Water = nonionic compound. It is converted to ions in a process called ionization. Water separates when one of the OH bonds breaks. This results in a.

Water = nonionic compound. It is converted to ions in a process called ionization.

Water separates when one of the OH bonds breaks. This results in a positively charged H+ (hydrogen ion)

and a negatively charged OH— (hydroxide ion).

ALL LIFE PROCESSES DEPEND ON THIS TINY IONIZATION PROCESS…

Imagine a water molecule that picks up a positively charged hydrogen proton.

When this happens, this water molecule becomes positively charged. 

The water molecule that gave up the hydrogen proton becomes negatively charged

because one 1 electron remained behind. 

The level of H+ and OH— ions in solution

is known as the pH scale

The proton exchange results in 2 water molecules out of every 1 billion splitting into a

positively charged H3O+ (called hydronium) ion and a negatively charge OH- (called hydroxide) ion. 

Pure water, contains hydronium ions equal to 1 x 10-7 moles per liter (0.0000001 moles per liter). 

In other words, the number of hydronium ions Is equal to number of hydroxide ions.

Therefore, the hydroxide ions are equal to1 x 10-7 moles per liter.

  This equilibrium between

hydronium and hydroxide ions is affected by the addition of substances

to water.

A proton donor is known as an acidacid. AcidsAcids increase the

[H+] ions in solution. 

A basebase functions as a proton acceptor,

it reduces the concentration of [H+] in solution

and increases the concentration of [OH--] ions.

1  X 10-1 [H+] = pH 1 HCl or stomach acid

1  X 10-13 [OH--] = pH 1 HCl or stomach acid

[H+]

pH 1 pH 7 pH 14

[OH—]

What happens to the pH of the solution if the level of [H+] increases?

What happens to the pH of the solution if the level of [OH–] increases?

CO2

What does exhalinginto the water

add to the water?H2O

Bromothymol Blue added

CO2How does this

‘change’ the water?

Why?

CO2 + H2O H2CO3

Carbonic Acid

H2OCO2

Buffer Systems—a buffer is a moleculethat tends to either bind or release hydrogen ions

in order to maintain a particular pH

What happens when the reactions go to the right?

What happens if the reactions go to the left?

Carbonic acid

BicarbonateIon

CarbonateIon

H2CO3

HCO3 --

= carbonic acid (H+ donor) responds to a rise in pH

= bicarbonate (H+ acceptor) responds to a drop in pH

[H+]

pH 1 pH 7 pH 14

Carbonic acid

BicarbonateIon

A diabetic’s blood pH dropped to 7.23. Why?The body enters a starving state due to no insulin output; body burns stored fat for energy and ketones are released into the bloodstreamas a by-product/or waste product of fat metabolism. Ketones are acidic!

What happens during HYPERventilation? Levels of Carbon dioxide decrease; less H+ ions will accumulate causing the pH of blood to increase = alkalosis

What happens during HYPOventilation?Carbon dioxide in blood increases; more H+ ions will accumulate causing the pH of blood to decrease

Maintaining blood pH—why?

Acidosis or Alkalosis = death

What do the lungs do?In general, acids (H+ ions) are stimulating to neurons.

As the carbon dioxide level in the blood increases, it also increases in the cerebrospinal fluid (CSF).

This causes the pH to drop; especially in the brain because there is less buffering ability in CSF than in blood. The low pH (excess H+ ions) stimulates neurons in the medullary respiratory centers to fire more impulses to the diaphragm to increase the rate and depth of breathing.

What do the kidneys do?Regulates HCO3- ions in blood loss of HCO3- ions in blood = decrease blood pH = metabolic acidosis gain of HCO3- ions in blood = increase blood pH = metabolic alkalosis

Parietal Cells of the stomach secrete HCl into the stomachto disrupt the extracellular matrix and kills most bacteria that are swallowed up with food…

HCl converts inactive pepsinogen (whichis secreted by chief cells of the stomach)into active pepsin

Pepsin begins the chemical digestionof proteins by splitting the polypeptidesinto smaller polypeptides…

pH in the Digestive System, producing HCl

Lumen of the

Stomach

Esophagus“peristalsis”

Small Intestine

H2CO3

HCO3

= carbonic acid (H+ donor) responds to a rise in pH

= bicarbonate (H+ acceptor) responds to a drop in pH

[H+]

pH 1 pH 7 pH 14

The Stomach—secretion of HClMovement of molecules by active transport or facilitated diffusion

Cl-

HCO3-

Cl-

H+

HCl

CO2+ H2O

H2CO3

H+HCO3-

CapillaryBloodvessel

Parietal cell

Lumen of stomach

Cl-

+

Bicarbonate ion

Carbonic Acid

H2CO3 HCO3- H++

Buffer system in place to regulate pH

Carbonic Acid Bicarbonate Hydrogen ion