Researchers all over the world are currently studying SARS-CoV-2, the virus responsible for the COVID-19 pandemic.  Instead of using human cells, some researchers are using African Green Monkey Kidney Cells ('Vero' cells) to successfully grow the virus in culture.

A.  Why are they using cells to culture the virus instead of artificial media such as nutrient agar?     (2 marks)

B.  We know this virus has most likely originated from animals (although probably not African Green Monkeys).  What important feature must these Vero cells have if they can be used to grow SARS-CoV-2 and why is this important?   (2 marks)

Rotavirus is a highly contagious disease that can cause severe vomiting and diarrhoea.  It is a viral disease that spreads through the faecal-oral route, either through contact with faeces from an infected person (e.g. while changing a child’s nappy) or through contact with the clothing or bedding of an infected person.

Rotavirus (the name of the virus that causes the disease rotavirus) is a double-stranded RNA virus surrounded by a triple-layer capsid, but no envelope.

Part B

Use a diagram (draw it on a piece of paper, take a photo and upload it as your answer*) to explain how a double-stranded RNA virus such as rotavirus undergoes protein expression. 

This question has two parts (A & B) on two different quiz pages)

Rotavirus is a highly contagious disease that can cause severe vomiting and diarrhoea.  It is a viral disease that spreads through the faecal-oral route, either through contact with faeces from an infected person (e.g. while changing a child’s nappy) or through contact with the clothing or bedding of an infected person.

Part A

Which one of the following statements BEST describes the route(s) of transmission for rotavirus?  You must briefly justify your answer.

(1 + 2 = 3 marks)

  (i)  Direct contact 

  (ii)  Indirect contact

  (iii) Both direct and indirect contact

Maddy was visiting Laos and was so excited to ride on elephants at a conservation park. She was particularly happy to donate her time to the park as it helps to raise awareness about illegal hunting. A few days later she noticed a lump on her leg that she is sure wasn’t there before.  

Part A

The lump is hot and red and about 1 cm diameter.  Describe why it is hot and red, including the cells that contribute to this, and the effects on her body.

     (3 marks)

Part B

The next day the lump is bigger and Maddy goes to a doctor. The doctor tells her it is a ‘Staph’ infection. She does some reading that learns that the Staphylococcus bacteria probably came from the skin of the elephant.

   (i)    Draw a timeline like the one below and use lines to show how the level of ‘Staph’ antigen in her body changed over time. 

   (ii)   Indicate when the adaptive immune response was triggered.

   (iii)  Indicate when memory cells were made.

   (iv)  What type of cells were the memory cells?

      (4 marks)

Jemima was infected with SARS-CoV-2 virus.  She started feeling very sick, but fortunately her adaptive immune response was activated to fight the virus.

Part B

Did linked recognition have a major role in the adaptive immune response that occurred in Jemima’s body? Explain your answer.

    (3 marks)

Jemima was infected with SARS-CoV-2 virus.  She started feeling very sick, but fortunately her adaptive immune response was activated to fight the virus.

Part C

Before the adaptive response became activated, natural killer cells interacted with epithelial cells in Jemima’s lungs.  Describe the molecular interactions that occurred between the NK cells and both infected and uninfected epithelial cells. 

On a clean sheet of paper, draw shapes like those below, and show the molecular interactions that happened between the cells on the drawing. Photograph your drawing and upload* here to receive feedback.

      (4 marks)

The following question has 3 parts over the next 3 pages:

Jemima was infected with SARS-CoV-2 virus.  She started feeling very sick, but fortunately her adaptive immune response was activated to fight the virus.

Part A

Describe the molecular interactions that occurred between dendritic cells and naïve CD8 T cells to start the adaptive immune response. 

On a clean sheet of paper, draw two circles like those below, and show the molecular interactions that happened between the cells on the drawing. Photograph your drawing and upload here to receive feedback.

      (4 marks)

Bacteria are able to fully break down a molecule of glucose by respiration just like our own mammalian cells.  Use the table in your answer box to compare and contrast respiration in bacterial and mammalian cells.

         (8 marks)

You have two different samples of bacteria (both growing on separate agar plates) - one is Escherichia coli, the other is Mycoplasma fermentans.  You tried a Gram stain on each bacterium: E. coli was clearly Gram-negative; M. fermentans also stained pink (Gram-negative).  You are somewhat confused because although you expected E. coli to be Gram-negative, you know that Mycoplasma spp. have evolved from Gram-positive bacteria, therefore, you were expecting a Gram-positive result. 

You approach your supervisor who suggests you add a colony of each type of bacterium to a test tube of water and see what happens (as shown below).  You add each type of bacteria to a sample of water, wait 10 minutes and then remove a sample from each tube and view it using phase-contrast microscopy.  You can visualise the E. coli, but you cannot visualise the M. fermentans. 

What happened when you added each bacterium to the water and how does this relate to the Gram staining result you had at the beginning?   (4 marks)

Gastric (stomach) ulcer disease is most often caused by the bacterium Helicobacter pylori. Urease is an enzyme produced by H. pylori which catalyses the hydrolysis of urea into carbon dioxide and ammonia. The synthesised ammonia immediately reacts with water in the stomach to produce ammonium hydroxide in the immediate microenvironment of the bacterium. 

Part A

What would be the purpose of urease in terms of survival of H. pylori?     (3 marks)

Part B

Would you classify H. pylori is as an acidophile?  Briefly justify your response.    (3 marks)

Part C

Virulence mechanisms of pathogenic bacteria can be classed as having a role in (i) colonisation of the host (ii) pathogenesis or (iii) evasion of the host immune response.  Urease is a virulence factor for H. pylori, how would you classify it in terms of (i)-(iii) above, give a rationale for your answer.  (2 marks)