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AP Test Biochemistry Review
AP Biology 2005-2006
Life requires ~25 chemical elements
About 25 elements are essential for life Four elements make up 96% of living
matter: • carbon (C) • hydrogen (H)
• oxygen (O) • nitrogen (N) Four elements make up most of
remaining 4%: • phosphorus (P) • calcium (Ca)
• sulfur (S) • potassium (K)
AP Biology 2005-2006
Ionic bonds Transfer of an electron Forms + & - ions
+ = cation – = anion
Weak bond
example: salt = dissolves
easily in water
AP Biology 2005-2006
Covalent bonds Two atoms need an electron Share a pair of electrons Strong bond
both atoms holding onto the electrons Forms molecules
example: water = takes energy to separate
AP Biology 2005-2006
Polar covalent bonds Pair of electrons not shared equally by
2 atoms Water = O + H
oxygen has stronger “attraction” for the shared electrons than hydrogen
oxygen has higher electronegativity
AP Biology 2005-2006
Polar covalent bonds 2 hydrogens in the water molecule form
an angle Water molecule is polar
oxygen end is – hydrogen end is +
Leads to many interesting properties of water….
AP Biology 2005-2006
Hydrogen bonds Positive H atom in
1 water molecule is attracted to negative O in another
Can occur wherever an -OH exists in a larger molecule
Weak bonds
AP Biology 2005-2006
Review Chapter 2 Matter is made of atoms Life requires ~25 chemical elements Atomic structure determines behavior of an
element Atoms combine by chemical bonding to form
molecules Weak chemical bonds play important roles in
chemistry of life A molecule’s biological function is related to its
shape Chemical reactions make & break chemical bonds
AP Biology 2004-2005
Chemistry of water H2O molecules form H bonds with each
other + attracted to – creates a sticky
molecule
AP Biology 2004-2005
Cohesion
H bonding between H2O creates cohesion water is “sticky” surface tension drinking straw Water bugs Water moves up a tree
AP Biology 2004-2005
Adhesion H2O molecules form H bonds with other
substances meniscus water climbs up fiber
ex. paper towel
AP Biology 2004-2005
Water is the solvent of life H2O is a good solvent due to its polarity
polar H2O molecules surround + & – ions solvents dissolve solutes creating
aqueous solutions
AP Biology 2004-2005
Hydrophilic Hydrophilic
substances have affinity for H2O Polar: they have a charge
AP Biology 2004-2005
Hydrophobic Hydrophobic
substances do not have affinity for H2O Non-polar Oil, wax, fats
fat (triglycerol)
AP Biology 2004-2005
Ice is less dense then liquid water Ice floats!
H bonds form a crystal with loose structure
Molecules are further apart and less dense
AP Biology 2004-2005
Specific heat H2O has high specific heat
due to H bonding: it takes a lot of energy to change the temperature of water
H2O resists changes in temperature takes a lot to heat it up takes a lot to cool it down
H2O moderates temperatures on Earth
AP Biology 2004-2005
Evaporative cooling Organisms rely on heat of vaporization (energy
required to turn liquid to gas) to remove heat
As bonds are broken, heat is released into the environment
AP Biology 2004-2005
Water forms ions Hydrogen ion (H+) splits off from water to
leave a hydroxide ion (-OH)
H20 ----> H+ + -OH
If concentration of 2 ions is equal, water is neutral
If [H+] > [-OH], water is acidic If [-OH] > [H+], water is basic pH scale = how acidic or basic a solution is
AP Biology 2003-2004
Chemistry of Life Organic chemistry is the study of
carbon compounds C atoms are versatile building blocks
4 electrons in outer shell 4 stable covalent bonds
AP Biology 2003-2004
Isomers Molecules with same molecular formula
but different structures different chemical properties
AP Biology 2005-2006
How to build a polymer Condensation reaction
dehydration synthesis joins monomers by “taking” H2O out requires energy
& enzymes
AP Biology 2005-2006
How to break down a polymer
Hydrolysis use H2O to break apart monomers
reverse of condensation reaction
H2O is split into H and OH
AP Biology 2005-2006
Carbohydrates Proteins
Lipids Nucleic Acids
AP Biology
Metabolism Metabolism is the sum of all chemical
reactions in your body. If a reactions breaks things down, it is
catabolic If a reaction builds things up, it is
anabolic
AP Biology
Energy is released or consumed In an exergonic reaction energy is released.
When you break things down, you release energy
All catabolic reactions are exergonic
Cellular respiration is exergonic. These are spontaneous
reactions Delta G (a measure of free
energy) is negative
AP Biology
Energy is released or consumed In an endergonic reaction energy is absorbed.
When you build things, you need energy
All anabolic reactions are endergonic
Photosynthesis is endergonic These are non-spontaneous
reactions Delta G is positive
AP Biology
Enzymes! Enzymes are proteins. They are
catalysts that speed up chemical reactions by lowering the amount of energy needed for those reactions to start (activation energy)