AP Biology Book Notes

The Chemistry of Life
o ELEMENTS

Everything is made up of matter, and matter is made of
elements, which are substances that cannot be broken any
further by chemical means.
o THE ESSENTIAL ELEMENTS OF LIFE

96% of human mass is made of OXYGEN, CARBON,
HYDROGEN, and NITROGEN

Trace elements – are elements that are only required by an
organism in very small quantities
o SUBATOMIC PARTICLES

If you break down an element you get an atome, the smallest
unit of an element that retains its characteristic properties.
The building blocks of the physical world. Are electrically
neutral usually by having the same number of protons and
electrons. The atom nucleus is made of protons and neutrons,
and around the nucleus are electrons that spin around nucleus.
Also if you change the number of neutrons in an element, the
element is the same but it creates an isotope.

Parts of An Atom – Protons, neutrons and electrons

Proton – Positively charged particles

Neutron – Uncharged particles

Electron – Negatively charged particles that spin around the
nucleus. They are considered massless.

Nucleus – Core of an atom where protons and neutrons are
packed together.

Isotope – Atoms that have the same number of protons, but
differ in the number of neutrons in the nucleus.
o Compounds

When 2 or more different types of atoms are combined into a
fixed ratio, you have a compound. Also you can have a chemical
reaction when multiple elements are combined. Another thing to
remember is that the atoms in a compound are held by chemical
bonds, which have 3 subgroups the ionic bonds, the covalent
bonds, and hydrogen bonds.

Chemical Bonds – A bond formed between the atoms of a
compound.

Ionic Bonds – When one atom of the compound gives 1 or more
electrons to the other atom(s).

Covalent Bonds – When atoms of a compound share electrons.

Nonpolar Covalent Bonds – Equal sharing of electrons.

Polar Covalent Bonds – Unequal sharing of electrons.
o Water: The Versatile Molecule

Water – One of the most important substances in nature is
water. More than 60% of our body weight consists of water.
Considered a unique and important molecule because it plays an
important role in chemical reactions.

Properties – 2 Hydrogen atoms and 1 Oxygen atom. The
hydrogen atoms have a partial positive charge, and the oxygen
atom has a partial negative charge. The positively-charged ends
of the water molecules strongly attract the negatively-charged
ends of the polar compound, and vice versa where negativelycharged ends attract positively-charged ends. This attraction
creates water beads or rain drops. Also water molecules tend to
stick together which is called cohesion or they tend to stick to
other substances which is called adhesion. Lastly water has a
high heat capacity, which means the energy needed to change
the degree of a substance by 1 degree.

Polar Water Molecules – Molecules that have a partial positive
and a partial negative charge.

Hydrogen Bonds – Weak chemical bonds that form when a
hydrogen atom that is covalently bonded to one electronegative
atom that is also attracted to another electronegative atom.
Collectively they are strong, individually they are weak.

Cohesion – The strong tendency to for 2 molecules to stick
together.

Adhesion –When molecules are attracted and stick to other
substances.

Surface Tension – a contractive tendency of the surface of a
liquid that allows it to resist an external force.

Capillary Action – the ability of a liquid to flow in narrow spaces
without the assistance of, and in opposition to external forces
like gravity.

REVIEW OF PROPERTIES – Polar and can dissolve other polar
substances, cohesive and adhesive properties, high heat
capacity, and high surface tension.
o The Acid Test

Acids – Contains a lot of hydrogen ions.

Bases – Do not release hydrogen ions.

Alkaline – The release of a lot of hydroxide ions.

pH scale – The measure of alkalinity or acidity.
o Organic Molecules

Organic Compounds – Contains carbon atoms

Inorganic Compounds – Doesn’t contain carbon atoms

Carbohydrates

Organic compounds that contain carbon, hydrogen, and
oxygen. Ratio 1:2:1.

Saccharide – fancy word for sugar

Monosaccharides – The simplest sugars, they serve as an
energy source for cells. Glucose is the most popular sugar
around, found in plants, and is a hexagonal ringed shape.
Fructose common sugar in fruits, and is a pentagonal
ringed shape.

Disaccharides – When 2 monosaccharides are chemically
linked. In order to create a disssacharide you must go
through Dehydration Synthesis or Condensation. Also in
order to break up a dissacharide you must go through
Hydrolysis.
o Dehydration Synthesis/Condensation – The loss of
a water molecule.
o Hydrolysis – The addition of a water molecule

Polysaccharides – When multiple units of minisaccharides
are liked (more than 3). They are a type of a polymer, pr
a molecule with repeating units. The most common types
are starch, cellulose, and glycogen. Also they are often
storage forms of sugar or structural components. When
starch (alpha glucose) is stored, it is stored in plastids.
Cellulose (beta glucose) serves as a structural molecule in
walls of things such as fungus and arthropods.
o Proteins

Made of amino acids. Amino acids are organic molecules that
serve as the building blocks of proteins. There are 4 parts of an
amino acid, the Amino Group, the Carboxyl Group, the Hydrogen
Group, and the R Group. R Group is also called the side chain.

Functional Groups

Distinctive groups of atoms that play a large role in
determining the chemical behavior of the compound they
are a part of.

Carboxyl Group –

To spot an amino acid keep your eye out for an Amino
Group (NH2), then look out for the Carboxyl Group
(COOH).

Polypeptides

When 2 amino acids form a dipeptide. The carboxyl group
of one amino acid combines with the amino group of
another amino acid.

Peptide Bond – The bond between 2 amino acids.

Polypeptide – A group of amino acids are joined together.
When these twist and folds on itself, it forms a 3-D
structure called a protein.
o Lipids

Consist of Carbon, Hydrogen, and Oxygen atoms, but not in the
1:2:1. The most common examples of lipids are fats, oils,
phospholipids, and steroids. A typical fat consists of 3 fatty
acids and 1 glycerol. Triglyceride is a fancy name for “fat.”

Making a Triglyceride – Each carboxyl must react with 1 of the
3 hydroxyl groups of the glycerol molecule. The creation of fat
involves the removal of 3 water molecules, Dehydration
Synthesis in action once again.

Ester Linkage – The linkage formed between the glycerol
molecule and the fatty acids.

Saturated Acid – Single covalent bond between each pair of
carbon atoms.

Unsaturated Acid – Adjacent carbons are joined by double
covalent bonds instead of single covalent bonds.

Polyunsaturated Acid – When a fatty acid has many double
covalent bonds within the fatty acid.

Phospholipids – 2 fatty acid tails and a phosphate head attached
to a glycerol chain. The head is hydrophobic (Positive head
opposes the positive end of a water molecule). The tail is
hydrophilic (Negative tail attracts positive end of water). A
amphipathic molecule has both a hydrophobic and hydrophilic
region (Ex: Phospholipid).

Steroids – Basic 4 carbon ring structure, with cholesterol,
vitamin D, and hormones.
o Nucleic Acids

Contains Carbon, Hydrogen, Oxygen, and Nitrogen, but also
contains phosphorus.

Made of simple units called nucleotides.

2 types of Nucleic Acids – Deoxyribonucleic Acid (DNA) and
Ribonucleic Acid (RNA)

DNA – Contains genes, the hereditary blueprints of life.

RNA – Is essential for protein synthesis.
o Heterotroph Hypothesis

The hypothesis that the earliest precursors of life arose from
nonliving matter.

Believed that gases collided, producing chemical reactions and
creating the organic molecules of today. Then simple cells
create complex cells.

Heterotroph – A consumer or something that rely on something
else to make food.

Autotroph – A self-producer, making its own food.