Chemistry

The basic substance of materials is the “element.”  Elements occur as atoms.

There are 92 elements that occur naturally.

There are 17 others that have been synthesized by humans.

There are a total of 109 elements.

Forms of life do not use all elements.

Atoms of elements are made up of protons, neutrons and electrons.  Different numbers of these subunits make different elements.  Usually the number of protons = the number of electrons.  When this balance is broken, the element is called an ion and may be positively or negatively charged.

When two or more atoms attach to each other the product is a molecule.  A molecule of water has two atoms of Hydrogen and one of Oxygen.  Table salt has one atom of Sodium and one atom of Chlorine.

Most common elements in the human body:

        Element                  Symbol                   % by weight

        Oxygen                           O                             65

        Carbon                           C                             18

        Hydrogen                       H                             10

        Nitrogen                         N                             3

        Calcium                          Ca                           2

        Phosphorus                    P                              1.1

        Potassium                       K                             .35

        Sulfur                             S                              .25

        Sodium                           Na                           .15

        Chlorine                         Cl                            .15

        Magnesium                    Mg                          .05

        Iron                                 Fe                            .004

Note that very few elements are commonly in life forms and most of humans consist of Oxygen, Carbon, Hydrogen and Nitrogen.

Over half of your weight is made up of Oxygen atoms.

Life is made up of millions of controlled chemical reactions.  By breaking down molecules the body extracts energy to build other molecules and create other chemical reactions.

Most of your body is made up of water.

Water is critical to life on earth.  Several reasons include:

        1.  Heat storage - It takes lots of energy to change the temperature of water.  Makes life forms more stable.

        2.  Ice formation – Ice is lighter in weight than is liquid water.

        3.  High heat of vaporization – allows for cooling by sweating

        4.  High polarity – soluble characteristics vary for other molecules.

        5.  Water ionizes.

pH – a means to express hydrogen ion concentration.

        Range is from 1 – 14

        7 = neutral

        Higher values are basic

        Lower values are acidic

Buffer – substance that acts as a reservoir for hydrogen ions.  Makes it more difficult to change the pH of a liquid.

Enzyme – Biological catalyst – speeds up a slow reaction.  Enzymes are usually proteins.  Without enzymes life would be slow.

Macromolecules – large molecules that appear common to all life forms.

        1^st – Long chains of carbons

                A – Carbohydrates (sugars)

                B – Lipids (Fats)

                C – Proteins

        2^nd – Nucleic acids

                A – DNA

                B – RNA

Carbohydrates – starch, glycogen, cellulose, chitin.

        Function – Energy storage

                           Component of plant cell wall

                           Outer skeleton of insects

Energy from sun is stored in Carbohydrates.

        Carbohydrates are broken down with the release of energy to make ATP, which is the cash molecule of most life forms.

Lipids – Fats, Steroids

        Function – Long term energy storage

                           Cell membranes

                           Hormones – message transmission

        Some pigments.

Protein – Globular and structural

        Function – Catalyst

                           Support and structure

Proteins are the molecules of Biological Specificity.

Carbohydrates in plants

CO₂ + H₂O + energy à C₆H₁₂O₆ + H₂O + O₂

Carbon     Water        from the sun        Glucose            Water      Oxygen

Dioxide

This reaction provides most energy for life.