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BASIC CHEMISTRY CH. 2
Copyright © 2010 Pearson Education, Inc.
Matter
•
Definition: Anything that has mass and
occupies space
•
States of matter:
1. Solid—
2. Liquid—
3. Gas—
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Energy
• Definition: Capacity to do work or put matter
into motion
• Types of energy:
• Kinetic—
• Potential—
• Electrical –
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Energy Form Conversions
• Energy may be converted from one form to
another
• Conversion is inefficient
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Composition of Matter
• Elements
• Atoms
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Atomic Structure
• Neutrons
• Protons
• Electrons
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Nucleus
Nucleus
Helium atom
Helium atom
Proton
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Neutron
Electron
Electron
cloud
Figure 2.1
Identifying Elements
• Atoms of different elements contain different
numbers of protons
• Compare hydrogen, helium and lithium
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Proton
Neutron
Electron
Hydrogen (H)
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Helium (He)
Lithium (Li)
Figure 2.2
Identifying Elements
• Atomic number =
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Identifying Elements
• Mass number =
• Mass numbers of atoms of an element are not
all identical
• Isotopes: Structural variations of elements;
differ in the # of neutrons they contain
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Proton
Neutron
Electron
Hydrogen (1H)
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Deuterium (2H)
Tritium (3H)
Figure 2.3
Molecules and Compounds
• Molecule—(H2 or C6H12O6)
• Compound—(C6H12O6)
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Chemical Bonds
• Electrons occupy up to seven electron shells
(energy levels) around nucleus
• Octet rule:
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Chemically Inert Elements
• Stable and unreactive
• Outermost energy level fully occupied or
contains eight electrons
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(a)
Chemically inert elements
Valence shell complete
8e
2e
Helium (He)
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2e
Neon (Ne)
Figure 2.4a
Chemically Reactive Elements
• Valence shell not fully occupied by electrons
• Tend to gain, lose, or share electrons (form
bonds) with other atoms to achieve stability
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(b)
Chemically reactive elements
Valence shell incomplete
1e
Hydrogen (H)
6e
2e
Oxygen (O)
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4e
2e
Carbon ©
1e
8e
2e
Sodium (Na)
Figure 2.4b
Types of Chemical Bonds
• Ionic
• Covalent
• Hydrogen
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Ionic Bonds
• Ions are formed by transfer of valence shell
electrons between atoms
• Anions (– charge)
• Cations (+ charge)
• Attraction of opposite charges results in: An
ionic bond
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–
+
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl–)
Sodium chloride (NaCl)
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Figure 2.5
Covalent Bonds
• Formed by sharing of two or more valence
shell electrons
• Allows each atom to fill its valence shell at
least part of the time
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Reacting atoms
Resulting molecules
+
Hydrogen
atoms
or
Carbon
atom
Molecule of
methane gas (CH4)
(a) Formation of four single covalent bonds:
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Figure 2.7a
Reacting atoms
Resulting molecules
+
Oxygen
atom
or
Oxygen
atom
Molecule of
oxygen gas (O2)
(b) Formation of a double covalent bond:
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Figure 2.7b
Reacting atoms
Resulting molecules
+
Nitrogen
atom
or
Nitrogen
atom
Molecule of
nitrogen gas (N2)
(c) Formation of a triple covalent bond:.
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Figure 2.7c
Covalent Bonds
• Sharing of electrons may be equal or unequal
• Equal sharing produces: Electrically balanced
nonpolar molecules
• CO2
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Figure 2.7
Covalent Bonds
• Unequal sharing by atoms with different
electron-attracting abilities produces: polar
molecules
• H2O
• Atoms with six or seven valence shell
electrons are electronegative, e.g., oxygen
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Figure 2.7
Hydrogen Bonds
• Attractive force between electropositive
hydrogen of one molecule and an
electronegative atom of another molecule
• Important in intramolecular bonds, holding a
large molecule in a three-dimensional shape
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+
–
Hydrogen bond
+
+
–
–
–
+
+
+
–
(a) The slightly positive ends (+) of the water
molecules become aligned with the slightly
negative ends (–) of other water molecules.
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Figure 2.8
(b) High surface tension of water, due to hydrogen bonds.
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Figure 2.8b
Synthesis Reactions
• A + B  AB
• Always involve bond formation
• Anabolic
• Endergonic
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(a) Synthesis reactions
Smaller particles are bonded
together to form larger,
molecules.
Example
Amino acids are joined to
Form protein.
Amino acid
molecules
Protein
molecule
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Figure 2.9a
Decomposition Reactions
• AB  A + B
• Reverse synthesis reactions
• Involve breaking of bonds
• Catabolic
• Exergonic
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(b) Decomposition reactions
Bonds are broken in larger
molecules, resulting in smaller,
less complex molecules.
Example
Glycogen is broken down to release
glucose units.
Glycogen
Glucose
molecules
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Figure 2.9b
Classes of Compounds
• Inorganic compounds
• Organic compounds
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Water
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Salts
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Acids and Bases
• Both are electrolytes
• Acids :
• HCl  H+ + Cl–
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Acids and Bases
• Bases• NaOH  Na+ + OH–
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Acid-Base Concentration
• Acid solutions contain [H+]
• Basic solutions contain bases (e.g., OH–)
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pH: Acid-Base Concentration
• pH =
• Neutral solutions:
• pH = 7
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pH: Acid-Base Concentration
• Acidic solutions
•  [H+],  pH
• pH = 0–6.99
• Basic solutions
•  [H+],  pH
• pH= 7.01–14
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Concentration
(moles/liter)
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Examples
[OH–]
[H+]
pH
100
10–14
14
1M Sodium
hydroxide (pH=14)
10–1
10–13
13
Oven cleaner, lye
(pH=13.5)
10–2
10–12
12
10–3
10–11
11
10–4
10–10
10
10–5
10–9
9
10–6
10–8
8
10–7
10–7
7 Neutral
10–8
10–6
6
10–9
10–5
5
10–10
10–4
4
10–11
10–3
3
10–12
10–2
2
10–13
10–1
1
10–14
100
0
Household ammonia
(pH=10.5–11.5)
Household bleach
(pH=9.5)
Egg white (pH=8)
Blood (pH=7.4)
Milk (pH=6.3–6.6)
Black coffee (pH=5)
Wine (pH=2.5–3.5)
Lemon juice; gastric
juice (pH=2)
1M Hydrochloric
acid (pH=0)
Figure 2.13
Carbohydrates
• Sugars and starches
• Three classes
• Monosaccharides
• Disaccharides
• Polysaccharides
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Carbohydrates
• Functions
• Primary role:
• Structural molecules (ribose sugar in RNA)
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Monosaccharides
• Simple sugars containing three to seven C
atoms
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(a) Monosaccharides
Monomers of carbohydrates
Example
Example
Hexose sugars (the hexoses shown
Pentose sugars
here are isomers)
Glucose
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Fructose
Galactose
Deoxyribose
Ribose
Figure 2.15a
Disaccharides
• Double sugars
• Too large to pass through cell membranes
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(b) Disaccharides
Consist of two linked monosaccharides
Example
Sucrose, maltose, and lactose
(these disaccharides are isomers)
Glucose
Fructose
Sucrose
PLAY
Glucose
Glucose
Maltose
Galactose Glucose
Lactose
Animation: Disaccharides
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Figure 2.15b
Polysaccharides
• Three/more simple sugars, e.g., starch and
glycogen
• Not very soluble
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(c) Polysaccharides
Long branching chains (polymers) of linked monosaccharides
Example
This polysaccharide is a simplified representation of
glycogen, a polysaccharide formed from glucose units.
Glycogen
PLAY
Animation: Polysaccharides
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Figure 2.15c
Lipids
• Insoluble in water
• Main types:
• Triglycerides
• Phospholipids
• Steroids
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Triglycerides
• Defined as:
• Composed of:
• Main functions
• Energy storage
• Insulation
• Protection
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(a) Triglyceride formation
+
Glycerol
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3 fatty acid chains
Triglyceride,
or neutral fat
3 water
molecules
Figure 2.16a
Phospholipids
• Modified triglycerides:
• “Head” and “tail” regions have different
properties
• Important in cell membrane structure
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(b) “Typical” structure of a phospholipid molecule
Two fatty acid chains and a phosphorus-containing group are
attached to the glycerol backbone.
Example
Phosphatidylcholine
Polar
“head”
Nonpolar
“tail”
(schematic
phospholipid)
Phosphoruscontaining
group (polar
“head”)
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Glycerol
backbone
2 fatty acid chains
(nonpolar “tail”)
Figure 2.16b
Steroids
• Steroids—interlocking four-ring structure
• Examples are cholesterol, vitamin D, steroid
hormones, and bile salts
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(c)
Simplified structure of a steroid
Four interlocking hydrocarbon rings form a steroid.
Example
Cholesterol (cholesterol is the
basis for all steroids formed in the body)
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Figure 2.16c
Proteins
• Composed of amino acids
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Amine
group
Acid
group
(a) Generalized
structure of all
amino acids.
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(b) Glycine
is the simplest
amino acid.
(c) Aspartic acid
(an acidic amino acid)
has an acid group
(—COOH) in the
R group.
(d) Lysine
(a basic amino acid)
has an amine group
(–NH2) in the R group.
(e) Cysteine
(a basic amino acid)
has a sulfhydryl (–SH)
group in the R group,
which suggests that
this amino acid is likely
to participate in
intramolecular bonding.
Figure 2.17
Structural Levels of Proteins
PLAY
Animation: Introduction to Protein Structure
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Amino acid
Amino acid
Amino acid
Amino acid
Amino acid
(a) Primary structure:
The sequence of amino acids forms the polypeptide chain.
PLAY
Animation: Primary Structure
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Figure 2.19a
a-Helix:
b-Sheet:
(b) Secondary structure:
The primary chain forms spirals (a-helices) and sheets (b-sheets).
PLAY
Animation: Secondary Structure
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Figure 2.19b
(c) Tertiary structure:
PLAY
Animation: Tertiary Structure
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Figure 2.19c
(d) Quaternary structure:
Two or more polypeptide chains, each with its own tertiary structure,
combine to form a functional protein.
PLAY
Animation: Quaternary Structure
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Figure 2.19d
Protein Denaturation
• Shape change and disruption of active sites
due to environmental changes
• A denatured protein is nonfunctional
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Enzymes
• Biological catalysts
• Increase the speed of a reaction
• Allows for millions of reactions/minute
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Enzyme Function
Substrates
+
Active site
Enzyme
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Nucleic Acids
• DNA and RNA
• Building block = nucleotide
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Deoxyribonucleic Acid (DNA)
• Four Nitrogen containing bases:
• adenine (A), guanine (G), cytosine (C), and
thymine (T)
• Double-stranded, helical
• Replicates before cell division, ensuring
genetic continuity
• Provides instructions for protein synthesis
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Phosphate
Sugar:
Deoxyribose
Base:
Adenine (A)
Thymine (T)
Adenine nucleotide
Sugar
Phosphate
Thymine nucleotide
Hydrogen
bond
(a)
Sugar-phosphate
backbone
Deoxyribose
sugar
Phosphate
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
(b)
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(c) Computer-generated image of a DNA molecule
Figure 2.22
Ribonucleic Acid (RNA)
• Four bases:
• adenine (A), guanine (G), cytosine (C), and
uracil (U)
• Single-stranded
PLAY
Animation: DNA and RNA
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Adenosine Triphosphate (ATP)
• Adenine-containing RNA nucleotide with two
additional phosphate groups
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High-energy phosphate
bonds can be hydrolyzed
to release energy.
Adenine
Phosphate groups
Ribose
Adenosine
Adenosine monophosphate (AMP)
Adenosine diphosphate (ADP)
Adenosine triphosphate (ATP)
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Figure 2.19
Function of ATP
• Phosphorylation:
• The chemical energy contained in the high
energy phosphate bonds can be used to
perform cellular work
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Solute
+
Membrane
protein
(a)Transport work
+
Relaxed smooth
muscle cell
Contracted smooth
muscle cell
(b) Mechanical work
+
(c) Chemical work
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Figure 2.20