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)