The Chemical Basis of Animal Life

Chapter 2

Chemistry 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 Matter: is anything that occupies space and

has mass. Solids – Liquids – Gases

Matter has many properties. PHYSICAL

different densities, melting points, boiling points, freezing points, color or smells.

CHEMICAL what elements combine with each other in reactions.

Matter Matter includes all solids, liquids and

gases Matter is composed of elements which

make up mass Currently, 92 naturally occurring

elements ~ 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 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 Atoms are the smallest parts of an

element that can enter into a chemical reaction.

Structure of AtomsAtoms are composed of

nucleus and electron cloud

Atomic Number The atomic number is equal to the

# of protons in an atom Oxygen At# = 8 Carbon At# = 6 Hydrogen At# = 1 Nitrogen At#= 7 Calcium At # = 20

Atomic Mass Atomic Mass = # of protons + # of neutrons

Oxygen = At. Mass of 16 Carbon = 12 Hydrogen = 1 (has no neutrons) Nitrogen = 14

ISOTOPES: Same atom but has different atomic weight due to + or – neutrons Carbon 13 has 7 neutrons instead of 6 (stable does

not break down RADIOISOTOPES

Unstable isotopes. 14C release small particles and energy.

Electron Shells 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 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 Compounds are composed of 2 or

more elements chemically united in fixed portions.

ie. Water has 2 Hydrogen atoms and 1 Oxygen atom

Molecules Compounds of atoms held together

by covalent bonds Covalent

Atoms share outer shell electrons with other atoms

i.e. O2

Hydrogen Bonds Hydrogen gains a slightly positive

charge as it is drawn toward another atom and leaves a proton behind.

Hydrogen bond is weak

Ionic bonds Atoms gain or lose electrons in outer

most shell creating a charge A charged atoms is called an ion

Acids, Bases, and Buffers Electrolytes conduct electricity in a

solution Acid –releases hydrogen (H+) ions in

water Base – releases hydroxyl ions (oh-) in

water

Acids, Bases, and Buffers pH – the measure of acidity or

alkalinity of a substance Range from 0-14

Two types of compounds Those that contain carbon

Those that do not contain carbon

Inorganic Compounds 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 Organic compounds contain

carbon

Why is carbon so special? 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 Carbon has 4 electrons in outer

shell

-

-

-

-

-

-

Hydrocarbons Are organic molecules that contain

only carbon and hydrogen (most are in a linear arrangement)

Form the framework of all organic molecules

H H H H H H H H-C-C-C-C-C-C-C-H H H H H H H H

Compounds of Life The four groups of organic

compounds found in living things are :

http://www.chem4kids.com/atoms/index.html