Viruses Flashcards
What are viruses made of?
Viruses are composed of a core of nucleic acid surrounded by a proton donor
Where do viruses grow?
Because they are not made of cells, they do not have the cell machinery for their own metabolism, so they only grow in living tissue.
What can viruses be considered outside of living cells?
Where they exist outside of living cells, they may be considered non-living chemicals, since they do not display any of the characteristics of life.
What can viruses do once inside a living cell?
Once they are inside a living cell they can replicate with the help of the host cell and so are clearly alive.
Do viruses have features of living or non-living material?
So, viruses have features of both living and non-living material.
What are viruses called because since they can only multiply inside living cells?
Since they can only multiply inside living cells, they are called obligate parasites
What can viruses do as parasites?
As parasites they cause many diseases in humans, domestic animals and crop plants.
What are viruses called because since they can only multiply inside living cells?
Since they can only multiply inside living cells, they are called obligate parasites
What does being obligate parasites mean in terms of agar?
This means that they cannot be grown on agar like bacteria or fungi
What does being obligate parasites mean to do with antibiotics?
It is also the reason why antibiotics do not work against them, as there is no cell machinery for the antibiotic to damage.
What is one way of recognising and classifying different viruses?
Different kinds of viruses have different shapes and this is one way of recognising and classifying them.
How can we only see viruses because they are so small?
Because viruses are so small, we can only see them with an electron microscope.
How many viruses could fit side by side on the tip of your pen?
10,000 viruses could fit side by side on the tip of your pen.
Draw virus replication.
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What are the disadvantages of viruses?
Diseases of humans, plants and animals
What are common human diseases?
Measles, Mumps, Rubella, Cold, Warts
How do plant diseases gain entry to a plant?
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What are examples of plant diseases?
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What are examples of animal diseases?
Foot and mouth, SARS (Sudden Acute Respiratory Syndrome) and Rabies
What are the advantages of viruses?
Genetic engineering, where they are used inject a gene into target cells.
Mosaic patterns give new variety to garden plants.
What is immunity?
Immunity is the ability of an organism to resist infection.
What are pathogens?
Pathogens are micro-organisms [microbes] that cause disease.
What is the human body designed to do in terms of foreign cells or invaders?
The human body is designed to protect itself from foreign cells or invaders, and we have two lines of defence - general and specific.
What does our general defence system consist of?
Our general defence system consists of skin, mucous membranes, platelets and white blood cells.
What is the barrier to entry?
Barrier to entry: the skin and mucous membrane lining of the respiratory, digestive and reproductive tract.
How does the skin act as a barrier to entry?
The skin, acting as a structural barrier, secretes chemicals from the sebaceous glands that harm or kill bacteria.
How does the respiratory and digestive tracts act as barriers to entry?
The respiratory and digestive tracts as well as other organs of the body secrete mucus and/or further chemicals that may remove foreign particles.
What does our specific defence system involve?
An antigen-antibody response, involving specialised white blood cells, called lymphocytes and monocytes [macrophages].
What is the function of lymphocytes?
Lymphocytes - stored in lymphatic system (spleen, lymph nodes, tonsils, adenoids and thymus gland), have large nucleus and make antibodies. (25% of white cells)
What is the function of monocytes?
Monocytes - digest bacteria, have kidney shaped nucleus and lilve for 6-9 days (5% of white cells)
What are monocytes?
Phagocytic white blood cells - also called macrophages. These engulf bacteria and viruses upon contact.
What do other types of monocytes do?
Others secrete chemicals that stimulate general defence and cause fever to destroy microbes at high temperatures
What makes up the specific defence system?
Organs specific to the immune system: the spleen, thymus and lymph nodes.
What do lymph and blood vessels contain?
Lymph and blood vessels contain cells called lymphocytes and monocytes - both are produced in the bone marrow and they respond to antigens
What are antigens?
Antigens are any foreign molecules capable of triggering and antibody response.
What is an antibody?
An antibody is a protein, made by a lymphocyte, which sticks to an antigen and marks it for destruction by other defence cells [monocytes].
Where may antigens be found?
Antigens may be found in bacterial cell walls, viral coats, foreign cells or produced in cancerous cells.
What does the lymphatic system consist of?
Lymphatic vessels that return excess tissue fluid to the blood circulatory system.
Lymph tissue [lymph nodes] that assist in fighting infection in the body.
What are the three functions of the lymphatic system?
Drainage, Transport and Defence
What does drainage do in the lymphatic system?
Drainage - returns leaked fluid to the blood.
What does transport do in the lymphatic system?
Transport - lipids (fats) are absorbed from the small intestine and carried to the skin or other organs for storage.
What does defence do in the lymphatic system?
Defence - filters blood. Germs that invade the body will enter the blood or tissue fluid and eventually get filtered through the lymph and lymph nodes, where white cells attack and destroy them. Swollen glands are lymph nodes that are actively fighting germs.
What is induced immunity? What types are there?
Induced immunity is immunity due to antibody production. There are two types - active and passive.
What is active immunity?
Active immunity develops after an infection or after vaccination (immunisation). It provides long lasting protection.
What is passive immunity?
Passive immunity involves antibodies that we get from elsewhere, e.g. in the womb or from mother’s milk.
What is a vaccine?
A vaccine is a dead microbe that is injected into the body and triggers antibodies but does not cause the disease.
If you have been vaccinated and the real germ ever attacks you, what happens? What are you then said to be?
If the real germ ever attacks you, the antibodies are present to remove it before it can cause the disease and do damage. You are then said to be immune to that disease.
What does passive immunity involve?
Antibodies that we get from elsewhere.
What does passive immunity provide and why?
Since these are not produced by the body’s own cells, it provides only short-lived protection.
Where are lymphocytes made?
Lymphocytes are made in the bone marrow and then move to the lymph nodes before or soon after birth.
What do monocytes do?
Monocytes engulf an invader, digest it and then display some of the invader’s antigen on its own cell membrane.
What do body cells do with viruses that get into them?
Engulf an invader, digest it and then display some of the invader’s antigen on its own cell membrane.
What are lymphocytes continually doing?
Inspecting monocytes and body cells for evidence of “foreign” antigen.
What happens when “foreign” antigen are detected?
When detected, the lymphocytes are stimulated to divide into huge numbers of cells.
Draw a diagram of the immune response.
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What are the two main types of lymphocytes?
B cells and T cells
Where to B cells mature and then move to?
Mature in bone marrow and move to lymph nodes
What can B cells do?
Recognise antigens
What are the two types of B cells?
Plasma B cells and Memory B cells
What do plasma B cells do?
Make antibodies
What do memory B cells do?
Live on after infection and prevent re-infection
Where do T cells mature?
In thymus gland
What are the four types of T cells?
Helper T cells, Killer T cells, Suppressor T cells and Memory T cells
What do Helper T cells do?
Stimulate B and killer T cells
What do Killer T cells do?
Destroy abnormal body cells
What do Suppressor T cells do?
Turn off immune responses
What do Memory T cells do?
If re-infection occurs they stimulate memory B cells and killer T cells.
How many types of lymphocytes are there?
2
How many types of B cells are there?
2
How many types of T cells are there?
4
What do T lymphocytes do?
They attack cells that have invading antigen on their cell membrane.
Do T cells produce antibodies?
T cells do not produce antibodies.
What do helper T cells do?
Recognise antigens, enlarge, and secrete chemicals such as interferon that stimulate production of B cells.
What do killer T cells do?
Attack cells containing a foreign antigen.
Secrete a chemical called perforin that perforates the membranes of cells.
Destroy virus-infected cells, tumour cells and transplant tissue.
What do suppressor T cells do?
stop the immune response after the pathogen has been destroyed.
What do memory T cells do?
Memory cells that form during the first response to an antigen do not engage in that first battle. They circulate in the body for years, and can intercept antigens far quicker. So they memorize the immunity, even for life.
Where do B lymphocytes mature?
B lymphocytes mature in the bone, before moving to the lymph nodes, where they acquire their receptor molecules.
What do B lymphocytes do?
B lymphocytes attack antigens in the blood or body fluids, by producing antibodies that surround them.
What happens when a B cell encounters matching antigen?
When a B cell encounters matching antigen, they divide into plasma and memory cells.
What do plasma cells produced by B cells do?
The plasma cells produce antibody molecules, that bind to pathogens and toxins that are circulating in tissues or body fluids, and mark them for destruction by monocytes.
How many types of antibody does each B cell produce?
Each B cell produces just one type of antibody.
When do memory B and T cells form? Do they engage in the first battle?
Memory B and T cells that form during the first response to an antigen, do not engage in that first battle.
What do Memory B and T cells do?
They circulate in the body for years, and can intercept antigens far quicker.
Why do memory B and T cells circulate in the body and can intercept antigens quicker?
This is how we achieve immunity against many diseases - either by getting the disease once or by preventing them using vaccines.
Draw a diagram of lymphocytes and antibody production.
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