Microbial Metabolism

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Microbial Metabolism
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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

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What is the difference between

• Hydrolysis
• Condensation (dehydration synthesis)
• Exergonic vs. endergonic

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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

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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

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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. anabolic
• Coenzyme A (CoA)pantothenic derivitive (another
  B vitamin)
• Others are metals Cu, Mg, Mn, Zn, Ca, Co
• Together these form holoenzyme

From niacin
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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

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How does an enzyme work?

• Inhibitors influence
• Competitive
• Fill active site sulfanilamide vs
  para-aminobenzoic acid (PABA)
• Non-competitive
• Allosteric inhibition

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Factors Influencing Enzyme Activity

• Enzymes can be denatured by temperature and pH

Figure 5.6
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Factors Influencing Enzyme Activity

• Temperature
• pH
• Substrate concentration

Figure 5.5a
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Factors Influencing Enzyme Activity

• Competitive inhibition

Figure 5.7ab
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Factors influencing enzyme activity

• Feedback inhibition

Figure 5.8
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Cell Energetics
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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
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Oxidation-Reduction

• In biological systems, the electrons are often
  associated with hydrogen atoms. Biological
  oxidations are often dehydrogenations.

Figure 5.10
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What happens in carbohydrate catabolism?

• Glucose usually is substrate
• Glycolysis
• 2 ATP
• Followed by either
• Aerobic respiration
• ___ ATP
• Anaerobic fermentation
• No more ATP

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What is ATP?

• Adenosine triphosphate
• Made by phosphorylating ______
• Equation

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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

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What happens next?

• If oxygen present ?
• No oxygen ?

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Preparatory Stage

• Two ATPs are used
• Glucose is split to form two Glucose-3-phosphate

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3
4
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Figure 5.12, step 1
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Energy-Conserving Stage

• Two Glucose-3-phosphate oxidized to two Pyruvic
  acid
• Four ATP produced
• Two NADH produced

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Figure 5.12, step 2
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Intermediate Step

• Pyruvic acid (from glycolysis) is oxidized and
  decarboyxlated.

Figure 5.13 (1 of 2)
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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)

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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

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What is the electron transport chain?

• Carrier molecules facilitate oxidation and
  reduction
• Oxidation loss of electron
• Reduction gain of electron
• Transfer electrons from higher to lower energy
  compounds
• Chemiosmosis w/ oxidative phosphorylation
• Prokaryotes PM
• Eukaryotes mitochondrial crista
• Disruption of ETC leads to death!
• Cyanide
• First ETC animation
• Second ETC animation

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What is the sum reaction for aerobic respiration?

• Glucose 6 H2O 38 ADP 38 Pi ?
• 6 CO2 6 H2O 38 ATP

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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

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What is fermentation?

• Pyruvic acid from glycolysis
• Converted to end-products
• If bacteria only produce lactic acid homolactic
• No additional ATP

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What is alcohol fermentation?

• Also happens after glycolysis
• Produces ethanol and CO2
• Heterolactic produces lactic acid other acids,
  alcohols

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What happens in lipid protein catabolism?

• Some bacteria dont 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

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Anaerobic Respiration
Electron acceptor Products
NO3 NO2, N2 H2O
SO4 H2S H2O
CO32 CH4 H2O
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Pathway Eukaryote Prokaryote
Glycolysis Cytoplasm Cytoplasm
Intermediate step Cytoplasm Cytoplasm
Krebs cycle Mitochondrial matrix Cytoplasm
ETC Mitochondrial inner membrane Plasma membrane
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• Energy produced from complete oxidation of one
  glucose using aerobic respiration.

Pathway ATP produced NADH produced FADH2 produced
Glycolysis 2 2 0
Intermediate step 0 2
Krebs cycle 2 6 2
Total 4 10 2
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• ATP produced from complete oxidation of one
  glucose using aerobic respiration.

Pathway By substrate-level phosphorylation By oxidative phosphorylation By oxidative phosphorylation
Pathway By substrate-level phosphorylation From NADH From FADH
Glycolysis 2 6 0
Intermediate step 0 6
Krebs cycle 2 18 4
Total 4 30 4
36 ATPs are produced in eukaryotes.