30.5 The action of anti cancer drugs

Question 1

What do all cancers have in common

Answer 1

• They are rogue cells that are undergoing uncontrolled cell division

Question 2

What is cisplatin

Answer 2

An anticancer drug discovered in 1950s and is one of the most successful cancer treatments

Question 3

What is the shape of cisplatin

Answer 3

It is square planar

Pt in the centre, then two Cls bonded and two NH3s bonded

Question 4

How does cisplatin work as an anti cancer drug

Answer 4

• It bonds to strands of DNA, distorting their shape and preventing replication of the cells
• It bonds to the nitrogen atoms on two adjacent guanine bases on a strand of DNA

Question 5

Why is cisplatin able to attach to DNA strand

Answer 5

. The nitrogen atoms on the guanine bases have lone pairs of electrons which form dative covalent bonds with the platinum

. The chloride ions in cisplatin are displaced by water. The water ligands are then displaced by nitrogen on guanine because nitrogen is a better ligand.

This is a ligand substitution reaction

Question 6

What are some side effects of cisplatin and why

Answer 6

• It binds to healthy cells as well as cancer cells
• However cancer cells replicate at a faster rate so it effects cancer cells more
• However healthy cells that replicate quickly eg hair follicles are significantly affected so hair falls out.