pH and Disassociation

H20 H+ + OH- Living organisms are composed mainly of

H2O. Some water molecules tend to separate into ions, forming solutions that are acidic or alkaline.

Therefore, in order to understand biochemical processes, we need to know a little about acids and bases

Ionization of Water

H2O H+ + OH-

Covalent dissociates

Bonding (splits)

Ionization of Water Same # of H+ as OH - = a neutral solution

Acids Acid = Have

more H+ ions in solution.

Examples

HCl H+ + Cl-

H2SO4 2 H++ SO4-

BASES Bases have more

OH- in solution

Examples:

NaOH Na+ + OH-

Al(OH)3 Al3+ + OH-

A pH scale (color coded)

What do the pH #’s mean?

pH = a measure of H+ concentrations

HUMAN pH Our bodies have a pH

of 7.4 Stomach pH =1 to 2 Acceptable range is

6.5- 7.5, otherwise its lethal (coma or death)

HOMEOSTASIS A mechanism to maintain body’s

stabilization, Human pH range is between 6.5 -7.5 One way to keep the body stable is through

pH and buffers.

H+ + HCO32- H2CO3 H2O + CO2

carbonic

acid

BUFFER Buffers are weak acids & bases that rxt with strong acid & bases in the body to maintain homeostasis.

A buffer is a substance which accepts H+ ions or gives off H+ in order to maintain the pH of a system

New Stuff =Water Polarity

Polarity H2O is a polar molecule

because of the unequal distribution of e- between hydrogen and oxygen.

Neg. pole near oxygen atom & positive pole is between the hydrogens

Cohesion The attraction

between molecules of the same substance Explains why H2O

beads up Explains why some

insects & spiders can walk on water

Adhesion Attraction between

molecules of different substances

Capillary Action Due to adhesion

between H2O & glass, the water can rise in a narrow tube against the force of gravity.