OCR AS Biology

Revision Notes

4.1.15 Sources of Medicine

Sources of Medicine

Discovering new drugs

  • The worrying increase of antibiotic-resistant bacteria strains means that scientists are always looking for new antibiotics
  • A lot of time and money is required to successfully develop a drug. There are several trials that a drug must pass before being approved by a national regulatory authority
  • There are several different ways in which new drugs are discovered and developed:
    • The analysis of an organism’s genome to find candidate genes that may code for potential drugs
    • Identifying molecules that fit into drug targets e.g. receptors and hormones or neurotransmitters and synapses
    • Modifying drugs that already exist (this is done by using computer programmes that model the molecular structures of drugs and target molecules)
    • Identification of useful compounds produced by organisms (e.g. fungi, plants, animals and actinobacteria)

Microorganisms and plants as a source of medicine

  • A large majority of the drugs we currently use have been obtained by studying other organisms
  • Bacteria and fungi have provided many antibiotics
    • Quite recently compounds called rifamycins have been discovered in marine actinobacteria. These compounds kill bacteria by inhibiting bacterial transcription
  • Plants have been a major source of drugs for hundreds of years
    • Artemisinin is a drug found in Sweet wormwood and it treats malaria by killing the pathogen while it is in the red blood cells
    • Quinidine is derived from the Quinine tree and it treats a fast heart rate by blocking channel proteins in cardiac muscle to reduce impulse conduction
    • Many plants are used in traditional Chinese medicine, scientists are keen to catalogue and study these plants to see what drugs they can provide
  • Continued access to these drugs and the discovery of new drugs is a strong argument for maintaining biodiversity at a global level
    • Microorganism and plant species may go extinct before we have the chance to discover what drugs they can provide

Personalised medicine

  • Currently, a “one type fits all” attitude is applied when prescribing drugs to individuals with the same disease or condition
  • Personalised medicine involves the development of more targeted and personalised drugs to treat a variety of human diseases as well as the development of synthetic tissues
    • For example, the drug isoniazid is used to treat TB. Some individuals metabolize the drug slowly (making it effective at treating the disease) while others metabolize it much faster (making it an ineffective treatment)
  • Information gathered from genome projects like the Human Genome Project (HGP) can be used to develop genomic medicine
  • Genomic medicine uses information about an individuals genes to influence their clinical care
  • Ideally, doctors could prescribe the most effective drugs for an individual based on their genome
    • Between individuals, there are differences in DNA base sequences. These differences can affect the tertiary structure of the proteins which are targeted by drugs
  • The information gained from genetic testing could be used to divide the population into subgroups according to how they are likely to respond to specific drugs. This would ensure that individuals receive the most effective drugs that cause the least side effects
  • Serious progress has been made in personalised cancer medicine
    • Herceptin is an antibody drug used to treat some breast cancers, it affects a specific cell surface receptor. A patient is only given the drug if they are found to have high numbers of this receptor
  • Genetic screening is also a form of personalised medicine as it allows for individuals with a high chance of developing specific diseases to be identified and for preventative measures or precautions to be taken

Synthetic biology

  • Synthetic biology is a recent area of research that aims to create new biological parts, devices, and systems, or to redesign systems that already exist in nature
  • It is much more complex than genetic engineering as it involves assembling an entire genome. This genome can cause a cell to operate in a novel way, not yet seen before
  • The assembly of the genome can be done using known existing DNA seqeunces or by using entirely new sequences
    • These new sequences can be written (using special computer programmes) so that they produce specific proteins or transcription factors

Producing artemisinin

  • The most well-known use of synthetic biology is the commercial production of artemisinin
  • Artemisisnin is an antimalarial drug that is difficult to produce in other ways
  • E.coli and yeast are completely gentically reprogrammed  so that they produce the precursor of the drug on a large scale
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