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Chapter 2: Chemistry
Raw materials and fuel for our bodies
Lectures by Mark Manteuffel, St. Louis Community College
Learning Objectives

Describe what atoms are, their structure, and how they
bond.

Understand water’s features that help it support all life.

Describe carbohydrates—their structure and function.
Learning Objectives

Describe lipids—their structure and function.

Describe proteins—their structure and function.

Describe nucleic acids—their structure and function.
2.1–2.3
Atoms form
molecules through
bonding.
2.1 Everything is made of atoms.

An element is a
substance that cannot
be broken down
chemically into any other
substances.

An atom is a bit of
matter that cannot be
subdivided any further
without losing its
essential properties.
Atomic Structure:
The nucleus, protons, and neutrons
Atomic Structure: Electrons
Atomic Numbers
Insert new figure 2.3
Take-home message 2.1
 Everything
around us, living or not, is made
from atoms, the smallest unit into which
material can be divided.
 Atoms
 They
all have the same general structure.
are made up of protons and neutrons in
the nucleus and electrons, which circle far
around the nucleus.
2.2 An atom’s electrons
determine how (and whether) the
atom will bond with other atoms.
Electron shells
Electron Shells
Insert new fig 2-6
The Versatility of Carbon
Insert fig 2-7
Isotopes
insert new fig 2.4
Radioactive Atoms
 A few
atomic nuclei are not stable and break
down spontaneously.
 These
 They
atoms are radioactive.
release, at a constant rate, a tiny, highspeed particle carrying a lot of energy.
Take-home message 2.2
 The
chemical characteristics of an atom
depend upon number of electrons in their
outermost shells.
 Atoms
are most stable and least likely to
bond with other atoms when their outermost
electron shell is full.
2.3 Atoms can bond together to
form molecules or compounds.
Molecules
Products of bonding!
Covalent Bonds
Insert fig 2-9 to right side of slide
Ions
Insert new fig 2-8
Ions and Ionic Bonds
Insert fig 2-10
Hydrogen Bonds
Insert fig 2-11
Insert fig 2-12
Take-home message 2.3
 Atoms
can be bound together in three
different ways.
 Covalent
bonds, in which atoms share
electrons, are the strongest.
Take-home message 2.3
 In
ionic bonds, one atom transfers its
electrons to another and the two oppositely
charged ions are attracted to each other,
forming a compound.
Take-home message 2.3
 Hydrogen
bonds, which are weaker than
covalent and ionic bonds, involve the
attraction between a hydrogen atom and a
polar molecule.
2.4–2.6
Water has
features that
enable it to
support all life.
2.4 Hydrogen bonds make water cohesive.
Insert fig 2-13
Take-home message 2.4
 Water
molecules easily form hydrogen
bonds, giving water great cohesiveness.
2.5 Water has unusual properties
that make it critical to life.
 Cohesion
 Large
 Low
heat capacity
density as a solid
 Good
solvent
Cohesion
Take home message 2.5
 The
hydrogen bonds between water
molecules give water several of its most
important characteristics:
•
•
•
•
cohesiveness
reduced density as a solid
the ability to resist temperature changes
broad effectiveness as a solvent for ionic and
polar substances
2.6 Living systems are highly
sensitive to acidic and basic
conditions.
Hydrogen Ions
and Hydroxide Ions
OH -
O
H
Ionized Hydroxide
Molecule
H2O
O
H
H
Non-Ionized Water
Molecule
pH Scale
 The
amount of H+ in a solution is a
measure of its acidity and is called pH.
 Acids
 Bases
H+ Ions and Acids
 H+
very reactive
 Acids
can donate H+ to other chemicals
 Stomach
acids
Bases
 Low
H+
 High OH
 Antacids
 Baking
soda, seltzer, milk of magnesia
Take-home message 2.6
 The
pH of a fluid is a measure of how acidic
or basic a solution is and depends on the
concentration of dissolved H+ ions present.
 The
lower the pH, the more acidic the
solution
 Acids,
such as vinegar, can donate protons
to other chemicals while bases, including
baking soda, bind with free protons.
2·7–2·10
Carbohydrates are
fuel for living
machines.
2.7 Carbohydrates include
macromolecules that function as fuel.
Health topics of
the year

Low-carb diet?

Hi-carb diet?

“Carbo-loading”?

Fiber intake?
What are
carbohydrates?
Four Types of Macromolecules
 Carbohydrates
 Lipids
 Proteins
 Nucleic
acids
Carbohydrates
 C,
H, and O
 Primary
fuel for
organisms
 Cell
structure
Energy is in the chemical
bonds!
Take-home message 2-7
 Carbohydrates
are the primary fuel for
running all cellular machinery and also
form much of the structure of cells in all
life forms.
Take-home message 2.7
 Carbohydrates
contain carbon, hydrogen,
and oxygen, and generally have the same
number of carbon atoms as they do H2O
units.
Take home message 2.7
 The
C-H bonds of carbohydrates store a
great deal of energy and are easily
broken by organisms.
 The simplest carbohydrates, including
glucose, are monosaccharides or simple
sugars.
 They contain from three to six carbon
atoms.
Take home message 2.7
 As
the chemical bonds of carbohydrates
are broken down and other more stable
bonds are formed, a great deal of energy
is released that can be used by
organisms.
2.8 Glucose provides energy for
the body’s cells.
 Fuel
for cellular activity
 Stored
temporarily as glycogen
 Converted
to fat
Glucose
 Most
carbohydrates
— ultimately
converted into
glucose
 Blood
sugar
Take home message 2.8
 Glucose
is the most important
carbohydrate to living organisms.
 Glucose
in the bloodstream can be used
as an energy source, can be stored as
glycogen in the muscles and liver for later
use, or can be converted to fat.
2.9 Many complex carbohydrates are
time-released packets of energy.
 More
than 1 sugar (monosaccharide) unit
 Disaccharides
•
•
sucrose
lactose
 Polysaccharides
•
•
starch
cellulose
Chemical Fuel
Preliminary Processing
Starch
>
100’s of glucose molecules joined
together
 Barley,
wheat, rye, corn, and rice
 Glycogen—“animal
starch”
Complex Carbohydrates
“Time-release” fuel pellets
Take-home message 2.9
 Multiple
simple carbohydrates sometimes
link together into more complex
carbohydrates.
 Types
of complex carbohydrates include
starch, the primary form of energy storage
in plants, and glycogen, a primary form of
energy storage in animals.
2.10 Not all carbohydrates are
digestible.
 Chitin
 Cellulose
Insert new fig 2-26
Fiber
 “Roughage”
 Colon
cancer prevention/reduction
 Termites
ecological role
Take-home message 2.10
 Some
complex carbohydrates, including
chitin and cellulose, cannot be digested by
most animals.
 Such
indigestible carbohydrates in the
diet, called fiber, aid in digestion and have
numerous health benefits.
2.11–2.13
Lipids store
energy for a rainy
day.
2.11 Lipids are macromolecules with several
functions, including energy storage.
Why does a salad dressing made with
vinegar and oil separate into two layers
shortly after you shake it?
 Hydrophobic
 Hydrophilic
Take-home message 2.11
 Lipids
are non-soluble in water and greasy
to the touch.
 They
are valuable to organisms in longterm energy storage and insulation,
membrane formation, and as hormones.
2.12 Fats are tasty molecules
too plentiful in our diets.
 Glycerol:
“head”
region
 Fatty
acid “tails”
 Triglycerides
Saturated and Unsaturated Fats


# of bonds in the hydrocarbon chain in a fatty acid
Health considerations
Fat molecules contain much more stored
energy than carbohydrate molecules.
Take-home message 2.12
 Fats,
including the triglycerides common in
the food we eat, are one type of lipid.
Take-home message 2.13
 Characterized
by long hydrocarbon tails, fats
effectively store energy in the many carbonhydrogen and carbon-carbon bonds.
 Their
caloric density is responsible for
humans’ preferring fats to other
macromolecules in the diet, and is also
responsible for their association with obesity
and illness in the modern world.
2.13 Cholesterol and
phospholipids are used to build
sex hormones and membranes.
 Not
all lipids are fats
 The
sterols
Phospholipids and Waxes
 Phospholipids
are the major component
of the cell membrane.
 Waxes
are strongly hydrophobic.
Saturated and Unsaturated Fats


# of bonds in the hydrocarbon chain in a fatty acid
Health considerations
Take-home message 2.13
 Cholesterol
and phospholipids are lipids
that are not fats.
 Both
are important components in cell
membranes.
 Cholesterol
also serves as a precursor to
steroid hormones, important regulators of
growth and development.
2.14–2.18
Proteins are
versatile
macromolecules
that serve as
building blocks.
2.14 Proteins
are bodybuilding
macromolecules.
Amino Acids
 Twenty
 Strung
different amino acids
together to make proteins
Take-home message 2.14
 Unique
combinations of 20 amino acids
give rise to proteins, the chief building
blocks of physical structures that make up
all organisms.
 Proteins
perform myriad functions, from
assisting chemical reactions to causing
blood clotting to building bones to fighting
microorganisms.
2.15 Proteins are an essential
dietary component.
 Growth
 Repair
 Replacement
 Food
labels indicate an item’s protein
content.
 Why
is this insufficient for you to
determine whether you are protein
deficient, even if your protein intake
exceeds your recommended daily amount?
Complete Proteins
 Have
all essential amino acids
 Incomplete
proteins
 Complementary
proteins
Insert new fig 2-38
Which answer below will provide all of the
essential amino acids in a meal?
1.
2.
3.
4.
Hamburger
Corn and a legume (complementary)
Apple
Both 1 and 2 are correct.
Take-home message 2.15
 Twenty
amino acids make up all the
proteins necessary for growth, repair, and
replacement of tissue in living organisms.
Take-home message 2.15
 Of
these amino acids, about half are
essential for humans: they cannot be
synthesized by the body so must be
consumed in the diet.
 Complete
proteins contain all essential
amino acids, while incomplete proteins do
not.
2.16 A protein’s function is
influenced by its three-dimensional
shape.
 Peptide
bonds
Primary Structure
 The
sequence
of amino acids
Secondary Structure
 Hydrogen
bonding
between amino acids
 The two most common
patterns:
• twist in a corkscrew-like
shape
• zig-zag folding
Tertiary Structure
 Folding
and
bending of the
secondary structure
 Due
to bonds such
as hydrogen bonds
or covalent sulfursulfur bonds.
Quaternary Structure
 When
two or more
polypeptide chains
are held together by
bonds between the
amino acids on the
different chains.
 Hemoglobin

Egg whites contain much protein.

Why does beating them change their
texture, making them stiff?
 Egg
 Why
whites contain much protein.
does beating them change their
texture, making them stiff?
Why is wet hair easier to style
than dry hair?
Why do some people have curly hair and
others have straight hair?
Getting hair straightened at a
hair salon involves…
2.
nd
1a
p.
..
he
ng
t
ng
i
Ch
a
in
fo
rm
Re
Ch
a
ng
i
ng
t
he
gh
yd
r..
t..
.
.
1. Changing the tertiary
25% 25% 25% 25%
structure of the hair
proteins.
2. Reforming hydrogen bonds
that have been broken.
3. Changing the primary
structure of the hair
proteins.
4. 1 and 2.
Take-home message 2.16

The particular amino acid sequence of a protein
determines how it folds into a particular shape.

This shape determines many of the protein's
features, such as which molecules it will interact
with.

When a protein's shape is deformed, the protein
usually loses its ability to function.
2.17 Enzymes are proteins that
initiate and speed up chemical
reactions.
Activation Energy
 Chemical
reactions occurring in organisms
can either release energy or consume
energy.
 In
either case, the reaction needs a little
“push” in order to initiate the
reaction―called activation energy.
 Enzymes
act as catalyst by lowering the
activation energy.
An enzyme can reduce the
activation energy in a variety of
ways.
1. By stressing, bending, or stretching
critical chemical bonds
2. By directly participating in the reaction
3. By creating a microhabitat that is
conducive to the reaction
4. By simply orienting or holding substrate
molecules in place so that they can be
modified.
Classroom Catalyst
 Why
can’t we digest cellulose?
The polysaccharides amylose and cellulose
are both made of glucose. Why can’t the
enzyme salivary amylase breakdown both?
1. The orientation of the covalent bonds are
different.
2. The active site of the enzyme cannot bind to
glucose.
3. The enzyme cannot digest cellulose at
normal body temperatures (32oC).
4. The covalent bonds in cellulose are stronger
than in amylose.
Take-home message 2.17
 Enzymes
are proteins that help initiate and
speed up chemical reactions.
 They
aren’t permanently altered in the
process but rather can be used again and
again.
2-18 Enzymes regulate
reactions in several ways
(but malformed enzymes can
cause problems).
The rate at which an enzyme catalyzes
a reaction is influenced by several
chemical and physical factors.
Insert new figure 2-43, preferably broken into 4 stepped segments
Insert fig 2-43, pt 2
Insert fig 2-43, pt 3
Insert fig 2-43, pt 4
“Misspelled” Proteins
 Incorrect
 Active
amino acid sequence
site disruptions
 Phenylketonuria
Insert fig 2-44 to right
Why do some adults get sick when
they drink milk?
Lactase cannot function properly
in this example because the….
1. shape is incorrect.
2. amino acid
sequence is
incorrect.
3. color is incorrect.
4. 1 and 2
When lactase is functioning
correctly it…
ac
t..
.
an
ac
ts
as
an
as
ac
ts
ea
se
in
cr
25%
in
h.
..
...
25% 25%
st
he
ac
t..
.
4.
th
e
3.
25%
er
s
2.
lowers the activation energy
required to digest lactose.
increases the activation energy
required to digest lactose.
acts as an inhibitor to decrease the
activity of enzymes that breakdown
lactose.
acts as an activator to increase the
activity of enzymes that breakdown
lactose.
lo
w
1.
Take-home message 2.18
 Enzyme
activity is influenced by physical
factors such as temperature and pH, as
well as chemical factors, including enzyme
and substrate concentrations.
Take-home message 2.18
 Inhibitors
and activators are chemicals that
bind to enzymes, and by blocking the
active site or altering the shape or
structure of the enzyme can change the
rate at which the enzyme catalyzes
reactions.
Learning Objectives

Describe what atoms are, their structure, and how they
bond.

Understand water’s features that help it support all life.

Describe carbohydrates—their structure and function.

Describe lipids—their structure and function.

Describe proteins—their structure and function.