Chapter 2

Part 2: Reactions & Inorganic Compounds

Chemical Reactions • Reactants Products

• 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 1. Synthesis = combining atoms/molecules to form larger,

more complex molecule

A + B AB

Anabolic reactions

2. Decomposition = breaking apart molecules

AB A + B

Catabolic reactions

3. 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: 1. Inorganic compounds: no carbon

Small, simple

Water, salts, acids, bases

2. 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 1. High heat capacity: absorb/release heat;

maintain constant temps

2. High heat of vaporization: liquid gas; evaporative cooling

3. Polar solvent: dissolve substances; universal solvent

4. Reactivity: involved in many chemical reactions

5. 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+