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TORTORA  FUNKE  CASE
ninth edition
MICROBIOLOGY
an introduction
2
Part B
Chemical
Principles
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
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Important Biological Molecules
 Organic compounds always contain carbon and
hydrogen.
 Inorganic compounds typically lack carbon.
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Inorganic Compounds: Water
 Polar molecule
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Figure 2.4a
Inorganic Compounds: Water
 Solvent
 Polar
substances
dissociate,
forming
solutes.
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Figure 2.5
Inorganic Compounds: Water
 H+ and OH participate in chemical reactions
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Inorganic Compounds: Water
 Hydrogen bonding
between water
molecules makes
water a
temperature buffer.
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Figure 2.4b
Acids, Bases, and Salts
 An acid is a substance
that dissociates into one
or more H+.
HCl  H+ + Cl
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Figure 2.6a
Acids, Bases, and Salts
 A base is a substance
that dissociates into one
or more OH.
NaOH  Na+ + OH
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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
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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.
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Acid-Base Balance
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Figure 2.7
Organic Compounds
 The chain of carbon
atoms in an organic
molecule is the carbon
skeleton.
 Functional groups are
responsible for most of
the chemical properties
of a particular organic
compound.
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Table 2.3 (1 of 2)
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Table 2.3 (2 of 2)
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.
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Organic Compounds
 Monomers join by dehydration synthesis or
condensation reactions.
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Figure 2.8
Carbohydrates
 Are important for structure and as energy sources.
 Consist of C, H, and O with the formula (CH2O)n.
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Figure 2.8
Carbohydrates
 Monosaccharides are simple sugars with three to
seven carbon atoms.
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Figure 2.8
Carbohydrates
 Disaccharides are formed when two monosaccharides
are joined in a dehydration synthesis.
 Disaccharides can be broken down by hydrolysis.
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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.
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Lipids
 Are the primary components of cell membranes.
 Consist of C, H, and O.
 Are nonpolar and insoluble in water.
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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.
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Figure 2.9c
Complex Lipids
 Contain C, H, and O +
P, N, or S.
 Membranes are made
of phospholipids.
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Figure 2.10a
Steroids
 Consist of four carbon
rings with an –OH
group attached to
one ring.
 Are part of
membranes.
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Figure 2.11
Proteins
 Are essential in cell structure and function.
 Enzymes are proteins that speed chemical reactions.
 Transporter proteins move chemicals across
membranes.
 Flagella are made of proteins.
 Some bacterial toxins are proteins.
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Proteins
 Consist of subunits called amino acids.
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Table 2.4 (1 of 4)
Proteins
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Table 2.4 (2 of 4)
Proteins
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Table 2.4 (3 of 4)
Proteins
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Table 2.4 (4 of 4)
Amino Acids
 Exist in either of two
stereoisomers, D or L.
 L-forms
are most often
found in nature.
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Figure 2.13
Peptide Bonds
 Peptide bonds between amino acids are formed by
dehydration synthesis.
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Figure 2.14
Levels of Protein Structure
 The primary structure is a polypeptide chain.
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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.
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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.
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Figure 2.15c
Levels of Protein Structure
 The quaternary structure consists of two or more
polypeptides.
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Figure 2.15d
Level of Protein Structure
 Conjugated proteins consist of amino acids and other
organic molecules
 Glycoproteins
 Nucleoproteins
 Lipoproteins
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Nucleic Acids
 Consist of nucleotides.
 Nucleotides consist of a
 Pentose
 Phosphate group
 Nitrogen-containing (purine or pyrimidine) base
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Figure 2.16 (1 of 2)
DNA
 Has deoxyribose
 Exists as a
double helix
 A hydrogen
bonds with T
 C hydrogen
bonds with G
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Figure 2.16 (2 of 2)
RNA
 Has ribose
 Is single-stranded
 A hydrogen bonds
with U
 C hydrogen bonds
with G
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Figure 2.17
ATP
 Has ribose, adenine, and three phosphate groups.
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Figure 2.18
ATP
 Is made by dehydration synthesis.
 Is broken by hydrolysis to liberate useful energy
for the cell.
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