AP Test Biochemistry Review

AP Biology 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 Ionic bonds  Transfer of an electron  Forms + & - ions  + = cation  – = anion  Weak bond  example:  salt = dissolves easily in water

AP Biology 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 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 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 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 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 Chemistry of water  H 2 O molecules form H bonds with each other  + attracted to –  creates a sticky molecule

AP Biology Cohesion  H bonding between H 2 O creates cohesion  water is “sticky”  surface tension  drinking straw  Water bugs  Water moves up a tree

AP Biology Adhesion  H 2 O molecules form H bonds with other substances  meniscus  water climbs up fiber  ex. paper towel

AP Biology Water is the solvent of life  H 2 O is a good solvent due to its polarity  polar H 2 O molecules surround + & – ions  solvents dissolve solutes creating aqueous solutions

AP Biology Hydrophilic  Hydrophilic  substances have affinity for H 2 O  Polar: they have a charge

AP Biology Hydrophobic  Hydrophobic  substances do not have affinity for H 2 O  Non-polar  Oil, wax, fats fat (triglycerol)

AP Biology 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 Specific heat  H 2 O has high specific heat  due to H bonding: it takes a lot of energy to change the temperature of water  H 2 O resists changes in temperature  takes a lot to heat it up  takes a lot to cool it down  H 2 O moderates temperatures on Earth

AP Biology 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 Water forms ions  Hydrogen ion (H + ) splits off from water to leave a hydroxide ion ( - OH) H > 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 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 Isomers  Molecules with same molecular formula but different structures  different chemical properties

AP Biology How to build a polymer  Condensation reaction  dehydration synthesis  joins monomers by “taking” H 2 O out  requires energy & enzymes

AP Biology How to break down a polymer  Hydrolysis  use H 2 O to break apart monomers  reverse of condensation reaction  H 2 O is split into H and OH

AP Biology Carbohydrates Proteins LipidsNucleic 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)