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Chemical Basis of Life
Basic Chemistry
 All
matter on Earth is made from
approx. 100 elements!!
 Element-a substance that cannot be
broken down by chemical processes
into simpler substances
– Atom-smallest form of an element
Compounds
A
substance that is made of two
or more elements chemically
combined in definite proportions
– Ex: H2O (water) Always two
hydrogen molecules for every
one Oxygen molecule
Organic Compounds
 Generally
associated with living
things
 All contain Carbon!!
Structure of an Atom
Protons:
positively charged
particles
Neutrons: neutral
particles
Electrons:
negatively
charged particles
Periodic Table:
Atomic Number = the
number of protons
H = 1,
O=8
Atom: Just the facts
 Atoms
of the same element have
the same number of protons and
electrons
 Atoms of the same element can
have different numbers of
neutrons = Isotopes
 Radioactive:
nucleus splits apart
spontaneously (gives off energy)
–
Releases charged particles and
radiation
Electrons
 Orbit
around the nucleus in
specific energy levels
– First energy level requires 2
electrons
– other energy levels require 8
electrons
Electrons (cont’d)
 Atoms
are most stable when their
outer energy levels are “full”
 Atoms will gain or lose electrons in
order to fill the outermost level
 The remaining atom is called an ion
Ions
 Atoms
with a positive or negative
charge
 Losing electrons = positive
 Gaining electrons = negative
Chemical bonds
 Attractions
that hold two or more
atoms together
– Whenever a chemical bond is
formed or broken energy is
absorbed or released (heat)
Three types: Ionic, Covalent, Hydrogen
1. Ionic Bonds
 Formed
between ions with opposite
charges resulting in a compound
that has no electrical charge
 IMPORTANT—electrons are lost by
one element and gained by another
EX: NaCl (table salt)
2. Covalent Bonds
 Electrons
are not gained or lost…
they are shared (ex: water)
 Covalent bonds create molecules!
 See
pages 40 & 41
Polar Molecules
 Molecules
in which electrons are
not shared equally between atoms
 This causes the molecules to have
one slightly positive end and one
slightly negative end
O
Figure 2.12
+
H
H
+
Hydrogen Bonds
 Bonds
that occur between
molecules containing hydrogen
 Important—properties of water
and the chemistry of living things!
Opposites attract
+
O
H
+
H
+
+
Chemical formulas

Shows what type of atoms are in a
compound or molecule
– Empirical formula: shows simplest
proportions of atoms in compounds
– Structural: shows number and type of
atoms as well as how they are bonded
– Molecular: Shows number and types of
atoms (most common)
Simple Variety
 Not
all living things are as
complex as humans
 Most living things are made up
of only four kinds of chemicals…
1. Carbohydrates
 “chemical
energy”
– Sugars, starches, and cellulose
– Store energy and provide shape
Carbohydrates (cont’d)

Three types of sugars
1. Monosaccharides
2. Disaccharides
3. Polysaccharides
Complex Carbohydrates
What do we use them for???
Energy storage! In the form of
glycogen (in muscles and liver)
Plants store energy also! In the form
of starch! (potatoes, wheat, grains)
Cellulose
 Most
abundant molecule on Earth
 Storage for simple sugars
 Found in desks, paper, pencils, etc.
2. Lipids
 “long
term energy storage”
 Fats, oils, waxes, steroids
 Lipids are converted into fat when
too many are consumed
Lipids are important!!
 Cell
membranes are made of
phospholipids
 Waxes repel water
– Fruits and leaves retain water
– Ducks are waterproof
3. Proteins
 Main
control system in your body
 Large complex molecules composed
of amino acids
– Only 20 amino acids combine to
make up the countless numbers of
proteins that make up all living
things!
The Importance of
Protein!
 Important
for movement, structure,
regulation, transport, nutrition,
defense
 Insects use proteins called
pheromones to communicate
4. Nucleic Acid
 Makes
you who you are!
 Large, complex molecules that
contain genetic information
DNA
 Deoxyribonucleic
acid
– Carries all of the instructions
needed to make an organism
 Heredity: the passing of genetic
information from parent to
offspring
RNA
 Ribonucleic
Acid
– Uses DNA’s instructions to make
proteins
Chemical Reactions
 The
breaking of bonds to change
one or more substances
Ex: remember the cracker, as the
saliva broke down the starch the
cracker began to have a sweet
taste!
How did it do that????
 Remember
starch is a
polysaccharide (carbohydrate)
– The saliva breaks down the
polysaccharide into simple
sugars!
You were a part of a
chemical reaction!!
Chemical Reaction
 One
or more substances is
changed into a new substance by
the breaking or forming of
chemical bonds
Chemical Equation
 Describes
what happens in a chemical
reaction
(reactants)
(products)
C6H12O6 + 6O2  6H2O + 6CO2 + energy
(Glucose)
Chemical Reactions &
Energy

1.
2.
All chemical reactions are either…
Absorb energy = endothermic
Release energy = exothermic
-The energy that is given off
when a substance is formed is
equal to the energy needed to
break it down!!
How to speed up a
chemical reaction…
1.
2.
Temperature—an increase in
temperature = an increase in
chemical reaction rate (why??)
Catalyst—a substance that
speeds up or slows down a
reaction (it is not used or
changed in the reaction)
Catalyst
 All
living organisms contain
catalysts = enzymes!
– An enzyme is a protein catalyst
that speeds up the chemical
reactions within an organism by
reducing the amount of
activation energy needed
Pg. 44 Figure 2.15
Enzyme Facts
 Names
usually end in –ase
 Have a specific shape so they only fit
one substrate (lock & key)
 They are never actually used up in
the reaction
 Allow reactions to occur in an
organisms without increasing the
organism’s temperature.
Enzyme Specifics
A substrate bonds to an enzyme at the
active site.
 Once the enzyme and substrate are
bonded together the enzyme changes
shape to ensure the substrate will stay
attached = induced fit
 The enzyme + substrate = E-S complex

1.
2.
3.
4.
What are enzymes made out of?
What do enzymes do?
Molecules that can bind with
enzymes are called_________.
Why does heating an enzyme change
its function?
1.
2.
3.
4.
What enzyme broke down H2O2?
Where was the enzyme located?
What were the products of the
reaction?
What are enzymes made out of?
Chemistry in Life
Processes

How does the food you eat keep you warm?
– Food releases energy when it breaks down
chemically, some is in the form of heat
– energy is stored in the chemical bonds of
the food we eat—it is released by
chemical reactions (digestion)
Major life processes
 Metabolism
 Communication
 Reproduction
 Homeostasis
 Growth
and Repair
Metabolism

The combination of all of the chemical
changes that takes place in an organism
– Organisms break chemical bonds
(digestion) in compounds to release
energy
– Plants and some organisms can use
sunlight to make energy-rich compounds
–
–
–
Products of chemical reactions = heat
and wastes
To grow and develop, cells of organisms
must make new carbohydrates,
proteins, and lipids—also to make
repairs
Regeneration-the process of growing
back a lost body part
Homeostasis
 Tendency
of an organism to
maintain stable internal conditions
– Ex: sweat to cool body, panting
Communication
 Internal
– neurotransmitters
 Feedback loop- series of reactions
that help maintain homeostasis by
controlling chemical reactions
 Pheromones—insects use this
protein to communicate(ants form
a line to food)
Water and Solutions
 Life
processes depend on the
properties of water and the
characteristics of solutions
– Solution: uniform mixture of 2
or more substances; cannot
distinguish between the
substances
Water and Solutions
(cont’d)
Solute: the dissolved substance in a
solution
– Solvent: the dissolving substance
Ex: Ice tea = solvent
Sugar = solute
-Suspension: mixture that separates
upon standing
–
Water-the universal
solvent
 Water
will form a solution with
most ionic compounds
Why????
Because it is a polar molecule!
(partial charges)
Water
 Cohesion—sticking
together
 Expansion—water expands when it
freezes….allowing it to float
Why is that important???
Allows pond-dwelling
organisms to survive
Acids, Bases, and Salts
 When
ionic compounds form solutions
the compound breaks apart and
releases ions
– Acid: releases H+ (hydrogen)ions
Ex: orange juice, HCl, vinegar
HCl  H + Cl
–
Base: releases OH(hydroxide)ions
Ex: NaOH (sodium hydroxide),
soaps, ammonia, baking soda
NaOH  Na + OH
–
Salt: releases ions other
than H+ and OHEx: NaCl (table salt)
NaCl  Na + Cl
 When
water breaks apart
(disassociates) in a solution it
releases both H+ and OH- ions
= Neutralization reaction
NaOH + HCl  H2O + NaCl
(base) (acid) (water) (Salt)
pH scale
 Measure
of the concentration of
H+ ions in a solution
1
2
3
4
ACID
5
6
7 8 9 10 11 12 13 14
Neutral
BASE
So, what mechanism keeps our pH at 7.4?
Why is this important???
 Burning
fuels such as coal, oil, and
gasoline releases sulfur and
nitrogen compounds into the air
What’s also in the air??
Water!!
Acid Rain
 When
these things mix H+ ions are
released…causing the rain to
become acidic
 Acid rain has a pH of less than 5.6
 Destroys minerals in the soil vital
to plants…no plants no people
 Decreases the Ph in lakes…killing
aquatic life
 Page
54
– Questions 1-5
– Write the answers
 Tell
me all you know about
enzymes and the liver lab.
– What is an enzyme? Why does
it have an active site? What
enzyme did we use in the lab?
What substrate did it break
down? Etc…
 Read
“The Molecules of Life”
– Answer post test questions 1-11