Cheatsheet: Chemistry of Life | AP Biology - Grade 9 PDF Download

 Page 1


   
UNIT I: CHEMISTRY OF LIFE 
A. Elements 
? All life forms made up of matter 
? All matter made up of elements 
¦ Elements 
? Substances that cannot be broken down into smaller substances by 
chemical means 
B. Essential Elements of Life 
? 96% of the mass of all living things made up of 4 elements: 
? Oxygen (O) 
? Carbon (C)  
? Hydrogen (H) 
? Nitrogen (N) 
? Other elements (collectively 4% of biomass) 
? Calcium (Ca) 
? Phosphorus (P) 
? Potassium (K) 
? Sulfur (S) 
? Sodium (Na) 
? Chlorine (Cl) 
? Magnesium (Mg) 
? Trace elements 
? IRon (Fe) 
? Iodine (I) 
? Copper (Cu) 
C. Subatomic Particles 
? Atom 
? Smallest unit of an element 
? Building blocks of physical world 
? Subatomic PArticles 
? Protons 
¦ Packed with neutrons in nucleus 
¦ Positively charged 
¦ Most atoms have same amount of protons as electrons, making them electrically 
neutral 
? Neutrons 
¦ Packed with protons in nucleus 
¦ No charge 
¦ Isotopes 
? Same element with different amount of neutrons in nucleus 
? Vary in mass 
 
Page 2


   
UNIT I: CHEMISTRY OF LIFE 
A. Elements 
? All life forms made up of matter 
? All matter made up of elements 
¦ Elements 
? Substances that cannot be broken down into smaller substances by 
chemical means 
B. Essential Elements of Life 
? 96% of the mass of all living things made up of 4 elements: 
? Oxygen (O) 
? Carbon (C)  
? Hydrogen (H) 
? Nitrogen (N) 
? Other elements (collectively 4% of biomass) 
? Calcium (Ca) 
? Phosphorus (P) 
? Potassium (K) 
? Sulfur (S) 
? Sodium (Na) 
? Chlorine (Cl) 
? Magnesium (Mg) 
? Trace elements 
? IRon (Fe) 
? Iodine (I) 
? Copper (Cu) 
C. Subatomic Particles 
? Atom 
? Smallest unit of an element 
? Building blocks of physical world 
? Subatomic PArticles 
? Protons 
¦ Packed with neutrons in nucleus 
¦ Positively charged 
¦ Most atoms have same amount of protons as electrons, making them electrically 
neutral 
? Neutrons 
¦ Packed with protons in nucleus 
¦ No charge 
¦ Isotopes 
? Same element with different amount of neutrons in nucleus 
? Vary in mass 
 
? Radioactive isotopes decay spontaneously, giving off particles and 
energy 
? Electrons 
¦ Negatively charged 
¦ Spin around nucleus 
¦ Very small; effectively massless 
¦ Electrons on an atom differ in their amounts of potential energy 
¦ Electron’s state of potential energy is called its energy level, or electron shell 
¦ Valence electrons are those in the outermost shell, or valence shell 
¦ Chemical behavior of an atom is mostly determined by the distribution of 
electrons in electron shells 
? Valence shell most important 
? Elements with full valence shells are chemically inert  
? Atoms with incomplete valence shells can share or transfer valence 
electrons with certain other atoms 
? Atoms of different various elements differ in number of subatomic particles 
? Atomic number=#protons in nucleus 
? Mass Number= protons+neutrons 
¦ Average of all isotopes 
? Atomic mass+atom’s weighted average total mass 
 
D. Compounds 
? Compound occurs as result of 2 or more individual elements combining in a fixed ratio  
? Different properties of individual elements 
? Formed by chemical reaction  
? Bonds that hold compounds together 
? Ionic bonds 
¦ nonmetal+metal 
¦ One or more electrons is transferred from one atom to another 
¦ One atom loses electrons (becomes positively charged) while the other gains 
electrons (becomes negatively charged) 
¦ Results from attraction of two oppositely charged ions 
 
Page 3


   
UNIT I: CHEMISTRY OF LIFE 
A. Elements 
? All life forms made up of matter 
? All matter made up of elements 
¦ Elements 
? Substances that cannot be broken down into smaller substances by 
chemical means 
B. Essential Elements of Life 
? 96% of the mass of all living things made up of 4 elements: 
? Oxygen (O) 
? Carbon (C)  
? Hydrogen (H) 
? Nitrogen (N) 
? Other elements (collectively 4% of biomass) 
? Calcium (Ca) 
? Phosphorus (P) 
? Potassium (K) 
? Sulfur (S) 
? Sodium (Na) 
? Chlorine (Cl) 
? Magnesium (Mg) 
? Trace elements 
? IRon (Fe) 
? Iodine (I) 
? Copper (Cu) 
C. Subatomic Particles 
? Atom 
? Smallest unit of an element 
? Building blocks of physical world 
? Subatomic PArticles 
? Protons 
¦ Packed with neutrons in nucleus 
¦ Positively charged 
¦ Most atoms have same amount of protons as electrons, making them electrically 
neutral 
? Neutrons 
¦ Packed with protons in nucleus 
¦ No charge 
¦ Isotopes 
? Same element with different amount of neutrons in nucleus 
? Vary in mass 
 
? Radioactive isotopes decay spontaneously, giving off particles and 
energy 
? Electrons 
¦ Negatively charged 
¦ Spin around nucleus 
¦ Very small; effectively massless 
¦ Electrons on an atom differ in their amounts of potential energy 
¦ Electron’s state of potential energy is called its energy level, or electron shell 
¦ Valence electrons are those in the outermost shell, or valence shell 
¦ Chemical behavior of an atom is mostly determined by the distribution of 
electrons in electron shells 
? Valence shell most important 
? Elements with full valence shells are chemically inert  
? Atoms with incomplete valence shells can share or transfer valence 
electrons with certain other atoms 
? Atoms of different various elements differ in number of subatomic particles 
? Atomic number=#protons in nucleus 
? Mass Number= protons+neutrons 
¦ Average of all isotopes 
? Atomic mass+atom’s weighted average total mass 
 
D. Compounds 
? Compound occurs as result of 2 or more individual elements combining in a fixed ratio  
? Different properties of individual elements 
? Formed by chemical reaction  
? Bonds that hold compounds together 
? Ionic bonds 
¦ nonmetal+metal 
¦ One or more electrons is transferred from one atom to another 
¦ One atom loses electrons (becomes positively charged) while the other gains 
electrons (becomes negatively charged) 
¦ Results from attraction of two oppositely charged ions 
 
¦ Cation has a positive charge 
¦ Anion has a negative charge 
¦ Cation and anion form to create ionic bond 
? Covalent bonds 
¦ nonmetal+nonmetal 
¦ Molecule consists of 2 or more atoms held together by covalent bonds 
¦ Formed when electrons are shared between atoms 
¦ In nonpolar covalent bond, electrons are shared equally 
¦ In polar covalent bond, electrons are shared unequally 
¦ In a single covalent bond, one pair of electrons is shared 
? Double covalent when 2 pairs are shared, etc.  
¦ Structural formula used to represent atoms and bonding 
? Ex. H-H 
¦ Molecular formula abbreviates structural formula 
? Ex. H
2
 
? Electronegativity is an atom’s attraction for the atoms in a covalent 
bond 
? The more electronegative an atom, the more strongly it pulls 
shared electrons toward itself 
? Hydrogen bonds 
¦ Hydrogen atom covalently bonds to one electronegative ato is also attracted to 
another electronegative atom 
¦ In living cells, hydrogen bonds are usually oxygen or other nitrogen atoms 
? Van der Waals Interactions 
¦ Weakest 
¦ If electrons are distributed asymmetrically in molecules or atoms, they can result 
in “hot spots” of positive or negative charge 
¦ Attractions between molecules that are close together as a result of these charges 
? How geckos climb 
E. Water: The Versatile Molecule 
? In water, electrons are not shared equally in the bonds between hydrogen and oxygen 
? Hydrogen atoms have a partial positive charge while oxygen atoms has a partial negative 
charge 
¦ Water is polar 
 
Page 4


   
UNIT I: CHEMISTRY OF LIFE 
A. Elements 
? All life forms made up of matter 
? All matter made up of elements 
¦ Elements 
? Substances that cannot be broken down into smaller substances by 
chemical means 
B. Essential Elements of Life 
? 96% of the mass of all living things made up of 4 elements: 
? Oxygen (O) 
? Carbon (C)  
? Hydrogen (H) 
? Nitrogen (N) 
? Other elements (collectively 4% of biomass) 
? Calcium (Ca) 
? Phosphorus (P) 
? Potassium (K) 
? Sulfur (S) 
? Sodium (Na) 
? Chlorine (Cl) 
? Magnesium (Mg) 
? Trace elements 
? IRon (Fe) 
? Iodine (I) 
? Copper (Cu) 
C. Subatomic Particles 
? Atom 
? Smallest unit of an element 
? Building blocks of physical world 
? Subatomic PArticles 
? Protons 
¦ Packed with neutrons in nucleus 
¦ Positively charged 
¦ Most atoms have same amount of protons as electrons, making them electrically 
neutral 
? Neutrons 
¦ Packed with protons in nucleus 
¦ No charge 
¦ Isotopes 
? Same element with different amount of neutrons in nucleus 
? Vary in mass 
 
? Radioactive isotopes decay spontaneously, giving off particles and 
energy 
? Electrons 
¦ Negatively charged 
¦ Spin around nucleus 
¦ Very small; effectively massless 
¦ Electrons on an atom differ in their amounts of potential energy 
¦ Electron’s state of potential energy is called its energy level, or electron shell 
¦ Valence electrons are those in the outermost shell, or valence shell 
¦ Chemical behavior of an atom is mostly determined by the distribution of 
electrons in electron shells 
? Valence shell most important 
? Elements with full valence shells are chemically inert  
? Atoms with incomplete valence shells can share or transfer valence 
electrons with certain other atoms 
? Atoms of different various elements differ in number of subatomic particles 
? Atomic number=#protons in nucleus 
? Mass Number= protons+neutrons 
¦ Average of all isotopes 
? Atomic mass+atom’s weighted average total mass 
 
D. Compounds 
? Compound occurs as result of 2 or more individual elements combining in a fixed ratio  
? Different properties of individual elements 
? Formed by chemical reaction  
? Bonds that hold compounds together 
? Ionic bonds 
¦ nonmetal+metal 
¦ One or more electrons is transferred from one atom to another 
¦ One atom loses electrons (becomes positively charged) while the other gains 
electrons (becomes negatively charged) 
¦ Results from attraction of two oppositely charged ions 
 
¦ Cation has a positive charge 
¦ Anion has a negative charge 
¦ Cation and anion form to create ionic bond 
? Covalent bonds 
¦ nonmetal+nonmetal 
¦ Molecule consists of 2 or more atoms held together by covalent bonds 
¦ Formed when electrons are shared between atoms 
¦ In nonpolar covalent bond, electrons are shared equally 
¦ In polar covalent bond, electrons are shared unequally 
¦ In a single covalent bond, one pair of electrons is shared 
? Double covalent when 2 pairs are shared, etc.  
¦ Structural formula used to represent atoms and bonding 
? Ex. H-H 
¦ Molecular formula abbreviates structural formula 
? Ex. H
2
 
? Electronegativity is an atom’s attraction for the atoms in a covalent 
bond 
? The more electronegative an atom, the more strongly it pulls 
shared electrons toward itself 
? Hydrogen bonds 
¦ Hydrogen atom covalently bonds to one electronegative ato is also attracted to 
another electronegative atom 
¦ In living cells, hydrogen bonds are usually oxygen or other nitrogen atoms 
? Van der Waals Interactions 
¦ Weakest 
¦ If electrons are distributed asymmetrically in molecules or atoms, they can result 
in “hot spots” of positive or negative charge 
¦ Attractions between molecules that are close together as a result of these charges 
? How geckos climb 
E. Water: The Versatile Molecule 
? In water, electrons are not shared equally in the bonds between hydrogen and oxygen 
? Hydrogen atoms have a partial positive charge while oxygen atoms has a partial negative 
charge 
¦ Water is polar 
 
 
? Hydrogen bonds 
? Weak attractions that result of water’s polarity 
¦ Positive end of another polar molecule attracted to oxygen negative charge, and 
vice versa with the hydrogen end 
¦ Hydrogen atom covalently bonded to one electronegative atom is also attracted to 
another electronegative atom 
¦ Weak Individually, but strong on a larger scale 
? Lends watermany special properties 
¦ Cohesion 
? Tendency for water to stick to water 
? Important during transpiration 
? Water evaporates, pulls other water molecules with it, pulling all 
the way down from leaves to roots 
¦ Adhesion 
? Tendency of water to stick to other substances 
? Cohesion + Adhesion = capillary action 
? Allows water to flow up roots/trunks/branches of trees in thin 
vessels 
¦ Surface tension 
? Results from cohesion of water molecules 
? Ex. water striders can sit on top of water without sinking 
¦ High heat capacity 
? Heat CApacity=ability of a substance to resist temperature changes 
? Keeps ocean temperatures stable 
? Allows organisms to keep constant body temperature, since most life 
forms are mostly made up of water 
? Heat is absorbed  when hydrogen bonds break, released when hydrogen 
bonds form 
¦ High heat of vaporization 
? Heat a liquid must absorb for 1g to be converted to gas 
 
Page 5


   
UNIT I: CHEMISTRY OF LIFE 
A. Elements 
? All life forms made up of matter 
? All matter made up of elements 
¦ Elements 
? Substances that cannot be broken down into smaller substances by 
chemical means 
B. Essential Elements of Life 
? 96% of the mass of all living things made up of 4 elements: 
? Oxygen (O) 
? Carbon (C)  
? Hydrogen (H) 
? Nitrogen (N) 
? Other elements (collectively 4% of biomass) 
? Calcium (Ca) 
? Phosphorus (P) 
? Potassium (K) 
? Sulfur (S) 
? Sodium (Na) 
? Chlorine (Cl) 
? Magnesium (Mg) 
? Trace elements 
? IRon (Fe) 
? Iodine (I) 
? Copper (Cu) 
C. Subatomic Particles 
? Atom 
? Smallest unit of an element 
? Building blocks of physical world 
? Subatomic PArticles 
? Protons 
¦ Packed with neutrons in nucleus 
¦ Positively charged 
¦ Most atoms have same amount of protons as electrons, making them electrically 
neutral 
? Neutrons 
¦ Packed with protons in nucleus 
¦ No charge 
¦ Isotopes 
? Same element with different amount of neutrons in nucleus 
? Vary in mass 
 
? Radioactive isotopes decay spontaneously, giving off particles and 
energy 
? Electrons 
¦ Negatively charged 
¦ Spin around nucleus 
¦ Very small; effectively massless 
¦ Electrons on an atom differ in their amounts of potential energy 
¦ Electron’s state of potential energy is called its energy level, or electron shell 
¦ Valence electrons are those in the outermost shell, or valence shell 
¦ Chemical behavior of an atom is mostly determined by the distribution of 
electrons in electron shells 
? Valence shell most important 
? Elements with full valence shells are chemically inert  
? Atoms with incomplete valence shells can share or transfer valence 
electrons with certain other atoms 
? Atoms of different various elements differ in number of subatomic particles 
? Atomic number=#protons in nucleus 
? Mass Number= protons+neutrons 
¦ Average of all isotopes 
? Atomic mass+atom’s weighted average total mass 
 
D. Compounds 
? Compound occurs as result of 2 or more individual elements combining in a fixed ratio  
? Different properties of individual elements 
? Formed by chemical reaction  
? Bonds that hold compounds together 
? Ionic bonds 
¦ nonmetal+metal 
¦ One or more electrons is transferred from one atom to another 
¦ One atom loses electrons (becomes positively charged) while the other gains 
electrons (becomes negatively charged) 
¦ Results from attraction of two oppositely charged ions 
 
¦ Cation has a positive charge 
¦ Anion has a negative charge 
¦ Cation and anion form to create ionic bond 
? Covalent bonds 
¦ nonmetal+nonmetal 
¦ Molecule consists of 2 or more atoms held together by covalent bonds 
¦ Formed when electrons are shared between atoms 
¦ In nonpolar covalent bond, electrons are shared equally 
¦ In polar covalent bond, electrons are shared unequally 
¦ In a single covalent bond, one pair of electrons is shared 
? Double covalent when 2 pairs are shared, etc.  
¦ Structural formula used to represent atoms and bonding 
? Ex. H-H 
¦ Molecular formula abbreviates structural formula 
? Ex. H
2
 
? Electronegativity is an atom’s attraction for the atoms in a covalent 
bond 
? The more electronegative an atom, the more strongly it pulls 
shared electrons toward itself 
? Hydrogen bonds 
¦ Hydrogen atom covalently bonds to one electronegative ato is also attracted to 
another electronegative atom 
¦ In living cells, hydrogen bonds are usually oxygen or other nitrogen atoms 
? Van der Waals Interactions 
¦ Weakest 
¦ If electrons are distributed asymmetrically in molecules or atoms, they can result 
in “hot spots” of positive or negative charge 
¦ Attractions between molecules that are close together as a result of these charges 
? How geckos climb 
E. Water: The Versatile Molecule 
? In water, electrons are not shared equally in the bonds between hydrogen and oxygen 
? Hydrogen atoms have a partial positive charge while oxygen atoms has a partial negative 
charge 
¦ Water is polar 
 
 
? Hydrogen bonds 
? Weak attractions that result of water’s polarity 
¦ Positive end of another polar molecule attracted to oxygen negative charge, and 
vice versa with the hydrogen end 
¦ Hydrogen atom covalently bonded to one electronegative atom is also attracted to 
another electronegative atom 
¦ Weak Individually, but strong on a larger scale 
? Lends watermany special properties 
¦ Cohesion 
? Tendency for water to stick to water 
? Important during transpiration 
? Water evaporates, pulls other water molecules with it, pulling all 
the way down from leaves to roots 
¦ Adhesion 
? Tendency of water to stick to other substances 
? Cohesion + Adhesion = capillary action 
? Allows water to flow up roots/trunks/branches of trees in thin 
vessels 
¦ Surface tension 
? Results from cohesion of water molecules 
? Ex. water striders can sit on top of water without sinking 
¦ High heat capacity 
? Heat CApacity=ability of a substance to resist temperature changes 
? Keeps ocean temperatures stable 
? Allows organisms to keep constant body temperature, since most life 
forms are mostly made up of water 
? Heat is absorbed  when hydrogen bonds break, released when hydrogen 
bonds form 
¦ High heat of vaporization 
? Heat a liquid must absorb for 1g to be converted to gas 
 
? Evaporative cooling 
? As a liquid evaporates, its remaining surface cools 
¦ How sweat works to cool body down 
¦ Expansion on freezing 
? Lattice structure of ice causes water to expand on freezing 
? Allows ice to float on top of lakes in winter 
? Animal life can live beneath ice 
¦ Versatility as a solvent 
? Solution is a liquid that is a homogenous mix of substances 
? Solvent is the dissolving agent of a solution 
? Solute is the substance that is dissolved 
? Aqueous solution is one where water is the solvent 
? Polarity of water allows it to be a versatile solvent 
? Can form hydrogen bonds easily 
? Hydrophobic substances do not dissolve in water, but hydrophilic ones 
will 
F. Acids and Bases 
? Solution is acidic if it contains a lot of H
+
  
? Solution is alkaline if it contains a lot of OH
-
 
? Measured on pH scale 
? Logarithmic 
? Numbered 1-14 
¦ Acids 1-7 pH 
¦ Bases 7-14 pH 
? Buffers maintain stable pH 
G. Organic Molecules 
?  Organic compound contains Carbon 
? Inorganic compound does not contain carbon 
? Carbon often surrounded by hydrogen 
? Carbon is a versatile atom 
? Can bind with many elements 
? Many “slots” to bind with elements 
¦ 4 valence electrons  
? Can form 4 covalent bonds 
¦ Makes large, complex molecules possible 
? In molecules with multiple carbons, each carbon bonded to 4 other atoms has a 
tetrahedral shape 
¦ When 2 carbons are formed by a double bond, the atoms joined to the carbons are 
one the same plane as the carbons 
? Electron configuration gives it covalent compatibility with other elements 
? Hydrocarbons consist of only carbon and hydrogen 
¦ Can undergo reactions that release a large amount of energy