Tuberculosis (TB) is an infectious disease caused by the bacterium _Mycobacterium tuberculosis_.

• Antibiotics block bacterial processes; 1 mark
• Example of bacterial process (e.g., cell wall formation); 1 mark
• Variations exist naturally in a population / some are naturally resistant to the antibiotic; 1 mark
• Bacteria that are not resistant to this antibiotic will die / only resistant will survive (when antibiotic given); 1 mark
• This characteristic could be passed to the next generation; 1 mark
• (Natural selection) leads to changes in the proportions/frequency in the population; 1 mark
• Human population will be exposed to antibiotic-resistant bacteria and will not have antibiotics to kill them; 1 mark
• (Antibiotic-resistant bacteria) may pass resistance to other bacteria species/types by means of plasmids (so other bacteria species turn resistant too); 1 mark

• Cell wall; 1 mark
• Pili/flagella; 1 mark
• 70S ribosomes; 1 mark
• Nucleoid / circular DNA
  OR
  Naked DNA; 1 mark
• Plasmids; 1 mark

As candidates do not need to know the structure of Mycobacterium tuberculosis, all prokaryotic structures are accepted.
Ignore references to membrane-bound organelles.

• Phagocytes/lymphocytes are white blood cells; 1 mark
• TB bacterium has a specific antigen; 1 mark
• This antigen is recognised by white blood cells; 1 mark
• A clone of lymphocytes/plasma cells/B cells are produced; 1 mark
• Antibodies are produced by lymphocytes; 1 mark
• Each lymphocyte produces just one type of antibody; 1 mark
• (This is) specific immunity; 1 mark
• (Part of the) antibody/immunoglobulin binds to the antigen / specific antibody binds to the specific antigen; 1 mark
• Antibodies are proteins/immunoglobulins; 1 mark
• (Some) plasma cells become memory cells; 1 mark
• Memory cells reproduce quickly; 1 mark
• Memory cells prevent infection in the future; 1 mark

Allow annotated diagrams to explain the process.