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Chapter 2- Microbiology and Parasitology

Organic Compounds
The Macromolecules of Life:
Carbohydrates, Proteins, Lipids, and
Nucleic Acids
3. Most Biological Macromolecules are Polymers
 Polymer:
Large molecule consisting of many
identical or similar “subunits” linked through
covalent bonds.
 Monomer: “Subunit” or building block of a
 Macromolecule:
Large organic polymer. Most
macromolecules are constructed from about 70
simple monomers.
 Only
about 70 monomers are used by all living things
on earth to construct a huge variety of molecules
 Structural
variation of macromolecules is the basis for
the enormous diversity of life on earth.
Relatively few monomers are used by cells to
make a huge variety of macromolecules
Monomers or Subunits
1. Carbohydrates
20-30 monosaccharides
or simple sugars
2. Proteins
20 amino acids
3. Nucleic acids (DNA/RNA) 4 nucleotides (A,G,C,T/U)
4. Lipids (fats and oils)
~ 20 different fatty acids
and glycerol.
Making Polymers
A. Condensation or Dehydration Synthesis reactions:
 Process in which one monomer is covalently linked to
another monomer (or polymer).
The equivalent of a water molecule is removed.
 Anabolic
Reactions: Make large molecules from smaller
ones. Require energy (endergonic)
General Reaction:
X - OH + HO - Y -------->
Monomer 1 Monomer 2
X - O - Y + H2O
(or Polymer)
(or Polymer)
Glucose + Fructose ---------> Sucrose +
(Monomer) (Monomer)
Breaking Polymers
B. Hydrolysis Reactions: “Break with water”.
 Break down polymers into monomers.
 Bonds between subunits are broken by adding water.
 Catabolic Reactions: Break large molecules into smaller
ones. Release energy (exergonic)
General Reaction:
X - O - Y + H2O ----------> X - OH + HO - Y
Monomer 1 Monomer 2
(or Dimer)
H2O ---------> Glucose + Fructose
(Monomer) (Monomer)
Synthesis and Hydrolysis of Sucrose
IV. Carbohydrates: Molecules that store energy and
are used as building materials
 General
 Simple
Formula: (CH2O)n
sugars and their polymers.
 Diverse
group includes sugars, starches, cellulose.
 Biological
• Fuels, energy storage
• Structural component (cell walls)
• DNA/RNA component
 Three
types of carbohydrates:
A. Monosaccharides
B. Disaccharides
C. Polysaccharides
A. Monosaccharides: “Mono” single & “sacchar” sugar
 Preferred
source of chemical energy for cells (glucose)
 Can be synthesized by plants from light, H2O and CO2.
 Store energy in chemical bonds.
 Carbon skeletons used to synthesize other molecules.
1. May have 3-8 carbons. -OH on each carbon; one with C=0
2. Names end in -ose. Based on number of carbons:
5 carbon sugar: pentose
 6 carbon sugar: hexose.
3. Can exist in linear or ring forms
4. Isomers: Many molecules with the same molecular
formula, but different atomic arrangement.
Example: Glucose and fructose are both C6H12O6.
Fructose is sweeter than glucose.
Monosaccharides Can Have 3 to 8 Carbons
Linear and Ring Forms of Glucose
B. Disaccharides: “Di” double & “sacchar” sugar
 Covalent
bond formed by condensation reaction
between 2 monosaccharides.
1. Maltose: Glucose + Glucose.
• Energy storage in seeds.
• Used to make beer.
2. Lactose: Glucose + Galactose.
• Found in milk.
• Lactose intolerance is common among adults.
• May cause gas, cramping, bloating, diarrhea, etc.
3. Sucrose: Glucose + Fructose.
• Most common disaccharide (table sugar).
• Found in plant sap.
Maltose and Sucrose are Disaccharides
C. Polysaccharides: “Poly” many (8 to 1000)
Functions: Storage of chemical energy and structure.
 Storage
polysaccharides: Cells can store simple sugars
in polysacharides and hydrolyze them when needed.
1. Starch: Glucose polymer (Helical)
Form of glucose storage in plants (amylose)
Stored in plant cell organelles called plastids
2. Glycogen: Glucose polymer (Branched)
Form of glucose storage in animals (muscle and liver
 Structural
Polysaccharides: Used as structural
components of cells and tissues.
1. Cellulose: Glucose polymer.
The major component of plant cell walls.
CANNOT be digested by animal enzymes.
 Only microbes have enzymes to hydrolyze cellulose,
found in digestive systems of:
• Cows, goats, and rabbits
• Termites
2. Chitin: Polymer of an amino sugar (with NH2 group)
Forms exoskeleton of arthropods (insects)
 Found in cell walls of some fungi
Three Different Polysaccharides of Glucose
V. Proteins: Large three-dimensional
macromolecules responsible for most
cellular functions
 Polypeptide
chains: Polymers of amino acids
linked by peptide bonds in a specific linear
 Protein:
Macromolecule composed of one or
more polypeptide chains folded into a specific
three-dimensional conformation.
Proteins have important and varied functions:
1. Enzymes: Catalysis of cellular reactions
2. Structural Proteins: Maintain cell shape
3. Transport: Transport in cells/bodies (e.g. hemoglobin).
Channels and carriers across cell membrane.
4. Communication: Chemical messengers, hormones, and
5. Defensive: Antibodies and other molecules that bind to
foreign molecules and help destroy them.
6. Contractile: Muscular movement.
7. Storage: Store amino acids for later use (e.g. egg white).
Protein function is dependent upon its 3-D shape.
Polypeptide: Polymer of amino acids
connected in a specific sequence
A. Amino acid: The monomer of polypeptides
 Central
carbon with:
H atom
Carboxyl group
Amino group
Variable R-group
Amino Acid Structure:
(Amino Group) NH2---C---COOH (Carboxyl group)
(Varies for each amino acid)
A Protein’s Specific Shape (Conformation)
Determines its Function
Conformation: The 3-D structure of a protein.
Determined by the amino acid sequence.
Four Levels of Protein Structure
1. Primary structure: Linear amino acid sequence,
determined by gene for that protein.
2. Secondary structure: Regular coiling/folding of
Alpha helix or beta sheet.
Caused by H-bonds between amino acids.
3. Tertiary structure: Overall 3-dimensional shape
of a polypeptide chain.
4. Quaternary structure: Only found in proteins
with 2 or more polypeptides.
Overall 3-D shape of all polypeptide chains.
 Example:
Hemoglobin (2 alpha and 2 beta
VI. Nucleic acids store and transmit hereditary
information for all living things
 There
are two types of nucleic acids in living things:
A. Deoxyribonucleic Acid (DNA)
Has segments called genes which provide information to
make each and every protein in a cell
 Double-stranded molecule which replicates each time a
cell divides.
B. Ribonucleic Acid (RNA)
Three main types called mRNA, tRNA, rRNA
 RNA molecules are copied from DNA and used to make
gene products (proteins).
 Usually exists in single-stranded form.
DNA and RNA are polymers of nucleotides
 Nucleic acid: A polymer of nucleotides
 Nucleotide: Subunits of DNA or RNA.
Nucleotides have three components:
1. Pentose sugar (ribose or deoxyribose)
2. Phosphate group to link nucleotides (-PO4)
3. Nitrogenous base (A,G,C,T or U)
Purines: Have 2 rings.
• Adenine (A)
• Guanine (G)
Pyrimidines: Have one ring.
• Cytosine (C)
• Thymine (T) in DNA or uracil (U) in RNA.
James Watson and Francis Crick determined the 3D shape of DNA in 1953
 Double
helix: The DNA molecule is a double helix.
 Antiparallel: The two DNA strands run in opposite
Strand 1: 5’ to 3’ direction (------------>)
 Strand 2: 3’ to 5’ direction (<------------)
 Complementary
Base Pairing: A & T (U) and G & C.
A on one strand hydrogen bonds to T (or U in RNA).
 G on one strand hydrogen bonds to C.
 Replication: The
double-stranded DNA molecule can
easily replicate based on A=T and G=C
--- pairing.
of nucleotides in a DNA molecule dictate
the amino acid SEQUENCE of polypeptides
DNA is a Double Helix Held Together by H-Bonds
A Gene is a specific segment of a DNA molecule with
information for cell to make one polypeptide
(transcribed into single stranded RNA “copy”)
(single stranded “copy” of the gene)
Polypeptide (mRNA message translated into polypeptide)
VII. Lipids: Fats, phospholipids, and steroids
Diverse groups of compounds.
Composition of Lipids:
 C, H, and small amounts of O.
Functions of Lipids:
 Biological
 Energy storage
 Insulation
 Structural components of cell membranes
 Hormones
Lipids: Fats, phospholipids, and steroids
1. Simple Lipids: Contain C, H, and O only.
A. Fats (Triglycerides).
Glycerol : Three carbon molecule with three hydroxyls.
 Fatty Acids: Carboxyl group and long hydrocarbon
 Characteristics
of fats:
Most abundant lipids in living organisms.
 Hydrophobic (insoluble in water) because nonpolar.
 Economical form of energy storage (provide 2X the
energy/weight than carbohydrates).
 Greasy or oily appearance.
Lipids: Fats, phospholipids, and steroids
Simple Lipids: Continued
Types of Fats
fats: Hydrocarbons saturated
with H. Lack -C=C- double bonds.
 Solid
at room temp (butter, animal fat, lard)
fats: Contain -C=C- double
 Usually
liquid at room temp (corn, peanut,
olive oils)
Fats (Triglycerides): Glycerol + 3 Fatty Acids
2. Complex Lipids: In addition to C, H, and O,
also contain other elements, such as phosphorus,
nitrogen, and sulfur.
A. Phospholipids: Are composed of:
 Glycerol
fatty acids,
 Phosphate group
 Amphipathic
Hydrophobic fatty acid “tails”.
 Hydrophilic phosphate “head”.
Function: Primary component of the plasma
membrane of cells
B. Steroids: Lipids with four fused carbon rings
Includes cholesterol, bile salts, reproductive, and adrenal
Cholesterol: The basic steroid found in animals
Common component of animal cell membranes.
Precursor to make sex hormones (estrogen, testosterone)
Generally only soluble in other fats (not in water)
Too much increases chance of atherosclerosis.
C. Waxes: One fatty acid linked to an alcohol.
Very hydrophobic.
 Found in cell walls of certain bacteria, plant and insect
coats. Help prevent water loss.