Warm-Up What 2 elements besides H and N make up the bulk of living matter? An element has a mass of 207 and has 125 neutrons in its nucleus. How many protons and electrons does it have and where are they located? What kinds of bonds form between water molecules?

Chapter 2 Part 2: Reactions & Inorganic Compounds Chemistry Comes Alive Chapter 2 Part 2: Reactions & Inorganic Compounds

Chemical Reactions Reactants  Products Some reactions are reversible: Eg. 6CO2 + 6H2O  C6H12O6 + O2 Some reactions are reversible: Eg. 3H2 + N2 2NH3 Chemical equilibrium: point at which forward and reverse reactions offset one another exactly Reactions still occurring, but no net change in concentrations of reactants/products

3 Patterns of Chemical Reactions Synthesis = combining atoms/molecules to form larger, more complex molecule A + B  AB Anabolic reactions Decomposition = breaking apart molecules AB  A + B Catabolic reactions Exchange Reaction = bonds made/broken to exchange parts AB + C  AC + B AB + CD  AD + CB

Factors influencing rate of reaction: Temperature: temp, rate Concentration: reactants, rate (as reactants , rate will ) Particle size: small particles move faster Catalysts: increase rate of reactions (enzymes)

Two classes of chemicals: Inorganic compounds: no carbon Small, simple Water, salts, acids, bases Organic compounds: contain carbon Usually large, complex Carbs, lipids, proteins, nucleic acids

Water Polar molecule = shares electrons (e-), but not shared equally Electrons spend more time around oxygen (very electronegative) Oxygen end of H2O slightly - Hydrogen end of H2O slightly +

Hydrogen bonds in water Attraction between (+) end of polar molecule with the (-) end of another polar molecule

Properties of Water High heat capacity: absorb/release heat; maintain constant temps High heat of vaporization: liquid  gas; evaporative cooling Polar solvent: dissolve substances; universal solvent Reactivity: involved in many chemical reactions Cushioning: protect, cushion organs

Salts Ionic compounds Dissolve in H2O Electrolytes – conduct electrical current in solution Common salts in body: NaCl, CaCO3, KCl, calcium phosphate (bones)

Acids & Bases Acid: release hydrogen (H+) ions (proton donor) HCl  H+ + Cl- Sour taste Eg. acetic acid, carbonic acid Base: take up H+ ions (proton acceptor) NaOH  Na- + OH- Bitter taste, feel slippery Eg. bicarbonate ion (HCO3-), ammonia (NH3)

pH Scale Acids: pH < 7 Neutral pH = 7 Bases: pH >7

Buffers Maintain homeostasis by resisting changes in pH of body fluids Blood pH: 7.35 – 7.45 Release H+ ions when pH rises; bind H+ ions when pH drops Weak acids or bases Major buffer: carbonic acid – bicarbonate system H2CO3 (carbonic acid)  HCO3- (bicarbonate) + H+