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The Chemistry of Life
Chapter 2
Atoms
• matter is anything that fills space
• atom-the smallest unit of matter
• nucleus-center of the atom
Atoms
Particle
Charge
Location
Weight
Proton
+
Nucleus
1
Neutron
0
Nucleus
1
Electron
-
Electron
Cloud
0
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Atoms
6
C
Carbon
12.011
Atomic Number = # of
protons (or electrons)
Symbol
Name
Average Atomic Mass
= protons + neutrons
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• element-pure substance that consists of
one type of atom
Isotopes
• Isotopes – atoms of the same element that
contain different numbers of neutrons.
– Ex: C-12, C-13, and C-14
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Chemical Compounds
• Compound – a substance formed by the
chemical combination of two more elements.
– Example: H20, NaCl
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2 Types of Chemical Bonds
Covalent Bonds
• A covalent bond forms when two atoms share
electrons
– Forms molecules like water
water (H20)
Ionic Bonds
• When an atom loses or gains electrons, it becomes
electrically charged
• Charged atoms are called ions
• Ionic bonds are formed between oppositely charged
ions
The Water Molecule
• Polar molecule – has a
positive and negative end
because electrons aren’t
shared evenly.
•Allows it to form
hydrogen bonds
Solutions
• Solution – mixture in which all
components are evenly distributed.
– Solvent – does the dissolving (water)
– Solute – gets dissolved (Kool-Aid)
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H2O-->H+ & OH•
= Hydrogen ion
• in excess= acid
• OH = Hydroxide ion
• in excess= base
+
H
Acids, Bases, and pH
• pH scale– measurement system used to
indicate the concentration of hydrogen ions
(H+) in solution; ranges from 0 to 14
Acids, Bases, and pH
• Acids – form H+ ions in solution, pH less than
7. (ex: stomach acid)
• Bases – form OH- ions in solution, pH greater
than 7. (ex: oven cleaner)
• Buffers – chemicals that prevent sudden
changes in pH.
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Carbon!
• Organic compounds – contain
carbon and are associated
with living things.
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2-3
Organic Polymers
• Polymers – macromolecules made of
repeating units called monomers.
• Four types: carbohydrates, lipids, nucleic
acids, proteins.
Monomers
Polymer
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Carbohydrates
• Carbohydrates – compounds made of
carbon, hydrogen, and oxygen in a ratio
usually 1 : 2 : 1.
– Energy source!!!
– Ex: sugars, starches, glycogen, cellulose
– Monosaccharides (monomer) (glucose)
– Polysaccharides (polymer) (starch)
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Carbohydrates
Lipids
• Lipids – made of mostly carbon and
hydrogen atoms.
– Fats, oils, waxes
– Three fatty acids and a glycerol
– Store energy, make membranes, waterproof
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Lipids
Nucleic acids
• Nucleic acids – contain hydrogen, oxygen,
carbon, nitrogen, and phosphorus.
– Carry genetic information
– Monomers = Nucleotides
– Ex: DNA and RNA
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Proteins
• Proteins – contain carbon, hydrogen,
oxygen, and nitrogen.
– Form bones/muscles, transport substances, fight
disease, control reactions, regulate cell
processes.
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Proteins
–Monomers = amino acids
–Peptide bond – bond
between amino acids.
Chemical Reactions
• chemical reaction: a process that
changes one set of chemicals into
another set of chemicals
CO2 + H2O → H2CO3
Reactants
Products
CO2 + H2O → H2CO3
Reactants
Products
Enzymes
• Enzymes – proteins that act as catalysts
(speed up reactions).
– Can be affected by temperature & pH
– Don’t get changed in the reaction.
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Enzymes
1. An organic catalyst is indicated by letter
A
C
B
D
2. An enzyme-substrate complex is
indicated by letter. Substrate goes into the
active site!