Microbial Metabolism & Growth
Basic Organic Chem Review
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Four Basic Types of Macromolecules
A) Proteins (Made up of Amino Acids)
B) Nucleic Acids (Made up of Nucleotides)
C) Carbohydrates (Mainly Carbon, Hydrogen,
and Oxygen in a 1:2:1 ratio)
• D) Lipids (Mainly Carbon & Hydrogen)
A. Proteins
• consist of long, complex chains of amino
acids (20 kinds)
• the most abundant organic components of
microbes
• function as structural materials as well as
__________
• destruction of the proteins in an organism
usually results in death
Protein structure: amino acids
• AMINO ACIDS are the building blocks of
proteins
a specific amino acid
Protein structure: amino acids
NOTE: All amino acids look alike except for the highlighted
portions. This is important in building
many different proteins.
Peptide bonding of amino acids
• Proteins are built by linking amino acids
end to end. Each link is a ____________.
Protein structure: Primary
Protein structure: Secondary
Protein structure: 3 dimensional
• The 3 dimensional shape of a protein
dictates its function.
• If the 3 dimensional shape is altered, the
protein is destroyed.
Protein structure: Quaternary
(Hemoglobin)
Protein _________
Altered 3-D shape = destroyed protein
B. Nucleic Acids
• Two types function in all living
things:
• _____ ( deoxyribonucleic acid )
acts
as the genetic material of the
chromosome
• _____ ( ribonucleic acid )
functions
in the construction of proteins
• Both DNA and RNA are
composed of
repeating units called
nucleotides
• As with proteins, the nucleic
acids cannot be altered without
disrupting
the organism or killing it.
C. Carbohydrates
• 1. general formula = (CH2O)n
• 2. sugars, starches, cellulose, etc
• 3. have a vital function as energy
sources in cells
• 4. also found in several cellular
structures such as cell walls and
bacterial capsules
• 5. monosaccharides are the simplest
carbohydrates, the building blocks
e.g. ________, fructose
C6H12O6
Carbohydrates
• 6. disaccharides are double sugars (2
monosaccharides bonded together)
– e.g. _______ (table sugar) is one glucose and
one fructose
– C12H22O11: one H2O lost when bond forms
Dehydration Synthesis (Putting together)
glucose
Hydrolysis (breaking apart)
fructose
NOTE: 2 monosaccharides linked together.
Macromolecules (How to Make Them)
CH2OH
H
HO
H
OH
H
CH2OH
O H
H
H
H
OH
OH HO
OH
H
Dehydration
Synthesis
Hydrolysis
CH2OH
O H
H
OH
OH
H
HO
H
OH
H
CH2OH
O H
H
OH
O
H
OH
H
O H
H
OH
OH
H2O
C. Carbohydrates
• 7. complex sugars are called
polysaccharides or complex carbohydrates
(e.g. starch, cellulose )
• long chains of sugars:
sugar—sugar—sugar—sugar—sugar—
sugar—sugar—
D. Lipids
• Broad group of organic compounds that
dissolve in oily solvents (e.g. acetone, or
benzene) and alcohol but generally do not
dissolve in water
• Mostly composed of carbon and hydrogen
D. Lipids
glycerine
fatty acid
• 1. Best known lipids are fats
– serve living organisms
as important energy
sources
– consist of glycerol
and up to three
long-chain fatty acids
• 2. Modified fats called phospholipids
are the major components of membranes
• 3. Other types of lipids include
waxes and steroids
Fatty Acids + Glycerol
Fats
Other important lipids you should
know!
Phospholipids
Steroids such as cholesterol
I. MICROBIAL PHYSIOLOGY
• _____________: the sum of all biochemical
processes taking place in a living cell. Two
phases:
• _____________: constructive metabolism;
the synthesis reactions; small molecules
bonded into larger molecules; energy is
“used up”
• _____________: destructive metabolism;
decomposition reactions; large molecules
split into smaller molecules; energy is
released
A._________
• the enzymes present in an organism
determine the nature of its physiology
• enzymes are biological catalysts (catalysts
are agents that speed up chemical
reactions)
• Enzymes “are reusable protein molecules
that brings about a chemical change while
remaining unchanged itself”
________________= the amount of
energy required to do the reaction
Without enzyme
lactose
glucose + galactose
activation energy
without enzyme
net energy released
from splitting of lactose
Activation Energy = the amount of
With enzyme
lactose
energy required to do the reaction
glucose + galactose
activation energy
with enzyme
net energy released
Enzymes
__________ =
what the
enzymes works
on
________
= what
is made
Enzymes
Active
Site
Competitive Inhibitor
Allosteric
Site
Noncompetitive inhibitor
Action of enzyme inhibitors
Examples of inhibitors:
1. Competitive=sulfa drug (sulfanilamide)
2. Noncompetitive=Certain poisons, such as cyanide and fluoride (enzyme
poison in bacteria)
Factors influencing enzyme action:
• a. Terms:
• optimum: the environmental state where the
enzyme works the fastest.
• maximum: The maximum environmental limit
where the enzyme works at all.
• minimum: The minimum environmental limit
where the enzyme works at all.
• e.g. temperature: every enzyme has its
optimum temperature (where it works
fastest). Curve is unusual:
enzyme activity vs temperature
• Measurement of
acid/base balance
• Logarithmic scale
• 0-6.9 = acid
• 7.1-14 = basic
(alkaline)
• 7 = neutral
(like pure water)
pH
enzyme activity vs pH
• every enzyme has its optimum pH (where
it works fastest). Bell curve
Naming of enzymes
• names end with -ase
• name of substrate + ase
e.g. sucrose is digested by sucrase
• kind of reaction + ase
e.g. an enzyme that causes oxidation is
called oxidase
Types of Enzymes based on
location
• endoenzymes: remain inside of the cell
(work internally)
– enzymes of cellular metabolism
– vulnerable enzymes
• exoenzymes: released to the exterior of
the cell (work externally)
– digestive enzymes and enzymes of virulence
Constitutive vs Induced Enzymes
• ___________ enzymes:
– always present
– necessary for life of cell
• __________ enzymes:
– produced only when substrates are present
– e.g. digestive enzymes
– provide efficiency and adaptability
B. Energy and ATP
• Energy released from catabolism of foods is stored in a
compound called ATP (adenosine triphosphate)
• a molecule of ATP acts like a portable battery—it’s instant
energy for a cell to use
• ATP molecules are used everywhere in a cell to meet
energy needs. (When the supply is exhausted, the cell dies)
ADP + Phosphate + Energy = ATP
captures heat
releases heat
ATP
• Although ATP molecules are used everywhere
in the cell to meet energy needs, they are not
suitable for storing energy. The molecules are
large and bulky, and surplus takes up too much
space in a cell.
• Therefore, cells synthesize or obtain small
molecules such as glucose or lipids for energy
storage. When needed, these energy storage
molecules can be converted to ATP!
• glucose is a principle source of energy for ATP
production.
C. Pathways of Energy Production
• Most of a cell’s energy is produced from
carbohydrate catabolism
• Glucose is the most commonly used
carbohydrate:
• C6H12O6 + 6 O2 + 38 ADP + 38 P
6 CO2 + 6 H2O + 38 ATP
• To produce energy (ATP) from glucose,
microbes use 2 general processes:
– 1. respiration
• in which glucose is completely broken down
– 2. fermentation
• in which glucose is partially broken down
• Both processes usually start with the same
first step (glycolysis), but follow different
subsequent pathways
Glycolysis
• the first stage in the breakdown of glucose
glucose
(energy
source )
series of controlled
reactions releasing a
little ATP
2 pyruvic acid
Overview of Respiration & Fermentation
glycolysis
respiration
pathways
Aerobic=
CO2 + H2O + 38 ATP
fermentation
pathways
an organic end-product
(like alcohol or lactic acid)
with low ATP yield
Classification of organisms by
oxygen use (study table 6.1)
• 1. obligate aerobes: (= strictly aerobic): must have
oxygen to grow (go dormant without oxygen)
• 2. microaerophiles: grow best at low oxygen levels
(less than atmospheric)
• 3. facultative anaerobes: use oxygen if it’s present,
but can also grow anaerobically (capable of growing
at any oxygen level, but greater growth with oxygen
present)
• 4. aerotolerant anaerobes: never use oxygen, but not
inhibited by it
• 5. obligate anaerobes: grow only in absence of
oxygen (inhibited by oxygen)
Good Essay Question! (This or the picture or BOTH)
Growth at different oxygen levels
E. Growth at different temperatures
• Each species has different temperature requirements
• minimum growth temperature: lowest temperature at which
growth will occur (very slow growth at this temp)
– below the minimum, most microorganisms go dormant,
but do not die
• optimum growth temperature: temp at which most rapid
growth occurs
• maximum growth temperature: highest temp at which
growth occurs
– above this temp, enzymes are denatured and death
might occur
• NOTE: Growth parallels rate of enzyme activity.
Growth speed vs temperature
F. Classification by temperature
requirements
• _____________ (= cryophiles): cold-loving
organisms; have optimum growth temp
below 25° C
mesophiles
• _____________
(meso = middle): have
optimum of 25-40°C
• ____________: heat-loving organisms; have
optimum > 40°C
hyperthermophiles growth range = 70-105oC;
• ______________:
optimum > 90oC
Good Essay Question Also!
Growth versus temperature
Does size of pan (with same
volume) matter?
G. pH and microbial growth
• every organism has its minimum,
optimum, and maximum growth pH
• microorganisms often change the pH of
their environment
– usually create acidity
– sometimes create alkalinity
Thus, the requirements for bacterial
growth include:
• Physical aspects
– Temperature
– pH
– Osmotic pressure
• Chemical aspects
– Carbon, nitrogen, sulfur, phosphorus, trace
elements, oxygen, and organic growth factors
H. Bacterial fission (cell division)
• less complex than mitosis (division of
eucaryotic cells)
– only one chromosome
• Binary fission (see figure 6.12)
Remember...
• When we talk about microbial growth, we
are really referring to the number of cells,
not the size of the cells.
• Microbes that are “growing” are
increasing in number, accumulating into
clumps of hundreds, colonies ( can be
seen with naked eye ) of hundreds of
thousands, or populations of billions.
How do we measure microbial
growth?
• Plate counts and serial dilutions
– We’ll do as part of the microbiology of water and milk lab
– See figure 6.16
• Filtration
– We’ll do as part of the microbiology of water lab
– See figure 6.18
• Direct Microscopic Count
– See figure 6.20
• Turbidity
– Using the spectrophotometer
– See figure 6.21
• Dry weight
I. Population dynamics
• potential populations:
– huge
– doubling time of 20-30 minutes for many
microorganisms
– from 1 cell to over a million in 10 hours (with 30
minute generation)
– See figure 6.13 & 6.14
• populations are self-limiting
– depletion of food supply
– accumulation of toxic metabolic wastes
• population growth curve
maximum
stationary
phase (aging population)
logarithmic (log)
phase: rapid growth
lag phase:
slow growth
death phase:
rapid decline
survivor phase
time