecules and 6 water molecules; 1 glucose molecule
(carbohydrate); 6 oxygen molecules.
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