Antibiotics

Stomach ulcers can be caused by bacteria.

Name the bacteria that cause stomach ulcers.

People with a stomach ulcer are treated with antibiotics and an alkaline medicine to reduce symptoms.

Give a reason why the alkaline medicine is used.

Antibiotics are used to treat stomach ulcers.

Bacteria have become resistant to some antibiotics.

A scientist has an agar plate spread with the bacteria that cause stomach ulcers and discs containing different antibiotics.

Describe how the scientist could use these to determine which antibiotic can kill the bacteria.

*(c) A bacteriophage is a type of virus that can infect bacterial cells.

Figure 12 shows a bacteriophage infecting a bacterial cell.

Scientists are investigating if a bacteriophage could be used as an alternative to antibiotics.

Describe the lytic lifecycle of a virus and suggest why a bacteriophage could be used as an alternative to antibiotics.

A student investigated the antibiotic properties of garlic.

Bacteria were spread on an agar plate.

A paper disc was soaked in garlic extract and placed on this agar plate.

Figure 9 shows the agar plate after 24 hours.

Suggest why there is an area with no bacterial growth.

The student repeated the investigation using three separate agar plates with different concentrations of garlic extract.

Figure 10 shows the results.

The concentrations of garlic extract used were 10 mg/cm³, 40 mg/cm³ and 100 mg/cm³.

Explain which agar plate, shown in Figure 10, has the paper disc containing the 100 mg/cm³ garlic extract.

Give one way the student could improve their results.

The area with no bacterial growth for agar plate B has a radius of 5 mm.

Calculate the area with no bacterial growth for agar plate B.

The area of a circle is πr².

Use π = 3.14

Figure 11 shows bacteria being spread on an agar plate.

State the reason for heating the spreader in the flame of a Bunsen burner before use.

Give two other ways of working safely with microorganisms.

Figure 17 shows colonies of bacteria growing on an agar plate.

Each colony starts as one bacterium.

Every time bacteria reproduce, the number of bacteria in each colony doubles.

Calculate the number of bacteria in a colony after five hours, if each bacterium reproduces every 30 minutes.

Some bacteria are pathogens.

State the meaning of the term pathogen.

Explain why antibiotics can be used to treat bacterial infections.

A rod-shaped bacterium is 0.005 mm long.

A student draws the rod-shaped bacterium.

The bacterium in the drawing is 80 mm long.

Calculate the magnification of this drawing.

* (c) Figure 18 shows a bacterial cell and a plant cell.

Describe the similarities and differences of a bacterial cell and a plant cell.

Figure 4 shows colonies of bacteria growing on an agar plate.

Each colony starts as one bacterium.

Every time bacteria reproduce, the number of bacteria in each colony doubles.

Calculate the number of bacteria in a colony after five hours, if each bacterium reproduces every 30 minutes.

Some bacteria are pathogens.

State the meaning of the term pathogen.

Explain why antibiotics can be used to treat bacterial infections.

A rod-shaped bacterium is 0.005 mm long.

A student draws the rod-shaped bacterium.

The bacterium in the drawing is 80 mm long.

Calculate the magnification of this drawing.

Figure 17 shows the number of people diagnosed with sexually transmitted infections (STIs) in the UK during 2017.

State the sexually transmitted infection that has the median number of people diagnosed.

The population of the UK in 2017 was 66 million people.

Calculate the total number of people diagnosed with chlamydia in the UK in 2017.

State why chlamydia can be described as a communicable disease.

Give one way the transmission of chlamydia can be prevented.

Explain why chlamydia can be treated with antibiotics.

*(b) When a person is infected with a disease, the immune system will respond to protect their body.

Explain how the immune system will respond to an infection caused by bacteria.

Figure 2 shows the number of people diagnosed with sexually transmitted infections (STIs) in the UK during 2017.

State the sexually transmitted infection that has the median number of people diagnosed.

The population of the UK in 2017 was 66 million people.

Calculate the total number of people diagnosed with chlamydia in the UK in 2017.

State why chlamydia can be described as a communicable disease.

Give one way the transmission of chlamydia can be prevented.

Explain why chlamydia can be treated with antibiotics.

HIV is another sexually transmitted infection.

Explain how HIV can lead to the onset of AIDS.

Figure 10 shows part of a method used to produce a bacterial culture on a Petri dish.

State why step 1 and step 2 are necessary.

Give one reason why step 3 is included.

*(iii) A student wanted to investigate how effective three different antiseptics were at killing bacteria.

The student was provided with:

• an inoculated Petri dish prepared using the method in Figure 10

• three different antiseptics

• filter paper discs

• sticky tape.

Devise a plan for the student to complete this investigation.

Include a control and any variables that the student would need to consider.

Viruses can cause disease.

Describe how the lytic pathway is involved in the reproduction of viruses.

10 Streptococcus mutans is one species of bacteria which causes tooth decay. A scientist tested the effectiveness of toothpaste at killing this species of bacteria. The scientist spread the bacteria Streptococcus mutans across an agar jelly plate.

(a) (i) Which word describes the techniques used to prevent contamination of the agar jelly plate?

(ii) Give two precautions needed to prevent contamination of the agar jelly plate.

(b) The scientist placed a filter paper disc soaked in toothpaste mixed with saliva (disc A) on one half of the agar jelly plate. A filter paper disc soaked in only saliva (disc B) was placed on the other half of the agar jelly plate. The agar jelly plate was kept at 37°C for 24 hours. Figure 20 shows the results.

Figure 20

(i) The diameter of the zone of inhibition around disc A is 9 mm. Calculate the area of this zone of inhibition using the equation πr². Use a value of 3.14 for π. Give your answer to 1 decimal place.

(ii) Give a reason why disc B, soaked in only saliva, was included in this test.

(iii) Suggest two reasons why this test does not prove that toothpaste kills all bacteria on teeth.

(c) Before a new toothpaste can be sold, the toothpaste has to be tested on cultured human cells. Cultured human cells were placed into four identical flasks. Saliva was added to each flask and a different brand of toothpaste was added to each of three flasks. The human cells were left for two hours and the percentage of cells that were healthy was recorded. Figure 21 shows the results.

Figure 21

Explain the conclusion that can be made from this data.

4 Streptococcus mutans is one species of bacteria which causes tooth decay. A scientist tested the effectiveness of toothpaste at killing this species of bacteria. The scientist spread the bacteria Streptococcus mutans across an agar jelly plate.

(a) (i) Which word describes the techniques used to prevent contamination of the agar jelly plate?

(ii) Give two precautions needed to prevent contamination of the agar jelly plate.

(b) The scientist placed a filter paper disc soaked in toothpaste mixed with saliva (disc A) on one half of the agar jelly plate. A filter paper disc soaked in only saliva (disc B) was placed on the other half of the agar jelly plate. The agar jelly plate was kept at 37°C for 24 hours. Figure 5 shows the results.

(i) The diameter of the zone of inhibition around disc A is 9 mm. Calculate the area of this zone of inhibition using the equation πr². Use a value of 3.14 for π. Give your answer to 1 decimal place.

(ii) Give a reason why disc B, soaked in only saliva, was included in this test.

(iii) Suggest two reasons why this test does not prove that toothpaste kills all bacteria on teeth.

(c) Before a new toothpaste can be sold, the toothpaste has to be tested on cultured human cells. Cultured human cells were placed into four identical flasks. Saliva was added to each flask and a different brand of toothpaste was added to each of three flasks. The human cells were left for two hours and the percentage of cells that were healthy was recorded. Figure 6 shows the results.

Explain the conclusion that can be made from this data.

Which part of the eye carries impulses to the brain?

Name the structure within the eye that controls the amount of light entering the eye.

Explain the functions of the two types of cell in the retina that detect light.

The eye can be infected by bacteria.

State the type of drug used to treat infections caused by bacteria.

*(d) Figure 12 shows two defects of the eye.

Describe the causes of short-sightedness and long-sightedness.

Use information from Figure 12 to help with your answer.

Figure 4 shows the structures in a leaf.

Explain how structure Z is involved in defence against pathogens.

Chemicals can be extracted from plants.

Some of these chemicals can kill bacteria.

A scientist spread some bacteria on a nutrient agar plate as shown in Figure 5.

What is being shown in Figure 5?

Explain why the scientist worked near to a Bunsen burner.

A scientist spread bacteria onto the surface of two agar plates.

A filter paper disc was placed in the centre of each plate.

Each filter paper disc had been soaked in a different chemical extracted from plants.

The results are shown in Figure 6.

The area of a circle is calculated using πr².

Calculate the area of the zone of inhibition for chemical A.

Use π = 3.14

The scientist concluded that chemical A was more effective than chemical B at killing bacteria.

Give two variables the scientist needed to control to make this conclusion valid.

Some crop plants have been genetically engineered to produce toxic chemicals in their leaves.

Explain one advantage of producing these genetically modified crop plants.

Pathogens cause disease.

Draw one straight line from each type of pathogen to the disease that is caused by that pathogen.

Antibiotics can be used to treat diseases.

Antibiotics kill

Figure 1 shows the number of white blood cells in blood samples from three patients.

Explain why the data suggests that Patient Z has a bacterial infection.

HIV is diagnosed by blood tests.

State two safety precautions that need to be taken when handling blood samples.

A scientist was planning to compare the effectiveness of the antibiotic myxopyronin on two different species of bacteria.

Figure 18 shows the equipment the scientist can use.

agar plates
two species filter discs of
spreader
incubator of bacteria myxopyronin

Figure 18

Describe how the scientist could determine the effectiveness of myxopyronin on the two species of bacteria.

Myxopyronin inhibits bacterial RNA polymerase.

Explain why the antibiotic myxopyronin can be used to treat bacterial infections in humans.

*(b) Infections can also be caused by viruses.

Describe the lytic pathway of a virus and how this causes the spread of infection through a population.

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