BIOLOGY CHAPTER 2
CHEMISTRY OF LIFE
Section 1 – Nature of Matter
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Atoms – smallest unit of matter that can’t be
broken down
Atoms are made of subatomic particles.
Proton – positive charge, nucleus of atom
 Neutron – neutral charge, nucleus of atom
 Electron – negative charge, outer cloud of atom
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# of electrons in outer shell determines properties of
atom
ELEMENTS
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Element – pure substance made of only 1 type of atom
Active elements on left side of periodic table
Inactive elements on right side of periodic table
Metals on left side of table
Nonmetals on right side of table
# of protons in nucleus makes elements different
Isotope – element with different # of neutrons
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Ex – Carbon 12 / Carbon 14
COMPOUNDS / BONDING
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Compound – substance made when atoms are
bonded together
Ex – H2O / C6H12O6 / CO2 / O2 / 3H2O2 / NaCl
 3 Types of Bonds
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Covalent – share electrons, weak bond, ex: sugar
 Ionic – transfer electrons, strong bond, ex: salt
 Hydrogen – electrons are shared by both O & H in water
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Section 2 – Water and Solutions
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70% of human body is water
2/3rd of all the molecules in your body are water
molecules
Properties which make water important to life
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Water stores energy/heat – cooling by sweating, pot of
boiling water cools slowly
Cohesion – water molecules stick to each other to form
drops
Adhesion – water molecules stick to other substances
Polarity – unequal areas of charge (both + & -). Able to
dissolve lots of substances because of this property. Lipids
are nonpolar, why don’t they dissolve in water?
Capillary Action
Acids / Bases
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Acid – pH of 0-6.9, H+ ions formed, taste sour
Base – pH of 7.1-14, OH- ions formed, taste
bitter
Neutral – pH of 7
pH of 3 is 10X stronger than pH of 4
Common acid – HCl – hydrochloric
Common base – NaOH – sodium hydroxide
Section 3 – Chemistry of cells
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Organic compounds – contain carbon / make up living
things
5 important types of molecules for living things
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Carbohydrates – C:H:O, source of energy, humans and
cellulose?
Lipids – fats, nonpolar, cell membranes, pigments
Proteins – made up of amino acids, enzymes, structural
components
Nucleic Acids – DNA / RNA – made up of nucleotides
ATP – form of ENERGY cells can use
Section 4 – Energy & chemical
reactions
Energy – ability to move or change matter
 Forms of energy – heat, light, chemical, electricity
 Chemical Reaction – chemical bonds between
substances are broken and new bonds form
Reactants  Products
NaCl  Na+ + ClPhotosynthesis – products have more energy
Respiration – reactants have more energy
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Enzymes
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Enzyme – protein which speeds up chemical reactions
Enzymes
are specific to each chemical reaction.
 are not used up after the reaction.
 lower activation energy (energy needed to begin) of chemical
reactions.
 may not work well if temperature is too hot or cold or if the
pH is too acidic or basic.
In the human body:
2H2O2  2H2O + O2
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ENZYME