Immune System - Chp 37 +38

Pathogen

a micro-organsim that causes disease

Immunity

the ability to resisit disease

How do microbes enter the body?

through openings such as the mouth or woundsa

What is the general defence system?

acts as a barrier to all pathogens attempting to gain entry into the human body

What is the specific defence system?

attack on a particular pathogen that have entered the body

also called the immune repsonse

Name some ways the general defence system prevents disease:

• mucus catches pathogens + lysozyme breaks down the cell wall of pathogens in the nose

• mucus catches pathogens + cilia helps remove pathogens from windpipe in the trachea

• acids kills bacteria in the stomach

• platelets clot wound preventing microbes enter

• phagocytic white blood cells engulf bacteria

• skin acts as a physical barrier

• inflammatory response

• friendly bacteria compete with harmful bacteria and control their populations

Antigen

a foreign molecules that stimulates the production of antibodies

Antibodies

proteins produced by white blood cells (lymphocytes) in response to an antigen

How do antibodies protect the body against microbes?

antibodies bind to the wall of a microbe and help destroy it

Where are lymphocytes produced?

red blood marrow

later mature in the lymphatic system

What happens when a foreign antigen is found in the body?

• triggers the immune response

• when it meets the correct antigen receptor clonal expansion occurs

• white blood cells produce antibodies which coat the microbes, and the cell wall of the pathogen becomes more permeable and bursts

• phagocytes produced engulf invaders marked with antibodies

• memory cells remembers how to fight the pathogen

Induced immunity

when the body contains (or has the ability to produce) specific antibodies against particular antigens

What are the 2 types of immunity?

• active immunity

• passive immunity

Active immunity

involves the production of a person’s own antibodies in response to antigens that enter the body

Passive immunity

when a person receives antibodies that have been made by another organism - eg breast feeding

What happens when a second dose of the antigen enters the body?

• the memory cells now know how to produce the correct antibody

What type of immunity is a vaccine?

artificially generated induced active immunity

Vaccine

a non-disease causing dose of a pathogen, which triggers the production of antibodies

What is immunisation?

injection of already made antibodies, short term solution as the body has not learned how to produce the suitable antibodies

What are the 2 types of lymphocytes?

• B lymphocytes/B cells

• T lymphocytes/T cells

Where are B lymphocytes made + mature?

• red bone marrow

• red bone marrow

What are the 2 types of B cells?

• plasma b cells

• memory b cells

Where are T lymphocytes made + mature?

• red bone marrow

• thymus gland

What is the function of B lymphocytes?

• each plasma b cell its own specific antibody attached to its surface

• attachs to an antigen when they come into contact

• the B cell replicates and releases lots of antibodies

• some these B cells are memory cells

What are the 4 types of T cells?

• Helper T cells

• Killer T cells/cytotoxic cells

• Suppressor T cells

• Memory T cells

What is the function of T cells?

• they do not produce antibodies

• helper t cells activate the immune response when they recognise an antigen, stimulate replication of b cells, killer t cells and slowly stimulat suppressor cells

• killer t cells destroy the pathogen

• suppressor t cells stops the immune response when it is no longer needed

• memory t cells remember how to activate the immune response if the antigen enters again

What protein is released by t cells + what does it do?

• perforin

• it forms pores in the membrane of the pathogenic cell, allowing water and ions to flow into it, causing it to swell and burst

Are Viruses living or dead?

they are on the boarder between living and non-living as they contain characteristics of both

Give the living and non-living characteristics of viruses?

Living

• contains genetic material

• can replicate inside a living cell

• contain a protein coat

Non-living

• non-cellular

• can’t reproduce by themselves

• only have one type of nucleic acid: RNA or DNA not both

What are the 3 possible shapes of viruses?

• round

• rod

• complex

Describe the structure of a virus?

• have an outer protein coat called a capsid

• some viruses have an outer layer complex for extra protection

• inside there is a single nucleic acid carrying genes for the formation of new viruses

• they contain no ribosomes, mitochondira or cytoplasmic organelles

What kind of parasites are viruses?

obligate parasites they need the organelles and enzymes of the host to carry out their reaction, and cannot do so on their own

Why are antibiotics ineffective for viruses?

• there are no organelles/cell machinery for the antibiotics to damage in the virus

Describe + draw the process of replication of a bacteriophage:

1. Attachment - viruses attach to the host cell wall or membrane, proteins on the virus match up with reception sites specific to the host

2. Entry - virus forms a hole and pushes its nucleic acid through, the protein coat stays outside if the host is a bacterium, and enters if the host is an animal cell

3. Synthesis - host nucleic acid is make inactive, viral nucleic acid uses hosts organelles to produce new viral nucleic acid and proteins

4. Assembly - new viruses are made inside the host cell

5. Release - the host cell bursts to release new viruses and the cell is destroyed in the process

What is a retrovirus?

• contains RNA + enzyme called reverse transcriptase which converts RNA to DNA

• they are very difficult to cure because they become part of the bodies makeup

Name a harmful effect of viruses to humans, plants and animals?

humans - rabies, meningitis

plants - potato mosaic disease, tomato mosaic disease

animals - rabies, cowpox

Who are particularly vulnerable to viruses?

• unvaccinated people

• people with a compromised immune system

  • babies

Give a beneficial effect of viruses?

• can be used as a vector in genetic engineering

• can be used to control antibiotic resistant bacterial infections

How are viruses treated?

• controlled by the body's general and specific defence systems

• cannot be treated with antibiotics

• can be protected using vaccinations and immunisation

• interferons

• some new drugs

What are interferons?

a range of substances produced by viruses to protect healthy cells and can be made artificially + help treat viral infections