Cisplatin and thalidomide – stereochemistry in action

This activity explores the implications of stereochemistry in drug design and action using the chemotherapy drug cisplatin and thalidomide as real life contexts.

In TOK knowledge questions are open-ended. Questions posed in this way are interesting because they do not have one straightforward correct answer and invite different ways of thinking about concepts.

Even though a specific real life context is being examined in this activity the way the students think about the context is general and open-ended.

The students watched the videos and responded to the following knowledge questions.

  • To what extent is scientific knowledge important?

  • What is the impact of history on what we know about medicines?

What are chemotherapy drugs and how do they work from American Cancer Society

Cisplatin mechanism (computer simulation)

BBC Horizon documentary on Thalidomide (0.00 – 9.00)

The importance of chirality in drug design (Richard Thornley)

The students shared their responses with a partner before sharing them with the class. As with any sharing there was a need to  push students the elaborate their responses by providing evidence / justification by asking “What makes you say that?” or “So what do you know that makes you say that?”

Students voices. What were they thinking

Scientific knowledge is important in that it can be used to develop technologies like computer generated 3d models to evaluate drugs.

Knowledge that cisplatin can distort DNA helped designers develop this drug.

Knowledge of the polarity of a molecule is important to cisplatin because it is the polarity that makes the chlorine atoms leave the molecule and bind with the nitrogen atoms on guanine. This is because we know that a nitrogen atom can form a stronger bond with platinum. If cisplatin was transplatin it would be nonpolar and less able to bond with the nitrogen atom on guanine.

Besides discovering that a drug could treat a disease scientists must also understand the chemistry because there may be unforseen side effects.

Scientific knowledge is important in drug design because it investigates the cause of a problem at a molecular level and not just treat the symptoms.

Scientific knowledge tells us how and why drugs are able to cure.

Science is sometimes responsible for linking cause and effect as in the case of thalidomide

Knowing that a drug cures a symptom is not enough.

A lack of scientific knowledge can have serious consequences.

Our current knowledge of drugs is built on prior knowledge

Drugs like thalidomide that have caused a disaster have lead to more rigorous drug development and this has led us to understand more about the issues involved in the testing of drugs.

History has shown that we need to be careful with how knowledge is used.

The history of drug development that shown us that side effects can be unknown.

The thalidomide case helped direct scientists work to the area of stereochemistry and drug action, for example the consequences of racemix mixtures and the development of drugs that contain only a single enantiomer.

References:

Ritchhart, R., Church, M., & Morrison. (2011). Making Thinking Visible. San Francisco: Josseyboss.

International Baccalaureate Organization (2013) Diploma Programme Theory of Knowledge Guide (first exams 2015). Cardiff. International Baccalaureate Organization (UK) Ltd.

International Baccalaureate Organization (2013) Diploma Programme Chemistry Guide (first exams 2016). Cardiff. International Baccalaureate Organization (UK) Ltd.

IB Links NOTES
Group 4 Aims
Prior knowledge What is Stereochemistry? Characteristics of geometric and optical isomers and their chemical and physical properties.
Chemistry syllabus & cross curricular links  20.3, D7
Learner Profile Thinkers, Knowledgeable, Reflective
Approaches to Teaching Inquiry based, Contextualized
Approaches to Learning Thinking skills
Nature of Science (NOS) How science works. Pathways to scientific discovery
TOK Historical development. What is the significance of the thalidomide incident in the historical development of our knowledge of drug action.
International mindedness Global impact of thalidomide
Links to other IB Subjects Biology

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