MACRONUTRIENTS: CARBOHYDRATES

Question 1

are the most abundant organic substances on
Earth, comprising approximately 70% of plant structure.

Answer 1

Carbohydrates

Question 2

The main or chief source of the body’s energy.

Answer 2

Carbohydrates

Question 3

What are the two forms of digestible carbs occur naturally in plant foods

Answer 3

sugars and starch

Question 4

Earth comes ultimately from the
sun and its action on plants. Using their internal
process of

Answer 4

photosynthesis

Question 5

Carbohydrates contain
the elements

Answer 5

carbon, hydrogen, and oxygen, with the hydrogen/oxygen ratio
usually that of water (CH2O).

Question 6

are classified according to the number of basic sugar or
saccharide units that make up their structure.

Answer 6

Carbohydrates

Question 7

The monosaccharides and disaccharides are referred to as __________
because of their relatively small size and structure.

Answer 7

simple carbohydrates

Question 8

including starch and certain fibers, are called complex
carbohydrates based on their larger size and more complicated structure.

Answer 8

polysaccharides,

Question 9

The simplest form of carbohydrate is the

Answer 9

monosaccharide or single sugar

Question 10

The three monosaccharides important
in human nutrition are

Answer 10

glucose, fructose, and galactose

Question 11

is a moderately sweet sugar found naturally in only a few foods
syrup.

common body fuel oxidized by cells.

Answer 11

Glucose

Question 12

The sweetest of the simple sugars, is found naturally in fruits and honey.
* Fructose intake has escalated dramatically since high-fructose corn syrup (HFCS)
was introduced for use in processed food.
* HFCS is the sweetener in many soft drinks, fruit drinks, commercial baked products,
and dessert mixes.

• In humans, fructose is converted to glucose and burned for energy. Fructose is
  absorbed less efficiently than glucose, and amounts of 25 g to 50 g or more can
  cause gastrointestinal distress.

Answer 12

Fructose

Question 13

The simple sugar galactose is never found free in foods but is released in the digestion of lactose
(milk sugar) and then converted to glucose in the liver.
* This reaction is reversible; in lactation, glucose is reconverted to galactose for use in milk
production.

Answer 13

Galactose

Question 14

are double sugars made up of two monosaccharides linked together.
* The three disaccharides of physiologic importance are sucrose, lactose, and maltose.
* Their monosaccharide components are as follows:

Answer 14

disaccharides

Question 15

= one glucose + one fructose
= one glucose + one galactose
= one glucose + one glucose

Answer 15

Sucrose, Lactose, Maltose

Question 16

is common “table sugar” and is made commercially from sugar cane and
sugar beets.
* It is found naturally in molasses and certain fruits and vegetables (e.g., peaches and
carrots) and is added to many processed foods.

Answer 16

Sucrose

Question 17

is the sugar found in milk and is the least sweet of the disaccharides, only about
one sixth as sweet as sucrose.

• Although milk is relatively high in lactose, cheese, one of milk’s products, may contain little
  or no lactose depending on how the cheese is made.
• When milk sours in the initial stage of cheese making, the liquid whey separates from the
  solid curd.
• The lactose from the milk dissolves into the whey, which is drained away and discarded.
  The remaining curd is processed into cheese, making it possible for many lactose intolerant
  individuals to digest cheese, although particular cheeses vary in lactose content.

Answer 17

Lactose

Question 18

occurs naturally in relatively
few foods but is formed in the body
as an intermediate product in
starch digestion.
* It is found in commercial malt
products and germinating cereal
grains.

Answer 18

Maltose

Question 19

(sometimes referred to as polyols)
are other forms of carbohydrate with sweetening
power. Sugar alcohols, such as sorbitol, mannitol,
and xylitol, are found in nature but are also used in
food processing.
* Under current labeling laws, processed foods in
which sugar alcohols replace sugar can be
labeled as sugar free. Sugar alcohols are poorly
absorbed in the small intestine and, if absorbed,
are poorly metabolized.
* Sugar alcohols commonly used as sugar replacers
add only 0.2 to 3.0 kcal/g when compared with
other sugars, which add 4 kcal/g.1

Answer 19

Sugar Alcohols

Question 20

Complex carbohydrates are called polysaccharides because they are made up of many (poly)
single glucose (saccharide) units.
* Starch is the most important digestible polysaccharide; others are glycogen and dextrin.
Nondigestible polysaccharides, such as cellulose, add important bulk to the diet and are
categorized as dietary fiber.

Answer 20

Polysaccharides

Question 21

consists of many coiled and
branching chains of single glucose units and
yields only glucose on complete digestion.
* Cooking not only improves the flavor of
starch but also softens and ruptures the
starch cells, making digestion easier.
* Starch mixtures thicken when cooked
because the substance encasing the starch
granules has a gel-like quality that thickens
mixtures in the same way as pectin causes
jelly to set.

Answer 21

Starch

Question 22

At one time it was thought that starch was
completely digested and absorbed in the small
intestine. Now we know that some starch in
particular foods, such as whole grains, potatoes,
bananas, and legumes, escapes digestion and
enters the colon generally intact.
* This starch, called ________, can make up as
much as 8% by weight of a food high in starch.

Answer 22

Resistant Starch

Question 23

is the storage form of carbohydrate in
animals, whereas starch is the storage form of
carbohydrate in plants.
* Glycogen is synthesized in liver cells and stored in
small amounts in liver and muscle.

• Liver glycogen helps sustain normal blood glucose
  levels during fasting periods such as sleep hours,
  and muscle glycogen provides immediate fuel for
  muscle action.
• Athletes sometimes practice pregame “glycogen
  loading” to add fuel stores for athletic competition

Answer 23

Glycogen

Question 24

are polysaccharide
compounds formed as intermediate
products in the breakdown of starch

Answer 24

Dextrin

Question 25

vare small fragments of partially digested starch ranging in size from 3 to
10 glucose units. They are formed in digestion and produced commercially by acid
hydrolysis.
* These small starch molecules are used in special formulas for infants and others with
gastrointestinal problems because they are easy to digest.
* Oligosaccharides are also common in sports drinks in which they often contribute almost
half of the total glucose.
* Some naturally occurring oligosaccharides are formed with bonds that cannot be broken
by human enzymes and therefore remain undigested.

Answer 25

Oligosaccharides

Question 26

Two of these—_____ and ____—are found in legumes such as beans, peas, and
soybeans, and provide a feast for bacteria in the colon, producing large amounts of gas
that result in discomfort and embarrassment.

Answer 26

stachyose and raffinose

Question 27

Carbohydrate foods are digested and absorbed at different rates. Refined carbohydrates, such as
white bread or corn flakes, are broken down quickly and rapidly absorbed into the blood.
* Less refined carbohydrate foods, such as brown rice, beans, or apples, also contain fiber and are
digested and absorbed more slowly.
* A food with a high GI will raise blood glucose to a greater extent than a food with a low GI. The
effect of particular foods is compared with the effect of a glucose solution on blood glucose. In
clinical practice, GI was measured by studying blood glucose levels over a 2-hour period following
ingestion of 50 g of glucose and after consuming a 50-g carbohydrate portion of the test food. Based
on its major effect on blood glucose, the glucose dose was assigned the rating of 100, and individual
foods were rated accordingly.

Answer 27

Glycemic Index

Question 28

Functions of Carb

Answer 28

1. Energy
2. Glycogen-Carbohydrate Storage
3. Protein-Sparring Action
4. Antiketogenic Effect
5. Heart Action
6. Central Nervous System

Question 29

The primary function of starch and sugars
is to supply energy to cells, especially brain
cells that depend on glucose.
* When carbohydrate is lacking, fats can be
used as an energy source by most organ
systems; however, body tissues require a
constant supply of glucose to function
most efficiently.

Answer 29

Energy

Question 30

Liver and muscle glycogen are in constant
interchange with the body’s overall energy
system. These energy reserves protect cells,
especially brain cells, from depressed
metabolic function and injury and support
urgent muscle responses.

Answer 30

Glycogen-Carbohydrate Storage

Question 31

Carbohydrates help regulate protein metabolism.
an adequate supply of carbohydrate to satisfy
ongoing energy demands prevents the

channeling of protein for energy. This protein-
sparing action of carbohydrate allows protein to

be reserved for tissue building and repair.

Answer 31

Protein-Sparing Action

Question 32

Carbohydrates influence fat metabolism. The
supply of carbohydrate determines how much
fat must be broken down to meet energy
needs, thereby controlling the formation of
ketones.

• Ketones are intermediate products of fat
  metabolism that normally are produced in very
  small amounts. However, when carbohydrate is
  inadequate to meet cell energy needs, as in

starvation or uncontrolled diabetes or very low-
carbohydrate diets, fat is oxidized at extreme

rates. Sufficient amounts of dietary
carbohydrates prevent any damaging excess
of ketones.

Answer 32

Antiketogenic Effect

Question 33

is a life-sustaining muscle activity.
Although fatty acids are the preferred fuel for the
heart, the glycogen stored in cardiac muscle is an
important emergency source of contractile
energy.

Answer 33

Heart Action

Question 34

depend on carbohydrate for energy but have
very low carbohydrate reserves enough to last
only 10 to 15 minutes.
* This makes them especially dependent on a
minute-to-minute supply of glucose from the
blood.

• Glucose increases the synthesis of acetylcholine, a
  neurotransmitter that acts on areas of the brain
  responsible for memory and cognitive function

Answer 34

Central Nervous System

Question 35

• Sustained _______________ causes irreversible
  brain damage. Providing an adequate morning
  supply of glucose for brain function may help to
  explain why individuals who eat breakfast do
  better in school than those who skip breakfast.

Answer 35

hypoglycemic shock

Question 36

Most of us have an inborn desire for foods that are sweet; however, we are faced with
the dilemma of moderating our energy intakes to maintain a healthy weight.
* ______________ allow us to indulge our taste for sweets while limiting
kilocalorie intake. Sweeteners are grouped as nutritive or nonnutritive depending on the
kilocalories they add to a food.
* Sucrose (table sugar) and other natural sugars yield 4 kcal/g. In contrast, NNSs,
sometimes referred to as noncaloric sweeteners, contribute no kilocalories or an
insignificant number of kilocalories.

Answer 36

Nonnutritive sweeteners (NNSs)

Question 37

is the nondigestible material found in whole-grain cereals, fruits, vegetables, and legumes
that our grandmothers referred to as roughage.
* Because humans lack the enzymes necessary to break down these complex carbohydrates into
forms that can be absorbed, they travel the length of the gastrointestinal tract and are
eliminated in the feces.

• Fiber’s ability to promote regular bowel function has been recognized for generations.
• All types of fiber are beneficial to health, but different fibers have different physiologic effects;
  therefore, we need a variety of foods that supply various types. Although most foods contain
  more than one type of fiber, they likely have more of one than another.

Answer 37

Fiber

Question 38

In the past, fibers were classified as ____ or ____, based on their chemical properties
in the laboratory.
* It was believed that these properties influenced their actions in the body as well. We have
since learned that health benefits of fiber are dependent on two characteristics: viscosity
and fermentability.

Answer 38

soluble or insoluble

Question 39

Viscous fibers, formerly referred to as _____ _____ influence blood glucose levels and
lower LDL-cholesterol levels.

Answer 39

soluble fibers

Question 40

Fibers that are fermented by the microflora in the gastrointestinal tract and provide bulk to
the stool were referred to as i___ ______; however, not all viscous fibers are soluble, and
not all fibers that influence laxation are insoluble, so these terms are no longer used to
describe health benefits, although food labels still use them.

Answer 40

insoluble fibers

Question 41

is the material in plant cell walls that
provides structure. We find it in the stems and leaves of vegetables, in the coverings of seeds and
grains, and in skins and hulls. Because humans are unable to break down cellulose, it remains in the
digestive tract and contributes bulk to the food mass.

Answer 41

Cellulose

Question 42

This polysaccharide is found in plant cell walls and often surrounds cellulose. Some
hemicelluloses help regulate colon pressure by providing bulk for normal muscle action, whereas
others are fermented by colonic bacteria.

Answer 42

Hemicellulose:

Question 43

is the only dietary fiber that is not a carbohydrate. It is a large molecule that forms the
woody part of plants and in the intestine combines with bile acids and prevents their reabsorption.
Lignin contributes the sandy texture to pears and lima beans.

Answer 43

Lignin

Question 44

fiber is found in plant cell walls. It forms a viscous, sticky gel that binds cholesterol and
prevents its absorption. Pectin also helps to slow gastric emptying and extend feelings of satiety.

Answer 44

Pectin

Question 45

Plants secrete____ in response to plant injury. In the intestine gums bind cholesterol and
prevent its absorption. Bacteria in the colon ferment gums to form short- chain fatty acids that nourish
colonic cells (this action is also true of resistant starch).

Answer 45

gums

Question 46

These water-soluble fibers are found in oats and oat bran, foods that carry a health
claim on the label indicating they can reduce the risk of heart disease. (β-glucans interfere with the
absorption of cholesterol.)

Answer 46

β-Glucans

Question 47

Examples of Pectin, B-Glucans, Gums

Answer 47

Oatmeal
Oranges
Kidney Beans
Carrots
Apples

Question 48

Examples of Cellulose, Hemicellulose, Lignin

Answer 48

Whole-wheat bread
popcorn
baked beans
bananas
pears

Question 49

K

Answer 49

N