Lecture 14: Nitrogen metabolism, Phototrophy Flashcards
Piece together reactions in the nitrogen cycle
- Nitrogen Fixation: N2 (g) to NH3
- This requires the nitrogenase enzyme
- Only performed by bacteria, needs to be in anaerobic environment
- NH3 -> Organic N (nucleic and amino acids)
- reductive (released into environment) - Dissimulation and Mineralization: NH3 to NH4
- Step 1: Nitrification:NH4+ to NO2-
- Nitrosomonas - Step 2: Nitrification: NO2 to NO3
- Nitrobacter
5.Fate of NO3- : Assimilation or denitrification
Assimilation: NO3 to Organic N
Denitrification: NO3 to N2
-When gases N2 and N2O are produced and released into the atmosphere.
Anammox:
NH4 to N2
Only performed by chemolithotrophs
Explain how nitrogen metabolism is connected to chemolithotrophy
-All the little organisms that work together in the electron transfer chain make up nitrogen metabolism
Nitrogen cycling is an important function of chemolithotrophs and anaerobic respiration
Describe the electron transport chains in phototrophy and predict reducing power
- Cyclic vs non-cyclic
- Start/end products
Anoxygenic ETC
- Reducing power: H2S
- Exclusively Cyclic
- Start products: Energy from light
- End products: Make ATP and high reducing power (usually for CO2 fixation, or lithotrophy)
Oxygenic Photosynthesis:
- Reducing power: H2O
- Involves cyclic and non-cyclic electron flow
- Start products: Energy from light
- End products: Make ATP and NADPH that are used to in the dark reactions to fix CO2
Compare and contrast oxygenic and anoxygenic photosynthesis
Examples:
What are the end products of these reactions?
Cyclic vs noncyclic electron flow?
Types of light absorbing molecules?
Electron donors?
Overall reduction potential? (more, less, equal?)
Oxygenic Photosynthesis:
What are the end products of these reactions?
-End products: Make ATP and NADPH that are used to in the dark reactions to fix CO2
Cyclic vs noncyclic electron flow?
-Involves cyclic and non-cyclic electron flow
Types of light absorbing molecules?
- Oxygenic phototrophs use chlorophylls
- Usually have 2 photosystems
- Chlorophylls absorb lower wavelengths compared to bacteriochlorophylls
Electron donors?
organic molecules
-H2O
Overall reduction potential? (more, less, equal?)
- Reducing power: H2O
- Excited chlorophyll pairs have a very negative reduction potential
Anoxygenic Phtosynthesis:
What are the end products of these reactions?
-Make ATP and high reducing power (usually for CO2 fixation, or lithotrophy)
Cyclic vs noncyclic electron flow?
-Exclusively Cyclic
Types of light absorbing molecules?
- Anoxygenic phototrophs use bacteriochlorophylls
- Bacteriochlorophylls absorb higher wavelengths compared to chlorophylls
- Have 1 photosystem
Electron donors?
-inorganic molecules that don’t aren’t O2
Overall reduction potential? (more, less, equal?)
-H2S
What are light reactions and what are dark reactions?
The light reactions:
-Chemical energy and reducing power
The Dark reactions:
-Using stored energy for CO2 fixation and biosynthesis
What is cyclic phosphorylation?
Cyclic phosphorylation involves the activity of PSI alone and generates ATP only through the cyclic cycle.
-Electron flow generates proton motor force which is used by ATP synthase to make ATP
What is non-cyclic phosphorylation?
Non-cyclic phosphorylation use both PSI and PSII together they move electrons from water to NADP+ producing ATP, NADPH and O2.
-Electron flow generates proton motor force which is used by ATP synthase to make ATP
How is NADH generated in anoxygenic photosynthesis?
Quinone is insufficiently electronegative to reduce NAD+ directly. Instead, electrons from the quinone pool travel
backwards against the thermodynamic gradient to eventually reduce NAD+ to NADH.
No need for reverse electron flow
How is oxygen generated in oxygenic photosynthesis?
The first step in oxygenetic electron flow is the splitting of water into oxygen and electrons.
