Biology: Microbiology: Bacteria, Viruses, and Antibiotics Worksheet

Question 1

List three major differences between bacteria and viruses. Include differences in cell structure, reproduction, and response to antibiotics.

Accepted Answer

Bacteria are living single-celled organisms with cell membranes, cytoplasm, ribosomes, and usually cell walls. Viruses are not cells and contain genetic material inside a protein coat, sometimes with an envelope. Bacteria reproduce on their own by binary fission, while viruses must infect host cells to make copies. Antibiotics can treat many bacterial infections, but they do not work against viral infections.

Question 2

A patient has a sore throat, fever, and swollen lymph nodes. The doctor performs a rapid test before deciding whether to prescribe antibiotics. Explain why the doctor should test before giving antibiotics.

Accepted Answer

The doctor should test because the symptoms could be caused by either bacteria or a virus. Antibiotics only help bacterial infections, so giving them for a viral infection would not treat the illness. Unnecessary antibiotic use can also increase the chance of antibiotic resistance and may cause side effects.

Question 3

Describe binary fission in bacteria. Explain how this process can lead to a rapid increase in bacterial population size.

Accepted Answer

Binary fission is a form of asexual reproduction in which one bacterial cell copies its DNA, grows, and divides into two genetically similar cells. Because each new cell can divide again, the population can double repeatedly under favorable conditions. This can cause bacterial numbers to increase very quickly.

Question 4

Viruses are often described as obligate intracellular parasites. Explain what this phrase means.

Accepted Answer

Obligate intracellular parasites must enter living host cells to reproduce. Viruses fit this description because they cannot make proteins, copy their genomes, or produce new virus particles without using the machinery and resources of a host cell.

Question 5

A student says, "Antibiotics kill viruses because viruses are germs." Write a correction to this statement using accurate biology vocabulary.

Accepted Answer

The statement is incorrect because antibiotics target structures or processes found in bacteria, such as bacterial cell walls, ribosomes, or DNA replication enzymes. Viruses do not have these bacterial structures and must reproduce inside host cells, so antibiotics do not kill viruses.

Question 6

Penicillin interferes with bacterial cell wall formation. Explain why this can kill many bacteria but does not harm human cells in the same direct way.

Accepted Answer

Penicillin can kill many bacteria because bacterial cell walls help them keep their shape and prevent bursting. When the cell wall cannot form correctly, the bacterium may rupture or fail to survive. Human cells do not have cell walls, so penicillin does not directly target a structure found in human cells.

Question 7

Explain how natural selection can lead to antibiotic-resistant bacteria in a population after antibiotic treatment.

Accepted Answer

In a bacterial population, a few cells may already have mutations or genes that allow them to survive an antibiotic. When the antibiotic is used, susceptible bacteria die or stop growing, while resistant bacteria survive. The resistant bacteria then reproduce and pass on resistance genes, making the population more resistant over time.

Question 8

A culture plate is treated with antibiotic A. After 24 hours, most bacteria are gone, but a few colonies remain and continue growing. What is the most likely explanation, and what could happen if those colonies are allowed to reproduce?

Accepted Answer

The remaining colonies were likely resistant to antibiotic A or were protected in a way that allowed them to survive. If they reproduce, they can create a new population with a higher proportion of antibiotic-resistant bacteria. This can make future treatment with the same antibiotic less effective.

Question 9

Compare the lytic cycle and the lysogenic cycle of viral reproduction.

Accepted Answer

In the lytic cycle, a virus infects a host cell, uses the cell to make new virus particles, and usually causes the host cell to burst or die. In the lysogenic cycle, viral genetic material becomes part of the host cell's DNA or remains dormant in the cell and is copied when the host cell divides. A lysogenic virus can later enter the lytic cycle.

Question 10

Explain why completing a full course of prescribed antibiotics can help reduce the development of antibiotic resistance.

Accepted Answer

Completing the full course helps ensure that as many harmful bacteria as possible are killed. If a person stops early, some bacteria may survive, including those with partial resistance. Those survivors can reproduce and spread resistance genes, increasing the chance that the infection returns and becomes harder to treat.

Question 11

Some bacteria exchange plasmids through conjugation. Explain how plasmid transfer can contribute to antibiotic resistance spreading between bacterial cells.

Accepted Answer

Plasmids are small circular DNA molecules that can carry genes, including antibiotic resistance genes. During conjugation, one bacterium can transfer a plasmid to another bacterium through a connection between the cells. If the plasmid contains a resistance gene, the receiving bacterium may become resistant and can pass that gene to its descendants or other bacteria.

Question 12

A new medicine blocks a viral enzyme needed to copy viral RNA. Predict whether this medicine would be more useful against a bacterial infection or a viral infection, and justify your answer.

Accepted Answer

This medicine would be more useful against a viral infection because it targets a viral enzyme needed to copy viral RNA. Bacteria do not rely on that same viral replication enzyme to reproduce. A good antimicrobial treatment targets a process that is essential to the pathogen while causing limited harm to the host.

Biology: Microbiology: Bacteria, Viruses, and Antibiotics

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