Amino Acids, Proteins and DNA: Action of Anticancer Drugs

Question 1

What is the name of the anticancer drug you need to learn about?

Answer 1

• Cisplatin

Question 2

Describe and draw the structure of cisplatin

Answer 2

• A complex of platinum (II) with two chloride ion ligands and two ammonia ligands in a square planar shape
• CGP textbook, page 489

Question 3

Define the term ligand

Answer 3

• An ion or molecule that binds to a metal atom by donating a lone pair of electrons and forming a coordinate (dative) bond

Question 4

What is the difference between cisplatin and transplatin?

Answer 4

• In cisplatin, the two chloride ions and ammonium ions are next to each other
• In transplatin, alike ions are opposite each other

Question 5

Briefly describe how cisplatin acts as an anticancer drug

Answer 5

• Cisplatin prevents DNA replication in cancer cells

Question 6

How does cisplatin prevent DNA replication in cancer cells?

Answer 6

• A nitrogen atom on a guanine base forms a coordinate (dative) bond with cisplatin’s platinum ion, replacing one of the chloride ion ligands
• A second nitrogen atom from a nearby guanine molecule (either on same or opposite strand of DNA) bonds to the platinum and replaces the second chloride ion
• DNA strands can’t unwind so cell can’t replicate

Question 7

What are the negative effects of cisplatin?

Answer 7

• Can prevent DNA replication in healthy cells, leading to hair loss and a suppressed immune system
• Can also cause kidney damage
• Patients may become resistant to cisplatin

Question 8

Why is cisplatin still used as an anticancer drug, despite its side effects?

Answer 8

• The long-term positive effects outweigh the negative short-term effects