Chapter 2: Chemistry of Life
Outline
Section 2-1: The Nature of Matter
The subatomic particles that make up atoms are protons, neutrons, and electrons.
 Protons and neutrons have about the same mass
 Protons carry a positive charge,
 Neutrons carry no charge (neutral)
 Electrons have a negative charge
 Because atoms have an equal number of electrons and protons, atoms are neutral
Atoms of the same element that differ in the number of neutrons, they are called isotopes
 Because they have the same number of protons, all isotopes of an element have the same
chemical properties. Ex. Carbon 12, Carbon 13, and carbon 14
 Radioactive isotopes are used to determine the age of rocks and fossils
 These isotopes are radioactive because they are unstable and breakdown at a constant rate
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The main types of chemical bonds are covalent bonds and ionic bonds.
Ionic bonds are formed when one or more electrons are transferred from one atom to another.
Covalent bonds are formed when electrons are shared between atoms
Van der Waals forces are the unequal sharing of electrons create regions of positive and
negative charges
o are not as strong as ionic or covalent bonds
o They can still hold molecules together, especially when they are large molecules
o Ex. geckos walking up a glass window
Section 2-2: Properties of Water
A water molecule is polar, because there is an uneven distribution of electrons between the oxygen
and hydrogen atoms.
 The electrons from the 2 hydrogen atoms hang out more around the oxygen atom. It is an
unequal sharing of electrons
 This gives the oxygen side a partially negative charge and the hydrogen side a partially
positive charge.
 Hydrogen bonds: are not as strong as ionic or covalent bonds. Water can form as many as 4
hydrogen bonds at the same time. This gives water its specific properties:
o Cohesion – linking of like molecules
o Adhesion- is the clinging of one substance to another
o High Specific heat: it takes a lot of energy to change water temperature
o Water is less dense when its frozen (ice floats)
o Universal solvent: things dissolve in water
pH Scale: to indicate the concentration of H+ ions in a solution.
 pH scale ranges from 0-14
 a pH of 7 is neutral meaning that there are an equal number of H+ and OH- ions in the solution
 for every number on the scale, you multiply by a factor of 10. So the concentration levels of H+
change dramatically from one number to the next
Acidic solutions contain higher concentrations of H+ ions than pure water and have pH values
below 7.
Basic, or alkaline, solutions contain lower concentrations of H+ ions than pure water and have
pH values above 7.
Section 2-3: Carbon Compounds
 Carbon can bond with many different elements.
 Carbon can bond with up to 4 other molecules with strong covalent bonds
 IT has the ability to form millions of different large complex structures.
Four groups of carbon compounds found in living things are carbohydrates, lipids, nucleic acids,
and protein.
 Made up of monomers linked together as polymers (polymerization)
Living things use carbohydrates as their main source of energy. Plants and some animals also
use carbohydrates for structural purposes.
 Starches and sugars are examples of carbohydrates used by living things for energy
 The monomers are sugars, polymers are starches
 A single sugar molecule is called a monosaccharide
 A larger molecule formed from monosaccharides linked together is polysaccharide
 Animals store excess sugar as glycogen or animal starch (polysaccharide)
Lipids can be used to store energy. Some lipids are important parts of biological membranes and
waterproof coverings.
 Large molecules that are generally not soluble in water
 Common categories are fats, oils and waxes
 Saturated and unsaturated fats: Saturated fats are solid at room temp and unsaturated fats are
liquids at room temp
Nucleic acids store and transmit hereditary, or genetic, information.
 DNA: deoxyribonucleic acid
 RNA: Ribonucleic acid
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Some proteins control the rate of reactions and regulate cell processes. Some proteins
build tissues such as bone and muscle. Others transport materials or help to fight
disease.
Proteins shape determines its function
Catalysts (enzymes) reduce the activation energy needed to start a chemical reaction
Section 2-4: Chemical Reactions and Enzymes
Chemical reactions always involve the breaking of bonds in reactants and the formation of new bonds
in products.
 CO2 + H20 H2CO3 (carbonic acid)
H2CO3  CO2 + H20
 Chemical reactions always involve changes in chemical bonds
Chemical reactions that release energy often occur spontaneously. Chemical reactions that
absorb energy will not occur without a source of energy.
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Cells use enzymes to speed up chemical reactions that take place in cells.