Lexture ??? Bacterial Energy metabolism FINISH Flashcards
(30 cards)
What does Hypoxic mean
Low oxygen conditions
What happens if oxygen remains absent
Lactate builds up in the blood within minutes
Acts as a buffer and can cause swelling
But does NOT cause pain/ache
That is due to acidosis from ATP hydrolysis
What are some anaerobic/ anoxic environments
water, soil, food, plant and animal tissues, and GI tract
What are some types of anaerobic metabolsim
Anaerobic phototrophy
Anaerobic respiration
Fermentation
What is Anaerobic phototrophy
Harvesting light without using oxygen
How is fermentation different to anaerobic respiration
When no terminal e- acceptor or iron for ETC
Limited to chemoorganotrophs
Fermentation of inorganic compounds not possible
Some bacteria are facultative fermenters whilst some are obligate fermenters
Describe the redox balance in fermentation
Oxidation of a substrate
Substrate is only partially oxidised
Reduction of e- carriers (NAD+, NADP+ or FAD) → NADH, NADPH or FADH2
NADH, NADPH or FADH2 is then oxidised (recycled)
Coupled to reduction of a derivative of the starting substrate (commonly) or an independent substrate
Typically, the e- acceptor is organic and ‘internally’ supplied
Endogenous
Reduced product is then excreted as a fermentation product
What type of heat reaction is fermentation
Exergonic
When is ATP produced in fermentation and how
Substrate level phosphorylation
Typically, during the 1st oxidation step(s)
Direct transfer of P group from an organic molecule to ADP
Significantly less ATP produced than in phototrophy or ETC respiration
Some instances of ATP production by alternative methods (see later)
SLide 8
What are some examples of electron carriers
NAD
NADP
FAD
FMN
Water-soluble coenzymes
Carry e- from oxidation reactions and donate them to wide variety of reduction reactions
What are the key features of NAD and NADP
Free moving from one enzyme to another
What are key features of FAD and FMN
Tightly bound to enzymes (flavoproteins)
Covalently or noncovalently
FAD rarely used in fermentation
FMN not used in fermentation
Describe the process of NAD cycling
Enzyme I reacts with e- donor and oxidised form of coenzyme, NAD+
NADH and reaction product are formed
Enzyme II reacts with e- acceptor and reduced form of coenzyme NADH
NAD+ is released
(SLIDE 11)
Which produces more energy, Fermentation or Respiration
Respiration
Obtain 2 ATP from fermenting glucose to lactate
But 30 - 32 ATP from respiration of glucose (depends on H+ leakage of the membrane and external conditions)
Simple vs complex pathways
Slide 13
What is the Strickland pathway
Unique to the genus Clostridium
Fermentation of amino acids
Paired amino acid redox reaction
One amino acid acts as e- donor
Only Histidine can not be used as a substrate
Different amino acids act as e- acceptors
Commonly glycine and proline
The exact pathway and energy yields depends on the amino acid mix in the environment
Anaerobic colon environment
Induces colonic collagen remodelling to release amino acids
Via toxin-induced inflammation but also possibly other unknown mechanisms
Disrupts competing bacteria fauna
Uses Strickland pathway to ferment amino acids
i.e., carves out a niche to provide nutrients
SLIDE 17 for diagram
What types of substrates can be fermented
Sugars
Polyalcohols
AA
Organic acids
nucleic acids
Xenobiotic compounds
Acetylene, citrate, glyoxylate, succinate, oxalate and malonate
What type of fermentation produces one product
homofermentative
What type of fermentation produces more than one product
Heterofermentative
What happens during the rare occurance of fermentation without substrate level phosphorylation
No external e- acceptor is used
Ion pumps produce a potential difference
Slide 23
What is an example process that uses a proton motive force
Flagella rotation
Some strict fermentative bacteria use ATP to run the ATPase in reverse
What is a primary fermenter
A Uses high level substrates
What is a secondary fermenter
Uses fermentation products of higher organisms
What happens if concentration of reaction products are kept low
Reaction becomes exergonic,
ΔG of a reaction varies depending on concentrations, temperatureand pressure
Bacteria are intimately associated with their environment
i.e., ΔG depends on the environment
