infectious diseases and immune system

• What is a pathogen?

  A microorganism that can cause disease
• What is the host in the context of pathogens?

  The organism infected by the pathogen
• What type of disease is bacterial meningitis?

  Communicable disease
• How can communicable diseases be spread?

  Between organisms of the same or different species
• What do pathogenic bacteria release that can damage host cells?

  Toxins
• Where is the genetic material found in bacteria?

  In the cytoplasm, not in a nucleus
• How do bacteria cause symptoms of disease?

  By releasing toxins that damage host cells
• What is a key feature of viruses?

  They cannot reproduce outside of a host cell
• What are the components of a virus?

  Genetic material and a protein capsid
• What do attachment proteins in viruses do?

  Allow the virus to attach to host cells
• How do viruses reproduce?

  By attaching to a host cell and using its enzymes
• How do fungi reproduce?

  By releasing a large number of spores
• What impact can pathogenic fungi have on plants?

  They can reduce photosynthesis and crop yield
• What are the main characteristics of bacteria?

  • Prokaryotic cells
  • Genetic material in cytoplasm
  • No membrane-bound organelles
  • Surrounded by a peptidoglycan cell wall
• What are the main characteristics of viruses?

  • Non-living
  • Consist of genetic material and a capsid
  • Cannot reproduce outside a host cell
  • Use host cell's enzymes for reproduction
• What are the main characteristics of fungi?

  • Eukaryotic organisms
  • Can be unicellular or multicellular
  • Obtain nutrients by digesting surrounding material
  • Reproduce by releasing spores
• What is a pathogen?

  A pathogen is a microorganisms that causes disease.
• What is the non-specific immune system?

  Present from birth and is effective against a wide range of pathogens and foreign substances. The response is always the same
• What is the specific immune system?

  Slow and effective against specific pathogens however response is faster after re-infection.
• What is an antigen?

  A protein (or glycoprotein), often on cell membranes that can cause an immune response involving antibodies.
• What do antigens help the immune system identify?

  Pathogens, cells from other organisms of the same species, abnormal body cells and toxins.
• What is the sequence of events of phagocytosis?

  - Phagocytes recognise and bind to antigen on the pathogen.

  - Phagocytes engulf pathogens

  - They are enclosed in a vesicle.

  - Lysosomes fuse with the vesicle.

  - Lysosoms contain lysozymes.

  - These digest the pathogens by hydrolysis.
• What happens after the phagocyte digests the pathogens?

  It places the antigen from the pathogen on its cell surface membrane so it becomes an antigen presenting cell.
• Name the two types of specific immune response

  Cellular response and humoral response
• What are T-lymphocytes?


  Cells that recognise specific non-self antigens presented in the surface of others body cells.
• Antigen presenting cells can be:

  Cells infected by virus, abnormal cells which has become cancerous and a phagocyte whic has engulfed and hydrolysed a pathogen.
• Give a summary of the role that T-cells have in cellular immunity

  Receptors on specific T cells fit exactly with the antigen presented on the phagocyte. This activates the T helper cell to divide rapidly via mitosis and form clones of genetically identical cells. It also releases chemicals that activate other T and B cells which are specific to the antigen
• What are cytotoxic T cells?

  Cells that destroy infected body cells by producing a protein called perforin which makes holes in the cell membranes.
• What are memory cells?

  Cells that enable a rapid response to future infections by the same pathogen.
• What are T helper cells?

  Cells that release chemical signals which stimulate other cells of the immune system.
• What is the humoral response?

  The response involving B cells and antibody production.
• What is the humoral response effective against?

  Pathogens circulating in the bloodstream.
• What do B cells contain?

  They contain specific antibodies.
• When is a B cell activated?

  When a complementary antigen binds to the antibody on the B cell and the chemicals are released by the specific T helper cells.
• What if clonal selection?

  When a B cell is activated and divides rapidly by mitosis to form a clone.
• What are plasma cells?

  Cells that secrete antibodies directly which survive a few days only. They release many antibodies which enter the blood and bind to the complementary antigens leading to destruction of circulating pathogens or toxins.
• What is the function of memory cells?

  If the body encounters the same antigen at a later date, memory cells divide rapidly and produce large numbers of memory and plasma cells so produce antibodies faster.
• What is the primary response?

  Antigen is taken in and needs time to activate a specific B lymphocyte which then has to clone itself, produce plasma cells, antibodies and memory cells.
• What is a secondary response?


  There are already memory cells against the antigen and so they can already divide by mitosis to produce large numbers of plasma cells and specific antibodies.
• Name two similarities of the cellular and humoral response

  Both produce memory cells and use lymphocytes