Biochemistry and the environment Flashcards
1
Q
What are Xenobiotics?
A
- Foreign chemical compounds that enter an organism and interfere with biological processes, compound usually not found there
- Can have negligible or severe effects on metabolic processes
- Xenobiotics come from pollutants that are disposed of in waste or landfills
- Foreign compounds: plastics, pesticides, pharmaceutical compounds, chemical solvents
2
Q
What is antibiotic waste? How is it harmful to the environment?
A
- Antibiotics are used to treat bacterial infections, expired or unused antibiotics can contaminate environment, antibiotic resistance
- Animals injected with antibiotics to prevent and control infections can also release them
- Excreted animal waste may contain antibiotic-resistant bacteria and flow into wastewater system or soil
- Antibiotics in bodies of water or soil can kill ‘good’ bacteria and allow ‘bad’ bacteria to grow
- To remove antibiotics, activated sludge process can be used (bacteria metabolise the compound, remove it from water), some are resistant to metabolism
3
Q
What is biomagnification? How is it harmful to the environment?
A
- It is the increase in concentration of a substance as it moves up through the food chain, concentration increases with each level
- When one organism eats another that has stored xenobiotics, concentration increases
- Non-polar and water-insoluble tend to accumulate, cannot easily dissolve in bloodstream, accumulate in liver or fatty tissues
4
Q
What are pesticides? How is it harmful to the environment?
A
- A DDT is a pesticide that is colourless, tasteless, nearly odourless, ideal for adding to crops (cannot be detected by consumer)
- Insects began to develop a resistance to DDT, decreasing the effectiveness of the compound
- DDT accumulated in insects, moving up the food chain, became toxic to larger animals, hence banned in 2004
5
Q
What are heavy metals? How is it harmful to the environment? Give an example.
A
- Heavy metals accumulate in organisms, results in biomagnification
- Cannot easily be broken down by metabolic processes because some have a high affinity for tissues and become stored and not excreted
- Mercury in the form of methylmercury is formed by aquatic microbes
- The presence of methyl group makes compound non-polar with poor water solubility, can easily cross fat layer, causes toxic neutral effects, interferes with functions of proteins
6
Q
What are properties of plastic and why are they harmful for the environment?
A
- Made from addition polymers formed from alkenes, long chain of hydrocarbons
- Make plastic rigid or flexible, higher or lower density, durability
- Very difficult to break down over time, high levels of plastic waste, requires high temp or sunlight to break down
- When breaking down, produce harmful compounds
- Plastic waste in landfill sites not exposed to sunlight, lack of decomposition and can travel to natural habitats (ingested, entangled, chemicals)
7
Q
What is photodegradation?
A
- When sunlight breaks the covalent bonds in the plastic to break
- Polymer breaks into shorter sections, still harmful and ingested by aquatic animals
8
Q
What are biodegradable plastics?
A
- Substances that can be broken down by the process of biodegradation, involving bacteria, they can be natural bioplastics or synthetic (PET)
- When bacteria or other living organisms break down waste over time by consuming or digesting
- A bacteria can break down a plastic called PET, used in beverage bottles. Enzyme PETase can digest the polymer into individual monomers
- Bacteria uses these monomers to metabolise for energy
9
Q
What are bioplastics?
A
- Most plastics are petroleum-based, criticised for their inability to break down, not renewable
- Biodegradable plastics however can easily be digested by bacteria into harmless carbon dioxide and water
- Bioplastics: substances developed from renewable plant-based materials, made of starches, cellulose or biopolymers
10
Q
What role does starch play in biodegradable plastics?
A
- Starch is present in half of all bioplastics, they are completely biodegradable, durable and perform like traditional petroleum-based plastics
- Starch-based bioplastics made from renewable plant-based sources (corn, grasses), suitable for storing foods without any unwanted chemicals
- Ordinary bacteria can digest starch on landfills
11
Q
What is bioremediation?
A
- Process of using microorganisms, bacteria, to clean up waste by metabolising the harmful or toxic compounds into smaller products
- The bacteria may use enzymes that can help in the degradation of plastic waste
12
Q
What is host-guest chemistry?
A
- Formation of supramolecular complex formed between two or more molecules or ions held together by non-covalent bonds e.g. intermolecular forces, ionic, hydrogen
- These weaker bonds allow allow large molecules to bind specifically to form supramolecular complex
13
Q
How does host-guest chemistry work?
A
- Larger compound ‘host’ and smaller compound ‘guest’ form the complex
- Hosts are enzymes, guest toxins/pollutants
- The host mimic some of the actions performed by enzymes, synthetically produced (bind to specific guest)
- Type of interactions: hydrogen, dipole-dipole, ionic bonds
- Binding follows specific lock-and-key model, allows specific targeting and removal or toxins
14
Q
How are enzymes applied in the removal or toxins?
A
- Enzymes (host) used to clean up waste (guest) from chemical spills
- Oil spils are difficult to clean up, especially when in bodies of water
- Oil is non-polar and sticks to plants and wildlife, forms a coat that is difficult to remove
- Enzymes metabolise the oil, converts them into CO2 and H2O through diodegradation
- More of the oil can be targeted, oil is converted chemically into harmless products
- Enzymes allow the reaction to occur multiple times
- Enzymes also used to clean up other wastes, sewage and treatment facilities
15
Q
Give three examples of enzymes, which compounds they target and their industrial application.
A
- Protease: proteins used in food, leather and pharmaceutical
- Cellulase: cellulose used in textile, pulp & paper
- Lipase: lipids used in food cosmetic, pulp & paper
16
Q
How are enzymes used in biological detergents?
A
- Detergents are water-soluble, sued to dissolve impurities, effective cleansing agents
- Detergents are amphiphilic, have polar and non-polar froups, allow to attract polar and non-polar impurities
- They form a micelle around impurities, allow them to become more soluble in water
- Enzymes digest impurities, make more soluble and easier to wash away
- Uses multiple enzymes: lipase, protease, amylase
17
Q
What are advantages of biological detergents?
A
- Washing at lower temperatures, reducing energy requirements
- Require less detergent
- More effective stain removal for a variety of stains
- Less pre-treating of stains required with other products
18
Q
What is green chemistry?
A
- Aims to reduce waste and energy to produce safer compounds, also limit the use and production of harmful compounds in the process into the environment
19
Q
What are the 7 principles of green chemistry?
A
- Prevention of waste
- Atom economy
- Less hazardous chemical design and synthesis
- Safer and restricted use of solvents
- Energy efficiency
- Design for degradation
- Catalysis
20
Q
Explain the first three principles of green chemistry.
A
- Prevention of waste: prevent waste, rather than cleaning up waste
- Atom economy: synthesis of a compound, all materials used should be incorporated into the final product, avoid leftover materials (byproducts)
- Less hazardous chemical design and synthesis: Compound with little or no toxicity should be developed
21
Q
Explain the last four principles of green chemistry.
A
- Safer and restricted solvents: safer solvents used, recycled when possible, use of no solvents preferred
- Energy efficiency: Amount of energy used to make compounds should be kept to a minimum
- Design for degradation: Compounds generated, designed to break down into harmless compounds, not remain in environment
- Catalysis: selective catalytic reagents should be used when possible, reduce waste generated
22
Q
How can enzymes be considered ‘green’?
A
- Enzymes provide more efficient reaction
- They are regenerated following a reaction (used over again), hence less material waste is generated
- Enzymes secreted by microorganisms can also be used to treat waste, safer for disposal
23
Q
How can the choice of a solvent be considered ‘green’?
A
- Solvent in aqueous medium, easier disposal
- Use bufffers to maintain a limited pH range
- Good choice of buffer agents ensures that the chemical waste produced is safe for disposal
24
Q
What is energy efficiency, how may high temperatures be disadvantageous?
A
- Biochemical reactions must be performed at same temperature the organism operates
- Many experiments performed at higher temps to increase rate of reaction, may lead to denaturation of biomolecules
25
Q
How can waste production be made safer?
A
- Waste generated can be infectious, may end up in water supply
- Treating living organisms (yeast) with bleach, can destroy them, can end in water supply
- Avoid further growth of organism and avoid contamination
- For robust pathogens, sterilisation with chemical agents often not enough
- Autoclaving method that uses heat and steam to sterilise waste and equipment
26
Q
How are substance classified as ‘green’?
A
- Several factors must be examined before a substance can be accepted as ‘green’.
- Uses Green chemistry metrics, system used to measure the ‘greenness’ of a substance
27
Q
How is the yield accessed to determine whether a substance is green? What are its challenges?
A
- Reactions with a percentage yield approaching 100%, there would be very little waste leftover
- The process would be efficient in terms of waste production, but it may be at the cost of other green chemistry principles
- Might require more energy, reducing overall greenness of the process or might produce large quantities of an undesirable byproduct
28
Q
How is the atom economy used to determine whether a substance is green?
A
- This encourages using all materials involved in the reaction to make the final product, restricting production of leftover compounds
- It takes the mass of reactants including catalysts into consideration
- The solvent used, is ignored in the final product
- Encourages the reduction of waste
- A high atom economy (near 100%) is valued as a green principle
29
Q
What is the challenge with atom economy?
A
- Many biochemical reaction involve use of enzymes, which are regenerated and not consumed in the reaction
- Hence the catalysts does not fulfill the catalysis principle, hence atom economy not always appropriate for all reactions assessing greenness
- Catalysts promote a pathway requiring less energy, not factored into atom economy measurement, but is important principle of green chemistry
- Hence a reaction without a catalyst might have a higher calculated atom economy but greater energy requirement, less green
