CHEMISTRY

Atom = smallest particle of an element

= smallest building block of organisms

• Chemical symbols = set of abbreviations which represent the atoms

Biologically Important Elements

Name Symbol

Oxygen O

Carbon C

Hydrogen H

Nitrogen N

PhosphorusP

Calcium Ca

What four atoms make about 96% of human body weight?

Molecule = two or more atoms chemically bonded together

Molecular formula = shorthand method for describing the chemical composition of a molecule or compound.

Any charge on the molecule is written as a superscript following the symbol.

If the molecule consists of more than one atom of a given element the number of atoms is written as a subscript following the symbol.

+ indicates positive charge↘H2O Na+

indicates two atoms of hydrogen

Biologically Important Molecules

Name Formula

Water H2O

Carbon dioxide CO2

Oxygen O2

Nitrogen N2

Glucose C6H12O6

Ammonia NH3

Different ways to represent a molecule

Air Molecules

Name Formula

Hydrogen H+

Calcium Ca+2

Phosphate PO4-3

Sodium Na+

Chloride Cl-

Nitrate NO3-

Ammonium NH4+

Ion = atom or molecule with a charge

Biologically Important Ions

Chemical reaction = change of one or more substances into one or more different substances

Reactants = substances that participate in (enter into) a chemical reaction= what you start with

Products = substances formed by a chemical reaction= what you end up with

Chemical equation = description of a chemical reaction, with reactants written on the left, products written on the right and an arrow in the center.

The arrow indicates that a change has occurred.

The number of molecules is written ahead of the molecular formula.

ENZYMESEnzymes are proteins which act as catalysts that speed

up specific chemical reactions in living organisms.

Enzymes are how living cells control chemical reactions.

Some of the same chemical reactions also occur in the nonliving world.

If you could ignite a cube of sugar with a match in the presence of oxygen, you would see a flame and feel the heat as the sugar burns to ash.

The light and heat are energy released from the bonds that held the atoms of the sugar molecules together.

Without Enzymes the reaction is hard to controland only produces heat & light

With enzymes the reaction can be controlled and the energy transferred to an ATP molecule,

which cells can use to do work

Four Groups ofBiological Molecules

Why does this list of molecules looklike the nutrition label on foods?

• Biological molecules have a backbone or skeleton made up of carbon atoms

• So, we are called carbon-based life forms on Earth

Glucose molecules (C6H12O6) are an important

energy source for many living cells

Glucose molecules can be stored by bonding them together into chains.Plants store glucose as starch.Animals store glucose as glycogen.Plants also use glucose to make cellulose, which strengthens stems, and branches.

Lipids are fats & oils

STEROIDS

PROTEINS are chains of amino acids

Proteins do importantjobs in cells

Nucleic Acids are important information molecules

DNA is made of onlyfour smaller molecules

Imagine writing all the instructions to build & operate your body, using an alphabet with only four letters.