Transcript Microbial Metabolism

Microbial Metabolism
What is metabolism?
• All chemical
reactions/activities in cell
– Catabolism
• Hydrolysis
• Use energy to make ATP
– ADP + Pi + energy  ATP
– Anabolism
• Dehydration synthesis
• Need energy for reaction
– ATP  ADP + Pi + energy
• Enzymes frequently catalyze
reactions
• Oxidation/reduction
What is the difference between…
• Hydrolysis
• Condensation (dehydration synthesis)
• Exergonic vs. endergonic
What are enzymes?
• Without enzymes,
collision theory
rules
– Need sufficient
activation energy
– Number of
molecules above
this activation level
= reaction rate
• Enzymes are
molecules that
lower the
______________
– Catalysts
– Work on
substrate…
What does the enzyme work on?
• Substrate
– Molecules which are changed during reaction
• Enzyme-substrate complex forms temporarily
– Lock and key model
– Highly specific fit
– End in -ase
• Turnover number
– Number of molecules enzyme converts per second
– DNA polymerase = 15; lactate dehydrogenase = 1,000
What are the parts of an enzyme?
• Some are only a polypeptide chain
• Most have two parts
– Apoenzyme (polypeptide chain)
– Cofactor (inorganic) or coenzyme (organic)
• NAD+ (nicotinamide adenine dinucleotide) us. catabolic
• NADP+ (nicotinamide adenine dinucleotide phosphate)
us.
From
anabolic
niacin
• Coenzyme A (CoA)—pantothenic derivitive (another B vitamin)
• Others are metals: Cu, Mg, Mn, Zn, Ca, Co
– Together these form holoenzyme
How does an enzyme work?
• Enzymes
controlled by
– Enzyme synthesis
• How much is
made
• Hormones can
influence (e.g.
TH)
– Enzyme activity
• Temperature
influences
– Denaturation
• pH influences
• Substrate
concentration
influences
– Saturation
point
How does an enzyme work?
• Inhibitors influence
– Competitive
• Fill active site: sulfanilamide vs para-aminobenzoic acid (PABA)
– Non-competitive
• Allosteric inhibition
Factors Influencing Enzyme Activity
• Enzymes can be denatured by
temperature and pH
Figure 5.6
Factors Influencing Enzyme Activity
• Temperature
• pH
• Substrate concentration
Figure 5.5a
Factors Influencing Enzyme Activity
• Competitive inhibition
Figure 5.7a–b
Factors influencing enzyme activity
• Feedback inhibition
Figure 5.8
Cell Energetics
Oxidation-Reduction
• Oxidation is the removal of electrons.
• Reduction is the gain of electrons.
• Redox reaction is an oxidation reaction
paired with a reduction reaction.
Figure 5.9
Oxidation-Reduction
• In biological systems, the electrons are
often associated with hydrogen atoms.
Biological oxidations are often
dehydrogenations.
Figure 5.10
What happens in carbohydrate catabolism?
• Glucose usually
is substrate
• Glycolysis
– 2 ATP
• Followed by
either
– Aerobic
respiration
• ___ ATP
– Anaerobic
fermentation
• No more ATP
What is ATP?
• Adenosine triphosphate
• Made by phosphorylating ______
• Equation:
What is glycolysis?
• First step to
making TP from
glucose
• Convert glucose to
_____________
• Some bacteria can
breakdown other
molecules
– Pentose phosphate
pathway
(pentoses)
• E. coli, Bacillus
subtilis
What happens next?
• If oxygen present 
• No oxygen 
Preparatory Stage
• Two ATPs are
used
• Glucose is split
to form two
Glucose-3phosphate
1
3
4
5
Figure 5.12, step 1
Energy-Conserving Stage
• Two Glucose-3phosphate oxidized
to two Pyruvic acid
• Four ATP produced
• Two NADH
produced
9
Figure 5.12, step 2
Intermediate Step
• Pyruvic acid (from
glycolysis) is
oxidized and
decarboyxlated.
Figure 5.13 (1 of 2)
What is the Krebs
Cycle?
• AKA citric acid
cycle
– Acetyl CoA (2
carbons) releases
energy
– Produces ATP,
CO2, NADH,
FADH2
• NADH and
FADH2 to
Electron transport
chain (ETC)
What are some intermediates in the
Krebs cycle?
• Some drugs are metabolized similar
to these:
• citric acid (6 carbons)
• iso-citric acid (6)
• alpha-ketoglutaric acid (5)
• succinyl CoA (4)
• succinic acid (4)
• fumaric acid (4)
• malic acid (4)
• oxaloacetic acid (4)
• Krebs cycle animation
What is the electron transport chain?
•
Carrier molecules facilitate oxidation and reduction
–
–
•
Transfer electrons from higher to lower energy compounds
–
•
•
•
Chemiosmosis w/ oxidative phosphorylation
Prokaryotes: PM
Eukaryotes: mitochondrial crista
Disruption of ETC leads to death!
–
•
•
Oxidation: loss of electron
Reduction: gain of electron
Cyanide
First ETC animation
Second ETC animation
What is the sum reaction for aerobic
respiration?
Glucose + 6 H2O + 38 ADP + 38 Pi 
6 CO2 + 6 H2O + 38 ATP
What happens in anaerobic respiration?
• Final electron
acceptor is not
oxygen
– Various amounts
of ATP produced
– Slower and less
ATP than aerobic
respiration
– Uses some parts
of Krebs cycle
– Thus slower
growth for
anaerobes than
aerobes
What is fermentation?
• Pyruvic acid from glycolysis
– Converted to end-products
– If bacteria only produce lactic acid = homolactic
– No additional ATP
What is alcohol fermentation?
• Also happens
after glycolysis
• Produces
ethanol and
CO2
• Heterolactic:
produces lactic
acid + other
acids, alcohols
What happens in lipid & protein
catabolism?
• Some bacteria don’t
like carbs!
• Lipases break down
______
– Krebs cycle
oxidizes products
– Useful for oil spill
clean up
• Extracellular
proteases &
peptidases break
down _______
– Deamination
converts amino
acids to usable
form for Krebs
cycle
• By production is
ammonia
Anaerobic Respiration
Electron acceptor
Products
NO3–
NO2–, N2 + H2O
SO4–
H2S + H2O
CO32 –
CH4 + H2O
Pathway
Eukaryote
Prokaryote
Glycolysis
Cytoplasm
Cytoplasm
Intermediate step
Cytoplasm
Cytoplasm
Krebs cycle
Mitochondrial matrix
Cytoplasm
ETC
Mitochondrial inner
membrane
Plasma
membrane
• Energy produced from complete oxidation of
one glucose using aerobic respiration.
ATP produced
NADH
produced
FADH2
produced
Glycolysis
2
2
0
Intermediate step
0
2
Krebs cycle
2
6
2
Total
4
10
2
Pathway
• ATP produced from complete oxidation of
one glucose using aerobic respiration.
Pathway
By substratelevel
phosphorylation
By oxidative
phosphorylation
From
From
NADH
FADH
Glycolysis
2
6
Intermediate step
0
6
Krebs cycle
2
18
4
Total
4
30
4
36 ATPs are produced in eukaryotes.
0