Microbial Metabolism (Catabolism) Flashcards
1
Q
What is substrate-level phosphorylation?
A
- used in fermentation and other pathways
- ATP is synthesized during steps in the catabolism of an organic compound (glycolysis)
- transferring a phosphate from an energy rich compound to ADP to make ATP
2
Q
What is oxidative phosphorylation?
A
- used in respiration
- ATP is produced by proton motive force
3
Q
What is fermentation?
A
- takes place in the absence of an exogenous electron acceptor (don’t need oxygen)
- uses pyruvate or a pyruvate derivative as the electron acceptor
- continues recycling of electron carriers (NADH from glycolysis oxidized to NAD+)
- forms ATP via substrate level phosphorylation
- produces various fermentation products (waste products)
- does not use an ETC or proton motive force
4
Q
What are the different kinds of fermentation products?
A
- ethanol: used to make breads, wine, and beer
- lactic acid (homolactic): lactic acid is the only fermentation product; used to make certain cheeses, sour cream, and yogurt
- lactic acid (heterolactic): makes lactic acid and other products; used to make sauerkraut, pickles, buttermilk; involved in food spoilage
- mixed acid: tested for by MR test
- 2,3-butanediol: tested for by the VP test, detects the intermediate acetoin
- propionic acid: used to make swiss cheese
5
Q
What is aerobic respiration?
A
- respiration in which the final electron acceptor is oxygen
- ATP is made primarily by oxidative phosphorylation where electron transport is used to generate proton motive force
- ATPase involved
6
Q
What is anaerobic respiration?
A
- respiration in which the final electron acceptor is a different exogeneous acceptor such as NO3-, SO4-, CO2, Fe3+, or SeO42-
- organic acceptors such as fumarate may also be used
- still uses oxidative phosphorylation and an electron transport chain
- yields less energy than aerobic respiration
- E0’ of final electron acceptor is less positive than the E0’ of oxygen
7
Q
What is the purpose of the MRVP test?
A
- the MR test detects the production of mixed acids as a product of fermentation
- the MR test uses methyl red as an indicator which turns red if the pH is below 5 (positive test)
- the VP test detects the production of butanediol as a product of fermentation by testing for the precursor acetoin
- the VP test uses Barritt’s A and Barrit’s B which will turn the solution red if acetoin is present, pH does not go below 5
- should only test positive for one or the other
8
Q
Where is the electron transport chain located in eukaryotes?
A
the inner mitochondrial membrane
9
Q
Where is the electron transport chain located in bacteria and archaeons?
A
the cytoplasmic membrane
10
Q
What is the electron transport chain?
A
- a series of electron carriers that operate together
- transfers electrons from NADH and FADH2 to a terminal electron acceptor
- electrons flow from carriers with a more negative E’0 to carriers with a more positive E’0
- as electrons are transferred, energy is released to make ATP via oxidative phosphorylation
11
Q
What is the P/0 ratio for NADH?
A
3 ATP per NADH
12
Q
What is the P/0 ratio for FADH2?
A
2 ATP per FADH2
13
Q
How does ATP synthase work?
A
- protons are moved from the mitochondrial matrix to the intermembrane space by the complexes of the electron transport chain
- the movement of protons establishes proton motive force
- ATP synthase uses the proton flow down the concentration gradient to make ATP
14
Q
What is the structure of ATPase?
A
- C12: spinning C cylinders
- a: channel for H+ ions to enter
- b2: holds headpiece stationary
- beta: brings ADP and Pi together and releases ATP
- F1: headpiece
- Fo: motor
15
Q
What are the functions of proton motive force?
A
- can be used to generate ATP
- can be used to rotate the flagella (explains why fermentative bacteria have ATPase because it can work backwards to generate PMF)
- PMF can sometimes be used instead of ATP to fuel active transport
