Biology
Class Notes
3-1
Topic: Biochemistry
Aim: Why is chemistry important for the study of Biology?
(A) Atoms
 Atom: basic unit of matter
 Made up of subatomic particles
i. Protons: positive charge
ii. Neutrons: no charge
iii. Electrons: negative charge
 Atoms have the same number of protons and electrons—makes them neutral
 Protons and neutrons are found inside the called in what is called the nucleus
 The electrons are found around the atom surrounding the nucleus
(B) Elements and Isotopes
 Element: pure substance that consists only of one type of atom
 There are over 100 elements—about 24 in organisms
 They are represented by a one or two letter symbol
 Ex: Na, C, H, O, N K, Cl, Au
 The 4 most abundant elements found in organisms is C, H, O,
N
 Atomic number of an elements is the number of protons
 Carbon has an atomic number of 6
 Helium has an atomic number of 2
(C) Chemical Compounds
 In nature, most elements are found as compounds
 Compounds: a substance formed when two or more elements are
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The physical and chemical properties of a compound are different from the
elements from which it is formed
H=gas O=gas water
Some compounds are carbon dioxide CO2, water H2O, sodium chloride NaCl,
glucose C6 H12O 6
Compounds are formed through chemical bonding
 Ionic: one electron is given to another atom
 Covalent: electrons are shared