Transcript The Chemical Basis of Animal Life

The Chemical Basis of
Animal Life
Chapter 2
Chemistry
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The branch of science dealing with
composition of substances and
reactions among these substances.
A knowledge of chemistry is essential
for understanding the structure and
function of animals because body
functions involve chemical changes.
Matter
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Matter: is anything that occupies space and
has mass.
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Solids – Liquids – Gases
Matter has many properties.
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PHYSICAL
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different densities, melting points, boiling points, freezing
points, color or smells.
CHEMICAL
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what elements combine with each other in reactions.
Matter
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Matter includes all solids, liquids and gases
Matter is composed of elements which make
up mass
Currently, 92 naturally occurring elements
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~ 15 found in most animals and 4 (C,H,O,N)
account for ~ 97% of animal’s body weight
A remaining ~ 3% are Ca, P, and K
Matter is composed of elements
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Elements: chemical substances that
ordinary chemical reactions cannot
break down into simpler units.
ATOMS
Atoms atoms everywhere. Don't laugh, it's true. There
are always atoms around unless you are inside of a
vacuum. There are different types of atoms, one for
each element. There are even different kinds of atoms
for each element called IONS. You'll understand what we
mean in a second.
We also introduce you to what happens when atoms
combine. There are millions of ways atoms bond and
make billions of COMPOUNDS. Don't know where to
start? Start with atomic STRUCTURE and learn what is
inside of an atom.
Atoms
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Atoms are the smallest parts of an
element that can enter into a chemical
reaction.
Structure of Atoms
Atoms are composed of
nucleus and electron cloud
Atomic Number
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The atomic number is equal to the # of
protons in an atom
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Oxygen At# = 8
Carbon At# = 6
Hydrogen At# = 1
Nitrogen At#= 7
Calcium At # = 20
Atomic Mass
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Atomic Mass = # of protons + # of neutrons
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ISOTOPES: Same atom but has different
atomic weight due to + or – neutrons
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Oxygen = At. Mass of 16
Carbon = 12
Hydrogen = 1 (has no neutrons)
Nitrogen = 14
Carbon 13 has 7 neutrons instead of 6 (stable
does not break down
RADIOISOTOPES
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Unstable isotopes.
energy.
14C
release small particles and
Electron Shells
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Electrons are arranged in energy shells
Seven possible shells
Each shell can only hold a certain # of
electrons
The nearest to the nucleus never has
more than two.
The 2nd and 3rd hold up to eight
electrons.
Chemical Compounds
in Living Things
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In varying combinations, the elements
carbon, hydrogen, oxygen, and nitrogen
make up practically all the chemical
compounds in living things.
Compounds and Molecules
Water is a compound
Compounds
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Compounds are composed of 2 or more
elements chemically united in fixed
portions.
ie. Water has 2 Hydrogen atoms and 1
Oxygen atom
Molecules
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Compounds of atoms held together by
covalent bonds
Covalent
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Atoms share outer shell electrons with
other atoms
i.e. O2
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Hydrogen Bonds
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Hydrogen gains a slightly positive charge
as it is drawn toward another atom and
leaves a proton behind.
Hydrogen bond is weak
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Ionic bonds
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Atoms gain or lose electrons in outer most
shell creating a charge
A charged atoms is called an ion
Acids, Bases, and Buffers
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Electrolytes conduct electricity in a
solution
Acid –releases hydrogen (H+) ions in water
 Base – releases hydroxide
ions (OH-) in water
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Acids, Bases, and Buffers
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pH – the measure of acidity or alkalinity
of a substance
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Range from 0-14
The pH scale and pH values
of various aqueous solutions
Increasingly Acidic
[H+] > [OH–]
pH Scale
0
Increasingly Basic
[H+] < [OH–]
Neutral
[H+] = [OH–]
Figure 3.8
1 Battery acid
2 Digestive (stomach)
3
4
juice, lemon juice
Vinegar, beer, wine,
cola
Tomato juice
5 Black coffee
Rainwater
6 Urine
7 Pure water
8
9
10
11
12
13
14
Human blood
Seawater
Milk of magnesia
Household ammonia
Household bleach
Oven cleaner
Two types of compounds
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Those that contain carbon
Those that do not contain carbon
Inorganic Compounds
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Primarily those that do not contain
carbon.
Exception is carbon dioxide
Water and minerals are both inorganic
Living things contain a great many
inorganic compounds
The compounds that make up bones
and form salts are inorganic
Organic Compounds
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Organic compounds contain carbon
Why is carbon so special?
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Carbon is a unique element because of its
remarkable ability to form covalent bonds
that are strong and stable.
Carbon has 4 electrons in its outer shell; thus,
it must share 4 electrons by covalent bonding
– either with single or double bonds.
This allows carbon to form chains and rings
Carbon Atom
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Carbon has 4 electrons in outer shell
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Hydrocarbons
Are organic molecules that contain only
carbon and hydrogen (most are in a
linear arrangement)
 Form the framework of all organic
molecules
HHHHHHH
H-C-C-C-C-C-C-C-H
HHHHHHH
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Compounds of Life
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The four groups of organic compounds
found in living things are :
http://www.chem4kids.com/atoms/index.html