Campbell Biology Concepts & ConnectionsTenth EditionChapter

Campbell Biology: Concepts & Connections
Tenth Edition
Chapter 3
The Molecules of Cells
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1
Introduction
Most adults cannot properly digest dairy products.
These people are lactose intolerant, because they lack the
enzyme lactase.
This illustrates the importance of biological molecules, such as
lactase, in the daily functions of living organisms.
2
Figure 3.0_1

Figure 3.0_1 What does evolution have to do with drinking
milk?
3
Figure 3.0_2
Figure 3.0_2 Chapter 3: Big Ideas
Long Description:
The details of the figure are as follows:
Introduction to organic compounds: An image shows ball-and-
stick model with a central black sphere bonded to 4 small, white
spheres in tetrahedral shape.
Carbohydrates: An image shows a colony of bees in a honey
comb.
Lipids: An image shows bilipid layer of a membrane with oval
heads on the outer side and two tails for each head on the inner
side.
Proteins: An image shows the three-dimensional structure of a
protein.
Nucleic acids: An image shows the double helical structure of a
D N A molecule.
4
Introduction to Organic Compounds
5

3.1 Life’s Molecular Diversity Is Based on the Properties of
Carbon (1 of 2)
Carbon’s ability to bond with four other atoms is the basis for
building large and diverse organic compounds.
Carbon chains form the backbone of most organic molecules.
Isomers have the same molecular formula but different
structures.
Hydrocarbons are composed of only carbon and hydrogen.
Student Misconceptions and Concerns
Students might need to be reminded about the levels of
biological organization. Without such a review, the relationship
between atoms, monomers, and polymers can be confusing as
each is discussed. Consider noting these relationships
somewhere in the classroom (such as on the board) where
students can quickly glance for reassurance. (3.1)
General biology students might not have previously taken a
chemistry course. The concept of molecular building blocks that
cannot be seen can be abstract and difficult to comprehend for
such students. Concrete examples from our diets and good
images will increase comprehension. (3.1–3.3)
Teaching Tips
One of the great advantages of carbon is its ability to form up to
four bonds, permitting the assembly of diverse components and
branching configurations. Challenge your students to find
another element that might also permit this sort of adaptability.
(Like carbon, silicon has four electrons in its outer shell.) (3.1)
Toothpicks and gumdrops (or any other pliable small candy)
permit the quick construction of chemical models. Different
candy colors can represent certain atoms. The model of the
methane molecule in Figure 3.1 can thus easily be demonstrated
(and consumed)! (3.1)

6
3.1 Life’s Molecular Diversity Is Based on the Properties of
Carbon (2 of 2)
Checkpoint question Methamphetamine occurs as two isomers:
one is the addictive illegal drug known as “crank”; the other is a
sinus medication. How can you explain these differing effects?
Checkpoint Question Response
Isomers have different structures, or shapes, and the shape of a
molecule usually determines the way it functions in the body.
Students might need to be reminded about the levels of
biological organization. Without such a review, the relationship
between atoms, monomers, and polymers can be confusing as
each is discussed. Consider noting these relationships
somewhere in the classroom (such as on the board) where
students can quickly glance for reassurance. (3.1)
Teaching Tips
One of the great advantages of carbon is its ability to form up to
four bonds, permitting the assembly of diverse components and
branching configurations. Challenge your students to find
another element that might also permit this sort of adaptability.
(Like carbon, silicon has four electrons in its outer shell.) (3.1)
Toothpicks and gumdrops (or any other pliable small candy)
permit the quick construction of chemical models. Different
candy colors can represent certain atoms. The model of the
methane molecule in Figure 3.1 can thus easily be demonstrated

(and consumed)! (3.1)
7
Figure 3.1a
Figure 3.1a A model of methane and the tetrahedral shape of a
molecule
8
Figure 3.1b
Figure 3.1b Four ways in which carbon skeletons can vary
Long Description:
Characteristics of Skeleton
Definition
Examples
Length
carbon skeletons vary in length
ethane is two single bonded carbons surrounded by hydrogens,
propane is three single bonded carbons surrounded by
hydrogens
Double bonds
carbon skeletons may have double bonds, which can vary in
location
1 butene which has a 4 carbon middle with the double bond

between the first and second carbon, 2 butene which has a 4
carbon middle with the double bond between the second and
third carbon
Branching
carbon skeletons may be unbranched or branched
butane is unbranched, isobutane is branched with a carbon
coming off the center, second carbon
Rings
carbon skeletons may be arranged in rings. In the abbreviated
ring structures, each corner represents a carbon and its attached
hydrogens.
cyclohexane is six carbons single bonded in a ring with two
hydrogens off of each carbon, benzene is a six carbon ring with
every other bond a double bond and one hydrogen off of each
hydrogen
9
Figure 3.1b_1
Figure 3.1b_1 Four ways in which carbon skeletons can vary
(part 1: length)
10
Figure 3.1b_2

(part 2: double bonds)
11
Figure 3.1b_3
(part 3: branching)
12
Figure 3.1b_4
(part 4: rings)
13
Animation: Isomers 2
14
Animation: Carbon Skeletons

15
Animation: Isomers
16
3.2 A Few Chemical Groups are Key to the Functioning of
Biological Molecules (1 of 2)
An organic compound’s properties depend on the
size and shape of its carbon backbone and
atoms attached to that skeleton.
Hydrophilic functional groups give organic molecules specific
chemical properties.
Table 3.2 illustrates six important chemical groups.
Teaching Tips
A drill with interchangeable drill bits is a nice anal ogy to
carbon skeletons with different functional groups. The analogy
relates the role of different functions to different structures.

(3.2)
17
Table 3.2 Important Chemical Groups Of Organic Compounds
(1 of 3)
Checkpoint question Identify the chemical groups that do not
contain carbon.
The hydroxyl, amino, and phosphate groups
Long Description:
The table is as follows.
Chemical group
Example
A hydroxyl, or O H, group shown as single bond O H.
A carbon skeleton of alcohol shows two carbons single bonded
to each other. The left carbon is bonded to three hydrogen
molecules. The right carbon is bonded to two hydrogen
molecules and a hydroxyl, or O H group.
A carbonyl, two single bonds connect to a carbon double
bonded to an oxygen, group.
• A carbon skeleton of three carbons. The first carbon is single
bonded to the second carbon and the second is single bonded to
the third carbon. The middle carbon is a carbonyl group. The
first and third carbons are single bonded to three hydrogens.
• Three carbons are single bonded together. The first two
carbons are bonded to three hydrogens and two hydrogens
respectively. The third carbon is double bonded to an oxygen as
a carbonyl group, and single bonded to a hydrogen.

A carboxyl. or C O O H group.
A carboxylic acid. Two carbons are single bonded to each other.
The left carbon is single bonded to three hydrogens, and the
right carbon is double bonded to an oxygen and single bonded
to an O H group. The carboxylic acid yields the following in a
reversible reaction. An ionized form of carboxylic acid which is
a single bonded C double bonded to an O with a O H also single
bonded to the C. The O H of the carboxyl group loses the
positive hydrogen atom becoming negative.
An amino group which is single bonded N H 2.
An amine. A carbon is single bonded to a nitrogen. The carbon
is also single bonded to three hydrogens. The nitrogen is single
bonded to two hydrogens. Beside the amine is an additional H
positive ion. The amine reacts with a hydrogen ion to produce
its ionized form in a reversible reaction. The ionized form is the
amine where the nitrogen now has a positive charge and is
bonded to three hydrogens.
A phosphate group, has a single bond O P O 3 with a charge of
negative 2.
An organic phosphate, A T P. Adenosine, is single bonded to a
chain of alternating oxygen and phosphorus atoms. Each
phosphorus is also double bonded to an oxygen and single
bonded to a negative oxygen. The last phosphorus in the chain
is double bonded to an oxygen, and single bonded to two
negatively charged oxygens.
A methyl C H 3 group with a single bond at one end.
A methylated compound shows a ring of four carbons and two
nitrogens. The carbon on the top right is the first carbon and the
carbons are numbered one to four in a clockwise direction.
Carbon one and two are double bonded to each other, carbon
two is single bonded to nitrogen, the nitrogen is single bonded
to carbon three, carbon three is single bonded to a second
nitrogen, the nitrogen is double bonded to the fourth carbon.
The first carbon has a methyl group attached to it, the second
carbon is single bonded to a hydrogen, the first nitrogen is
single bonded to a hydrogen, the third carbon is double bonded

to an oxygen, and the fourth carbon is bonded to amino group.
18
3.2 A Few Chemical Groups Are Key to the Functioning of
Biological Molecules (2 of 2)
The sex hormones testosterone and estradiol (a type of estrogen)
differ only in the groups of atoms highlighted in Figure 3.2.
Teaching Tips
A drill with interchangeable drill bits is a nice analogy to
carbon skeletons with different functional groups. The analogy
relates the role of different functions to different structures.
(3.2)
19
Figure 3.2
Figure 3.2 Differences in the chemical groups of sex hormones
Long Description:
Estradiol has a hydroxyl group where testosterone has a

carbonyl group, and doesn’t have a group where testosterone
has a methane group.
20
Figure 3.2_1
Figure 3.2_1 Differences in the chemical groups of sex
hormones (part 1)
21
Figure 3.2_2
Figure 3.2_2 Differences in the chemical groups of sex
hormones (part 2)
22
3.3 Cells Make Large Molecules from a Limited Set of Small
Molecules (1 of 2)
The four classes of biological molecules contain very large
molecules.
They are often called macromolecules because of their large
size.
They are also called polymers because they are made from
identical or similar building blocks strung together.
The building blocks of polymers are called monomers.

Teaching Tips
Train cars linking together to form a train is a nice analogy to
linking monomers to form polymers. Consider noting that as the
train cars are joined, a puff of steam appears—a reference to
water production and a dehydration reaction when linking
molecular monomers. (3.3)
The authors note that the great diversity of polymers mainly
results from variable arrangements of monomers, with different
sequences possible from combinations or permutations of the
same monomers. Consider illustrating this by simply asking
students how many different ways we can arrange the letters A,
B, and C, using each letter, and only once, to form three-
lettered words. The answer is six permutations: ABC, ACB,
BAC, BCA, CBA, CAB (the factorial of 3). And if letters can be
repeated, the answer is 27 (= 33): AAA, BBB, CCC, ABB, ACC,
etc. (3.3)
23
3.3 Cells Make Large Molecules from a Limited Set of Small
Molecules (2 of 2)
Monomers are linked together to form polymers through
dehydration reactions.
Polymers are broken apart by hydrolysis.
These reactions are mediated by enzymes, specialized

macromolecules that speed up reactions.
Checkpoint question Suppose you eat some cheese. What
reactions must occur for the protein of the cheese to be broken
down into its amino acid monomers and then for these
monomers to be converted to proteins in your body?
During digestion, proteins are broken down into amino acids by
hydrolysis. New proteins are formed in your body cells from
these monomers by dehydration reactions.
Teaching Tips
Train cars linking together to form a train is a nice analogy to
linking monomers to form polymers. Consider noting that as the
train cars are joined, a puff of steam appears—a reference to
water production and a dehydration reaction when linking
molecular monomers (3.3)
The authors note that the great diversity of polymers mainly
results from variable arrangeme nts of monomers, with different
sequences possible from combinations or permutations of the
same monomers. Consider illustrating this by simply asking
students how many different ways we can arrange the letters A,
B, and C, using each letter, and only once, to form three-
lettered words. The answer is six permutations: ABC, ACB,
BAC, BCA, CBA, CAB (the factorial of 3). And if letters can be
repeated, the answer is 27 (= 33): AAA, BBB, CCC, ABB, ACC,
etc. (3.3)

24
Figure 3.3
Figure 3.3 Dehydration reaction building a polymer (left);
hydrolysis breaking down a polymer (right)
Long Description:
The first illustration shows a dehydration reaction. Monomers
are depicted by purple circles. In the dehydration reaction, a
polymer is built and a new bond is formed. Polymers and
monomers are flanked by a hydrogen and a hydroxyl group. A
short polymer made up of three monomers reacts with an
unlinked monomer. The hydroxyl group of the short polymer
reacts with the hydrogen of the unlinked monomer. This
releases a water molecule and creates a longer polymer made up
of 4 monomers. The second illustration shows a hydrolysis
reaction. In a hydrolysis reaction, a polymer is made into
smaller parts and a bond is broken. A polymer made up of 4
monomers is flanked by a hydrogen and a hydroxyl group. A
water molecule comes in and helps to break the bond between
the third and fourth carbons, and the polymer breaks up into a
polymer made up of three monomers and an unlinked monomer.
25
Figure 3.3_1_1

Figure 3.3_1_1 Dehydration reaction building a polymer (part 1,
step 1)
Long Description:
In this illustration, monomers are depicted by purple circles.
Polymers and monomers are flanked by a hydrogen and a
hydroxyl group. A short polymer made up of three monomers
reacts with an unlinked monomer. The hydroxyl group of the
short polymer reacts with the hydrogen of the unlinked
monomer.
26
Figure 3.3_1_2
Figure 3.3_1_2 Dehydration reaction building a polymer (part 1,
step 2)
Long Description:
In this illustration, monomers are depicted by purple circles. In
the dehydration reaction, a polymer is built and a new bond is
formed. Polymers and monomers are flanked by a hydrogen and
a hydroxyl group. A short polymer made up of three monomers
reacts with an unlinked monomer. The hydroxyl group of the
short polymer reacts with the hydrogen of the unlinked
monomer. This releases a water molecule and creates a longer
polymer made up of 4 monomers.
27

Figure 3.3_2_1
Figure 3.3_2_1 Hydrolysis breaking down a polymer (part 2,
step 1)
28
Figure 3.3_2_2
Figure 3.3_2_2 Hydrolysis breaking down a polymer (part 2,
step 2)
Long Description:
In this illustration, monomers are depicted by purple circles.
Polymers and monomers are flanked by a hydrogen and a
hydroxyl group. In a hydrolysis reaction, a polymer is made into
smaller parts and a bond is broken. A polymer made up of 4
monomers is flanked by a hydrogen and a hydroxyl group. A
water molecule comes in and helps to break the bond between
the third and fourth carbons, and the polymer breaks up into a
polymer made up of three monomers and an unlinked monomer.
29
Animation: Polymers

30
Carbohydrates
31
3.4 Monosaccharides are the Simplest Carbohydrates
Carbohydrates range from small sugar molecules (monomers) to
large polysaccharides.
Sugar monomers are monosaccharides.
A monosaccharide generally has a formula that is a multiple of
C H 2 O and contains hydroxyl groups and a carbonyl group.
Checkpoint question Write the formula for a monosaccharide
that has three carbons.
C3H6O3
The abstract nature of chemistry can be discouraging to many
students. Consider starting out this section of class by
examining the chemical groups on a food nutrition label. Candy
bars with peanuts are particularly useful because they contain
significant amounts of all three sources of calories
(carbohydrates, proteins, and lipids). (3.4)
Consider reinforcing the three main sources of calories with
food items that clearly represent each group. Bring clear
examples to class as visual references. For example, use a can
of Coke or a bag of sugar (or cotton candy) for carbohydrates, a
tub of margarine for lipids, and some beef jerky for protein
(although some fat and carbohydrates might also be included).

(3.4–3.7)
Teaching Tips
If your lectures will eventually include details of glycolysis and
aerobic respiration, this is a good point to introduce the basic
concepts of glucose as fuel. Just introducing this conceptual
formula might help: consuming glucose and breathing oxygen
produce water and usable energy (that can be used to build
ATP) plus heat and carbon dioxide exhaled in our breath. (3.4)
Active Lecture Tips
See the Activity “Reviewing Macromolecules” on the Instructor
Exchange. Visit the Instructor Exchange in the
MasteringBiology instructor resource area for a description of
this activity. (3.4–3.7)
32
Figure 3.4a
Figure 3.4a Bees with honey, a mixture of two monosaccharides
33
Figure 3.4b
Figure 3.4b Structures of glucose and fructose
Long Description:
The glucose skeleton is made up of a vertical chain of six
carbons labeled 1 through 6 from top to bottom. Carbon one is

part of a carbonyl group. It is double bonded to an oxygen and
single bonded to a hydrogen. Carbons two, four, and five are
single bonded to a hydroxide group on the right and a hydrogen
on the left. Carbon three is single bonded to a hydrogen on the
right and a hydroxide group on the left. Carbon five is single
bonded to a hydroxide on the right, a hydrogen on the left, and
another hydrogen. The fructose skeleton is made up of a vertical
chain of six carbons as well. The skeleton is identical to that of
glucose from carbons 3 through 6. The only changes are carbon
one is single bonded to a hydroxyl to the right and an additional
hydrogen and carbon two is a carbonyl carbon.
34
Figure 3.4c
Figure 3.4c Three representations of the ring form of glucose
Long Description:
In the first ring, the structural formula is given. There is a
hexagon of carbons and an oxygen. The top right vertex of the
hexagon is the oxygen, and carbons one through five are found
on the hexagon moving clockwise.
● Carbon one is bonded to a hydrogen and a hydroxyl group.
The hydroxyl group is below the hydrogen group.
● Carbon two is bonded to a hydrogen and a hydroxyl group.
The hydroxyl group is down and the hydrogen is up.
● Carbon three is bonded to a hydrogen and a hydroxyl group.
The hydroxyl group is up and the hydrogen is down.
● Carbon four is bonded to a hydrogen and a hydroxyl group.
The hydroxyl group is below the hydrogen group.
● Carbon five is bonded to carbon six found in C H 2 O H.

In the second ring, an abbreviated structure is shown. The
hexagon is the same, but the carbons in the ring are not shown.
In the third ring, a simplified structure is shown. The only
element shown in the structure is the oxygen on the top right
vertex of the hexagon.
35
3.5 Two Monosaccharides Are Linked to Form a Disaccharide
Two monosaccharides (monomers) can bond to form a
disaccharide in a dehydration reaction.
Checkpoint question Lactose, as you read in the chapter
introduction, is the disaccharide sugar in milk. It is formed from
glucose and galactose. The formula for both these
monosaccharides is C 6 H 12 O 6. What is the formula for
lactose?
C12H22O11
(3.4–3.7)
Teaching Tips
Learning the definitions of word roots is invaluable when
learning science. Learning the meaning of the prefix word roots
“mono” (one), “di” (two), and “poly” (many) helps to
distinguish the structures of various carbohydrates. (3.5)
Active Lecture Tips

36
Figure 3.5_1
Figure 3.5_1 Disaccharide formation by a dehydration reaction
(step 1)
37
Figure 3.5_2
Figure 3.5_2 Disaccharide formation by a dehydration reaction
(step 2)
Long Description:
The two monosaccharides are both glucose. The O H group of
carbon one from one glucose molecule and the hydrogen from
the OH group of carbon four from the other glucose react to
release a water molecule and make a disaccharide, maltose.
38
Animation: Disaccharides

39
3.6 Connection: Are We Eating Too Much Sugar?
The F D A recommends that only 10% of daily calories come
from added sugar.
Research supports the correlation between high sugar intake and
adverse health effects.
Checkpoint question Sugars are often described as “empty
calories.” What do you think that means from a nutrition
standpoint?
Added sugars provide energy but they do not provide other
nutrients, such as protein, fats, vitamins, or minerals.
(3.4–3.7)
Teaching Tips
The extent of sugar consumption can be surprising to students.
Consider asking each student to identify a product that they
have consumed that has added sugar. (3.6)
Consider an assignment for students to find reliable sources that
discuss high rates of sugar consumption in the modern diet. The
key, of course, is in the quality of the resource. Consider
limiting their search to established nonprofit organizations
(American Cancer Society, American Heart Association, etc.)
and peer-reviewed journals. (3.6)

Active Lecture Tips
See the Activity “What Ingredients Make Up Your Snack Food”
on the Instructor Exchange. Visit the Instructor Exchange in the
this activity. (3.6)
40
Figure 3.6
Figure 3.6 The amount of sugar an average U.S. adult eats in a
year compared to recommendations from the World Health
Organization (WHO) and the Food and Drug Administration
(FDA)
Long Description:
The graph has the row headings W H O, F D A, and average
American. The graph reads as the table below indicates.
Yearly Consumption, shown with 5 pound bags of sugar
4 bags, 20 pounds
8 bags, 40 pounds
26 bags, 130 pounds
41
3.7 Polysaccharides Are Long Chains of Sugar Units
Starch and glycogen are storage polysaccharides.
Cellulose is structural, found in plant cell walls.

Chitin is a component of insect and crustacean and fungal cell
walls.
Checkpoint question Compare and contrast starch and cellulose,
two plant polysaccharides.
Both are polymers of glucose, but the bonds between glucose
monomers have different shapes. Starch functions mainly for
sugar storage. Cellulose is a structural polysaccharide that is the
main material of plant cell walls.
(3.4–3.7)
Teaching Tips
A simple exercise demonstrates the enzymatic breakdown of
starches into sugars. If students place an unsalted cracker in
their mouths, holding it in their mouths while it mixes well with
saliva, they might soon notice that a sweeter taste begins to
emerge. The salivary enzyme amylase begins the digestion of
starches into disaccharides, which may be degraded further by
other enzymes. These disaccharides are the source of the sweet
taste. (3.7)
The text notes that cellulose is the most abundant organic
molecule on Earth. Ask your students why this is true. (3.7)
The cellophane wrap often used to package foods is a
biodegradable material derived from cellulose. Consider
challenging students to create a list of other cellulose-derived
products (such as paper). (3.7)
An adult human may store about half a kilogram of glycogen in

the liver and muscles of the body, depending on recent dietary
habits. A person who begins dieting might soon notice a weight
loss of 2–4 pounds (1–2 kilograms) over several days, reflecting
reductions in stored glycogen, water, and intestinal contents
(among other factors). (3.7)
Active Lecture Tips
42
Figure 3.7
Figure 3.7 Polysaccharides of plants and animals
Long Description:
All examples of polysaccharides are made up of glucose
monomers.
Polysaccharide
Found in
Made up of
Starch
potato tuber cell
long chains of glucose molecules
Glycogen
muscle tissue
long chains of glucose molecules, more branched than starch.
Cellulose
plant cell wall
parallel chains of cellulose molecules are joined by hydrogen

bonds. the bonds between the glucose molecules are different
than the ones in starch and glycogen, they alternate rather than
being all on one side
43
Figure 3.7_1
Figure 3.7_1 Polysaccharides of plants and animals (part 1:
starch)
44
Figure 3.7_2
glycogen)
45
Figure 3.7_3
cellulose)

Long Description:
The chemical structure of cellulose consists of parallel chains of
cellulose molecules that are joined by hydrogen bonds. The
bonds between the glucose molecules are different than the ones
in starch and glycogen; they alternate rather than being all on
one side
46
Figure 3.7_4
photo)
47
Animation: Polysaccharides
48
Lipids
49

3.8 Fats Are Lipids That Are Mostly Energy-Storage Molecules
(1 of 2)
Lipids are diverse hydrophobic (water-fearing) compounds
composed largely of carbon and hydrogen.
Fats (triglycerides) consist of glycerol linked to three fatty
acids.
Some fatty acids contain one or more double bonds, forming
unsaturated fatty acids. Unsaturated fatty acids are typical of
plant oils.
Fats with the maximum number of hydrogens are called
saturated fatty acids. Saturated fatty acids are found in animal
fats.
Students may struggle with the concept that a pound of fat
contains more than twice the calories of a pound of sugar. It
might seem that a pound of food would potentially add on a
pound of weight. Other students may have never understood the
concept of calories in the diet, simply following general
guidelines of avoiding fatty foods. Furthermore, fiber and water
have no caloric value but add to the weight of food. Consider
class discussions that explore student misconceptions about
calories, body weight, and healthy diets. (3.8)
Students might struggle to extrapolate the properties of lipids to
their roles in an organism. Ducks float because their feathers
repel water instead of attracting it. Hair on our heads remains
flexible because of oils produced in our scalp. Examples such as
these help connect the abstract properties of lipids to concrete
examples in our world. (3.8–3.11)
Teaching Tips
The text in Module 3.8 notes the common observation that
vinegar and oil do not mix. A simple demonstration can help
make this point. In front of the class, mix together colored
water and a yellow oil (corn or canola oil works well). Shake up

the mixture and then watch as the two separate. (You may have
a mixture already made ahead of time that remains separated;
however, the dye may bleed between the oil and the water.)
Placing the mixture on a well-illuminated imaging device makes
for a dramatic display of hydrophobic activity! (3.8)
The text notes that a gram of fat stores more than twice the
energy of a gram of polysaccharide, such as starch. You might
elaborate with a simple calculation to demonstrate how a
person’s body weight would vary if the energy stored in body
fat were stored in carbohydrates instead. If a 100-kg man
carried 25% body fat, he would have 25 kg of fat in his body.
Fat stores about 2.25 times more energy per gram than
carbohydrate. What would be the weight of the man if he stored
kg of carbohydrate + 75 kg (nonfat body weight) = 131.25 kg,
an increase of 31.25%.) (3.8)
Active Lecture Tips
this activity. (3.8, 3.9)
See the Activity “Drawing Hydrophobic and Hydrophilic
Interactions” on the Instructor Exchange. Visit the Instructor
Exchange in the MasteringBiology instructor resource area for a
description of this activity. (3.8, 3.10)
50
3.8 Fats Are Lipids That Are Mostly Energy-Storage Molecules
(2 of 2)
Hydrogenated vegetable oils are unsaturated fats that have been
converted to saturated fats by adding hydrogen.

This hydrogenation creates trans fats, which are associated with
health risks.
Checkpoint question Explain why fats are hydrophobic.
The three fatty acid tails of a fat molecule contain only
nonpolar C—H bonds, which do not mix well with polar water
molecules.
flexible because of oils produced in our scalp. Examples s uch as
Teaching Tips

Active Lecture Tips
51
Figure 3.8a
Figure 3.8a A dehydration reaction that will link a fatty acid to
glycerol
Long Description:

The fatty acid is a chain of sixteen carbons. The carbon at the
end of the chain is part of a carboxyl group. The glycerol is
made up of a chain of three carbons and each carbon i s bonded
to a hydroxyl group. The O H from the carboxyl group of the
fatty acid reacts with the hydrogen from the hydroxyl group of
the glycerol to release a water molecule and link the fatty acid
and the glycerol.
52
Figure 3.8b
Figure 3.8b A fat molecule (triglyceride) consisting of three
fatty acids linked to glycerol
Long Description:
Two of the fatty acids are chains of sixteen carbons where the
carbon at the end of the chain is a carbonyl group. The third
fatty acid is a chain of sixteen carbons where the end is a
carbonyl group and carbons eight and nine share a double bond.
53
Figure 3.8c
Figure 3.8c Types of fats
54

Figure 3.8c_1
Figure 3.8c_1 Types of fats (part 1: saturated fats)
55
Figure 3.8c_2
Figure 3.8c_2 Types of fats (part 2: unsaturated fats)
56
Animation: Fats
57
3.9 Scientific Thinking: Scientific Studies Document the Health
Risks of Trans Fats (1 of 2)
By the 1990s, partially hydrogenated oils were common in
countless foods.
Recent research has shown that trans fats pose an even greater
health risk than saturated fats.
The scientific studies establishing the risks of trans fats were of

two types.
In experimental controlled feeding trials, diets contained
different proportions of saturated, unsaturated, and partially
hydrogenated fats.
Many other scientific studies on dietary health effects are
observational.
Teaching Tips
Margarine in stores commonly comes in liquid spray or squeeze
containers, in tubs, and in sticks. These forms reflect increasing
amounts of hydrogenation, gradually increasing the stiffness
from a liquid, to a firmer spread, to a firm stick of margarine.
As noted in the text, recent studies have suggested that
unsaturated oils become increasingly unhealthy as they are
hydrogenated. Students might therefore remember that as
margarine products increase in stiffness, they generally become
less healthy. Public attention to hydrogenation and the health
risks of the resulting trans fats are causing changes in the use of
products containing trans fats. (3.9)
Active Lecture Tips

58
3.9 Scientific Thinking: Scientific Studies Document the Health
Risks of Trans Fats (2 of 2)
Checkpoint question What is the difference between a
retrospective and a prospective study?
A retrospective study “looks backward” to assess risk factors or
benefits that correlate with current health status. A prospective
study follows a group forward, monitoring certain factors and
recording health outcomes over a period of time.
Teaching Tips
Margarine in stores commonly comes in liquid spray or squeeze
containers, in tubs, and in sticks. These forms reflect increasing
amounts of hydrogenation, gradually increasing the stiffness
from a liquid, to a firmer spread, to a firm stick of margarine.
As noted in the text, recent studies have suggested that
unsaturated oils become increasingly unhealthy as they are
hydrogenated. Students might therefore remember that as
margarine products increase in stiffness, they generally become
less healthy. Public attention to hydrogenation and the health
risks of the resulting trans fats are causing changes in the use of

products containing trans fats. (3.9)
Active Lecture Tips
59
Figure 3.9
Figure 3.9 Relative risk of heart disease associated with
increased intake of specific types of fats
Long Description:
The data is represented by the following table.
Relative Risk
Change in risk
Type of fat
2.00
100% increase in risk
blank
1.93
between 50 and 100%
Trans fat
1.50
50% increase in risk
blank

1.17
between 0 and 50%
Saturated fat
1.00
Baseline, no risk difference
blank
0.81
Under 0%
Monounsaturated fat
0.62
Under 0%
Polyunsaturated fat
0.50
50% decrease in risk
blank
0.25
75% decrease in risk
blank
60
3.10 Phospholipids and Steroids Are Important Lipids with a
Variety of Functions
Phospholipids are components of cell membranes.
Steroids include cholesterol and some hormones.
Cholesterol is a common component in animal cell membranes
and is also the precursor for making other steroids, including
sex hormones.
Checkpoint question Compare the structure of a phospholipid
with that of a fat.

molecules.
Teaching Tips
water and a yellow oil (corn or canola oil works well ). Shake up

Active Lecture Tips
on the Instructor Exchange. Visit the Instructor Exchange i n the
61
Figure 3.10a
Figure 3.10a Chemical structure of a phospholipid molecule
Long Description:
The figure shows that a phospholipid is made up of a glycerol
and two fatty acids. One of the fatty acids is a chain of sixteen
carbons, where the carbon at the end of the chain is a carbonyl
group. The second fatty acid is a chain of sixteen carbons where
the end is a carbonyl group and carbons eight and nine share a
double bond. The glycerol is made up of a three carbon chain
where the last carbon is attached to a phosphate group. The
head of the phospholipid is made up of the glycerol and
phosphate group and is hydrophilic. The tails of the
phospholipid are made up of the two fatty acid chains and are

hydrophobic. The phospholipids are shown as gray ovals that
represent the heads, and yellow arms that represent the tails
62
Figure 3.10b
Figure 3.10b Section of a phospholipid membrane
Long Description:
The figure shows a section of the membrane to depict how the
phospholipids interact. The phospholipids group by their heads
into a sheet, and two sheets interact by their tails so that the
hydrophobic tails are not exposed to water and the hydrophilic
heads are
63
Figure 3.10c
Figure 3.10c Cholesterol, a steroid
64
3.11 Connection: Anabolic Steroids Pose Health Risks
Anabolic steroids are synthetic variants of the male hormone
testosterone that are abused by some athletes with serious
consequences.

Checkpoint question Explain why fats and steroids, which are
structurally very different, are both classed as lipids.
molecules.
Teaching Tips

Active Lecture Tips
65
Figure 3.11
Figure 3.11 Bodybuilder
66

Proteins
67
3.12 Proteins Have a Wide Range of Functions and Structures (1
of 2)
Proteins are involved in nearly every dynamic function in your
body and are very diverse.
Proteins function as
enzymes,
transport proteins embedded in cell membranes,
defensive proteins, such as antibodies,
signal proteins such as many hormones,
receptor proteins,
contractile proteins found within muscle cells,
structural proteins such as collagen, and
storage proteins.
The functional significance of protein shape is an abstract
molecular example of form and function relationships, which
might be new to some students. The binding of an enzyme to its
substrate is a type of molecular handshake, which permits
specific interactions. To help students think about form and
function relationships, share some concrete analogies in thei r
lives—perhaps flathead and Phillips screwdrivers that match the
proper type of screws or the fit of a hand into a glove. (3.12)
Teaching Tips
Most cooking results in changes in the texture and color of
food. The brown color of a cooked steak is the product of the
denaturation of proteins. Fixatives such as formalin also

denature proteins and cause color changes. Students who have
dissected vertebrates will realize that the brown color of the
muscles makes it look as if the animal has been cooked. (3.12)
Active Lecture Tips
68
3.12 Proteins Have a Wide Range of Functions and Structures (2
of 2)
Proteins are composed of differing arrangements of a common
set of just 20 amino acid monomers.
The functions of different types of proteins depend on their
individual shapes.
In the process of denaturation, a protein unravels, loses its
specific shape, and loses its function.
Checkpoint question Why does a denatured protein no longer
function normally?
The function of each protein is a consequence of its specific
shape, which is lost when a protein denatures.
The functional significance of protein shape is an abstract
molecular example of form and function relationships, which
might be new to some students. The binding of an enzyme to its
substrate is a type of molecular handshake, which permits
specific interactions. To help students think about form and
function relationships, share some concrete analogies in their

lives—perhaps flathead and Phillips screwdrivers that match the
proper type of screws or the fit of a hand into a glove. (3.12)
Teaching Tips
Most cooking results in changes in the texture and color of
food. The brown color of a cooked steak is the product of the
denaturation of proteins. Fixatives such as formalin also
denature proteins and cause color changes. Students who have
dissected vertebrates will realize that the brown color of the
muscles makes it look as if the animal has been cooked. (3.12)
Active Lecture Tips
69
Figure 3.12a
Figure 3.12a Ribbon model of the protein lysozyme
70
Figure 3.12b
Figure 3.12b Space-filling model of the protein lysozyme

71
Figure 3.12c
Figure 3.12c Fibrous silk proteins of a spider’s web.
72
3.13 Proteins Are Made from Amino Acids Linked by Peptide
Bonds (1 of 2)
Protein diversity is based on different sequences of amino acids,
monomers that contain
an amino group,
a carboxyl group,
an H atom, and
an R group, all attached to a central carbon.
The R groups distinguish 20 amino acids, each with specific
properties.
Teaching Tips
Many analogies help students appreciate the diversity of
proteins that can be made from just 20 amino acids. The authors
note that our language uses combinations of 26 letters to form
words. Proteins are much longer “words,” creating even more
diversity. Another analogy is to trains. This builds upon the
earlier analogy suggested when polymers were introduced.
Imagine making different trains about 100 cars long, using any
combination of 20 types of railroad cars. Mathematically, the
number of possible trains is 20100, a number beyond

imagination. (3.13)
The difference between a polypeptide and a protein is analogous
to the relationship between a long strand of yarn and a sweater
knitted from yarn. Proteins are clearly more complex! (3.13,
3.14)
Active Lecture Tips
73
3.13 Proteins Are Made from Amino Acids Linked by Peptide
Bonds (2 of 2)
Amino acid monomers are linked together in a dehydration
reaction,
joining the carboxyl group of one amino acid to the amino
group of the next amino acid, and
creating a peptide bond.
Additional amino acids can be added by the same process to
create a chain of amino acids called a polypeptide.
Checkpoint question By what process do you digest the proteins
you eat into their individual amino acids?
By hydrolysis, adding a molecule of water back to break each
peptide bond
Teaching Tips

imagination. (3.13)
3.14)
Active Lecture Tips
74
Figure 3.13a
Figure 3.13a General structure of an amino acid
75
Figure 3.13b

Figure 3.13b Examples of amino acids with hydrophobic and
hydrophilic R groups
Long Description:
A table of example R groups of amino acids.
Hydrophobic
Hydrophilic
Leucine, has a r group of two carbon backbone with two C H 3
groups at the end
Serine has an r group of a C H 2 linked to O H, Aspartic acid
has an r group with a two carbon backbone with a negatively
charge O attached and a double bonded O attached
76
Figure 3.13c_1
Figure 3.13c_1 Peptide bond formation (step 1)
77
Figure 3.13c_2
Figure 3.13c_2 Peptide bond formation (step 2)
Long Description:
The carboxyl group of one amino acid reacts with the amino
group of another amino acid. This releases water and forms a

bond between the carboxylic carbon and nitrogen called a
peptide bond.
78
3.14 Visualizing the Concept: A Protein’s Functional Shape
Results from Four Levels of Structure (1 of 2)
A protein can have four levels of structure:
A protein’s primary structure is the sequence of amino acids in
its polypeptide chain.
Its secondary structure is the coiling or folding of the chain,
stabilized by hydrogen bonds.
The tertiary structure is the overall three-dimensional shape of a
polypeptide, resulting from interactions among R groups.
Proteins made of more than one polypeptide have quaternary
structure.
Teaching Tips
3.14)
An examination of the fabrics and weave of a sweater might
help students understand the levels of protein structure.
Although not a perfect analogy, levels of organization can be
better appreciated. Teasing apart a single thread reveals a
simpler organization of smaller fibers woven together. In turn,
threads are interlaced into a connected fabric, which may be
further twisted and organized into a pattern or structural
component of a sleeve. Challenge students to identify the limits
of this analogy and identify aspects of protein structure not
included (such as the primary structure of a protein, its
sequence of amino acids). (3.14)

Active Lecture Tips
79
3.14 Visualizing the Concept: A Protein’s Functional Shape
Results from Four Levels of Structure (2 of 2)
Checkpoint question If a genetic mutation changes the primary
structure of a protein, how might this destroy the protein’s
function?
Primary structure determines the secondary and tertiary
structure due to the chemical nature of the R groups of the
amino acids in the chain. Even a slight change may affect a
protein’s shape and thus its function.
Teaching Tips
3.14)
An examination of the fabrics and weave of a sweater might
help students understand the levels of protein structure.
Although not a perfect analogy, levels of organization can be
better appreciated. Teasing apart a single thread reveals a
simpler organization of smaller fibers woven together. In turn,
threads are interlaced into a connected fabric, which may be
further twisted and organized into a pattern or structural
component of a sleeve. Challenge students to identify the limits
of this analogy and identify aspects of protein structure not
included (such as the primary structure of a protein, its

sequence of amino acids). (3.14)
Active Lecture Tips
80
Figure 3.14_0_1
Figure 3.14_0_1 A protein’s functional shape results from four
levels of structure (step 1)
Long Description:
The details of the diagram are as follows:
In primary structure, the amino acids are bonded in a chain with
an amino end and a carboxyl end. Each amino acid in the chain
are represented by three letter abbreviations. Each specific
amino acid has an R group. The repeated sequence of single
bond N single bond C single bond C single bond, with attached
single bond H and double bond O, but not the R groups, is
called the polypeptide backbone. An example shows polypeptide
bonds that connect the 127 amino acids of a transthyretin
polypeptide and part of the chain is shown.
81
Figure 3.14_0_2

Long Description:
The details of the primary and secondary structures are as
follows:
Type of Structure
Description
Primary
The amino acids are bonded in a chain with an amino end and a
carboxyl end. Each amino acid in the chain are represented by
three letter abbreviations. Each specific amino acid has an R
group. The repeated sequence of single bond N single bond C
single bond C single bond, with attached single bond H and
double bond O, but not the R groups, is called the polypeptide
backbone. An example shows polypeptide bonds that connect
the 127 amino acids of a transthyretin polypeptide and part of
the chain is shown.
Secondary
Secondary structures are maintained by hydrogen bonds between
atoms of the polypeptide backbone, shown as dotted lines.
There are two types of secondary structures. Alpha helix and
beta pleated sheet. In the beta pleated sheets, the carboxyl end
is pointed to by a flat arrow.
82
Figure 3.14_0_3

Long Description:
The details of the primary, secondary, and tertiary structures are
as follows:
Type of Structure
Description
Primary
the chain is shown.
Secondary
Tertiary
A tertiary structure is stabilized by interactions between R
groups, such as the clustering of hydrophobic R groups in the
center of the molecule, and hydrogen bonds, ionic bonds, and
disulfide bridges between hydrophilic R groups. An example of
a transthyretin polypeptide has one alpha helix region and
several beta pleated sheets, which are compacted into a globular
shape.
83

Figure 3.14_0_4
Long Description:
The details of the primary, secondary, tertiary, and quaternary
structures are as follows:
Type of Structure
Description
Primary
the chain is shown.
Secondary
Tertiary

several beta pleated sheets, which are compacted into a globular
shape.
Quaternary
The four identical polypeptides, or subunits, of transthyretin are
precisely associated into a functional protein. Interactions
similar to those involved in tertiary structures hold these
subunits together.
84
Figure 3.14
Figure 3.14 A protein’s functional shape results from four
levels of structure
Long Description:
A series of diagrams explain four different structures of
proteins.
Type of Structure
Description
Primary
the chain is shown.

Secondary
There are two types of secondary structures. alpha helix and
Tertiary
several beta pleated sheets, which are compacted into a gl obular
shape.
Quaternary
subunits together.
85
Figure 3.14_1
Figure 3.14_1 A protein’s functional shape results from four
levels of structure (part 1: primary structure)
Long Description:
In primary structure, the amino acids are bonded in a chain with
an amino end and a carboxyl end. Each amino acid in the chain
are represented by three letter abbreviations. Each specific

amino acid has an R group. The repeated sequence of single
bond N single bond C single bond C single bond, with attached
single bond H and double bond O, but not the R groups, is
called the polypeptide backbone. An example shows polypeptide
bonds that connect the 127 amino acids of a transthyretin
polypeptide and part of the chain is shown.
86
Figure 3.14_2
levels of structure (part 2: secondary structures)
Long Description:
87
Figure 3.14_3
levels of structure (part 3: tertiary structure)

Long Description:
The details of the diagram are as follows: A tertiary structure is
stabilized by interactions between R groups, such as the
clustering of hydrophobic R groups in the center of the
molecule, and hydrogen bonds, ionic bonds, and disulfide
bridges between hydrophilic R groups. An example of a
transthyretin polypeptide has one alpha helix region and several
beta pleated sheets, which are compacted into a globular shape.
88
Figure 3.14_4
levels of structure (part 4: quaternary structure)
Long Description:
subunits together.
89
Animation: Protein Structure Introduction

90
Animation: Primary Protein Structure
91
Animation: Secondary Protein Structure
92
Animation: Tertiary Protein Structure
93
Animation: Quaternary Protein Structure
94

Nucleic Acids
95
3.15 The Nucleic Acids D N A and R N A Are Information-Rich
Polymers of Nucleotides (1 of 2)
The monomers that make up nucleic acids are nucleotides.
Nucleotides are composed of a sugar, a phosphate group, and a
nitrogenous base.
D N A is a double helix.
R N A is a single polynucleotide chain.
D N A and R N A serve as the blueprints for proteins and thus
control the life of a cell.
D N A is the molecule of inheritance.
Module 3.15 is the first time the authors present the concept of
transcription and translation, discussed extensively in later
chapters. The basic conceptual flow of information from DNA
to RNA to proteins is essential to these later discussions. A
flow chart that also relates the location where these processes
occur in a eukaryotic cell will help to cement this fundamental
transmission of genetic information. (3.15)
Teaching Tips
The “NA” in the acronyms DNA and RNA stands for “nucleic
acid.” Students often do not make this association without
assistance. (3.15)
When discussing the sequence of nucleotides in DNA and RNA,
consider challenging your students with the following questions
based on prior analogies. If the 20 possible amino acids in a
polypeptide represent “words” in a long polypeptide sentence,

how many words are possible in the language of a DNA
molecule? (Answer: Four nucleotides, GCAT, are possible). Are
these the same “words” used in RNA? (Answer: No. Uracil
substitutes for thymine.) (3.15)
Active Lecture Tips
96
Figure 3.15a
Figure 3.15a A nucleotide
Long Description:
The oxygen of the phosphate group is bonded to the methyl
group on the fourth carbon of the deoxyribose cyclopentene
ring. The nitrogenous base’s nitrogen is bonded to the first
carbon of the deoxyribose cyclopentene ring.
97
Figure 3.15b
Figure 3.15b A polynucleotide

98
Figure 3.15c
Figure 3.15c DNA double helix
99
Figure 3.15d_1
Figure 3.15d_1 The flow of genetic information in the building
of a protein (step 1)
100
Figure 3.15d_2
101
Figure 3.15d_3

Long Description:
A gene is transcribed from D N A into R N A. The R N A. is
then translated into a protein that is made up of a chain of
amino acids. The gene a section of D N A which is shown at the
top with a blue, ribbon like double helix. The transcription
occurs to change the D N A into R N A which is shown as a
single pink wavy line. And the protein which is a chain of
amino acids is shown at the bottom as a series on connected
spheres.
102
3.15 The Nucleic Acids D N A and R N A Are Information-Rich
Polymers of Nucleotides (2 of 2)
Checkpoint question What roles do complementary base pairing
play in the functioning of D N A?
Complementary base pairing makes possible the precise
replication of DNA, ensuring that genetic information is
faithfully transmitted every time a cell divides. It also ensures
that RNA molecules carry accurate instructions from DNA for
the synthesis of proteins.
Module 3.15 is the first time the authors present the concept of
transcription and translation, discussed extensively in later
chapters. The basic conceptual flow of information from DNA
to RNA to proteins is essential to these later discussions. A
flow chart that also relates the location where these processes
occur in a eukaryotic cell will help to cement this fundamental

transmission of genetic information. (3.15)
Teaching Tips
The “NA” in the acronyms DNA and RNA stands for “nucleic
acid.” Students often do not make this association without
assistance. (3.15)
When discussing the sequence of nucleotides in DNA and RNA,
consider challenging your students with the following questions
based on prior analogies. If the 20 possible amino acids in a
polypeptide represent “words” in a long polypeptide sentence,
how many words are possible in the language of a DNA
molecule? (Answer: Four nucleotides, GCAT, are possible). Are
these the same “words” used in RNA? (Answer: No. Uracil
substitutes for thymine.) (3.15)
Active Lecture Tips
103
3.16 Evolution Connection: Lactose Tolerance Is a Recent
Event in Human Evolution
Different mutations in D N A have led to lactose tolerance in
several human groups whose ancestors raised dairy cattle.
Researchers identified three new mutations in 43 ethnic groups
in East Africa that keep the lactase gene permanently turned on.
Checkpoint question Explain how lactose tolerance involves
three of the four major classes of biological macromolecules.

By hydrolysis, adding a molecule of water back to break each
peptide bond
Teaching Tips
imagination. (3.13)
3.14)
Active Lecture Tips
104
Figure 3.16
Figure 3.16 Lactose tolerance: two different cultures, two
different mutations—same adaptations

105
Figure 3.16_1
Figure 3.16_1 Lactose tolerance: two different cultures, two
different mutations—same adaptations (part 1)
106
Figure 3.16_2
Figure 3.16_2 Lactose tolerance: two different cultures, two
different mutations—same adaptations (part 2)
107
You Should Now Be Able to (1 of 2)
Describe the importance of carbon to life’s molecular diversity.
Describe the chemical groups that are important to life.
Explain how a cell can make a variety of large molecules from a
small set of molecules.
Define monosaccharides, disaccharides, and polysaccharides
and explain their functions.
Define lipids, phospholipids, and steroids and explain their
functions.

108
You Should Now Be Able to (2 of 2)
Explain how trans fats are formed in food. Describe the
evidence that suggests that eating trans fats is more unhealthy
than consuming saturated fats.
Describe the chemical structure of proteins and the importance
of proteins to cells.
Describe the chemical structure of nucleic acids and explain
how they relate to inheritance.
Explain how lactose tolerance has evolved in humans.
109
Figure 3.10
Figure 3.10 Detail of a phospholipid molecule
Long Description:
A phospholipid is made up of a glycerol and two fatty acids.
One of the fatty acids is a chain of sixteen carbons, where the
carbon at the end of the chain is a carbonyl group. The second
fatty acid is a chain of sixteen carbons where the end is a
carbonyl group and carbons eight and nine share a double bond.
The glycerol is made up of a three carbon chain where the last
carbon is attached to a phosphate group. The head of the
phospholipid is made up of the glycerol and phosphate group
and is hydrophilic. The tails of the phospholipid are made up of

the two fatty acid chains and are hydrophobic. The
phospholipids are shown as gray ovals that represent the heads,
and yellow arms that represent the tails. The section of the
membrane shows how the phospholipids interact. The
phospholipids group by their heads into a sheet, and two sheets
interact by their tails so that the hydrophobic tails are not
exposed to water and the hydrophilic heads are.
110
Table 3.2 Important Chemical Groups of Organic Compounds (2
of 3)
Table 3.2_1 Important chemical groups of organic compounds
(part 1)
Long Description:
The details of the table are as follows.
Chemical group
Example
A hydroxyl, or O H, group shown as single bond O H.
A carbon skeleton of alcohol shows two carbons single bonded
to each other. The left carbon is bonded to three hydrogen
molecules. The right carbon is bonded to two hydrogen
molecules and a hydroxyl, or O H group.
A carbonyl, two single bonds connect to a carbon double
bonded to an oxygen, group.
• A carbon skeleton of three carbons. The first carbon is single
bonded to the second carbon and the second is single bonded to
the third carbon. The middle carbon is a carbonyl group. The
first and third carbons are single bonded to three hydrogens .
• Three carbons are single bonded together. The first two

carbons are bonded to three hydrogens and two hydrogens
respectively. The third carbon is double bonded to an oxygen as
a carbonyl group, and single bonded to a hydrogen.
A carboxyl, or C O O H group.
A carboxylic acid. Two carbons are single bonded to each other.
The left carbon is single bonded to three hydrogens, and the
right carbon is double bonded to an oxygen and single bonded
to an O H group. The carboxylic acid yields the following in a
reversible reaction. An ionized form of carboxylic acid which is
a single bonded C double bonded to an O with a O H also single
bonded to the C. The O H of the carboxyl group loses the
positive hydrogen atom becoming negative.
111
Table 3.2 Important Chemical Groups of Organic Compounds (3
of 3)
Table 3.2_2 Important chemical groups of organic compounds
(part 2)
Long Description:
The details of the table are as follows:
Chemical group
Example
An amino group which is single bonded N H 2.
An amine. A carbon is single bonded to a nitrogen. The carbon
is also single bonded to three hydrogens. The nitrogen is single
bonded to two hydrogens. Beside the amine is an additional H
positive ion. The amine reacts with a hydrogen ion to produce
its ionized form in a reversible reaction. The ionized form is the

amine where the nitrogen now has a positive charge and is
bonded to three hydrogens.
A phosphate group, has a single bond O P O 3 with a charge of
negative 2.
An organic phosphate, A T P. Adenosine, is single bonded to a
chain of alternating oxygen and phosphorus atoms. Each
phosphorus is also double bonded to an oxygen and single
bonded to a negative oxygen. The last phosphorus in the chain
is double bonded to an oxygen, and single bonded to two
negatively charged oxygens.
A methyl C H 3 group with a single bond at one end.
A methylated compound shows a ring of four carbons and two
nitrogens. The carbon on the top right is the first carbon and the
carbons are numbered one to four in a clockwise direction.
Carbon one and two are double bonded to each other, carbon
two is single bonded to nitrogen, the nitrogen is single bonded
to carbon three, carbon three is single bonded to a second
nitrogen, the nitrogen is double bonded to the fourth carbon.
The first carbon has a methyl group attached to it, the second
carbon is single bonded to a hydrogen, the first nitrogen is
single bonded to a hydrogen, the third carbon is double bonded
to an oxygen, and the fourth carbon is bonded to amino group.
112
Figure 3.UN01
Figure 3.UN01 Reviewing the concepts, 3.3
Long Description:
In the dehydration reaction, the short polymer is made up of a
chain of at least two amino acids. The monomer is made up of

one amino acid, flanked by two hydrogen atoms. One of the
hydrogen atoms of the monomer and the hydroxyl group of the
short polymer react to form a longer polymer and release a
water molecule. In the hydrolysis reaction, which is just the
reverse of the dehydration reaction, the longer polymer is made
up of three amino acid flanked by hydrogen. The polymer reacts
with a water molecule and breaks down into a monomer and a
short polymer. The monomer is made up of one amino acid
flanked by two hydrogen atoms. The short polymer is made up
of a chain of at least two amino acids.
113
Figure 3.U N02
Figure 3.UN02 Connecting the concepts, question 1
Long Description:
A table of important molecule types has 4 rows and 3 columns.
Classes of Molecules and Their Components
Functions
Examples
Carbohydrates
A monosaccharide is made up of a carbon hexagon.
Energy for cell, raw material, blank b, plant cell support
blank a, starch, glycogen, blank c
Lipids. don’t form polymers
The components of a fat molecule, a rectangular glycerol and
long fatty acid tail.
Energy storage, blank e, hormones
blank d, phospholipids, blank f
Proteins

An amino acid with blanks g, h, and i for the three components
of the amino acid. The amino acid is a center c connected to an
H and three structures.
blank j, blank k, blank l, transport communication, blank n,
storage, receive signals
lactase, hair, tendons, muscle proteins, blank m, signal proteins,
antibodies, proteins in seeds, receptor protein
Nucleic Acids
A nucleotide with blanks o, p, and q for the three components of
the nucleotide.
heredity, blank s
blank r, D N A and R N A
114
Figure 3.U N02_1
Figure 3.UN02_1 Connecting the concepts, question 1 (part 1)
Long Description:
Functions
Examples
Carbohydrates
A monosaccharide is made up of a carbon hexagon.
Energy for cell, raw material, blank b, plant cell support
blank a, starch, glycogen, blank c
Lipids. don’t form polymers
The components of a fat molecule, a rectangular glycerol and
long fatty acid tail.
Energy storage, blank e, hormones

blank d, phospholipids, blank f
115
Figure 3.U N02_2
Figure 3.UN02_2 Connecting the concepts, question 1 (part 2)
Long Description:
Functions
Examples
Proteins
An amino acid with blanks g, h, and i for the three components
of the amino acid. The amino acid is a center c connected to an
H and three structures.
blank j, blank k, blank l, transport communication, blank n,
storage, receive signals
lactase, hair, tendons, muscle proteins, blank m, signal proteins,
antibodies, proteins in seeds, receptor protein
Nucleic Acids
A nucleotide with blanks o, p, and q for the three components of
the nucleotide.
heredity, blank s
blank r, D N A and R N A
116

Figure 3.U N03
Figure 3.UN03 Testing your knowledge, question 10
117
Figure 3.U N04
118
Figure 3.U N05
119
Figure 3.U N06

Long Description:
On the horizontal axis temperature, temperature is shown in
Celsius.. On the vertical axis, the rate of reaction is shown.
Enzyme A has a hill leaning slightly to the right and has its
peak at 38 degrees Celsius and its activity ranges from 0
degrees Celsius to 50 degrees Celsius. Enzyme B is also a hill
leaning slightly to the right and has its peak at 78 degrees
Celsius and its activity ranges from 40 degrees Celsius to 90
degrees Celsius.
120
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Campbell Biology: Concepts & Connections
Tenth Edition
Chapter 6
How Cells Harvest Chemical Energy
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1

Introduction
Oxygen is a reactant in cellular respiration, the process that
breaks down sugar and other food molecules and generates A T
P, the energy currency in cells, and heat.
Brown fat cells have a “short circuit” in their cellular
respiration, which generates only heat, not A T P.
In this chapter, we explore the stages of cellular respiration and
how cells produce A T P in the presence of oxygen.
2
Figure 6.0_1
Figure 6.0_1 Can brown fat keep a newborn warm and help keep
an adult thin?
3
Figure 6.0_2
Figure 6.0_2 Chapter 6: Big Ideas
Long Description:
The details of the figure are as follows:
Cellular respiration: Aerobic harvesting of energy. An
illustration shows the connection between breathing and cellular

respiration.
Stages of cellular respiration. An illustration shows the three
stages of cellular respiration, namely, (1) glycolysis which
occurs in the cytosol, (2) pyruvate oxidation and citric acid
cycle, and (3) oxidative phosphorylation which occur in the
mitochondrion.
Fermentation: Anaerobic harvesting of energy. A photo shows
wine barrels in a storage room.
Connections between metabolic pathways. A photo shows a few
giraffes.
4
Cellular Respiration: Aerobic Harvesting of Energy
5
6.1 Photosynthesis and Cellular Respiration Provide Energy for
Life (1 of 2)
Life requires energy.
In almost all ecosystems, energy ultimately comes from the sun.
In photosynthesis,
the energy of sunlight is used to rearrange the atoms of carbon
dioxide (C O2) and water ( H 2 0),
producing organic molecules, and
releasing oxygen (O2).
Caution students against the assumption that energy is created
when it is converted from one form to another. This might be a

good time to review the principle of conservation of energy (the
first law of thermodynamics, addressed in Module 5.10). (6.1–
6.5)
Teaching Tips
You might wish to elaborate on the amount of solar energy
striking Earth. Every day Earth is bombarded with solar
radiation equal to the energy of 100 million atomic bombs. Of
the tiny fraction of light that reaches photosynthetic organisms,
only about 1% is converted to chemical energy by
photosynthesis. (6.1)
Energy coupling at the cellular level may be new to many
students, but it is a familiar concept when related to the use of
money in our society. Students might be discouraged if the only
benefit of work was the ability to make purchases from the
employer. (We all might soon tire of a fast-food job that only
paid employees in food!) Money permits the coupling of a
generation of value (a paycheck, analogous to an energy-
releasing reaction) to an energy-consuming reaction (money,
which allows us to make purchases in distant locations). This
idea of earning and spending is a common concept we all know
well. (6.1–6.3)
Active Lecture Tips
See the Activity “Photosynthesis and Respiration: Are They
Similar?” on the Instructor Exchange. Visit the Instructor
description of this activity. (6.1)
Ask your students why they feel warm when it is 30ºC (86ºF)
outside. If their core body temperature is about 37ºC (98.6ºF),
shouldn’t they feel cold? Have students discuss ideas with
others seated near them. Our bodies are always producing heat.
At these higher temperatures, we are producing more heat than
we need to maintain a body temperature around 37ºC. Thus, we
sweat and behave in ways that help us get rid of the extra heat
from cellular respiration. (6.1–6.5)
6

6.1 Photosynthesis and Cellular Respiration Provide Energy for
Life (2 of 2)
In cellular respiration,
O2 is consumed as organic molecules are broken down to C O2
and H 2 O and
the cell captures the energy released as A T P.
Checkpoint question What is misleading about the following
statement? “Plant cells perform photosynthesis, and animal cells
perform cellular respiration.”
The statement implies that cellular respiration does not occur in
plant cells. In fact, almost all eukaryotic cells use cellular
respiration to obtain energy for their cellular work.
Caution students against the assumption that energy is created
when it is converted from one form to another. This might be a
good time to review the principle of conservation of energy (the
first law of thermodynamics, addressed in Module 5.10). (6.1–
6.5)
Teaching Tips
You might wish to elaborate on the amount of solar energy
striking Earth. Every day Earth is bombarded with solar
radiation equal to the energy of 100 million atomic bombs. Of
the tiny fraction of light that reaches photosynthetic organisms,
only about 1% is converted to chemical energy by
photosynthesis. (6.1)
Energy coupling at the cellular level may be new to many
students, but it is a familiar concept when related to the use of
money in our society. Students might be discouraged if the only
benefit of work was the ability to make purchases from the
employer. (We all might soon tire of a fast-food job that only
paid employees in food!) Money permits the coupling of a
generation of value (a paycheck, analogous to an energy-

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