Summary
Summary CIE A level Biology notes on unit 11 - Immunity
- Module
- Year 1 notes
- Institution
- CIE
Everything you need to know about unit 11 of the CIE A level Biology course, including diagrams and notes.
[Show more]
Content preview
11.1 - The Immune System:External defence systems:
• Many pathogens do not harm us because if we are healthy, then we have physical, chemical and cellular defences that prevent them
from entering.
◦The epithelia that cover the airways are an effective carrier to the entry of pathogens
◦Hydrochloric acid in the stomach kills many bacteria that we ingest in our food
◦Blood clotting is a defence mechanism that stops the loss of blood and prevents the entry of pathogens through wounds in the
skin.
◦The movement of air-filled pathogens by coughing or sneezing removes these bacteria from our body.
Internal defence systems:
• The immune response is the complex series of responses of the body, to the entry of a foreign antigen; it involves the activity of
lymphocytes and phagocytes.
• If pathogens enter the body, then WBCs can recognise them as something foreign and destroy them.
• They recognise the pathogens by the distinctive large molecules which cover their surfaces - any foreign molecules is an antigen.
◦Lympchytes can respond by producing antibodies or by killing cells that have become infected with pathogens.
• Antibodies - glycoprotein molecules, made by plasma cells, that bind to specific antigens in the immune response.
◦They have a variable region with differing aa chains, which provides the specificity of complementary shapes of the antigen
• Non-self - any substance or cell that is recognised by the immune system as being foreign and will stimulate an immune response
• Self - substances produced by the body, that the immune system does not recognise as foreign, so they don’t stimulate a response.
Types of cells:
Phagocytes:
• They are produced in the bone marrow, and remain there until they are distributed around the body in the
bloodstream.
• Neutrophils (60% of WBCs) travel in the body and leave the blood by squeezing through capillary walls to the
tissues.
◦During infection, they are released in high numbers from their stores, but are short lived - have a lobed
nucleus structure.
• Macrophages are much larger than neutrophils - they are made in the bone marrow and travel through the
blood as monocytes, only developing into macrophages once they have settled in the organs or lymph nodes.
◦They are much longer-lived and are key in initiating the immune response, since they do not destroy
pathogens completely, but instead cut them up for displaying.
Phagocytosis:
• Cells which are under attack, respond by releasing histamine chemicals, which attracts passing neutrophils to the site (chemotaxis)
• The neutrophils move towards the pathogens, which may be clustered and covered in antibodies (which may cause more stimulation),
and attaches to the pathogen.
• Once attached, the neutrophil’s cell membrane engulfs the pathogen by Endocytosis, forming a phagosome.
• Digestive enzymes produced in the lysosomes, fuse with the phagosome to form a phagolysosome, and the pathogen is destroyed.
• Due to their short life’s, they may die after this and form pus at the site of infections.
Macrophage and antigen presentation:
• The macrophage engulfs the antigen by phagocytosis, creating a phagosome due to Endocytosis.
• The macrophage breaks down the antigen into fragments in the lysosome, but not destroyed.
• A class II MHC protein binds to an antigen fragment and it presents it on the exterior of the macrophage to a T cell.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller olivertraherne. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £5.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52510 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now