Antibiotics are drugs that kill or inhibit the growth of bacteria.

Antibiotics target bacterial enzymes and ribosomes used in metabolic reactions, which are different from human enzymes and ribosomes.

1. Preventing the synthesis of bacterial cell walls
2. Disrupting protein activity in the cell membrane
3. Disrupting enzyme action
4. Preventing DNA synthesis
5. Preventing protein synthesis

Antibiotics don't work against viruses because viruses lack cell structures and rely on host cells for metabolic reactions. Antibiotics cannot target and disrupt these reactions.

Also, viruses invade cells, meaning antibiotics cannot reach them. 

Antibiotic resistance is when bacteria become unaffected by antibiotics, making bacterial infections more difficult to treat.

Antibiotic resistance can develop when genetic mutations occur, making some bacteria resistant to antibiotics. Resistant bacteria survive treatment, reproduce, and pass on the resistance alleles to offspring.

Genes for antibiotic resistance often occur on plasmids, which can be transferred between bacteria through conjugation.

Antibiotic resistance makes bacterial infections more difficult to treat, as some bacteria become resistant to multiple antibiotics.

1. Choosing appropriate antibiotics for treatment 
2. Using antibiotics only when needed
3. Avoiding the use of wide-spectrum antibiotics 
4. Ensuring that patients complete courses of antibiotic treatment 
5. Avoiding the use of antibiotics in farming 

It is important for patients to complete courses of antibiotic treatment to ensure that all bacteria are killed and to reduce the chance of antibiotic resistance development.

Penicillin prevents the formation of bacterial cell walls by inhibiting the enzymes responsible for building cross-links between peptidoglycan polymers.

When they are treated with penicillin, the weakened bacterial cell walls burst because water enters the cells by osmosis.