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Chapter 6 – Chemistry in Biology
Section 1 – Atoms, Elements &
Compounds

Everything we see, are and experience
comes from stardust
Atoms

Chemistry is the study of matter
 Atoms are building blocks of matter
 Although discussion began in the 5th century
B.C., evidence was not in place until the
1800’s for the existence of the “atom”

Atoms are made up of even smaller
particles
 Nucleus (made up of p+’s and n0’s
 Protons (+)
 Neutrons (0)
 Electrons (-)
○ Move around the nucleus
 Atom is a result of attraction between
particles
 Overall charge on an atom is zero
Examples of “H” and “O” Atoms
Elements
Pure substance that cannot be broken
down by physical or chemical means
 Collected in the periodic table

 Atomic mass
 Chemical & physical behavior/characteristics
 State
 92 naturally occurring
 Horizontal rows called periods & vertical
columns called groups/families
Isotopes

When atoms have different # of
neutrons

Isotopes will have the same chemical
characteristics
Radioactive Isotopes
Changing the number of neutrons can
affect the stability of the nucleus
 Radiation can be given off as a result
 Ages can be taken by measuring the
rate of decay in these radioactive
isotope
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Compounds
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Two or more different elements combined
i.e. water, sodium chloride, methane
Must be in a fixed ratio
Are chemically & physically different from
the elements that make them up
Cannot be broken down by physical means
Can be separated by chemical means (i.e.
electrolysis
Chemical Bonds
Force that holds substances together
 Energy levels & electrons control
bonding
 Forming chemical bonds stores energy
while breaking them provides energy for
life processes
 There are two types

 Covalent
 ionic
Covalent Bonds
Share electrons in the outer shell
 Majority of compounds in a living
organism
 Called a molecule
 Can have single, double or triple bonds

Covalent Bond Example
Ionic Bond
Higher melting points
 Give or take an electron
 Electrical attraction
 Most dissolve in water
 Called ions most solid at room
temperature
 Helps maintain homeostasis in
organisms
 Transmits signals

Ionic Bond Example
Van de Waal Forces
Attraction between molecules
 Dutch physicist named Johannes
 Depends on the size, shape & ability to
attract electrons
 Not as strong as covalent or ionic
 Key role in biological processes
 This is why water droplets form

HOMEWORK 6-1
Find a covalent (molecule) & ionic (ion)
example not mentioned in the text or in
class. Give the formula and explain the
bond in picture form or words
 Write a poem about the difference
between ionic & covalent. Have at least
one line dedicated to Van de Waals
forces (no examples from class or text)

Section 2 – Chemical Reactions
This is why we grow, develop, reproduce
& adapt
 Reactant & products

 Chemical reactions (i.e. rust)
○ Creates a new substance (change in color,
production of heat or light, formation of new
gas, liquid or solid)
 Chemical equation
○ reactants on the left → products on the right
○ “→” meaning yields or reacts to form
○ Balanced equations – conservation of mass –
use of coefficients
Unbalanced
Balanced
Energy of Reactions

Most compounds cannot undergoes
chemical reactions without energy

Activation energy – the minimum
amount of energy that it takes for
reactions to occur (high or low)
 Example: a candle will not light without a
flame

Energy change in chemical reactions
 Exothermic – releases energy in the form of
heat (i.e. candle)
 Endothermic – it absorbs heat energy (i.e.
internal body homeostasis)
Enzymes
All living functions require numerous
chemical reactions
 Catalyst – a substance that lowers the
activation energy & does NOT get used
up in the reaction
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Enzymes or biological catalysts will
speed up biological processes, are
essential to life & can be reused.
 i.e. amylase that is found in saliva
 Most enzymes are specific to one reaction
 Substrates (reactants that bind to enzyme)
 Active site is where the substrates attach
themselves (like puzzle pieces)
 Once binding occurs, active site changes to
an enzyme-substrate complex
 pH, temperature & other substances can
affect the enzyme
Example of Enzyme as catalyst
Substrate at Active Site of
Enzyme
6-2 Homework
Apple Lab pg. 159 at home. Create a table
to record findings and take photographs
(possible groups of 2)
 Give an example of enzyme not mentioned
in book or class and tell me name and
function of said enzyme
 Balance equations on the handout and list
products and reactants
 Other than book or class topics, let me
know a specific example (real world
please) of an endothermic and exothermic
reaction.

Section 3 – Water and Solutions
Water’s Polarity
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Is water covalent or ionic?
Unequal distribution of electrons in the
water molecule
Polar molecules (i.e. tug o war)
Opposites attract (electrostatic attraction) –
in water this is called a hydrogen bond
(F,O,N) – Van de Waal force
So what is the formula for water? What is
it made of? What is the formula for ice?
For water vapor?
Mixtures

Combo of two or more substance
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Homogeneous (solution)
 Solvent & solute
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Heterogeneous
 Suspension
 colloid

Acids & Bases
 Acids (release H+ ions when dissolved in
H₂O)
 Bases (release OH- ions when dissolved in
H₂O)
 pH & Buffers
○ Biological processes carried out in pH range of
6.5 to 7.5
○ Buffers are mixtures that react with acid &
bases to keep pH in that safe range
6-3 Homework
Paragraph on H₂O importance in the
body
 Examples (that were not mentioned in
class or text) of a solution, a colloid, a
suspension and a homogenous mixture
with the reasons why.

Section 6-4 The Building Blocks
of Life (Carbon based)
Organic Chemistry
Study of organic compounds (containing
C)
 Can be a straight, branched or
ringed molecule – which leads to
diversity of life on the planet

Macromolecules
Large molecules formed by joining
smaller organic molecules together
 Also called polymers which are large
molecules made up of repeated
molecules called monomers
 There are 4 types of
macromolecules/polymers
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Carbohydrates
Lipids
Proteins
Nucleic acids
Carbohydrates (see pg. 168)

Carbohydrates
 Stores energy, provides structure
 Made up of 1 C, 2 H’s, 1 O (CH₂O) n
 Where “n” is 3 – 7 then the carb. is a simple
sugar ( see glucose illustration)
 When 2 monosaccharides are put together
(ex. Sucrose or lactose) it is called a
disaccharide
 Even longer chained monosaccharides are
called polysaccharides
 Makes up plants mass, exoskeletons, ect.

Lipids
 Store energy, provide barriers
 Fats, oils & waxes
 Fatty acids, glycerol & other compounds
 Prevents water loss from plants
 Needed to carry out body functions
 Saturated (will not accept H’s) & unsaturated
(will accept H’s)
 Polyunsaturated can accept more H’s
 Phospholipids – responsible for structure
and function of cell membrane since lipids
are hydrophobic they create wonderful
barriers between cells
 Steroids
○ Cholesterol & hormones
Proteins
Transport substances, speed reactions,
structural support, hormones
 Made up of amino acids (C,N,O,H and
sometimes S)
 Bonds covalently with H, amino group (NH₂), carboxyl (-COOH) & variable(-R)
 There are 20 variables
 Peptide bonds amino acids together
forming proteins
 Makes up 15% of body mass
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Amino Acids Making a Protein
Protein Shapes
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Nucleic acids
 Store and transmit genetic information
 Made up of nucleotides (C, N, O, P, H)
 6 major nucleotides (all have)
○ A phosphate
○ A nitrogenous base
○ A ribose sugar
 DNA & RNA (deoxyribonucleic acid &
ribonucleic acid)
 ATP (Adenosine triphosphate)
Nucleic Acids
6-4 Homework
Comprehension Sentences
 Handout
 Tutorials
 Awesome grade on test
