Chapter 3

Most of the molecules from which living organisms are made are based on the element carbon

Carbon’s ability to form large and complex molecules has contributed to the great diversity of life

Organic compounds – compounds made primarily of carbon atoms

Why is there such a variety of carbon compounds?• Four valence electrons• Carbon readily bonds with other carbon

atoms, forming straight chains, branched chains, or rings

Single bond – one pair of electrons shared Double bond – two pairs of electrons

shared Triple bond – three pairs of electrons

shared

Functional Groups – clusters of atoms in organic compounds that influence the characteristics of the molecules they compose and the chemical reactions the molecules undergo

Monomers – small, simple molecules

Polymers – molecules that consist of repeated, linked units

Large polymers are called macromolecules

Monomers link to form polymers through a chemical reaction called a condensation reaction• Each time a monomer is added to a

polymer, a water molecule is released

Living things also must break down polymers

In a hydrolysis reaction, water is used to break down a polymer

Life’s processes require a constant supply of energy

Energy is available in certain compounds that store energy in their structure• Common compound is ATP (adenosine triphosphate)

Covalent bonds between phosphate groups are easy to break

Every time a bond is broken, energy is released

The cell uses this energy to drive chemical reactions that allow organisms to function