exam questions

• Give 2 differences between the genetic material of bacteria and viruses (2)

  -       Genetic material of bacteria is always DNA and viruses can be DNA or RNA

  -       Bacterial genetic material is double stranded, virus genetic material can be single stranded or double stranded

  -       Bacteria have circular DNA, viruses have linear/straight

  -       Bacteria may have plasmids, viruses don’t have plasmids
• Explain the transmission of TB (5) 

  -       Infected person coughs or sneezes, released mycobacterium tuberculosis bacteria into the air in tiny liquid droplets 

  -       If inhaled, the bacterium in the lungs is injected by phagocytes, bacteria can still survive and reproduce 

  -       Over time phagocytes are encased by tubercles in the lungs, the bacteria are dormant 

  -       Bacteria can become active and overcome the immune system if suppressed or compromised 

  -       Active bacteria can cause extensive damage to the lungs and lead to respiratory failure.
• Hiv particles contain (2) 

  -       RNA 

  -       Reverse transcriptase
• Describe how HIV particles can enter T helper cells (3)

  -       Lack of T helper cells reduces cytokine production 

  -       Therefore, reducing activation of B cells 

  -       Reducing antibody production 

  -       There is an increased risk of opportunistic infections
• Explain why these stem cells may prevent HIV causing AIDS (4)

  -       These stem cells from the bone marrow can differentiate into specialised cells 

  -       The stem cells will differentiate into T helper cells with the mutated protein 

  -       Therefore, no glycoproteins of HIV can bind to receptors and cause death of T helper cells 

  -       Increases number of t helper cells in the body therefore more B cells are activated by cytokines – t helper cells not destroyed.

  -       Therefore, antibodies can be produced which reduces risk of developing opportunistic diseases
• Describe the term retrovirus (1)

  -       Virus containing reverse transcriptase enzymes

  -       Can make DNA from RNA
• Describe the steps by which HIV can lead to death caused by a bacterium (4)

  • HIV enters t-helper cells and releases its RNA
  •  Reverse transcriptase synthesises viral DNA- inserted into host cell’s DNA
  • New viral components are synthesised, and viruses released, killing T cell 
  •  new viral particles infect other t cells which destroys them over time 
  • B cells no longer activated, and antibodies are not produced 
  • So, an opportunistic infection can cause death due to compromised immune system.