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The Chemistry Of Life
Chemistry of Life
Life depends on chemistry.
When we eat food or breathe oxygen, our body
uses these materials to keep us alive.
Just as buildings are made from bricks, steel,
glass, and wood, living things are made from
chemical compounds.
If the first task of an architect is to understand
building materials, then the first task of a
biologist is to understand the chemistry of life.
Periodic Table of the Elements
Atoms
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The study of chemistry begins with the basic unit of matter, the
atom. The Greek word atomos, which means unable to cut was first
used to refer to matter by the Greek philosopher Democritus nearly
2500 years ago. Democritus asked a question.........how small can
things be broken down to????

Atoms are incredibly small: 100 million in a row = 1 cm long. Despite
its extremely small size, atoms are actually made-up of three smaller
parts called sub-atomic particles: Protons (+), Neutrons (o), &
Electrons (-).

The electron is a negatively charged particle (-) with 1/1836 the size
of a proton. Electrons are in constant motion around the nucleus of
atoms. They are attracted to the opposite charge of the protons in
the nucleus, but remain outside due to the energy of their motion.
The Atom
Elements and isotopes
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A chemical element is a pure substance that consists
entirely of one type of atom. Over 100 elements are
known, but only about two-dozen are commonly found in
living organisms.

Elements are represented by 1 or 2 letters: H hydrogen, Na – sodium
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The number of protons in an atom of an element is its
atomic number. For example, carbon's atomic number is
6. This means that each atom of carbon has 6 protons,
and consequently, 6 electrons.
Elements and isotopes (cont)

Isotopes: Atoms of an element can have different numbers of
neutrons. For example, some atoms of carbon have 6 neutrons,
some have 7, and a few have 8.
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Atoms of the same element that differ in the number of neutrons
they contain are known as isotopes.

The sum of the protons and neutrons in the nucleus of an atom is
called its mass number. BECAUSE THEY HAVE THE SAME
NUMBER OF ELECTRONS, ALL ISOTOPES OF AN ELEMENT
HAVE THE SAME CHEMICAL PROPERTIES.

Radioactivity???
Isotopes
Chemical compound

In nature, most elements are found combined with other elements in
compounds.

Scientist show the composition of compounds by a kind of shorthand
known as a chemical formula.

Water which has 2 hydrogen atoms for every 1 oxygen atom has a
chemical formula of H2O.

The formula for table salt is NaCl, meaning that salt has a 1:1 ratio
of sodium (Na) and Chlorine (Cl).

The physical and chemical properties of compounds are usually
very different from the elements that formed them.
Chemical Bonds

The atoms in compounds are held together by chemical bonds.

Much of chemistry is devoted to understanding how and when
chemical bonds form.

Bond formation involves the electrons that surround each atomic
nucleus.

The electrons that are available to form bonds are called valence
electrons.

The main types of chemical bonds are ionic bonds and covalent
bonds.

Ionic bonds are formed when 1 or more electrons are transferred
from one atom to another.
Ionic Bonds (transferred of electrons)
Chemical Bonds (cont)

Sometimes electrons are shared by atoms instead of
being transferred.

What does it mean to share electrons? It means that the
moving electrons actually travel in the orbits of both
atoms. (single, double, triple bonds???)

The structure that results from the joining of atoms by
covalent bonds in called a molecule.

The molecule is the smallest unit of most compounds.

Van der Waals Forces & Gecko's grip???
Van der Waals Forces
Properties of Water

Water is one of the few compounds that is liquid at the
temperatures found over much of the Earth's surface.

Unlike most substances, water expands as it freezes.
Thus, ice is less dense than liquid water, which explains
why ice floats on the surface of lakes and rivers.

If ice sank to the bottom, the situation would be
disastrous for fish and plant life in regions with cold
winters.

Like all molecules, a water molecule (H2O) is neutral.
The positive charges on its 10 protons balance out the
negative charges on its 10 electrons. However, there is
more to the story...
Water is cohesive (sticky)
POLARITY

With 8 protons in its nucleus, an oxygen atom
has a much greater attraction for electrons than
does the hydrogen atom with a single proton in
its nucleus.

Hydrogen Bonds???

1. Water strider?

2. Double Helix?
Hydrogen Bonding
Water Strider
The End