Ch2_rcA&P

Ionic Bonds:
• Formed when electrons are transferred from one atom to
another atom
• The attraction between a cation and an anion forms a very

strong bond between the ions, called an ionic bond.

Bonding of Atoms: Ionic Bonds

7

Bonding of Atoms: Polar Molecules

9

Polar Molecules:
• Molecules with a slightly negative end & a slightly positive end
• Results from unequal sharing of electrons in covalent bonds
• Water is an important polar molecule

In this water molecule, the
O nucleus pulls the
electrons more strongly
than the H nuclei, since
it contains more positively
charged protons.

Electrolytes: Substances that release ions in water. The
solution can conduct an electric current, so it is called an
electrolyte.
NaCl 🡪 Na+ + Cl-

Acids: Electrolytes that dissociate to release hydrogen ions in
water
HCl 🡪 H+ + Cl-

Bases: Substances that release ions that can combine with
hydrogen ions
NaOH 🡪 Na+ + OH-

Salts: Electrolytes formed by the reaction between an acid
and a base
HCl + NaOH 🡪 H2O + NaCl

Acids, Bases, and Salts

12

• Concentrations of acids and bases affect chemical

reactions in living organisms.

• H+ ion concentration is measured in g/L of body fluid
• pH scale is used as shorthand for H+ ion concentration; it

is based on the number of decimal places in the
concentration

• If H+ ion concentration = 0.01 g/L, the pH = 2
• If H+ ion concentration = 0.000000001 g/L, the pH =9
• pH scale runs from 0 – 14; each number represents a

tenfold difference in H+ ion concentration

• Acids have a pH <7, and bases have a pH >7
• A pH of 7 is neutral

Acid and Base Concentrations

13

Acid and Base Concentrations

14

The higher the H+
concentration, the
lower the pH, and
the higher the
acidity.

The lower the H+

concentration, the
higher the pH, and
the lower the acidity
(which corresponds
to higher alkalinity).

Acid and Base Concentrations

15

• pH Scale: Indicates the concentration of hydrogen ions in a

solution

• Neutral: A pH of 7 indicates equal concentrations of H+ and

OH-. This is the pH of water.

• Acidic: A pH of <7 indicates a greater concentration of H+

than OH-

• Basic (alkaline): A pH >7 indicates a higher concentration of

OH- than H+

Acid and Base Concentrations

16

Normal range of blood pH is 7.35 – 7.45

Acidosis occurs when blood pH drops to 7.0 – 7.3
•

Makes a person feel disoriented, fatigued

•

Caused by vomiting of alkaline intestinal contents,
diabetes, lung disease with impaired CO2 exhalation

Alkalosis occurs when blood pH rises to 7.5 – 7.8
•

Makes a person feel dizzy and agitated

•

Caused by high altitude breathing, vomiting of acidic
stomach contents, high fever, taking excess antacids

•

Homeostatic mechanisms help regulate pH

•

Buffers are chemical systems which act to resist pH

changes; bind and release H+ ions to regulate pH

Organic vs. Inorganic Molecules

• Organic molecules:

• Contain C and H
• Dissolve in water and organic liquids
• Water-soluble organic compounds do not release ions,
and are non-electrolytes
• Carbohydrates, proteins, lipids, and nucleic acids

• Inorganic molecules:

• Generally do not contain C and H
• Usually dissolve in water and dissociate, forming
ions, and are electrolytes
• Water, oxygen, carbon dioxide, and inorganic salts

2.3: Chemical Constituents of Cells

17

A triglyceride is composed of 1 glycerol molecule and 3 fatty
acids.

Organic Substances: Lipids

23

• Proteins are used as structural materials, energy source,

hormones, receptors, enzymes, antibodies

• Consist of building blocks called amino acids
• An amino acid contains an amino (-NH2) group, a carboxyl

(COOH) group, and a unique R (side chain) group

Organic Substances: Proteins

26

Two major types of nucleic acids: DNA and RNA
DNA:
• Stores the genetic code
• Contains the sugar deoxyribose
• Structure—double helix
• Composed of nucleotides
RNA:
• Interacts with DNA to conduct protein synthesis
• Contains the sugar ribose
• Structure—single strand
• Composed of nucleotides

Organic Substances: Nucleic Acids

29

Inorganic Substances

19

Carbon dioxide (CO2):

•Waste product released during metabolic reactions
• Must be removed from the body through exhaling

Inorganic salts:

•Abundant in body fluids
• Sources of necessary ions (Na+, Cl-, K+, Ca+2, etc.)
• Play important roles in metabolism
• Help control H2O concentration, pH, blood clotting,
nerve and muscle processes
• Electrolyte balance exists when gains equal losses

21

Organic Substances:

Carbohydrates