Defence Against Disease (SL IB Biology)

Which of the following are considered primary defence against infectious disease?

Bacteria and viruses are the main pathogens in humans. Antibiotics can be used to treat bacterial infections but not viral infections.

Which of the following statements explains why?

An antibiotic sensitivity test was performed on bacteria isolated from a patient’s throat.

The diagram shows the results of the four antibiotics tested.

Which one should be used to treat the disease?

When a phagocyte responds to the presence of a pathogen the following events happen:

1. Enzymatic digestion. 
2. Endocytosis.
3. Phagocyte membrane extends out.
4. Vacuole formation.

Which of the following would be the correct order of events?

Which of these statements correctly describes a lymphocyte?

The diagram represents the process of blood clot formation.

What is the correct sequence of events 

What is adaptive immunity?

Which of the following is not a contributing factor towards the development of antibiotic resistance in bacteria?

The following statements are about people infected with HIV/AIDS.

1. They will have symptoms.
2. They can be treated and completely cured.
3. They may live for many years after infection.

Which ones are correct?

The bacterium Staphylococcus aureus (S. aureus) is one of the main human pathogens and can cause many serious infectious diseases. Mutations in the mec A gene has allowed S.aureus to become resistant to many antibiotics. The table below shows a (Clustal W) partial nucleotide sequence alignment of mec A for different isolates of S. aureus. The drug resistant strain has a base substitution mutation (shown in bold) which changes the amino acid residue from serine to threonine.

Which of the following statements most likely explains how an amino acid change can cause antibiotic resistance?

Which of the following statements are true for antigens?

1. Antigens are proteins, glycolipids or glycoproteins found on the surface of the cell membrane
2. The symptoms of allergies, such as a runny nose or itchy eyes, are directly caused by antigens
3. Blood cells have antigens which determine blood type

Identify which of the combinations of blood types are compatible for a blood transfusion from donor to recipient.

What is required to initiate a specific immune response?

Which of the following statements about plasma cells is incorrect?

Which words or phrases can be used to fill spaces (I) and (II) in the following sentence?

Scientists have particular concerns about the spread of diseases in animals that may result in …....(I)....... transfer of pathogens to humans. Examples of these diseases include tuberculosis and .......(II)........

Which of the following would reduce the likelihood of antibiotic resistance evolving?

1.  Reducing the use of antibiotics.
2. Taking measures to reduce the spread of infectious bacteria.
3. Researching new antibiotics.

Research was carried out into the emergence of antibiotic resistance in the antibiotics used to treat infection X between the years 2000-2016.

Different antibiotics were recommended during different time periods due to concerns about developing resistance. Note that ciprofloxacin is used to treat a range of infections and not just infection X, while tetracycline is not used to treat infection X but is used to treat many other mild infections.

Some of the results of the research are shown below.

 What conclusion can be drawn from these results?

Routine use of antibiotics in animal feed has been common practice in livestock farming, but is now no longer widely practised.

Which statements best explain why?

1. Use of antibiotics allows sub-standard hygiene conditions for farm animals to be kept in
2. It encourages antibiotic resistance
3. It is expensive
4. Farm animals get more nutrition from antibiotic-free feed

The image below shows a petri dish viewed from above. A lawn of bacteria is growing across the whole surface of the agar. 

Different antibiotics, X and Y were applied to the agar before inoculating it with bacteria. Both antibiotics were applied to the discs of filter paper at the same concentration. 

The plates were then incubated for 24 hours at 25°C. Zones of inhibition (areas of the dish with no bacterial growth) are shown on the diagram.

After growth, the following results were obtained. 

How many times more effective was antibiotic Y versus antibiotic X in this study? 

Which is a reason why fungi such as Penicillium have evolved to produce antibiotics?

Some bacteria develop resistance to antibiotics by forming biofilms, which are large colonies of bacteria clumped together.

Which statement best explains how forming a biofilm might give a bacterial species resistance to antibiotics?

Lefamulin™ is a newly-developed antibiotic that binds to the 50S bacterial ribosomal subunit.

It was approved by the US Food and Drug Administration (FDA) in August 2019 for the treatment of pneumonia.

Which is the mode of action of Lefamulin™?

If a patient is given a transfusion of the wrong blood type, an immune response results. This response involves agglutination followed by haemolysis, where red blood cells are destroyed and blood may then coagulate. Blood typing involves mixing blood samples with antibodies. The diagram below shows the results of a blood typing test, showing the reactions between blood types (rows) and antibody serums (columns). The first column shows the appearance of each blood sample before testing occurred.

Identify the row in the table below that correctly identifies the blood type of blood samples I - IV.

When a phagocyte responds to the presence of a pathogen, the following events happen:

1. Enzymatic digestion
2. Exocytosis
3. Phagocytosis
4. Vacuole formation
5. Endocytosis

Which of the following would be the correct order of events?

The pneumococcal conjugate vaccine (PCV13) provides protection against infection caused by the bacterium Streptococcus pneumoniae. The graph shows the number of cases of invasive pneumococcal disease (IPD) caused by antibiotic resistant S. pneumoniae before and after the introduction of PCV13.

Which statement correctly explains the number of cases of IPD caused by antibiotic resistant S. pneumoniae after the introduction of PCV13?