Water and Ph Biochem

WATER AND PH

Raymond Oliver A Cruz, MD FPAFP

OBJECTIVES

• Describe the structure of water

• Define pH, acids, and bases

• Differentiate between the differrent types of

chemical bonds

• Illustrate the concepts of hydrogen bonding

• Calculate and determine pH and pOH given the

hydrogen ion concentration

• Describe how blood pH is regulated

- Define the role of buffers and describe its

mechanism for maintaining pH

• Explain the characteristics of the different clinical

abnormalities of blood pH

WATER IN THE BODY

• Total body water is roughly 50 to

60% of body weight in adults and

75% of body weight in children

• Because fat has relatively little

water associated with it, obese

people tend to have a lower

percentage of body water than

thin people, women tend to have

a lower percentage than men,

and older people have a lower

percentage than younger people

• Approximately 60% of the total body water

is intracellular and 40% extracellular.

• The extracellular water includes the fluid in

plasma (blood after the cells have been

removed) and interstitial water (the fluid in

the tissue spaces, lying between cells)

FLUID COMPARTMENTS IN A

70 KG MAN

Dehydration, or loss of water, occurs when

salt and water intake is less than the

combined rates of renal plus extrarenal

(non-kidney-related) volume loss

THE “POWERS” OF WATER

• Can dissolve most organic and inorganic

molecules because of its dipolar structure and

ability to form hydrogen bonds

• Water is an excellent nucleophile, which enables

it to participate in many chemical reactions

• It exhibits a slight but important tendency to

dissociate, enabling it to act either as an acid or

base and playing a role in maintaining pH

WATER AS A TETRAHEDRON

• With oxygen in the

center, water

assumes a

tetrahedral shape

• 2 hydrogen atoms

and the unshared

electrons of the

remaining sp3

hydbridized orbitals

occupy the corners

of the tetrahedron

UNSHARED...