Antibiotics

Bacteria causing skin wounds may develop resistance to the antibiotic usually used to kill them. Which statement explains how these bacteria could develop resistance to the antibiotic?

Feb/March 2018

Why are most viruses that cause disease in humans not affected by antibiotics?

Feb/March 2019

In March 2019, a tropical cyclone in the south-west Indian Ocean led to extensive flooding across several countries. Because the cyclone flooded areas and caused damage, many people faced a very high risk of cholera. Once the natural disaster had happened, cholera outbreaks were reported in many different places. Soon afterwards the disease had spread broadly and affected large numbers of people.

Feb/March 2021

Which statement gives the correct reason that penicillin has no effect on viruses?

Feb/March 2023

The diagram illustrates one method used to test the effect of an antibiotic on bacteria. The table gives the results from testing five different types of bacteria. Zones smaller than $13\ \text{mm}$ indicate that resistant bacteria are present. Which statement can be supported by these data?

May/June 2011

Some antibiotics are mixed into animal feed to lower disease. What is the reason that these antibiotics should not be used to treat disease in humans?

May/June 2013

Certain strains of Mycobacterium have been identified as: • multiple drug-resistant (MDR) - resistant to the drugs most frequently used to control tuberculosis (TB) • extensively drug-resistant (XDR) - resistant to the drugs most frequently used to control TB and to some of the drugs less frequently used to control TB • totally drug-resistant (TDR) - resistant to all known drugs used to control TB. When some of these Mycobacterium strains were compared, differences were seen in the thickness of their cell walls, as shown in the table. Mycobacterium: non-resistant $15\,\text{nm}$; MDR $17\,\text{nm}$; TDR $20\,\text{nm}$. What conclusions can be drawn from this information?

May/June 2015

An antibiotic prevents cross-links from forming between the molecules that make up bacterial cell walls. Which statements account for bacteria being killed by the antibiotic?

May/June 2016

Tuberculosis (TB) is an infectious disease brought about by the bacterium Mycobacterium tuberculosis.

May/June 2016

Several common antibiotics are shown below, and the process blocked by each one is given. 1 rifampicin - blocks RNA polymerase 2 streptomycin - blocks $70\text{S}$ ribosomes 3 neomycin - blocks DNA synthesis 4 ampicillin - blocks peptidoglycan synthesis Which of these antibiotics will influence only the activities of bacterial cells?

May/June 2017

Certain antibiotics are added to animal feed to help lower disease. Why should these antibiotics not be used to treat human diseases?

May/June 2017

In what sequence do the following processes take place so that a population of bacteria becomes resistant to a new antibiotic?

May/June 2017

The diagram illustrates one method used to investigate the effect of an antibiotic on bacteria. Colonies of bacteria are cultured on a petri dish containing nutrient agar with bacteria. A filter paper disc that has been soaked in antibiotic is put onto the agar. The bacteria are left to grow for 5 days, and the diameter of the zone is measured each day for 5 days. The table presents the results of testing five different types of bacteria. Zones smaller than $13.0\,\text{mm}$ indicate that resistant bacteria are present. Which statement is supported by this data?

May/June 2018

Certain antibiotics act by attaching to ribosomes. Which statement accounts for the fact that these antibiotics kill bacterial cells but do not kill most human cells?

May/June 2018

Bacteria can be grouped by differences in cell wall structure. These differences are revealed by the Gram stain. A Gram-positive bacterium has a cell wall that consists mainly of a thick peptidoglycan (murein) layer. A Gram-negative bacterium has a more elaborate cell wall made up of a much thinner peptidoglycan layer together with an outer layer called the outer membrane. Escherichia coli is a Gram-negative bacterium. Fig. 3.1 is a diagram of the cell surface membrane and the cell wall of E. coli.

May/June 2018

A bacterial population is treated with the antibiotic penicillin. The majority of the bacteria die. Nevertheless, some bacteria in the population possess an allele that codes for an enzyme capable of breaking down penicillin. These bacteria are able to survive. Which could account for how these bacterial cells obtained this allele?

May/June 2020

The table shows a comparison of total antibiotic use $(X)$ with the percentage of antibiotic-resistant pneumonia cases $(Y)$ across five countries. Which statement is supported by the data?

May/June 2020

Which statement about how bacteria develop resistance to antibiotics is correct?

May/June 2020

A list of some common antibiotics is shown below. The effect of each antibiotic is given. 1 rifampicin - prevents RNA polymerase from functioning 2 streptomycin - prevents $70$S ribosomes from functioning 3 neomycin - stops DNA synthesis 4 ampicillin - blocks peptidoglycan synthesis Which of these antibiotics would affect only the activities of bacterial cells?

May/June 2020

By what first process do bacteria acquire resistance to antibiotics?

May/June 2021

What has caused the rise in antibiotic resistance in bacteria?

May/June 2021

Antibiotics work through different mechanisms. In an ideal situation, the antibiotic destroys the bacteria while leaving the infected human unharmed. One antibiotic, tetracycline, may interfere with how human mitochondria operate. What accounts for tetracycline’s effect on human mitochondria?

May/June 2021

Smallpox, measles and HIV/AIDS are infectious diseases caused by different viruses. These viruses have some shared structural features.

May/June 2021

What action will slow down the speed at which bacteria develop resistance to antibiotics?

May/June 2022

If bacteria are cultured in a Petri dish with discs that contain antibiotics, zones of inhibition of bacterial growth will form. The chart presents the diameters of the zones of inhibition when a species of bacteria was incubated on five separate agar plates, each with a disc carrying a different antibiotic. Which conclusions can be drawn about the most and least effective antibiotics for this species of bacteria?

May/June 2023

A scientist studied how an antibiotic affected the treatment of cholera. 320 people who had cholera were split into two groups. One group received the antibiotic, whereas the other group did not receive the antibiotic. Both groups were given fluids that contained sugars and mineral salts (oral rehydration therapy). The scientist noted the number of days each person had diarrhoea. The table below gives the results. Treatment: antibiotic and oral rehydration therapy, mean time person had diarrhoea = 3.2 days; oral rehydration therapy, mean time person had diarrhoea = 5.3 days. Calculate the percentage decrease in the mean time that a person had diarrhoea when the antibiotic was used.

May/June 2024

Scientists examined multidrug-resistant bacterial infections in children that were caused by one type of bacteria from 2007 to 2015. The proportion of multidrug-resistant infections increased from 0.2% to 1.5%. What percentage increase in multidrug-resistant infections occurred between 2007 and 2015?

May/June 2024

An antibiotic prevents cross-links from forming between the molecules that make up bacterial cell walls. Which statements explain why bacteria are killed by the antibiotic?

May/June 2024

Researchers studied how raising the concentration of an antibiotic affected the development of antibiotic resistance in bacteria. Four bacterial groups were cultured, and each group received a different antibiotic concentration. For each group, the number of resistant bacteria and the total bacterial population were recorded at intervals over 24 hours. The graphs present the findings. The antibiotic concentrations shown are $0\,\text{mg dm}^{-3}$, $90\,\text{mg dm}^{-3}$, $215\,\text{mg dm}^{-3}$ and $600\,\text{mg dm}^{-3}$. The bacterial population is measured as $\times 10^6$. Which statements are valid conclusions that can be drawn from these results?

May/June 2024

Bacteria can be grouped by comparing differences in cell wall structure. These differences can be revealed with the Gram stain. The diagram below shows part of a Gram-positive bacterium and part of a Gram-negative bacterium, both drawn on the same scale. The antibiotic penicillin destroys bacteria by preventing the formation of cell walls during bacterial cell growth. Which type of bacteria would be killed more readily by penicillin, and why?

May/June 2024

Lysozyme is an antibacterial enzyme first identified in 1921 by Alexander Fleming, the scientist who discovered penicillin. Lysozyme catalyses hydrolysis of glycosidic bonds in peptidoglycan molecules, producing the smaller products NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid).

May/June 2024

Antibiotic resistance poses a serious threat to health worldwide. Which statement identifies a measure that can be taken to lessen the impact of antibiotic resistance?

May/June 2025

Antibiotics are used in the treatment of many infections. Each antibiotic has one or more biochemical targets. Tetracycline inhibits 70S ribosomes, while Rifamycin inhibits prokaryotic RNA polymerase. Which antibiotics could be used to treat an infection caused by the influenza virus?

May/June 2025

Which diseases can antibiotics be used to cure?

Oct/Nov 2010

Antibiotics are medicines that are essential in treating and curing some diseases.

Oct/Nov 2012

Which illnesses are treated using antibiotics?

Oct/Nov 2014

The diagram illustrates one method of investigating the effect of an antibiotic on bacteria. The table presents the outcomes of tests on five different types of bacteria. Zones of less than $13\,\text{mm}$ indicate that resistant bacteria are present. Which statement can be supported by this data?

Oct/Nov 2015

Explain how enzymes reduce the activation energy needed for reactions to occur.

Oct/Nov 2016

The antibiotic tetracycline attaches to the small subunit of bacterial ribosomes and prevents protein synthesis. Bacteria have developed resistance to tetracycline because of mutations. Which effect could lead to resistance to tetracycline?

Oct/Nov 2018

Which diseases are not treatable using antibiotics?

Oct/Nov 2018

Which use of antibiotics helps to lower the spread of resistance in bacteria?

Oct/Nov 2019

Antibiotics work in different ways. It is essential that an antibiotic destroys the bacteria without injuring the infected human. The antibiotic tetracycline has been discovered to influence the way human mitochondria work. Which statements could account for human mitochondria function being affected by tetracycline?

Oct/Nov 2019

Scientists investigated multidrug resistant bacterial infections in children, which were caused by one type of bacteria, during 2007 and 2015. The proportion of multidrug resistant infections increased from $0.2\%$ to $1.5\%$. What was the percentage increase in multidrug resistant infections between 2007 and 2015?

Oct/Nov 2019

Fig. 2.1 shows, as a transmission electron micrograph, the bacterial pathogen responsible for tuberculosis (TB).

Oct/Nov 2019

Countries with a large number of malaria cases also experience problems from bacterial diseases. As a result, many people in these countries are prescribed antibiotics, such as penicillin, to treat bacterial infections.

Oct/Nov 2019

Species X is a unicellular eukaryote. Species X has been genetically engineered to make penicillin, which does not damage the cell walls of species X. What can be inferred from this information?

Oct/Nov 2020

Mammals have a circulatory system with double circulation.

Oct/Nov 2020

Treatment for people with active tuberculosis (TB) continues for six months and uses a mixture of antibiotics. This is usually highly effective when the person has a susceptible (non-resistant) strain of $\textit{Mycobacterium tuberculosis}$, the organism that causes TB. Table 2.1 gives one recommended treatment plan based on combined antibiotics.

Oct/Nov 2020

Antibiotic sensitivity tests may be used to select the most suitable antibiotics for treating bacterial disease. A researcher performed an antibiotic sensitivity test on two pathogenic bacteria, X and Y. Two Petri dishes of agar were prepared, and a culture of each bacterium was spread across the agar surface. Filter paper discs soaked with antibiotics were then placed on the agar in each dish. The Petri dishes were incubated at $25^{\circ}\text{C}$ for two days. The outcomes for the test with three antibiotics, P, Q and R, are shown in Fig. 4.1.

Oct/Nov 2020

Which statement correctly describes multiple drug resistance in bacteria?

Oct/Nov 2021

The graph illustrates how the antibiotic resistance of a bacterium species changed from 2000 to 2016 in one country. Each year, bacteria samples were taken from 48 hospitals. The bacteria were then examined to determine whether they were resistant to five different antibiotics. What conclusion can be drawn from the data shown in the graph?

Oct/Nov 2023

Organism X makes molecule Y, and this molecule inhibits the activity of $70\text{S}$ ribosomes. An experiment was performed to examine the effect of Y on bacterial cells. An agar plate covered with bacteria growing across its entire surface had four wells made in the agar. Each well received a different substance, and the agar plate containing the bacteria was incubated for one week. The diagram shows the outcomes after one week. Which conclusions can be drawn from these results?

Oct/Nov 2023

A patient has experienced several infections caused by the same pathogen over a period of a few months. Each time, the patient has been given the same antibiotic. Which treatment could stop the pathogen from becoming more antibiotic-resistant?

Oct/Nov 2023

Bacteria may develop resistance to antibiotics. What action can help slow the emergence of antibiotic resistance in bacteria?

Oct/Nov 2023

Which structures or compounds in a typical cell can be destroyed by penicillin?

Oct/Nov 2024

Which of these statements about penicillin are correct?

Oct/Nov 2024

Which organisms can have their cell walls affected by penicillin?

Oct/Nov 2024

Inhibitors are substances that stop biological processes in a range of different ways. Table 5.1 presents some antibiotics, their modes of action and the diseases they are used to treat.

Oct/Nov 2025