Chapter 2: The Chemistry of Life

Introductory Terms

Chemistry: science of the structures and interactions of matter

Matter:

Mass:

Weight:

Section 2.1

Elements

1) Simplest form of matter to have unique chemical properties

a. Pure substances composed of atoms of only one type

2) Atomic number

3) Chemical symbols: designations; one or two letters of the elements’ English or Latin names

4) 6 elements compose 98.5% of the human body

a. Why does oxygen compose 65% of the body’s weight?

b. Trace elements

5) Minerals: inorganic elements extracted from soil by plants and ingested by humans

Atoms

1) Smallest stable units of matter

2) Responsible for unique characteristics of every object

3) Structure

a. Nucleus

i. Protons

ii. Neutrons

iii. Atomic mass

b. Electron shell(s)

i. Surround nucleus and house electrons

ii. For example: shell 1: 2 electrons and shell 2: 8 electrons

iii. Valence electrons

4) Atoms contain the same number of protons and electrons

a. Net electrical charge of an atom:

b. Many atoms in this state are reactive

i. Why?

ii. Benefit?

iii. Octet rule: Must have 8 electrons in valence shell to be stable

1. Exceptions: H and He (only have shell 1 so to be stable 2 electrons must

be present)

iv. Atoms have characteristic ways of losing, gaining, or sharing electrons to “fill” the

valence shell

Ions, Electrolytes, and Free Radicals

1) Ions: charged particles with unequal numbers of protons and electrons

a. Why do they form?

b. Ionization

i. Cation

ii. Anion

iii. Examples:

2) Electrolytes: substances that ionize in water and form solutions that can conduct electricity

a. Importance:

3) Free radicals: chemical particles with an odd number of electrons

a. How are they produced?

b. Why are they dangerous?

c. Antioxidants

Molecules and Chemical Bonds

1) Molecules: chemical particle composed of two or more atoms united by a chemical bond

(covalent)

a. Compounds

2) Molecular formulae

a. Isomers

3) Chemical bonds hold atoms together

4) Four types of chemical bonds with the most physiological importance

a. Ionic Bonds

i. Weak bonds easily broken in water

ii. How do they form?

1. Formation of Cation

2. Formation of Anion

3. Attraction of opposite charges

iii. Form ionic compounds

1. Where are they found in the body?

a. Crystals

b. Electrolytes

b. Covalent Bonds

i. Atoms share electrons rather than gaining or losing them

ii. Most common bonds, high energy bonds

iii. The more electrons shared, the stronger the bond

1. Single covalent

2. Double covalent

3. Triple covalent

iv. Types of covalent bonds

1. Nonpolar Covalent Bonds

a. Electrons are shared equally

b. Electrically neutral

c. Very common

d. Examples

2. Polar Covalent Bonds

a. Electrons shared unequally

b. One atom is more electronegative

c. Creates molecule with partial electrical charges

i. Partial negative charge on more electronegative atom

ii. Partial positive on electron-deficient atom

d. “Polar” tells you opposite sides of the bond have opposite charges

c. Hydrogen Bonds

i. Cannot build new molecules or compounds

ii. Links together existing molecules or parts of molecules

iii. Formed by attraction of partial positive and partial negative charges in polar

molecule

iv. Examples

d. Van der Waals forces

i. Weak, brief attractions between neutral atoms

1. A strong attraction can occur if the attraction is between large numbers of

atoms

ii. Due to changes in electron distribution around the nucleus of the atom

1. Crowding of electrons in one area creates a slightly negative side, with the

opposite side being slightly positive

Section 2.2

Water

1) 50-75% of body weight

2) Important to remember: