AQA A-Level Biology - Immunity and Disease Questions And Answers

AQA A-Level Biology - Immunity and Disease Questions And Answers Self Cells The body's own cells and molecules Non-Self Cells Foreign cells and molecules invading someone Non Specific Defense A bodily response that is immediate and applies to all pathogens entering the body Specific Defense A slower bodily response that is specific based on each pathogen entering the body Cellular Response Involves T lymphocytes and only occurs in cells Humoral Response Involves B lymphocytes and occurs in liquids in the body How Self Cells are Recognised Lymphocytes are constantly colliding with cells. Some lymphocytes have receptors that are complimentary to self cells, these get suppressed or die. The only lymphocytes that remain are those that respond to non-self cells Apoptosis Programmed cell death that occurs when lymphocytes show an immune response to self-cells, this occurs before lymphocytes mature Phagocytosis The process by which a lymphocyte digests a pathogen and absorbs the useful nutrients into its cytoplasm Process of Phagocytosis Chemical products of the pathogen act as attractants, allowing phagocytes to move towards the pathogen. The receptors on the cell membrane attaches to chemicals on the surface of the pathogen. The phagocyte engulfs the pathogen and forms a phagosome. The lysosomes inside the phagocyte bind to the phagosome and release lysozyme to hydrolyse the pathogen. The phagocyte absorbs the useful products Lysozyme The enzyme that hydrolyses the pathogen enclosed by the phagosome Phagosome The vesicle inside the phagocyte that contains the pathogen Lysosome The small vesicle that contains lysozyme Antigens Unique glycoproteins on the surface of pathogens. The presence of these stimulates an immune response B Lymphocytes Produced in the bone marrow and mature in the bone marrow. Involved in the humoral response T Lymphocytes Produced in the bone marrow and mature in the thymus gland. Involved in the cellular response Cytotoxic T-Cells Produces perforin which makes holes in the antigen presenting cells, allowing the contents to leave the cell (ions and water) Helper T-Cells Simulates the phagocytosis of pathogens therefore multiply rapidly during the cellular response Memory T-Cells Remembers the specific shape of the antigen on the antigen presenting cells, this helps maintain immunity from that one specific pathogen Process of the Cellular Response T lymphocytes are complimentary to the specific shaped tertiary structure of the antigen, so they bind to one another, forming a sensitised T-Cell. This stimulates rapid mitotic division and differentiation into the three types of T-Cells Primary Immune Response Performed by plasma cells. They secrete 2000 antibodies per second. Only survive a few days but stimulate chemical destruction of the pathogen. This allows for antibody-antigen complexes to form Secondary Immune Response Performed by memory cells. They circulate in blood and tissue and recognise the antigens if they are presented again. This stimulates division of the memory cells to