[OLD] The Immune System Flashcards
what is a pathogeN?
a microorganism that causes disease e.g virus, bacteria, fungus
what is the body’s first line of defence?
tears skin large intestine saliva respiratory tract bladder stomach earwax
what is an antigen?
a molecule that triggers an immune response
always large complex molecules
what is an antibody?
a protein which binds to antigens, they are specific
what are antibodies made by?
white blood cells
what is a toxin?
a substance released by pathogens, they are toxic
what do antitoxins do?
neutralise toxins
what makes antitoxins?
white blood cells
what is an antibiotic?
a substance that kills bacteria or prevents its growth
describe phagocytosis
pathogens release chemical products that attract phagocytes
the phagocyte engulfs the pathogen in a phagosome
the phagosome fuses with a lysosome already within the phagocyte to form a phagolysome
lysosyme from the lysosome is released which hydrolysed the pathogen, breaking it down
debris is released by exocytosis
Why do mutations cause antibiotic resistance?
If you Change the DNA sequence resulting in a different amino acid, the shape of the protein i.e the tertiary structure will change, giving rise to a new strain of bacteria.
how does antibiotic resistance happen so quicklY?
the short generation time of bacteria mean there are more opportunities for mutations to be passed on
how are t-cells activated?
they have receptor proteins on their surface that bond to complementary antigens presented to them by phagocytes
what do helper T cells do?
release chemical signals that activate and stimulate phagocytes and cytotoxic T cells, which kill abnormal and foreign cells.
they also activate B cells, which secrete antibodies.
name 3 types of white blood cells
phagocytes
T cells
B cells
what are B cells covered with?
antibodies - proteins that bind antigens to form an antigen-antibody complex
why do different B cells bind to different shaped antigens?
each B cell has a different shaped antibody on its membrane.
how do B cells work?
1) when the antibody on the surface of a B cell meets a complementary shaped antigen, it binds to it.
2) this, together with substances released form helped T cells, activates the B cell. this process is called clonal selection.
3) the activated B cell divides into plasma cells.
what do plasma cells do?
secrete monoclonal antibodies
what are monoclonal antibodies?
antibodies specific to the antigen
what do monoclonal antibodies do?
bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes.
how many binding sites does an antibody have?
2
why can agglutination occur?
an antibody can bind to two pathogens at the same time as it has two binding sites.
what is agglutination?
when pathogens become clumped together
what forms the cellular response?
the T cells and other immune system cells that they interact with, e.g phagocytes
what forms the humoral response?
B cells, clonal selection and the production of monoclonal antibodies.
what is the primary immune response?
when an antigen enters the body for the first time and activates the immune system
why is the primary immune response slow?
there aren’t many B cells that can make the antibody needed to bind to it
what happens while the body is producing enough of the right antibodies to overcome an infection?
the infected person will show symptoms of the disease
what happens after being exposed to an antigen?
t and B cells produce memory cells, which remain in the body for a long time.
what do memory T cells do?
remember the specific antigen and will recognise it a second time around
what do memory B cells do?
record the specific antibodies needed to bind to the antigen
what is being immune?
when a persons immune system has the ability to respond to a second infection
what is the secondary response?
the quicker, stronger immune response produced by the immune system if the same pathogen enters the body for the second time
what happens during the second immune response?
clonal selection happens faster
memory B cells are activated and divide into plasma cells that produce the right antibody to the antigen.
memory T cells are activated and divide into the correct type of T cells to kill the cell carrying the antigen.
what is active immunity?
the type of immunity you get when your immune system makes own antibodies being stimulated antigen
name the two types of active immunity
natural
artificial
what is natural active immunity?
when you immune after catching a disease
what is artificial active immunity?
when you become immune after you’ve been given a vaccination containing a harmless dose of antigen
what is passive immunity
the type of immunity you get from being given antibodies made by a different organism - your immune system doesn’t produce any antibodies of their own
what is natural passive immunity?
when a baby becomes immune due to the antibodies it receives from its morgen through the placenta and in breast milk
what is artificial passive immunity?
when you become immune after being injected with antibodies from someone else.
e.g if you contract tetanus you can be injected with antibodies against the tetanus toxin, collected from blood donations.
