Chapter 2:
Chemistry of
Life
Powerpoint Templates
I. Matter – anything that has mass and takes
up space
A. Atoms – small particles that make up all
matter & cannot be broken down
chemically
1. Nucleus – positively charged core
• Protons (+)
• Neutrons (neutral)
2. Electron Cloud – region where electrons (-)
orbit around the nucleus
3. Atomic # = # protons = # electrons
4. Mass # = protons + neutrons
5. Atomic Mass = mass of atom (in Daltons) ≈
mass #
# of Protons =
# of Neutrons =
# of Electrons =
Atomic Number =
Mass Number =
Atomic Mass =
Diagram of an Atom
6. Isotopes – atoms that have a different
number of neutrons
• Neutrons have mass, so isotopes are
heavier than their normal atom
• Identified by atomic mass
• Carbon 12 (normal) Carbon 13 (isotope)
• Have same number of electrons, so
isotopes have the same properties
• Radioactive isotopes break down over
time
B. Elements – substance made of atoms
that have the same number of protons
1. Ex: Each atom of the element Carbon (C)
has 6 protons
2. 90% of the mass living things is made of only
4 elements: oxygen, carbon, hydrogen,
nitrogen
Checkpoint
• In a neutral atom the # of protons is equal to
the # of
• Different # of protons gives different
• Different # of neutrons gives an
II. Chemical Bonds
A. Valence Electrons – electrons in the
outermost level of the electron cloud
1. The innermost level can only hold 2
electrons.
2. Levels further out
hold 8 electrons.
3. Atoms tend to combine with each other so
that the outer level will have 8 electrons.
B. Chemical Bonds – the force that holds
atoms together
1. Form because atoms become stable when
they have 8 electrons (or full levels) in the
valence (outer) level.
2. Compound – substance made of atoms of 2
or more different elements, and has different
properties from those of the atoms.
3. Ex: water, H2O: 2 hydrogen atoms and 1
oxygen atom
C. Types of Bonds
1. Covalent Bonds – atoms sharing electrons
• Molecule – atoms held together by covalent bonds
• Ex: Carbon Dioxide CO2
2. Ionic Bonds - one atom transfers electrons to
another
• Results in positive & negative charged atom = ion
• Ions of opposite charge are attracted to each other,
and this attraction is the ionic bond.
• Ex: Sodium Chloride NaCl
3. Hydrogen Bonds – bond between
molecules (holds water together)
4. Van der Waals bond – weakest of bonds
(bonds between Gecko’s foot & the
molecules of a wall)
III. Water
A. Polarity
1. In some covalent bonds, electrons are attracted
more strongly to one atom than another.
2. One end of the molecule will then be partially
positive, & the other end will be partially
negative. These molecules are polar.
3. Ex: water!
B. Hydrogen bonds (H-bonds)
1. When bonded to O2, N2, or F, a hydrogen
has a partial positive charge nearly as great
as a proton.
2. This hydrogen is then attracted to the
negative region of polar molecules, forming
hydrogen bonds.
C. Properties of Water – most result because
water forms hydrogen bonds with itself
1. Polarity
2. Density = Ice Floats – solid water is less
dense than liquid water (h-bonds)
3. Water absorbs & retains heat – large
bodies of water keep Earth’s temp. regulated;
water maintains organisms’ internal body
temp.
• High Heat of Vaporization: water absorbs
a lot of energy before it evaporates
• High Specific Heat: water absorbs a lot of
energy before its temperature is raised
4. Cohesion – h-bonds hold water molecules
together
5. Adhesion – water sticks to other polar
substances
•
both cohesion and adhesion allow water to move
upward through roots and stems of plants
D. Mixtures – 2 or more elements or
compounds mixed together physically, not
chemically
E. 2 Types of Mixtures:
1. Solutions – one or more substances mixed
evenly in another substance
• Solute – substance that is dissolved (salt)
• Solvent – substance that does the
dissolving (water)
2. Suspension – material don’t dissolve
E. Acids & Bases
1. Dissociation – a molecule breaks into its ions
•
H2O ↔ H+ + OH-
H+ = hydronium ion
OH- = hydroxide ion
2. Acid – solution with more hydronium ions
•
HCl = hydrochloric acid
3. Base – solution with more hydroxide ions
•
NaOH = sodium hydroxide
4. pH scale – measures the concentration of
hydronium ions; is logarithmic, so each step is
10 times more acidic or basic
•
•
•
pH of 0-6 is acidic
pH of 7 is neutral
pH of 8-14 is basic or alkaline
o pH of 1 is 10 times more acidic than pH of 2
o pH of 14 is 100 times more basic than pH of 12
5. Buffers – chemicals that neutralize acids and
bases
IV. Energy & Metabolism
A. Energy – ability to do work
1. Comes in multiple forms – light, heat,
chemical, mechanical, electrical, nuclear
2. Free energy – energy in a system (our
bodies) that is available to do work
B. Chemical Reactions – bonds between
atoms are broken, and new ones form
Ex: CO2 + H2O  H2CO3
Reactants  Products (# reactant atoms = # of
product atoms)
1. Energy in Reactions
•
•
•
Exergonic Reactions – reactions that release free
energy (feel hot)
Endergonic Reactions – reactions that absorb
energy (feel cold)
Activation Energy – energy needed to start (or
activate) a chemical reaction
C. Biological Reactions
1. Reactions in living things require large
amounts of activation energy.
2. Catalysts are chemicals that lower the
amount of activation energy needed.
3. Enzymes are biological catalysts!
D. Enyzme Activity – reactions depend on a
physical fit between an enzyme’s active site
and its specific substrate (Lock and Key)
1. Two substrates bind to an enzyme’s active
site, like a key into a lock.
2. Enzyme’s shape changes slightly, breaking
bonds in each substrate.
3. New bonds form, creating new product(s).