Biodegradation and Bioremediation Exam 4 - Final Exam Flashcards
What are the processes that control the fate of pollutants?
-Physiochemical processes
Ex: sorption/desorption, volatilization, leaching & runoff, hydrolysis, photolysis, oxidation-reduction reaction
-Biological processes:
Mostly mediated by microbes (plants can transform some pollutants). Microbes are the most important agent when it comes to biodegradation*
Abiotic degradation vs. Microbial degradation
Abiotic: Typically incomplete degradation of organic contaminants, produces biproducts, and occurs relatively fast.
Microbial (biological): Break down the carbon compound and mineralize these organic pollutants and produce benign product (CO2 and water).
What is biodegradation?
The biologically catalyzed reactions that reduce the complexity of chemicals. Larger molecules becoming smaller. Molecular weight decreases.
What is transformation?
The alteration in the structure of the original compound without consideration if what the products are. Products can be smaller or larger than original compound.
What is mineralization (or ultimate biodegradation)?
The conversion of organic compounds to cell material and inorganic constituents such as CO2, water, chloride, ammonium, nitrate, and phosphate. Most desirable form of biodegradation.* Want to convert toxic compound to carbon and water.
What is cometabolism?
The transformation of an organic compound by a microorganism that is unable to use the substrate as a source of carbon or energy.
What is bioremediation?
Is the use of biological agents to detoxify contaminants in the soil and other chemical compounds. This reaction leads to detoxification and happens in the environment (in the field).
What does anthropogenic mean?
Produced by humans.
What does Xenobiotic mean?
A chemical that is foreign to the biosphere. Derived from the Greek words xeno (stranger) and bios (life).
What is bioaccumulation?
The accumulation of a pollutant in living tissue. Hydrophobic compounds in fat tissue, for example.
What does biomagnification mean?
The increase in concentration of pollutant in organisms as one moves up the food chain. For those hydrophobic compounds that accumulate in living organisms at the lower part of the food chain, then the predators would prey on these organisms containing these toxic compounds and then it builds up and increases in predators.
What is bioavailability?
The accessibility of a chemical for microbial degradation or assimilation. A lot of times, when chemical compounds are absorbed by soil or sediments, then their degradation is slowed and then less biodegradable.
What is the most oxidized form of carbon? Most reduced? All other organic compounds have a valence in between. What does that mean in terms of biodegradation?
Most oxidized: CO2
Most reduced: Methane
-This means that any carbon compounds with chemical valence in between, can undergo reactions and are unstable to a certain extent.
In terms of biodegradability, there are two key factors. What are they?
Thermodynamically: all organic chemicals are unstable to varying degrees.
Kinetically: their degradation can be very slow.
What is the NPL?
National Priorities List.
Is a federal list of the nation’s hazardous waste sites eligible for investigation and cleanup under the Superfund program.
What affects the stability and toxicity of a compound, and whether or not they are biodegradable?
The structure of organic compounds.
Classification of organic compounds:
What are functional groups?
Individual atoms and small clusters of atoms with a definable set of chemical activities. Ex: Carboxyl group, hydroxyl group, methoxyl group
What are examples of ring structures?
Aromatic rings: 6C like benzene
Saturated rings: No double bond
Homocyclic rings: Same atom on all parts of the ring, like benzene
Heterocyclic rings: Different atoms in the ring structure. Ex: benzene ring but change out a carbon for nitrogen.
Classes of organic compounds:
What are hydrocarbons? What’s the difference between a hydrocarbon and carbohydrate?
Hydrocarbons have carbon-hydrogen in their structure.
Carbohydrate has carbon, hydrogen, and oxygen in its structure. This is what we eat.
Hydrocarbon is what we feed our cars, for example.
What are the different classes of organic compounds?
- Hydrocarbons
- Organic compounds containing oxygen
- Organic compounds containing nitrogen
- Other
What are the different types of hydrocarbons?
Alkanes: C-C
Alkenes: C - - C (double bond)
Alkynes: C - - - C (triple)
Aromatic hydrocarbons: Arenes (like benzene). Alternating double and single bonds between carbon atoms.
What are the different organic compounds containing oxygen?
Alcohols, ethers, aldehydes & ketones, carboxylic acids, carboxylic acid derivatives
What are the different organic compounds containing nitrogen?
Amines, amides, nitriles (has triple bond)
What are the “other” classified organic compounds?
Halides (acyl halide, alkyl halide, aryl halide) (a lot of resistant compounds are halides) and sulfur containing compounds (thiols).
Persistent Organic Pollutants (POPs):
How many are there? What are they called? A few examples?
- Called the “dirty dozen”
Ex: DDT, Mirex, Aldrin, Hexachlorobenzene
Persistent Organic Pollutants (POPs):
What do they all have in common?
All have saturated and unsaturated ring structures, some are aromatic, some aren’t.
Lot of Cl in structures, the more Cl then the more resistant they are. Br and Cl are trouble for biodegradation.
Saturated rings are fairly stable, too. Benzene is hard to break, but when two are linked together, even harder to break.
What is important to note about the EPA’s priority toxic pollutant list?
There are more organic than inorganic compounds on the list. Many of the organic compounds on the list are chlorinated solvents.
In order for microbes to metabolize carbohydrates, they must go through…?
Glycolysis and TCA cycle
What are the two intermediate products produced in glycolysis?
Pyruvate and acetyl-coA, and they will enter the TCA cycle.
What happens if microbes encounter a compound that they have never seen before?
They will modify it into something that that they are familiar with (by making new enzymes, for ex) and more easily to breakdown. Then, these products are funneled into the central pathways.
The degradation of organic pollutants is really an extension of the …?
Carbon cycle in the natural ecosystem.
What are the central pathways?
Why are the pathways a key for?
Glycolysis and Tricarboxylic acid cycle (TCA).
Key for carbon and energy that microbes need for growth.
Describe glycolysis and what is generated in the pathway.
8 ATP molecules are generated from one glucose molecule that is metabolized. There are two key intermediate products (The last two): pyruvate and acetyl-coA. Acetyl-CoA will enter the TCA cycle.
Describe the TCA cycle and what is generated in this pathway.
Additional 30 ATP molecules produced. CO2 is also a product. All the carbon compounds in the TCA cycle are called metabolites, and are the building blocks for microbes to grow. These carbon compounds are used for microbes to undergo biosynthesis. Also called the Krebs cycle and citric acid cycle.
Central Metabolism:
Peripheral pathways.
Microbes develop peripheral pathways in order to metabolize toxic organic compounds. For example, hydrocarbons are attacked by oxygenases and then degraded via peripheral pathways. Then these degraded compounds are funneled into the central pathways.
