Bacterial Metabolism Flashcards
What is bacterial fermentation?
Fermentation is an anaerobic metabolic process where bacteria break down organic molecules (like glucose) to produce ATP without using an external electron acceptor (like oxygen)
Through what biochemical pathways is ATP produced during fermentation?
Substrate-level phosphorylation during glycolysis/embden-meyerhof pathway
What is the Embden-Meyerhof pathway?
The EMP pathway (also known as glycolysis) is a metabolic pathway in bacteria that breaks down glucose to generate ATP and NADH, as well as providing precursors for biosynthesis
What is the oxygen requirement for the EMP pathway?
It is anaerobic (no oxygen required), however pyruvate produced from EMP can feed into aerobic pathways
What is the start and end products of EMP pathway?
Start products:
Glucose (+ 2 ATP for breakdown)
End products:
4 ATP (2 net gain)
2 NADP
Biochemical precursors like pyruvate
What are the main types of fermentation and their products?
Lactic Acid Fermentation: Produces lactic acid (e.g., Lactobacillus) - used in dairy industry e.g. yogurts
Alcoholic Fermentation: Produces ethanol and CO₂ (e.g., Saccharomyces cerevisiae) - used in brewing, baking etc
Mixed Acid Fermentation: Produces a mixture of acids, ethanol, CO₂, and H₂ (e.g., Escherichia coli).
What is a scientific name for a yeast commonly used in industry?
Saccharomyces cerevisiae - it’s fermentation is used in the production bioethanol, which is an important source of fuel (as well as being used in alcohol and baking etc)
What are some sources of biofuels?
- Crops
- Plant waste
What are the two types of bacteria respiration?
Aerobic and anaerobic respiration
What are the similarities of anaerobic respiration to fermentation?
Like fermentation, anaerobic respiration also begins with glycolysis, producing pyruvate, ATP, and NADH
What are the differences of anaerobic respiration to fermentation?
In anaerobic respiration an electron transport chain is used
What are the final electron acceptors in anaerobic respiration?
It can be:
- Nitrate (NO3)
- Sulfate (SO4)
- Carbonate (CO3)
How does the electron transport chain work in anaerobic respiration?
- Electrons from NADH and FADH2 are passed through a series of carriers
- This generates a proton motive force
- Protons are translocated across membrane
- Electrochemical gradient across the membrane
- The protons flow back in via the membrane enzyme complex ATP synthase, generating ATP (oxidative phosphorylation)
How much ATP does anaerobic respiration generate?
It varies dependent on the final electron acceptor, however it is generally more than fermentation but less than aerobic respiration
What is the role of the Krebs cycle in respiration?
Pyruvate is converted to acetyl-CoA after glycolysis.
Acetyle-CoA enters the Krebs cycle.
This generates high-energy electron carriers (for the ETC) like NADH, FADH2
Does both anaerobic and aerobic respiration use Krebs cycle?
Yes
What are the main products of anaerobic respiration?
The products depend on the electron acceptor:
Nitrate reduction: N₂ or NH₃
Sulfate reduction: H₂S
Carbon dioxide reduction: CH₄
What are the main products of aerobic respiration?
CO₂, H₂O, and approximately 38 ATP molecules per glucose.
What is the difference in reduction potentials in fermentation vs. aerobic respiration?
Fermentation: Small difference in reduction potentials between electron donors and acceptors = less ATP
Aerobic Respiration: Large difference in reduction potentials between electron donors and oxygen, the final electron acceptor = more ATP
How much ATP is produced by aerobic respiration?
Around 38 ATP
Give examples of microbes that perform fermentation:
Lactobacillus, Saccharomyces cerevisiae, Escherichia coli
Microbe that uses anaerobic respiration
Pseudomonas spp.
Microbe that uses aerobic respiration
Mycobacterium TB
What is a bacteria that can switch between all 3?
Escherichia coli
What is a facultative anaerobe?
Bacteria that can switch between aerobic and anaerobic
How is the TCA cycle/Krebs/citric acid cycle central to metabolism?
Key pathway for the oxidation of carbohydrates, fats, and proteins, providing energy and precursors for various biosynthetic pathways
What are some key intermediates/precursors produced by the Krebs cycle?
- Oxaloacetate
- Citrate
Give an example of a microbe engineered for industrial production using the TCA cycle
Corynebacterium glutamicum has been engineered to improve L-lysine production by manipulating the activity of isocitrate dehydrogenase
