Bacteria and virusesEdexcel A-Level Biology A: Mind map

Exam questions on Bacteria and viruses

1. A microbiologist is comparing two pathogens: Mycobacterium tuberculosis, a bacterium about 3 µm long, and the Human Immunodeficiency Virus (HIV), a virus about 120 nm across.
   State two structural differences between Mycobacterium tuberculosis and HIV.2 marks
2. A patient has had a persistent cough, fever, night sweats and weight loss for several weeks. Tests show that she is infected with Mycobacterium tuberculosis. The bacteria entered her lungs and were engulfed by macrophages in the alveoli, but many of the bacteria were not destroyed.
   Suggest how untreated tuberculosis could eventually lead to the death of the patient.2 marks
3. HIV has a lipid envelope containing attachment proteins, a protein capsid, two single-stranded RNA molecules and the enzyme reverse transcriptase. It infects helper T cells, which have CD4 receptors on their surface.
   Describe how HIV enters a helper T cell and how its genetic material is used to produce viral DNA.3 marks