B.6 - Biochemistry and the Environment

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Xenobiotics are chemicals found in an organism are unnatural and are not usually present there for example antibiotics, heavy metals and pesticides. These xenobiotics often stay in the organism because they are unable to be metabolized or broken down further.

Xenobiotics get into organisms through contaminated water or through feed. Pesticides and antibiotics run off fields into streams and rivers where other organisms consume them..


Coming soon…

Biodegradable plastics

Why plastics are bad for the environment: They’re petroleum based and they don’t degrade easily.

The idea of biodegradable plastics: To be broken down and composted by microorganisms eventually into water and carbon dioxide

How they do it: They try to make the plastic with natural polymers that contain ester or glycosidic linkages that microogranisms can hydrolyse and break down. The main one IB wants you to know about is adding starch to plastics, it comes up almost every year in paper 3 biochem.


  • Increases ability of microorganisms to break down the plastic
  • Reduces amount of petrochemicals neede to make the plastic
  • Makes the plastic more water soluble
  • Microorganisms create holes/channels in the plastic, making it more accessibile
  • Starch is a reneable resource


  • Plastic may degrade before use
  • Starch requires land to produce (which could be used for food)
    • Requires pesticides and fertilisers

Green Chemistry

Green chemistry is the assessment of chemical reactions based on their ‘greenness’. This is done by considering the principles of green chemistry, which aim to reduce the environmental impact of industrial chemical processes.

  • Reduce chemical waste of reactions
  • Increase atom economy
  • Reduce amount of toxic waste
  • Use more environmentally friendly solvents
  • Reduce electricity usage
  • Use catalysts to increase rate of reaction and reduce waste
  • Reduce amount of toxic/greenhouse gases produced

Host-Guest Chemistry

Coming soon…


Coming soon…

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