Ch. 2 Some Basic Chemistry

Made of only 1 type of atom 92 naturally occurring

◦ H, Fe, O, Ca, N, C Compounds – H2O, CO2, C6H12O6(glucose) C,H,N,O,P,S found in all life

◦ Previous + Ca = 99% of human body > 20 elements in body (Table 2-1)

Elements

Smallest part of an element retaining element’s properties

Consists of protons (+), neutrons (0), and electrons (-)◦ Protons, neutrons in nucleus◦ Electrons orbiting nucleus in electron cloud (shell)

Atomic number = # of protons Atomic weight = #protons + #neutrons

Atoms

# protons = # electrons◦ Atom is neutral

Electrons bond to other atoms to form molecules◦ Molecule – combination of atoms that are tightly

bound and behave as a single unit Electrons orbit nucleus in shells (energy

levels)◦ First – holds 2 electrons (stable)◦ Second – holds 8 electrons (stable)◦ Higher– stable with 8 or a multiple of 8 electrons

Atoms (cont.)

Few atoms are naturally stable (He, Ne) Most atoms gain, lose, or share electrons to

fill their outer shell◦ Atoms form chemical bonds with other atoms to

become stable

Atoms (cont.)

Force or attraction between (+) and (-) charges that joins atoms to form a molecule

Molecules often have characteristics different from original elements◦ H2 and O2 are gases, but H2O is a liquid

4 kinds of bonds◦ Ionic◦ Covalent◦ Disulfide◦ Hydrogen

Chemical Bonds

Involves loss of electron(s) by one atom and gain of electron(s) by another atom(s) (Fig. 2-2)

1. Na loses electron in outer shell 2. Has a charge of (+1); now a sodium ion 3. Cl atom gains an electron in outer shell 4. Has a charge of (-1); now is a chloride ion 5. (+) and (-) charges attract 6. Result in NaCl (table salt)

◦ Held together by ionic bond

Ionic Bonds

CaCl2 is another example Cations – ions with (+) Anions – ions with (-) Ionic bonds are strong in solid form, but

weakened in aqueous (water) solution◦ Dissociation

e.g. sodium chloride ionizes into Na and Cl ions

Ionic Bonds (cont.)

Sharing of electrons b/w atoms An oxygen atom shares 2 electrons with

another oxygen atom, also sharing 2 electrons (Fig. 2-3)

Oxygen atom may share 2 electrons with 2 hydrogen atoms, each sharing a single electron (Fig. 2-3)

Single covalent bond – pair of shared electrons; single line

Double covalent bond – 2 pairs of shared electrons; double line

Covalent Bonds

C forms 4 covalent bonds◦ e.g. CH4 (methane)

May form bonds with other C, H, O, N, etc. Covalent bonds are relatively strong; not

weakened in water sol’n

Covalent Bonds (cont.)

Disulfide bonds (disulfide bridge) – covalent bond between 2 sulfur atoms◦ Insulin has 2 disulfide bonds◦ Straightening curly hair breaks disulfide bonds

Disulfide Bonds

H atom shares electron in a covalent bond with another atom

Its proton is slightly (+) and may be attracted to nearby O or N atom, which are slightly (-)

Weak bonds, but important◦ Proteins, DNA◦ Make water cohesive (water molecules stick

together)

Hydrogen Bonds

Change brought about by forming or breaking chemical bonds

Two types◦ Synthesis – bonds are formed to make a new

compound Require energy

◦ Decomposition – bonds are broken, resulting in smaller molecules Release energy

Chemical Rxns

Inorganic compounds - simple molecules often consisting of 1 or 2 different elements

Water◦ Essential to life

Solvent Lubricant Changes temp. slowly

Inorganic Compounds of Importance

Solvent ◦ solutes can dissolve in water

Lubricant ◦ prevents friction where surfaces meet & move

Changes temperature slowly◦ Has high heat capacity

Will absorb a lot of heat before temp. rises much Must lose a lot of heat before temp. drops much

◦ Has high heat of vaporization Can release a great deal of heat, without much water

loss

Water

Intracellular fluid (ICF)◦ Water within cells; 65% of total water

Extracellular fluid (ECF)◦ 35% of total water

Plasma – in blood vessels Lymph – in lymphatic vessels Tissue or interstitial fluid – in small spaces b/w cells Specialized fluids – synovial, cerebrospinal fluid

(CSF), aqueous humor in eye

Water Compartments

O2 is 21% of atmosphere, which we inhale Essential for cell respiration

◦ Cells break down glucose to release energy◦ ATP used for cellular processes requiring energy

Oxygen

Waste product of cell respiration If amount in body fluids increases, fluids

become too acidic (acidosis)

Carbon Dioxide

Energy production within cells Involves oxygen, carbon dioxide

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP + heat

CO2 is exhaled Water becomes part of intracellular fluid Heat contributes to normal body temp. ATP used for cell processes

Cell Respiration