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Mrs. Williams
Biology Honors
Semester One
CHAPTER 2: THE CHEMISTRY OF
LIFE
Section 1: Atoms, Ions, and
Molecules
 Atoms are the
smallest unit of an
element
 Three particles
 Protons (+ charge)
 Electrons (- charge)
 Neutrons (no charge)
 Nucleus contains
protons and neutrons
Elements
 Elements are pure substances consisting of
only one type of atom
 Cannot be broken down further!
 Listed in the periodic table
 Atoms of each element differ by the # of
protons
Isotopes
 Isotopes are atoms
of an element with
different number of
neutrons
 Atomic # is the
same; mass # is
different
 Most have same
chemical properties
Radioactive Isotopes
 Radioactive isotopes have unstable nuclei
that break down at a constant rate over
time
 Uses for radioactive isotopes
 Dating of rocks and fossils
 Treating cancer
 Killing bacteria on food
 Trace movements of substances within the body
Ions and Bonding
 Ions are formed when an atom gains or loses
an electron
 Ionic bonds vs. covalent bonds
 Read on pages 38 & 39 about ionic and covalent
bonding to yourself
 Compare and contrast the two bonding types with
your table partner
Bonding
Ionic
Covalent
 Forms through the
 Forms when atoms share a
electrical force between
oppositely charged ions
 Ex: NaCl
pair of electrons
 Generally very strong
bonds
 Depending on the # of
electrons, two atoms may
form several covalent
bonds
 Ex: CO2 - Fig. 2.4
 Sodium (Na+), a positively-
charged ion is attracted to
chlorine (Cl-), a negativelycharged ion.
Chemical Compounds
 A chemical compound is a substance of
two or more elements in definite
proportions
 Different chemical properties than the
original elements
 Compound composition given in chemical
formula
 For example: NaCl and H2O
Chemical Reactions
 Chemical reactions are the breaking and
forming of chemical bonds
 Reactants- original elements or
compounds
 Products- ending elements or compounds
Section 2: Properties of
Water
 Water – H2O
 Polar molecule
 Has a region with a slight positive charge and a
region with a slight negative charge (page 40 - fig.
2.5)
 Hydrogen bond
 An attraction between a slightly positive
hydrogen atom and a slightly negative atom
(often O or N)
Properties Related to
Hydrogen Bonds – page 41
 1. High Specific Heat
 Water resists changes in temp; very important in
cells!
 2.Cohesion
 The attraction among molecules of a substance
 Caused by hydrogen bonds
 Produces surface tension
 3. Adhesion
 Attraction among molecules of different
substances
Water is a Solvent! Page 42
 Solution
 Mixture of substances that is the same throughout
(a homogenous mixture)
 Has two parts
 Solvent – the substance that is present in the
greater amount and that dissolves another
substance
 Solute – a substance that dissolves in a solvent
Acids and Bases
 Some compounds break up into ions (an
atom that has gained or lost electrons) when
they dissolve in water
 Acids release a proton (H+) when they
dissolve in water
 Bases remove H+ ions from a solution
 A solution’s acidity is measured by the pH
scale (page 43, figure 2.9)
Dissociation of Water
pH Scale
 Scale measuring
amount of H+ (really
H3O+)
 Ranges from 0-14
 Below 7- acids
 Higher H+
 Above 7- bases
 Higher OH-
 7- Neutral
 Equal numbers of both
Origin Statement – August 7th
 In your notebook, answer the following
WITHOUT USING NOTES:
1. Describe an atom. List all parts and their
charges.
2. How do we determine atomic number?
3. What is an isotope?
4. Describe the 3 properties of hydrogen bonding.
5. Acids have a pH between ? and ? Bases have a
pH between ? and ?
Section 3: Carbon-based
molecules
 Carbon-based compounds
 A monomer is a basic repeating building
block
 A polymer is many monomers connected
together
 Draw a visual representation of a monomer
and polymer!
Dehydration Synthesis
 Building larger molecules from smaller
ones (requires energy)
 Monomer → Polymer
Hydrolysis
 Break down large molecules into smaller
ones (releases energy)
 Polymer → Monomer
Carbon Compounds
 Condensation/Synthesis
Polymer
Monomer
Hydrolysis
Carbohydrates
 Made of C, H, and O in a 1:2:1 ratio
 Monomers
 Monosaccharide
 Examples: glucose, fructose, galactose
 Dimers
 Disaccharides
 Examples: sucrose and lactose
 Polymers
 Polysaccharides
 Examples: starch, glycogen, chitin, and cellulose
Carbohydrates
Carbohydrates (Starch)
Carbohydrates (Glycogen)
Carbohydrates (Chitin and
Cellulose)
Chitin
Cellulose
Uses for Carbohydrates
 Provide energy for body functions
 Used to build nucleic acids
 Other structural functions
Tests for Carbohydrates
 Benedict’s Test for Simple sugars
 Iodine Test for Complex Sugars
Lipids (Fats & Oils)
 Made of C, H, and O (phospholipids have P)
 Triglyceride
 1 Glycerol, 3 Fatty Acid Chains
 Examples: Fats found in adipose tissue
 Phospholipid
 1 Glycerol, 2 Fatty Acid Chains
 Example: Molecules found in cell membrane
 Steroid
 4 Carbon ring structure
 Example: cholesterol, testosterone, estrogen, and
other hormones
Lipids
Lipids
Lipids
Lipids
Testosterone
Progesterone
Cholesterol
Uses for Lipids
 Energy source
 Padding and insulation
 Structural
 Hormones
 Water-proofing
Tests for Lipids
 Sudan IV Test
 Sudan IV turns red in the
presence of lipids
 Newspaper Test
 Lipids leave a
translucent spot on
newspaper/brown paper
bags (think fast food
bags)
Protein
 Made of C, H, O, S, and N
 Monomer
 Amino acids (20 found in the body; 12 made by
you…the others come from foods you eat)
 Polymer
 Polypeptide
 Amino acids are held together by a peptide bond
Amino Acid Structure
H
H3N+
C
R
COOH
Amino Acid Structure
Polypeptide
H
H3N+
C
R
H
COOH
H3N+
C
R
H
COOH
H 3 N+
C
R
H
COOH
H3N+
C
R
COOH
Uses for Proteins
 Structural – form bones and muscles
 Enzymes - speed up rates of reactions
 Transport – Help bring substances into or out
of cells
 Antibodies – Helps fight diseases/immunity
Test for Proteins
Biuret Test –
purple or pink
indicates protein
Energy of Reactions
 Reaction Types
 Energy Releasing
 Reaction is spontaneous (not fast, necessarily)
 Activation energy – energy need to get the reaction
started
 At the end of the reaction, energy is released into the
environment
 Energy Absorbing
 Rxn is not spontaneous
 Activation energy- energy needed to get the rxn started
 At end of the rxn, energy is absorbed from environment
Energy Reaction Diagrams
Enzymes - Intro
 Catalyst for the reaction (speeds it up)
 Substrate (reactant) enters the active site of
the enzyme to form an enzyme-substrate
complex
 After the rxn, the product leaves
 The enzyme remains unchanged
Enzymes
Action of Enzymes
 Speeds up the reaction by lowering activation
energy
Enzyme Reaction Rates
 Rates can be affected by:
 Temperature
 pH
 Amount of enzyme
Nucleic Acids
 Made of C, H, O, N and
P
 Monomer- Nucleotide
 DNA
Phosphate
Sugar
 Sugar - Deoxyribose
 Nitrogen Bases – A, T, G,
C
 RNA
 Sugar- Ribose
 Nitrogen Bases- A, U, G,
C
Nitrogen Base
DNA Nucleotide
= Phosphate
Purines
= Deoxyribose
Pyrimidines
= Adenine
= Thymine
= Guanine
= Cytosine
A=T
G=C
A
G
T
C
Nucleic Acids
RNA Nucleotide
= Phosphate
Purines
= Ribose
Pyrimidines
= Adenine
= Uracil
= Guanine
= Cytosine
RNA Structure
•Single-stranded
Uses for Nucleic Acids
 They work together to make proteins by
storing genetic information
ATP Structure
Adenine
High Energy Bonds
Adenosine
Ribose
Phosphates
ADP Structure