SC BIOL 110 - 2, Chemistry for Biology-1 (31 pages)

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Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter Matter is anything that takes up space and has mass Matter is made up of elements An element is a substance that cannot be broken down to other substances by chemical reactions A compound is a substance consisting of two or more elements in a fixed ratio A compound has characteristics different from those of its elements Elements and Compounds Sodium Chlorine Sodium chloride Essential Elements of Life About 25 of the 92 elements are essential to life Carbon hydrogen oxygen and nitrogen make up 96 of living matter Most of the remaining 4 consists of calcium phosphorus potassium and sulfur Trace elements are those required by an organism in minute quantities e g Iodine I Iron Fe An element s properties depend on the structure of its atoms Each element consists of unique atoms An atom is the smallest unit of matter that still retains the properties of an element Atoms are composed of subatomic particles Relevant subatomic particles include Neutrons no electrical charge Protons positive charge Electrons negative charge Neutrons and protons form the atomic nucleus Electrons form a cloud around the nucleus Neutron mass and proton mass are almost identical and are measured in daltons An element s atomic number is the number of protons in its nucleus An element s mass number is the sum of protons plus neutrons in the nucleus Atomic mass the atom s total mass can be approximated by the mass number Isotopes All atoms of an element have the same number of protons but may differ in number of neutrons Isotopes are two atoms of an element that differ in number of neutrons Radioactive isotopes decay spontaneously giving off particles and energy Some applications of radioactive isotopes in biological research are Dating fossils Tracing atoms through metabolic processes Diagnosing medical disorders TECHNIQUE Incubators Compounds including radioactive tracer 3 1 2