Lecture # 2

Atoms: All matter is made of atoms.

Matter is anything that occupies space and is
perceptible to the senses in some way.

Atoms are made of subatomic particles.

Electrons: - charge
Protons: + charge
Neutrons: neutral

A given atom will have a certain number of
electrons, protons and neutrons as part of
its structure.

All atoms of a particular element have the same
number of protons in their nucleus.

Hydrogen (H) has 1 proton.
Helium (He) has 2 protons.
Lithium (Li) has 3 protons.

C   Carbon
H   Hydrogen
N   Nitrogen
O   Oxygen
P   Phosphorus
S   Sulfur

If an atom has an excess of electrons, it has a net
negative charge and is called an anion.

Examples: Cl‾   chloride
                  Br‾   bromide

If an atom has an excess of protons, it has a net
positive charge and is called a cation.

Examples: Ca⁺²  calcium
                   K⁺    potassium
                   Na⁺  sodium

Atoms get to be anions or cations by losing or gaining
electrons, not protons.

  Fe⁺²  →  Fe⁺³  + e‾¹

A molecule is a group of atoms that are held
together by chemical bonds.

Ways to classify molecules:
1. By the type of bond that is holding the atoms
together.

covalent bonds and electrostatic bonds:

Lose e‾
              > electrostatic bonds
Gain e‾       

                [cation]⁺[anion]‾

Share e‾  covalent bond               

(nucleus)→ e‾ ←(nucleus)

2. Organic molecules and inorganic molecules

All organic molecules contain carbon, particularly
carbon atoms bonded to other carbon atoms.

Inorganic molecules generally do not contain
carbon and never have carbon atoms bonded to
other carbon atoms.

Inorganic molecules: Acids, alkalis and salts

An acid releases H⁺ when dissolved in water.

Example: HCl 

hydrochloric acid

An alkali releases OH‾ when dissolved in water.

Example: NaOH 

sodium hydroxide

If you react an acid with an alkali, the products
are a salt and water.

Example:

HCl        →  Cl‾  +  H⁺
NaOH    →  Na⁺ +  OH‾
HCl + NaOH → NaCl + H₂O

            Sodium chloride

Acids, alkalis and salts are electrolytes.  If you dissolve
them in water, the solution will conduct electric current.

Acids, alkalis and salts are found in various biological
fluids and are required for the normal activity of cells.

Organic Molecules:

Carbohydrates: structural compounds and energy
storage

Lipids (fats): energy storage and membrane components
Proteins: structural compounds and enzymes
Nucleic Acids: informational molecules

These molecules are also known as biological polymers.

A polymer is a very large, long molecule that is
made by linking smaller molecules together.  

The smaller molecules are called monomers. 

The monomers, in turn, are made of atoms. 

Carbohydrates

Examples: sugars and starches

Carbohydrates always contain carbon, hydrogen
and oxygen in the ratio C₁H₂O₁

This basic formula is multiplied some X number
of times in the actual molecules: 

(C₁H₂O₁)_x

C₆H₁₂O₆           C₄H₈O₄

The monomers of carbohydrates are called
simple sugars or monosaccharides. 

Examples: glucose, fructose, ribose
and deoxyribose.

A molecule made of two simple sugars linked
together is called a disaccharide. 
Example: sucrose, which is a molecule of
glucose linked to a molecule of fructose.

A molecule made of three simple sugars
linked together is called a trisaccharide.

Tetrasaccharide
Pentasaccharide
Hexasaccharide

Oligosaccharide

Polysaccharide (or carbohydrate)

Examples:
Glycogen which is the energy storage
carbohydrate in animals.
Cellulose which is the most abundant of all
carbohydrates and is found in plant cell walls.

Lipids or fats are all soluble in organic solvents,
such as chloroform, ether or methanol.

Lipids contain carbon, hydrogen and oxygen,
but much less oxygen than carbon. 

Classes of lipids:

1.True fats are made of glycerol and
three fatty acids.

True fats are also called triglycerides and are
commonly found as oils in plants.

2. Phospholipids are made of glycerol,
phosphate and two fatty acids.

The phosphate end of a phospholipid interacts
with water easily and is said to be hydrophilic.

The fatty acid “tail” of a phospholipid does not
interact with water easily and is said to be
hydrophobic.

When dispersed in water, phospholipids will form
micelles. 

3. Steroids are complex molecules made of a
monomer called isoprene. 
Examples of steroids are vitamin D, the sex
hormones, and cholesterol.