Selective Toxicity Flashcards
Define the term chemotherapy
The use of synthetic chemicals to destroy infective agents
Also applied to the use of chemicals (natural or synthetic) used to inhibit the growth of cancer cells
Antibiotics
Substances produced by some micro-organisms that kill or inhibit the growth of other microorganisms
Chemotherapeutic Agents
What do these depend on?
Chemicals intended to be toxic for parasitic cells but harmless for the host
Depends on existence of biochemical differences between the parasite and host cell
Differences depends on how far apart host and parasite are evolutionary
Describe Class I Biochemical Reactions
Generation of energy and small carbon compounds
No marked differences between bacteria and human cells in mechanisms used to derive glucose
Describe Class II Biochemical Reactions
Generation of necessary small molecules (eg amino acids, nucleotides, amino sugars etc)
Better targets as some differences (eg folate synthesis, inhibited by sulphonamides. Dihydrofolate reductase more sensitive to folate antagonist trimethoprim in bacteria than in man.
Example of differential sensitivity
Describe Class III Biochemical Reactions
Generation of macromolecules (eg proteins, RNA, DNA etc)
Good targets due to very distinct differences between bacteria/viruses and human cells
State and describe two examples of Class III Biochemical Reactions
- Penicillin inhibits the synthesis of bacteria cell wall peptidoglycan (via inhibition of the Penicillin binding protein, PBP)
- Protein Synthesis Inhibitors- structural differences in ribosomal structure (bacterial= 50S and 30S; mammalian= 60S and 40S subunits)
State the five examples of targeting nucleic acids
- Inhibit nucleotide synthesis
- Altering the base-pairing properties of the template
- Inhibition of DNA polymerase and RNA polymerase
- Inhibition of DNA gyrase
- Direct effects on DNA itself- alkylating agents
