TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
Chapter 2, part B
Chemical Principles
Important Biological
Molecules
• Organic compounds always
contain carbon and hydrogen.
• Inorganic compounds typically
lack carbon.
Inorganic Compounds: Water
• Polar molecule
Figure 2.4a
Inorganic Compounds: Water
• Solvent
– Polar
substances
dissociate,
forming
solutes
Figure 2.5
Inorganic Compounds: Water
• H+ and OH participate in chemical
reactions
Inorganic Compounds: Water
• Hydrogen
bonding
between water
molecules
makes water a
temperature
buffer.
Figure 2.4b
Acids, Bases, and Salts
• An acid is a
substance that
dissociates into
one or more H+.
HCl  H+ + Cl
Figure 2.6a
Acids, Bases, and Salts
• A base is a
substance that
dissociates into
one or more OH.
NaOH  Na+ +
OH
Figure 2.6b
Acids, Bases, and Salts
• A salt is a
substance that
dissociates into
cations and anions,
neither of which is
H+ or OH.
NaCl  Na+ + Cl
Figure 2.6c
Acid-Base Balance
• The amount of H+ in a solution is expressed
as pH.
• pH = log[H+]
• Increasing [H+], increases acidity.
• Increasing [OH] increases alkalinity.
• Most organisms grow best between pH 6.5
and 8.5.
Acid-Base Balance
Figure 2.7
• The chain of
Organic
carbon atoms in
an organic
molecule is the
carbon
skeleton.
• Functional
groups are
responsible for
most of the
chemical
properties of a
particular
organic
Compounds
Table 2.3.1
Organic Compounds
• Small organic molecules can combine
into large macromolecules.
• Macromolecules are polymers
consisting of many small repeating
molecules.
• The smaller molecules are called
monomers.
Organic Compounds
• Monomers join by dehydration synthesis or
condensation reactions.
Figure 2.8
Carbohydrates
• Are important for structure and as energy
sources.
• Also for structures like cell walls
• Consist of C, H, and O with the formula
(CH2O)n
Figure 2.8
Carbohydrates
• Monosaccharides are simple sugars with 3
to 7 carbon atoms.
Figure 2.8
Carbohydrates
• Disaccharides are formed when two
monosaccharides are joined in a
dehydration synthesis.
• Disaccharides can be broken down by
hydrolysis.
Figure 2.8
Carbohydrates
• Oligosaccharides consist of 2 to 20
monosaccharides.
• Polysaccharides consist of tens or hundreds
of monosaccharides joined through
dehydration synthesis.
• Starch, glycogen, dextran, and cellulose are
polymers of glucose that are covalently
bonded differently.
• Chitin is a polymer of two sugars repeating
many times. What is Chitin?
Lipids
• Three types of lipids:
– Simple fats also known as triglycerides
– Phospholipids
– Steroids
• Are the primary components of cell membranes.
• Function as storage of energy, membrane structure
and some act as hormones (steroids).
• Consist of C, H, and O.
• Are nonpolar and insoluble in water.
Simple lipids
• Called fats or triglycerides contain glycerol
and fatty acids; formed by dehydration
synthesis.
• Unsaturated fats have one or more double
bonds in the fatty acids.
Figure 2.9c
Phospholipids lipids
• Contain C, H,
and O + P, N,
or S.
• Membranes
are made of
phospholipids
Figure 2.10a
Steroids
• Consist of four
carbon rings,
with an –OH
group
attached to
one ring.
• Are part of
membranes.
Figure 2.11
Proteins
• Are essential in cell structure and function as
enzymes.
• Enzymes are proteins that speed chemical
reactions.
• Transporter proteins move chemicals across
membranes.
• Flagella are made of proteins.
• Some bacterial toxins are proteins.
Proteins
• Consist of monomer subunits called
amino acids.
Table 2.4.1
Proteins
Table 2.4.2
Amino Acids
• Exist in
either of two
stereoisomer
s, D or L.
• L-forms are
most often
found in
nature.
Figure 2.13
Peptide Bonds
• Peptide bonds between amino acids are
formed by dehydration synthesis.
Figure 2.14
Levels of Protein Structure
• The primary structure is a polypeptide
chain
Figure 2.15a
Levels of Protein Structure
• The secondary structure occurs when the
amino acid chain folds and coils in a regular
helix or pleats.
Figure 2.15b
Levels of Protein Structure
• The tertiary structure occurs when the helix
folds irregularly, forming disulfide bonds,
hydrogen bonds, and ionic bonds between
amino acids in the chain.
Figure 2.15c
Levels of Protein Structure
• The quaternary structure consists of two
or more polypeptides.
Figure 2.15d
Level of Protein Structure
• Conjugated proteins consist of amino
acids and other organic molecules:
• Glycoproteins
• Nucleoproteins
• Lipoproteins
Nucleic Acids
• Consist of monomer units called nucleotides.
• Nucleotides consist of a:
• Pentose
• Phosphate group
• Nitrogen-containing (purine or pyrimidine) base
• Adenine, thymine, guanine or cytosine
Figure 2.16
DNA
• Has the sugar
deoxyribose
• Exists as a
double helix
with sugar and
phosphate as
backbone
• A hydrogen
bonds
with T
• C hydrogen
bonds
with G
Figure 2.16
RNA
• Has sugar ribose
• Is single-stranded
• A hydrogen
bonds
with U
• C hydrogen
bonds
with G
Figure 2.17
ATP
• Has ribose, adenine, and 3 phosphate
groups
Figure 2.18
ATP
• Is made by dehydration synthesis.
• Is broken by hydrolysis to liberate useful
energy for the cell.