Biochemistry Flashcards
What are the main components of a prokaryotic cell?
A prokaryotic cell lacks a distinct nucleus and organelles. It typically has a cytoplasmic membrane, a cell wall, ribosomes, and may have flagella for movement
How does a eukaryotic cell differ from a prokaryotic cell?
A: A eukaryotic cell contains visibly evident nuclei and organelles such as mitochondria, lysosomes, and endoplasmic reticulum. It is found in plants, animals, fungi, and protozoa
Describe the phases of microbial growth in a batch culture.
- Lag Phase: Cells adapt to the environment.
- Exponential (Log) Phase: Rapid cell division occurs.
- Decelerating Growth Phase: Nutrient depletion or waste accumulation slows growth.
- Stationary Phase: Growth rate equals the death rate.
- Death Phase: Death rate exceeds growth rate.
What is aerobic decomposition, and what electron acceptor is used?
Aerobic decomposition is the process where microorganisms use dissolved oxygen (O₂) as the terminal electron acceptor to convert organic matter into carbon dioxide (CO₂), water (H₂O), and new cell mass, yielding high energy
What is denitrification in the context of wastewater treatment?
Denitrification is an anoxic process where microorganisms use nitrate ions (NO₃⁻) as electron acceptors, converting them into nitrogen gas (N₂) when dissolved oxygen is no longer available.
Define anaerobic decomposition and its typical electron acceptors.
Anaerobic decomposition occurs in the absence of both oxygen and nitrate. Microorganisms switch to using compounds like sulfate ions (SO₄²⁻), which are reduced to hydrogen sulfide (H₂S) and other compounds with lower energy yields
Explain the hierarchical sequence of electron acceptor usage in microbial oxidation processes.
Microorganisms typically use electron acceptors in the following order, based on availability and energy yield:
Oxygen (O₂) - Highest energy yield, used in aerobic conditions.
Nitrate (NO₃⁻) - Used in anoxic conditions when oxygen is depleted (denitrification).
Sulfate (SO₄²⁻) - Used in anaerobic conditions when both oxygen and nitrate are unavailable
What defines heterotrophic bacteria in wastewater treatment?
Heterotrophic bacteria use organic material as their energy and carbon source. They are the predominant type in wastewater treatment processes
How do heterotrophic bacteria reduce nitrate under anoxic conditions?
In the absence of oxygen, heterotrophic bacteria (specifically denitrifiers) use nitrate as an electron acceptor, reducing it to nitrogen gas (N₂) through a process called denitrification
What environmental conditions are required for denitrification by heterotrophic bacteria?
Denitrification requires anoxic conditions, where oxygen is absent, and nitrate is available as an alternative electron acceptor for bacteria
What type of bacteria can function in both aerobic and anaerobic conditions?
Facultative bacteria can operate in both environments. They use dissolved oxygen when available and switch to other electron acceptors like nitrate when oxygen is absent
What process do facultative anaerobes undergo in the absence of oxygen?
They undergo denitrification, where nitrate ions are used as electron acceptors, converting them into nitrogen gas (N₂). This process occurs under anoxic conditions
When do facultative bacteria switch to nitrate as an electron acceptor?
When dissolved oxygen is depleted, facultative bacteria use nitrate as the next most energetically favorable electron acceptor in the absence of oxygen
What conditions are necessary for bacteria to reduce nitrate to nitrogen gas?
Anoxic conditions, where oxygen is not present, are necessary. In these conditions, bacteria like denitrifiers use nitrate ions as an alternative to oxygen
What distinguishes obligate anaerobes from facultative anaerobes?
Obligate anaerobes can only function in the absence of oxygen, using compounds like nitrate and sulfate for electron acceptors, while facultative anaerobes can adapt to both oxygen-rich and oxygen-depleted environments
