Biology Chapter 2 Atoms Molecules and Life Energy the capacity to do work 1 kinetic involves motion 2 potential stored form of energy that mass may possess due to its position Matter anything that takes up space or has mass made up of elements cannot be broken down into other substances by ordinary chemical means and compounds Table 2 2 Elements in the human body Atom o Number of protons is equal to the number of electrons o Has a dense core called the nucleus which contains protons and neutrons o Protons positive and are 1 AMU atomic mass unit o Neutron neutral and are also 1 AMU atomic mass unit o Surrounding the nucleus are electrons o Ions are atoms that have either an extra electron or lost an electron o Molecules can be ions made with atoms joined together with covalent bond o Atomic number refers to the number of protons in an atom o Atomic mass weight number of protons plus number of neutrons measured in AMUs o Isotopes atoms with an unusual number of neutrons o Radioisotopes unstable isotope radioactive used to treat cancers Electron Stability and Chemical Bonds o Electron shells level around the nucleus k 2 L 8 m 8 o Electron orbitals within the shells Atoms want to achieve stability 1 electrons get as close to the nucleus as possible 2 have a completely full valence shell outermost shell of an atom that contains electrons done by forming chemical bonds o Noble gases don t form chemical bonds because valence full o Valence number number of electrons an atom needs to fill valence shell Chemical Bonds 1 Covalent involve sharing electron pairs 2 Polar Covalent involves un equal sharing of electron pairs 3 Ionic electron transfer ex NaCl Electronegativity atoms ability to attract electrons Atom molecule and life cont Covalent bonds involve electron sharing A pair of atoms share a pair of electrons Molecule a molecule is two or more atoms joined together by covalent bonds Hydrogen 1 covalent bond Carbon 4 covalent bonds Oxygen 2 covalent bonds Nitrogen 3 covalent bonds Sulfur 2 covalent bonds Polar covalent bonds when two atoms unequally share a pair of electrons One atom is quite electronegative and the other atom isn t very electronegative o If oxygen or nitrogen is bonded to anything besides each other that will be a polar covalent bond o The charged end of a PC bond are often indicated by the greek letter delta Ionic bonds involve an electron transfer They are not shared as in covalent bonds Once the electron transfer happens there is an electrostatic attraction between the ions Compounds are produced as a result of ionic bonds Ionic bonds are very strong and stable in dry air But in water they will dissolve o Salt is a compound but not a molecule Hydrogen bond is when a hydrogen nucleus which is the same thing as a proton is shared by two electromagnetic atoms Covalent bonds a solid line Hydrogen bond dots o Hydrogen bonds are incredibly weak Chapter 3 Water The only substance that can exist in all three forms of matter at the same time in the same place Water is what makes life possible Water forms hydrogen bonds cohesion water molecules stick together because they form hydrogen bonds o This is important to plants because water molecules stick together to form a tube from the roots to the plant Adhesion water will stick to molecules of living things by forming hydrogen bonds Mediation of temperatureo Heat is the measure of the kinetic energy of matter o Temperature is a measure of heat o Calorie the amount of heat necessary to raise the temperature of 1 gram of water ml o Specific heat of water 1 calorie Alcohol 6 calorie Iron 1 calorie o It takes more heat to raise the temperature of water because it has a higher specific heat requiring more kinetic energy Water moderates our climate and keeps the temperature stable Ice water gets less dense as it freezes than when it is a liquid This means that ice floats It floats because in liquid water there is still enough heat to break some hydrogen bonds Therefore the water is denser Surface tension at the surface water molecules stick together with hydrogen bonds Evaporative cooling when water evaporates it takes a lot of energy to change the water from a liquid to a gas Therefore it feels cool In order to do that you have to break all of the hydrogen bonds that are holding the water to your skin Water is the solvent of life Meaning many ions and compounds that we need are dissolved in the water in our body Water is sometimes referred to as the universal solvent because it can dissolve almost anything o Solution solutes dissolved in a liquid the solvent homogenous mixture o Aqueous solution water solvent o Solutes can be dissolved into water Hydrophilic water loving Hydrophobic water fearing like dissolves like Water polar substance dissolves polar substances o Polar substance will dissolve polar solutes lots of oxygen or nitrogen ex ethanol glucose o Non polar ex fats and oils water wont dissolve very little oxygen Hydration sphere Hydration shell ex table salt how water dissolves Soaps and detergents are examples of amphipathic molecules both polar and non polar Colloid a suspension of fine particles in a liquid ex blood rbcs are suspended in solution Molarity M o 1 molar solution of glucose o Atomic mass mass of atom p n measured in Daltons or amus o Molecular mass mass of molecules glucose C6H1206 180 Daltons sum of atomic masses o Mole is the A M or M M in grams o Mole 6x10 23 particles Avogadro s o Solutions 1 molar solution of glucose 180 g of glucose in beaker 1 L of H2O Acids Bases PH o Deal with protons hydrogen nuclei hydrogen ions H o Hydrogen atom extremely reactive o Acids proton donors increase proton number in a solution ex sulfuric acid strong acids dissociate completely weak acids dissociate incompletely don t completely break apart ex carbonic acid o Bases proton accepters decrease in a solution ex ammonia will grab onto protons and form ammonia ions ex potassium hydroxide dissociate hydroxide forms water o pH less than 7 is acidic move H than OH lower the pH the more acidic it is basic more OH most basic is pH of 14 o pH of blood ranges from 7 35 7 45 pH of 7 would be fatal o Buffers aqueous solution consisting of a mixture of a weak acid and corresponding base Ex carbonic acid weak acid dissociates incompletely equilibrium reaction occurs to balance Chapter 4 Biological Molecules Organic Chemistry Organic chemistry chemistry of organisms study of carbon study of molecules in which C C and C H bonds are