envi micro final Flashcards
(25 cards)
Define photosynthesis.
The process by which light energy is converted into chemical energy by phototrophs.
Define phototrophy.
A mode of metabolism in which light is used as the energy source.
Define photoautotrophy.
A form of phototrophy where organisms use light for energy and CO₂ as the carbon source.
Define photoheterotrophy.
A form of phototrophy where organisms use light for energy and organic compounds for carbon.
Compare oxygenic and anoxygenic photosynthesis.
Oxygenic uses water as an electron donor and produces O₂; anoxygenic uses other donors like H₂S and does not produce O₂.
What pigments are found in cyanobacteria, green, and purple bacteria?
Cyanobacteria: chlorophyll a and phycobilins; Green: bacteriochlorophylls and carotenoids; Purple: bacteriochlorophylls and carotenoids.
How is light harvested differently among cyanobacteria, green, and purple bacteria?
Cyanobacteria use thylakoids; green bacteria use chlorosomes; purple bacteria use chromatophores or lamellae.
Explain the importance of pigment diversity in phototrophic bacteria.
It allows absorption of different light wavelengths, enabling coexistence and ecological specialization.
What is the carbon cycle?
The biogeochemical cycle involving the conversion between organic and inorganic forms of carbon, mainly CO₂ and CH₄.
Which parts of the carbon cycle are anoxic?
Methanogenesis, fermentation, anaerobic respiration, and anammox occur under anoxic conditions.
Describe nitrogen fixation.
Conversion of N₂ gas to NH₃ by prokaryotes using the enzyme nitrogenase under anaerobic or microaerophilic conditions.
Which organisms are most efficient at nitrogen fixation?
Symbiotic bacteria like Rhizobium in legumes; also cyanobacteria and some free-living soil microbes.
What is ammonification?
The release of NH₄⁺ from organic nitrogen compounds by decomposition.
What is nitrification?
The two-step aerobic oxidation of NH₃ to NO₂⁻ by AOB/AOA and NO₂⁻ to NO₃⁻ by NOB.
What is denitrification?
Anaerobic reduction of NO₃⁻ to N₂ gas, removing bioavailable nitrogen from ecosystems.
What is the anammox process?
Anaerobic ammonium oxidation using NO₂⁻ as an electron acceptor to produce N₂ gas.
Explain assimilatory sulfate reduction.
Reduction of SO₄²⁻ to sulfide for incorporation into organic molecules.
Explain dissimilatory sulfate reduction.
Anaerobic respiration where SO₄²⁻ serves as terminal electron acceptor, producing H₂S.
What are the steps of biodegradation?
- Biofragmentation, 2. Bioassimilation, 3. Mineralization.
What is mineralization in biodegradation?
Complete oxidation of organic contaminants to CO₂ and H₂O.
What is partial biodegradation and why is it undesirable?
Incomplete degradation leading to accumulation of potentially harmful intermediates.
What is reductive dehalogenation?
Anaerobic process where halogen atoms are removed, e.g., by Dehalococcoides.
What are dispersants and how do they work?
Surfactants that break oil into droplets, increasing surface area for microbial degradation.
What is marine snow?
Organic matter aggregates sinking through the ocean, serving as a nutrient source for microbes.
