Chapter 2 The Chemistry of Life

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Chapter 2 The Chemistry of Life
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• The atom is the basic unit of all matter. It is
  the smallest piece of a substance that can still
  be a particular substance. Break it down any
  more and you have something different.
• The subatomic particles that make up an atom are
  protons, neutrons, and electrons.

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• Protons and neutrons have about the same mass.
• Protons have a positive charge.
• Neutrons have no charge. They are neutral.
• Protons and neutrons make up the nucleus of the
  atom. (the center)

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• The electron is negatively charged.
• It is very small compared to the proton and
  neutron. (1840 times smaller)
• Electrons are in constant motion around the
  nucleus of the atom.
• Normal atoms have equal amount of electrons and
  protons, so the positive and negative charges
  cancel out the atom is neutral.

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• A chemical element is a pure substance that
  consists entirely of one kind of atom.
• Elements have a one or two letter symbol.
• Atomic number is the number of protons in the
  elements nucleus.

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An Element in the Periodic Table
Section 2-1
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C
Carbon
12.011
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• Isotopes-atoms of the same element that have
  different numbers of neutrons.
• Mass number-the sum of the protons and the
  neutrons in the nucleus.
• Carbon-12, Carbon-13, and Carbon-14 are examples
  of Carbon isotopes.
• The weighted average of the masses of the
  elements isotopes is called its atomic mass.

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• Weighted means that the abundance of each isotope
  in nature is considered when the average is
  calculated.
• Some isotopes are radioactive.
• This means that their nuclei are unstable and
  break down at a constant rate over time.

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Figure 2-2 Isotopes of Carbon
Section 2-1
Nonradioactive carbon-12
Nonradioactive carbon-13
Radioactive carbon-14
6 electrons 6 protons 6 neutrons
6 electrons 6 protons 8 neutrons
6 electrons 6 protons 7 neutrons
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• Chemical Compounds-a substance formed by the
  chemical combination of two or more elements in
  definite proportions.
• Water H2O 2 atoms of H for every O
• Table Salt NaCl 1 atom of Na for every Cl

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• Chemical Bonds-hold atoms together in compounds.
• Bond formation involves the electrons that
  surround the nucleus.
• The electrons that are available to form bonds
  are called valence electrons.
• The 2 main types of bonds are called ionic and
  covalent bonds.

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• Ionic Bonds-are formed when one or more electrons
  is transferred (stolen) from one atom to another.
• When a neutral atom loses an electron it becomes
  more positive.
• When a neutral atom gains an electron it becomes
  more negative.
• These positive and negative atoms are ions.

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• Oppositely charged atoms are strongly attracted
  to each other. This is the basis for an ionic
  bond.

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• Covalent Bonds-occur when electrons are shared by
  two or more atoms instead of being transferred or
  stolen.
• The structure that results when atoms are joined
  together by a covalent bond is called a molecule.
• A molecule is the smallest unit of most compounds.

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Figure 2-3 Ionic Bonding
Section 2-1
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na)
Chloride ion (Cl-)
Transfer of electron
Protons 11 Electrons -11 Charge 0
Protons 17 Electrons -17 Charge 0
Protons 11 Electrons -10 Charge 1
Protons 17 Electrons -18 Charge -1
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Section 2-2 Properties of Water

• Water is POLAR
• Oxygen has 8 protons while hydrogen atoms only
  have 1 proton. This causes the oxygen atoms to
  have a greater attraction for the electrons in
  the water molecule.
• This creates the probability that you will find
  the shared electrons in a water molecule to be
  closer to the oxygen atom.

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• Since a water molecule has a bent shape, the
  oxygen end will have a slight negative charge
  while the hydrogen end will have a slight
  positive charge.
• This causes a water molecule to act like a magnet
  with poles.

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Hydrogen Bonds

• Because water is polar, it can attract other
  water molecules.
• Weak bonds called hydrogen bonds hold water
  molecules together. Water molecules can be
  involved in as many as 4 hydrogen bonds at one
  time.

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• COHESION is an attraction between molecules of
  the same substance. Hydrogen bonding makes water
  extremely cohesive.
• This is why water beads up on smooth surfaces and
  some insects and spiders can walk on water.
• ADHESION is an attraction between molecules of
  different substances. (Graduated cylinder)

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• A MIXTURE is a material made of two or more
  elements or compounds that are physically mixed
  together but not chemically combined.
• Examples salt and pepper, sand and sugar.
• 2 types of mixtures are Solutions and Suspensions.

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• Solutions consists of a SOLUTE, that substance
  that is dissolved, and a SOLVENT, the substance
  that does the dissolving.
• Waters polarity gives it the ability to dissolve
  ionic and polar compounds. It is known as the
  universal solvent.

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• Suspensions contain material that does not
  dissolve when placed in water. Instead, these
  particles separate into very small pieces.
• The pH Scale A scale derived to measure the
  amount of H ions in a solution.
• The pH scale ranges from 0-14. 7 is neutral, and
  the amount of H and OH- ions is equal.

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• pH numbers between 0-7 are acids.
• The lower the pH, the stronger the acid.
• pH numbers between 7-14 are bases.
• The higher the pH, the stronger the base.
• An acid is a compound that forms H ions in
  solution.
• A base is a compound that for OH- ions in
  solution.

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• Buffers are weak acids or bases that react with
  strong acids or bases to prevent sudden, sharp
  changes in pH.
• This is one way your body maintains homeostasis.
  Most fluids in your body cells must stay in a pH
  range between 6.5 and 7.5

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pH Scale
Section 2-2
Oven cleaner
Bleach
Ammonia solution
Increasingly Basic
Soap
Sea water
Human blood
Neutral
Pure water
Milk
Normal rainfall
Acid rain
Increasingly Acidic
Tomato juice
Lemon juice
Stomach acid
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Figure 2-9 NaCI Solution
Section 2-2
Cl-
Cl-
Na
Na
Water
Water
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2-3 Carbon Compounds

• Carbon is so important and interesting that a
  whole branch of Chemistry is devoted to it
• Organic Chemistry
• Why? Because carbon has 4 valence electrons
  which can join with an electron from another atom
  forming a strong covalent bond.

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• Even more important, carbon can bond to other
  carbon atoms, which gives carbon the ability to
  form long chains that are almost unlimited in
  length.
• These carbon-carbon bonds can be single, double,
  or even triple bonds.

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Figure 2-11 Carbon Compounds
Section 2-3
Methane
Acetylene
Butadiene
Benzene
Isooctane
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Macromolecules

• The word macromolecule means giant molecule.
• Macromolecules are made from thousands or even
  hundreds of thousands of smaller molecules.
• You call the process of making macromolecules
  polymerization.

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• Polymerization is accomplished by joining small
  compounds together to make really large ones.
• The small compounds are called monomers.
• Monomers are joined together to form polymers.

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• There are 4 groups of carbon compounds found in
  living things
• 1. Carbohydrates
• 2. Lipids
• 3. Nucleic Acids
• 4. Proteins

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Concept Map
Section 2-3
Carbon Compounds
include
that consist of
that consist of
that consist of
that consist of
which contain
which contain
which contain
which contain
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Carbohydrates

• Carbohydrates are made up of carbon, hydrogen,
  and oxygen atoms, usually in ratios of 121
• Carbohydrates are the main energy source for
  living things.
• Plants and some animals also carbs for structural
  purposes.

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• Simple sugars provide immediate energy for cell
  activities.
• Extra sugars are stored as complex structures
  called starches.
• A single sugar is called a monosaccharide
  (glucose, galactose, and fructose)

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• When you put monosaccharides together to form
  larger sugars you have created a polysaccharide.
  (glycogen and cellulose)

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Figure 2-13 A Starch
Section 2-3
Starch
Glucose
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Lipids

• Lipids are generally not soluble in water.
• Lipids are made mostly from carbon and hydrogen
  atoms.
• Common lipids are fats, oils, and waxes.
• Lipids can be used to store energy, and some
  lipids play a part in cell membranes and
  waterproof coverings.

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• Lipids are formed when a glycerol combines with a
  fatty acid.
• If each C atom is joined to another C atom by a
  single bond, it is called saturated.
• If a (CC) double bond exists, it is called
  unsaturated.
• More than one (CCC) double bond is said to be
  polyunsaturated.

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Nucleic Acids

• Nucleic acids are macromolecules containing
  hydrogen, oxygen, nitrogen, carbon, and
  phosphorus.
• The monomers that make up nucleic acids are
  called Nucleotides.
• Nucleotides have 3 parts

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• 1. a 5-carbon sugar
• 2. a phosphate group
• 3. a nitrogenous base
• Individual nucleotides are joined together by
  covalent bonds to form nucleic acids.
• Their purpose is to store and transmit hereditary
  (genetic) information.

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• There are 2 kinds of nucleic acids
• 1. Ribonucleic Acid (RNA)
• 2. Deoxyribonucleic Acid (DNA)
• The difference in these 2 are their 5-carbon
  sugars
• Ribose and Deoxyribose

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Proteins

• Proteins are macromolecules that contain
  nitrogen, carbon, hydrogen, and oxygen.
• The monomers that make up proteins are called
  amino acids.
• There are 20 amino acids your body uses to make
  proteins. Only about half can be made by your
  body, the others must be consumed in your diet.

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2-4 Chemical Reactions/Enzymes

• A chemical reaction is a process that changes, or
  transforms one set of chemical into another.
• Mass and energy are conserved during chemical
  reactions, which means that you end up with the
  same amount of mass and energy that you start
  with when the reaction is over.

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• The elements or compounds that enter into a
  reaction are called the reactants.
• The elements or compounds produced by a chemical
  reaction are called the products.

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Energy in Reactions

• Some chemical reactions release energy. These
  reactions often happen spontaneously.
• Exothermic
• Other reactions absorb energy in order to start.
  These will not occur without a source of heat or
  energy.
• Endothermic

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Activation Energy

• Chemists call the energy needed to start a
  reaction Activation Energy.

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Figure 2-19 Chemical Reactions
Section 2-4
Energy-Releasing Reaction
Energy-Absorbing Reaction
Activation energy
Products
Activation energy
Reactants
Reactants
Products
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Enzymes

• A catalyst is a substance that speeds up the rate
  of a reaction.
• Catalysts work by lowering a reactions
  activation energy.
• Enzymes are proteins that act as biological
  catalysts.
• Enzymes speed up the chemical reactions that take
  place within the cell.

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Effect of Enzymes
Section 2-4
Reaction pathway without enzyme
Activation energy without enzyme
Activation energy with enzyme
Reactants
Reaction pathway with enzyme
Products