Metabolism IV: VI. Anaerobic respiration VII. Chemolithotrophy VIII. Anabolism
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Transcript of Metabolism IV: VI. Anaerobic respiration VII. Chemolithotrophy VIII. Anabolism
1Metabolism IV:
VI. Anaerobic respirationVII. ChemolithotrophyVIII. Anabolism
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Reoxidation of reduced electron carriers by a process analogous to aerobic respiration, but using a terminal electron acceptor other than O2.
VI. Anaerobic respiration
PMF is formed and ATP is synthesized by electron transport phosphorylation.
Used by microbes capable of anaerobic respiration when O2 is not available.
TB
3A. Anaerobic respiration
external terminal electron acceptoris not O2
eg. NO3- (nitrate), Fe3
+, SO4-,
CO2, CO32-, fumarate or
another organic molecule
O2
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Growth substrates
Oxidized products
Oxidized electron carriers
Reduced electron carriers
fumarateNO3
-
SO42-
CO2
succinateNO2
-, N2
H2SCH4 PMF
various electrontransport chains
51. Nitrate reduction
NO3- NO2
-
• a form of anaerobic respiration in which NO3
- is the terminal electron acceptor
nitrate reductase
• used by Escherichia coli and some other microorganisms when O2 is absent
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NO3-
denitrification
2. Denitrification reduction of nitrate all the way to N2 through anaerobic respiration
Important in agriculture and sewage treatment
N2gas
73. Respiration with sulfur or sulfate
SO42- H2S
• elemental sulfur or SO42- is the
terminal electron acceptor
S0 H2Sreduction
smelly gases
8B. Less free energy is released in anaerobic respiration than in aerobic respirationOxidized form / Reduced form Reduction potential
Eo' (Volts)
CO2 / glucose (C6H12O2) (- 0.43)2 H+ / H2 (- 0.42)NAD+ / NADH (- 0.32)SO4
2- / H2S (- 0.22)pyruvate / lactate (- 0.19)
O2 / H2O (+ 0.82)
fumarate / succinate (+ 0.03)NO3- / NO2- (+ 0.42)
9VII. ChemolithotrophyUse of inorganic compounds as the energy source (primary electron donor)
Many chemolithotrophs use O2 as the terminal electron acceptor
H2 + 1/2 O2 H2O
10A. Examples of chemolithotrophs
H2 hydrogen-oxidizing bacteriaH2S sulfide-oxidizing bacteria
Fe2+iron-oxidizing bacteriaNH3 ammonia-oxidizing bacteria
(NH3 NO2
- )
NO2- nitrite-oxidizing bacteria
(NO2- NO3
- )
111. Example of chemolithotrophy: aerobic sulfide (H2S) oxidation
H2S + 2 O2
inorganic electron donor
Boiling sulfur pot, Yellowstone National Park
SO42- + 2H+
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Ammonia oxidizer NH3 NO2
-
Nitrite oxidizerNO2
- NO3-
2. Examples of chemolithotrophy: ammonia oxidation and nitrite oxidation
13B. Possible metabolic strategies for generating energy on early earth
anaerobic chemolithotrophyfermentationanaerobic respirationanoxygenic photosynthesis
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H2
ADP + Pi
ATP
Cytoplasmic membrane
In
Out
A hypothetical primitive energy- generating system on early earth
primitive ATPase
primitivehydrogenase
Proton motive force (PMF)
2 H+
2 e-
inorganic electron acceptor (not O2)
15VIII. Anabolism (Biosynthesis)
Nutrients
Nutrients
Macromolecules and other cell components
Anabolism Energy
Energy source(eg. sugar or H2)
Waste
Catabolism
Energy
16Cells are made of molecules.
Nucleic acids
ProteinsPolysaccharides
Lipids
small molecules
17A. Building cell components requires
energy (ATP) reductant (NADPH)
C H O N P S
a source of carbona source of nitrogensome P and other nutrients
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carbon source
(organic carbon)heterotroph autotroph
(CO2)
energy source
chemoorganotroph (organic chemical) chemolithotroph
(inorganic chemical
e.g. H2S, H2, NH3)
phototroph (light)
B. Classification of organisms according to
19C. Cell carbon
sugarsacetyl CoA organic acids
CO2
autotrophs
NH3
aminoacids protein
fattyacidslipid
nucleotidesnucleicacids
P, NH3
Cell carbon:
organic carbon source (e.g. glucose)
glycolysis, TCA heterotrophs
20D. Sugar / polysaccharide metabolismSugars are needed for
polysaccharides (cell wall, glycogen)nucleic acids (DNA, RNA)
O O
hexoses pentoses
small molecules (ATP, NAD(P)+
cAMP, coenzymes, etc.)
211. UDP-glucose is a precursor to polysaccharides and peptidoglycan.
O — P-O- O -
O O= P-O O -
HOCH2O
CH2
OH OH
O N
ONH
O
(don't memorize structure)
UDP = uridine
diphosphate
222. Gluconeogenesis
A pathway for making glucose-6-P from noncarbohydrate sources (e.g. acids from TCA).
233. Gluconeogenesis is the reversal of glycolysis starting with PEP, but with a few different enzymes.
glucose-6-P
PEP CO2
pyruvate
TCA
OAA
succinate
gluconeogenesis
244. Pentose phosphate pathway
a. makes pentoses (ribulose-5-P) from the decarboxylation of glucose-6-P
b. also makes NADPH for biosynthetic reactions
255. Deoxyribonucleotides for DNA are made from the reduction of the 2'- hydroxyl of ribonucleotides.
OCH2
HOH
O N
NH2
N
N
N
OP PPOCH2
OHOH
O N
NH2
N
N
N
OP PP
NADPH NADP+
ATPdeoxy-ATP
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ribose-5-P
ribonucleotides RNA
deoxyribo-nucleotides DNA
glucose
glucose-6-P
glucose-1-P
UDP-glucose(uridine diphosphoglucose)
ribulose-5-P
Sugar summary Gluconeogenesis TCA
PEP OAAglycolysis
UTP
polysaccharides peptidoglycan, cell walls
pentose phosphate pathway
NADPHNADP+
pyruvate
27E. Amino acid biosynthesis
1. Requires an acid (carbon skeleton) and an amino group
O C – OH
H2N – C – H R
carboxylic acidaminogroup
282. Some carbon skeletons are made in glycolysis and the TCA cycle
5 main amino acid precursorsa. -ketoglutarate (5C)b. oxaloacetate (4C)c. pyruvate (3C)d. phosphoglycerate (3C)e. PEP (3C), (erythrose-4-P)
29Carbon skeletons for amino acids
PEP CO2pyruvate
TCA
OAA
(glucose)
(acCoA)
-KG
phosphoglycerate
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O C - O-
O = C CH2
CH2
COO-
-ketoglutarate
O C - O-
H3N - C - H CH2
CH2
COO-
glutamate
+NH3
NADPH NADP+
3. The amino group for glutamate can come directly from ammonia.
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O C - O-
O = C CH2
COO-
-ketoglutarateglutamate
4. The amino group for most other amino acids comes from glutamate through transamination (amino transfer).
oxaloacetate (OAA) aspartate
O C - O-
H3N - C - H CH2
COO-
+
32F. Purine and pyrimidine biosynthesis is very complex.
1. The carbons and nitrogens come from amino acids, NH3, CO2, and formyl (HCOO-) groups.
N
N
N
N
CC
from formyl attached to folic acid
**
332. Folic acid carries the formyl groups in purine biosynthesis.
3. Sulfanilamide is a "growth factor analog" that inhibits purine biosynthesis by inhibiting the production of folic acid.
34D. Fatty acids1. In general, saturated fatty acids are built two carbons at a time from acetyl CoA.
CH 3
C~SCoAO(8)
ATP, NADPHCOO-
palmitic acid
352. Unsaturated fatty acids • have 1 or more cis-double bonds • increase fluidity of membranes
COO-
363. Acetyl CoA and succinyl CoA and play important roles in anabolism.
acetyl CoA fatty acid biosynthesissuccinyl CoA heme biosynthesis
37Study objectives1. Understand anaerobic respiration and the examples presented in class. Define nitrate reduction, denitrification, sulfate reduction.2. Understand chemolithotrophy and the examples presented in class.3. Examples of integrative questions: Compare and contrast aerobic respiration, anaerobic respiration, chemolithotrophy, and fermentation. Given the description of a catabolic strategy, be prepared to identify the type of metabolism being used. Contrast sulfate reduction and sulfide oxidation. 4. Be able to classify microorganisms based on energy source and carbon source.5. Understand the roles of glycolysis and the TCA cycle in the synthesis of cellular macromolecules.6. What type of polymers are synthesized from UDP-glucose?7. What are the functions of gluconeogenesis and the pentose phosphate pathway?8. How are deoxyribonucleotides for DNA made from ribonucleotides?
3810. Know the sources of carbon and nitrogen for amino acid biosynthesis. How are amino groups transferred to acids to make amino acids?11. Understand the role of folic acid in nucleotide biosynthesis.12. How does sulfanilamide inhibit the growth of microorganisms? 13. Humans do not make their own folates. Why is the drug sulfanilamide toxic to certain microorganisms but not to humans? 14. Know the anabolic roles of acetyl CoA and succinyl CoA as described in class.