Bacterial Metabolism Metabolism – Sum up all the chemical processes that occur within a cell 1....
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Transcript of Bacterial Metabolism Metabolism – Sum up all the chemical processes that occur within a cell 1....
Bacterial MetabolismMetabolism
– Sum up all the chemical processes that occur within a cell1. Anabolism: Synthesis of more complex
compounds and use of energy
2. Catabolism: Break down a substrate and capture energy
Overview of cell metabolism
Bacterial Metabolism– Autotroph:
Photosynthetic bacterial
Chemoautotrophic bacteria
– Heterotroph:
Parasite
Saprophyte
– After Sugars are made or obtained, they are the energy source of life.
– Breakdown of sugar(catabolism) different ways:
• Aerobic respiration• Anaerobic respiration • Fermentation
Energy Generating Patterns
Photosynthesis(1) Higher plants
– Light reaction: Photolysis of H2O produce ATP and NADPH
– Two photosystem (I & II)Dark fixation: use the production from light reaction (ATP and NADPH) to fix CO2
Reaction:6CO2 + 6H2O -----> C6H12O6 +6O2
(Light and chloroplast)
Bacteria Photosynthesis
i. Only one photosystem can not do photolysis of H2O
ii. H2O not the source of electron donor
iii. O2 never formed as a productiv. Bacterial chlorophyll absorb light at longer W.L.
v. Similar CO2 fixationvi. Only has cyclic photophosphorylation
How the Bacteria synthesize NADPH Grow in the presence of the H2 gas
H2 + NADP+ ------------- NADPH2
hydrogenase Reverse the electron flow in the e- transport
chainH2S S
S + NADP+-------- SO4-2 + NADPH2
Succinate Fumarate Simple non-cyclic photosynthetic e- flow
Chlorophyll a and bacteriochlophyll a(1)
Chlorophyll a and bacteriochlophyll a(2)
Anoxygenic photosynthesis
Anoxygenic versus oxygenic phototrophs(2)
Anoxygenic versus oxygenic phototrophs(1)
Photosynthetic bacteria(1) Chlorobium-green sulfur bacteria
Use green pigment chlorophyll
Use H2S (hydrogen sulfide), S (sulfur), Na2S2O3 (sodium thiosulfate) and H2 as e- donors.
(2) Chromatium-purple sulfur bacteria Use purple carotenoid pigment, same e-donors
(3) Rhodospirillum-non sulfur purple bacteria Use H2 and other organic compounds such as isopropanol etc,
as e-donors.
Reaction: CO2 + 2H2A -----> CH20 + H20 +2A A is not O
Chemautotroph– Some bacteria use O2 in the air to oxidize
inorganic compounds and produce ATP (energy). The energy is enough to convert CO2 into organic material needed for cell growth.
– Examples:Thiobacillus (sulfur S)
Nitorsomonas (ammonia)
Nitrobacter (nitrite)
– Various genera (hydrogen etc.)
Aerobic respiration– Most efficient way to extract energy from
glucose.– Process: Glycolysis
Kreb Cycle
Electron transport chain– Glycolysis: Several glycolytic pathways– The most common one:
glucose-----> pyruvic acid + 2 NADH + 2ATP
Aerobic respiration– Euk. glucose -----> G-6-P----->F-6-P-----> …... 2 pyruvate +2ATP + 2NADH– Prok. glucose-----> G-6-P------>F-6-P– Process take places during transport of the
substrate. Phosphate is from phosphoenolpyruvate (PEP)
.....-----> 2 pyruvate +2ATP + 2NADH
– Kreb cycle:Pyruvate + 4NAD + FAD ----->
3CO2 +4NADH + FADHGDP + Pi -----> GTPGTP + ADP -----> ATP + GDP
– Electron trasnport Chain4HADH -----> 12 ATPFADH ------> 2 ATP Total 15 ATP Glycolysis -----> 8 ATP
– Total equation:C6H12O6 + 6O2 ------> 6CO2 + 6H2O + 38 ATP
Generation of a proton-motive force(1)
Generation of a proton-motive force(2)
Mechanism of ATPase
Anaerobic respiration– Final electron acceptor : never be O2 Sulfate reducer: final electron acceptor is sodium
sulfate (Na2 SO4) Methane reducer: final electron acceptor is CO2 Nitrate reducer : final electroon acceptor is
sodium nitrate (NaNO3)
O2/H2O coupling is the most oxidizing, more energy
in aerobic respiration.
Therefore, anaerobic is less energy efficient.
Fermentation Glycosis:Glucose ----->2 Pyruvate + 2ATP + 2NADH
Fermentation pathwaysa. Homolactic acid F.
P.A -----> Lactic Acideg. Streptococci, Lactobacilli
b.Alcoholic F.P.A -----> Ethyl alcoholeg. yeast
c. Mixed acid fermentationP.A -----> lactic acid
acetic acid H2 + CO2 succinic acid ethyl alcohol
eg. E.coli and some enterbacterd. Butylene-glycol F.
P.A -----> 2,3, butylene glycoleg. Pseudomonas
e. Propionic acid F.P.A -----> 2 propionic acideg. Propionibacterium
Alternative energy generating patterns(1)
Alternative energy generating patterns(2)
Alternative energy generating patterns(3)
Alternative energy generating patterns(4)
Energy/carbon classes of organisms
Chlorophyll a and bacteriochlophyll a(3)
Comparison of reaction centers of anoxyphototrophs