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Question 1

Describe action of penicillin

Answer 1

Bacterial Cell Wall

Inhibits transpeptidase enzyme that forms cross-links in cell wall. Osmotic pressure causes cell lysis

Question 2

Describe action of Rifampicin

Answer 2

Bacterial Transcription

Binds to bacterial RNA Polymerase preventing transcription.

Question 3

Describe action of tertcycline

Answer 3

Bacterial Protein Synthesis

Competes with tRNA at A site of bacterial ribosome.

Question 4

Describe action of methtrexate

Answer 4

Anti-Folates in Cancer Therapy
Impairs the synthesis of tetrahydrofolate, which is essential for DNA synthesis, from folic acid. Competitively inhibits dihydrofolate reductase (DHFR)

Question 5

Give ways in which cells can become resistant to antibiotic or drug

Answer 5

High rate of division
Decreased influx
Increased efflux
Increased transcription of target
Altered target

Question 6

Describe high rate of division

Answer 6

High rate of division in both bacteria and cancer cells means that there is a higher rate of mutation.
Positive mutations, such as drug resistance will be positively selected for and breed a population of drug resistant cells.

Question 7

Describe how decresed influx works?

Answer 7

For drugs, which require to be taken up by their target cells to take effect (Rifampicin, Tetracycline, Methotrexate), influx can be reduced.
Cells achieve this by expressing a reduced amount or altered version that reduces affinity of the carrier protein that allows the drug through the cell membrane.

Question 8

Describe how increased efflux works

Answer 8

P-Glycoprotein, or Multi-Drug Resistance Protein 1 (MDR1) is a protein similar in structure to CFTR that is responsible for the efflux of toxic products from a cell.
In many cancers, expression of P-Glycoprotein is up-regulated. This allows the cells to increase the efflux of chemotherapy drugs, eg Methotrexate.

Question 9

Describe how increased transcription of target works

Answer 9

If the drug targets a specific product of transcription, eg a ribosome or enzyme, the cell can acquire resistance by increasing the transcription of the target to overwhelm the drug

Question 10

Describe how altered target works

Answer 10

Specific target of drug acquires a mutation, lowering the affinity of the drug for it.