summary of virusesviruses maybe considered either living or non-living. give one reason to support...
TRANSCRIPT
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Viruses
1
Summary of Viruses
Non-cellular
o But maybe classified as either living or non-living (need to justify your answer)
o Living: have DNA or RNA (plasmid)and a protein coat
o Non-Living: non-cellular and no nucleus or other cell
organelles. They are obligate parasites- must live and
reproduce inside a living host cell
Structure:
o Protein coat
o Either DNA or RNA (will have one or the other but
not both)
o Tip: just name protein and DNA/RNA when asked
what group of biomolecules viruses belong to
Shapes of viruses:
o Round
o Rod
o Complex
Feeding: Obligate Parasites
o Must live and reproduce inside a living host cell
Reproduction of Viruses
o Virus attaches itself to the surface of the host cell
o Virus pierces a hole in the membrane of the host cell
o DNA/RNA enters host cell
o Protein coat remains outside
o DNA/RNA replicates inside the host cell multiple times asexually
o Host cell bursts and releases the replicated viruses which then go on to repeat the
process again
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22(Monday 28th
-3rd
April)
Title: Viruses
2
Advantages and disadvantages of viruses
Advantages Disadvantages
Production of vaccines Cause of harmful diseases such as
Small pox
Chicken pox
HIV
Flu/cold
Measles
Polio
Leaf mosaic
Genetic engineering
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22(Monday 28th
-3rd
April)
Title: Viruses
3
Antibiotics and viruses
Antibiotics: are chemical that are made by micro organisms used to kill other micro
organisms. They are used in the treatment of bacterial and fungal infections which
stimulate the production of antibodies by the white blood cells to kill
antigens/pathogens/microorganism.
Misuse/Overuse: of antibiotics will cause the surviving bacteria (not all bacteria die
when treated with an antibiotic) to adapt through mutations and will not die when
treated when an antibiotic in the future. (survival of the fittest and natural
selection).This is known as antibiotic resistance. Tip: do not use the word resist when
giving a definition/explanation of antibiotic resistance
Why cannot antibiotics be given to treat a viral infection?
Antibiotics do not work on a viral infection. They only work on bacterial and fungal
infections.
With a foreign antigen/ pathogen of a bacterial nature, the bacteria sits on the surface
of the host cell; hence changing the shape of the host cell. When antibodies are
produced, they recognise the shape of the cell has changed and attack and destroy the
cell because it considers it to be “sick”
However, with regard a virus, it lives inside the host cell (not on the surface) so the
antibodies don’t consider the cell to be “sick” as the shape has not changes and do not
attack it. Hence allowing the virus to replicate. As a result it is of no effect using
antibiotics to treat a viral infection and the only result is giving bacteria present great
opportunity to mutate, leading to further antibiotic resistance
Vaccines
Introducing either a dead form or a small quantity of a living form of the virus that the
body’s natural defence system will be able to kill without any other form of help. Once
the body has destroyed a virus once, its memory (memory T cells) will remember this
and be able to destroy the virus again if it attacks in larger numbers
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22(Monday 28th
-3rd
April)
Title: Viruses
4
Revision Questions on Viruses 1. Viruses maybe considered either living or non-living. Give one reason to support either side
of the argument
2. Draw the structure of a virus
3. State how viruses reproduce
4. Outline the event of viral reproduction
5. What are the two main biochemical components of a virus structure
6. Name the main group of biomolecules contained within the structure of DNA
7. Name the two main groups of biomolecules that make up viruses
8. State two beneficial uses of viruses
9. State two harmful effects of viruses
10. What are antibiotics
11. What are antibiotics used to treat
12. Why cannot antibiotics be used to treat a viral infection
13. Explain a consequence of the misuse of antibiotics
14. What is a vaccine
15. Explain how a vaccine works
16. Is a vaccine a long or short term use in the treatment of viruses
17. Explain the term “obligate parasites”
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22(Monday 28th
-3rd
April)
Title: Viruses
5
Virus Exam Paper Questions
2015 Q3
2013 12(a)
(a) (i) A virus has been described as a piece of genetic material that has escaped from a cell.
Give one piece of evidence that supports this description.
_____________________________________________________________________________________
_______________________________________________________________________________
(ii) Viruses are examples of obligate parasites. Explain why this is the case.
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22(Monday 28th
-3rd
April)
Title: Viruses
6
_____________________________________________________________________________________
_______________________________________________________________________________
(iii) Give an example of how a virus might be beneficial to mankind.
_____________________________________________________________________________________
_______________________________________________________________________________
2010 Q6
(a) (i) What is part A made of ? ……………………………………………………………………..
(ii) What is part B made of ? ……………………………………………………………………..
(b) Briefly describe how viruses reproduce
….………………………………………………………………………………………………………
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
(c) During 2009 swine flu spread through the population of many countries. Younger people
were more at risk of becoming ill with swine flu than older people. Using your
knowledge of the immune system, suggest a reason for this.
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
2009 15 (c)
Write a note on (10 marks-3-5 valid pieces of information)
(v) The economic and medical importance of viruses. ______________________________________
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22(Monday 28th
-3rd
April)
Title: Viruses
7
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
______________________________________________________________________
2008 15 (b)
Just over fifty years ago the myxoma virus was brought to Ireland. The disease for which it is
responsible in rabbits, myxomatosis, quickly decimated the wild population. Now, however, the
disease is much less common and is responsible for far fewer deaths.
(i) Why do you think that the rabbit population was decimated when the myxoma virus was
first brought to Ireland?_______________________________________________________________
__________________________________________________________________________________
(ii) Suggest a reason why myxomatosis is no longer a major threat to the Irish rabbit population.
_____________________________________________________________________________________
_______________________________________________________________________________
(iii) The use of one species to control the population of another species is called biological
control. Suggest one advantage and one disadvantage of biological control.
Advantage ________________________________________________________________________
__________________________________________________________________________________
Disadvantage ______________________________________________________________________
__________________________________________________________________________________
(iv) The human immunodeficiency virus (HIV) is responsible for AIDS in the human
population. Would you expect a similar trend to that shown by myxomatosis as time
passes? Explain your answer.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_________________________________________________________________________
(v) Outline briefly how a virus replicates (reproduces).
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
________________________________________________________________________
2007 Q14 (b)
(i) Comment on the difficulty of defining viruses as living organisms.
__________________________________________________________________________________
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22(Monday 28th
-3rd
April)
Title: Viruses
8
(ii) What are the two main biochemical components of a virus particle?
__________________________________________________________________________________
(iii) Name two diseases caused by viruses.
1. ______________________________ 2._________________________________________
(iv) Give an example of a beneficial application of a virus.
__________________________________________________________________________________
(v) What is an antibiotic?
_____________________________________________________________________________________
_______________________________________________________________________________
(vi) Antibiotics should not be prescribed for a person suffering from a viral infection.
Suggest a reason for this.
_____________________________________________________________________________________
_____________________________________________________________________________________
____________________________________________________________________________
2005 15 (a)
(i) Comment briefly on the difficulty in classifying viruses as living organisms.
_________________________________________________________________________________
___________________________________________________________________________
(ii) Name two diseases of humans caused by viruses.
1._____________________________ 2.________________________________________________
(iii) Name two types of lymphocyte and state a role of each when viruses or other microorganisms
enter the blood.
1. ________________________ 2. ____________________________________________
(iv) “Immunity that results from vaccination is effectively the same as the immunity that
develops following an infection”. Do you agree with this statement? Explain your answer.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_________________________________________________________________________
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
1
Summary of Human Defence System
Antibody:
Antibiotic:
Immunity:
Active Immunity:
Passive Immunity:
Vaccine:
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
2
General Specific
1st and 2nd 3rd
Targets and protects the entire body from attack by foreign bodies
Targets specific antigens (foreign bodies), similarly to enzymes only one antibody will work
with on antigen
1st- skin and mucous (physical barrier) Spleen, lymph nodes, thymus
2nd –phagocytes (member of white blood cell family) wander through blood engulf foreign
body
Produce lymphocytes (B and T cells) and work in conjunction with phagocytes
Skin: produces oil and sweat which creates an acidic environment so bacteria will not grow
Mucous: traps microbes and helps create acidic environment within body so that bacteria die
Examples of General Line of Defence (within the blood)
1. Phagocytes: kidney shaped engulfer
2. Macrophages: larger and longer living phagocytes
3. Monocytes: are immature macrophages/phagocytes. They will eventually develop into
macrophages
4. Interferons: are defence proteins produced by the body when it detects it is “sick”
5. Inflammation: production of histamines as part as a protection mechanism
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
3
Specific in detail:
White Blood Cells subdivided into:
Lymphocytes (produce antibodies- B Cells only)
Phagocytes (engulf)
Lymphocytes
B Cells T Cells
Produces Antibodies-leads to resistance for life Do not produce antibodies directly
Produced in bone marrow of spleen and lymph Produced in bone marrow
Mature in bone marrow Mature in thymus
Production and activation triggered in response to antigens
Production and activation triggered in response to antigens
Form a complex around antigen which inactivates antigen
Different T cells work in different ways
Inactivated antigen is then engulfed by phagocytes
4 types: helper, killer, suppressor, memory
Helper T cells: help the B cells. When T cells detect antigens (before B cells), send a message
to the B cells (via interlucons) to produce antibodies
Killer T cells: secrete chemicals (aka perforin) directly into antigen causing antigen to burst
Suppressor T cells: when antigen has been destroyed, suppressor cells stop the production
of B cells and Killer T cells
Memory T cells: these cells remember the antigen that has just invaded such that if it reappears will stimulate the production of antibodies much faster next time around
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
4
Induced Immunity
Active Passive
Produce antibodies internally by living organism Obtain antibodies from another living organism or antibiotics
Long lasting Short lasting
2 types; natural and artificial 2 types; natural and artificial
Natural: body produces antibodies in response to be exposed to antigen
Natural: mother to baby via placenta. Whatever antibodies the mother has will be passed on to
baby
Artificial: vaccine a small quantity (living or dead) of antigens are administered which will cause the body to respond by producing antibodies
such that the body will be able to react v fast if the antigens appear again
Artificial: a course of prescribed antibiotics from doctor
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
5
What are antibodies?
Produced internally (by b-cells) by living organism
In response to antigen
What are antibiotics?
Protein in nature and chemicals
Produced by micro organisms
Administered to a living organism
To kill micro organisms
Immunity:
Recognition of a specific antigen by memory t cells to produce antibodies resulting in the ability
to resist infection
What is the issue with prescribing antibiotics for bacterial infections?
Antibiotics will stimulate the production of antibodies which
Inactivates the antigen by creating an Antigen/antibody complex and result in the destruction of
the antigen.
Antigens are reproducing and mutating at such a rapid rate, it will evolve to avoid being
destroyed again.
next time it attacks the immune system, the previously produced antibodies will not recognise
the evolved species of the antigen and the immunity process has to start all over again
Leads to antibiotic resistance. This means bacteria will not die in the presence of an antibiotic.
Results from:
o Misuse or overuse of antibioitcs
What is the issue of prescribing antibiotics for a viral infection?
This is a waste of time. A viral antigen is a parasite and only lives inside a host cell. Antibodies (produced
from taking antibiotics) will only work if the antigen is outside the host cell (or sitting on the surface of
the cell). Because the antigen is inside the host cell, it cannot be exposed to the antibiotic and will not
stimulate the production of the antigens to destroy the virus. Antibiotics will not kill the virus.
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
6
Vaccine: is a small dose of an antigen (non- disease causing or dead) which stimulates an antibody
response so that the body will be able to defend against antigen in the future.
Human Defence System Revision Questions
1. state two features of the body involved in the first line of defence
2. the 1st and 2nd line of defence are considered to be part of the ______ line of defence
3. Lymphocytes and phagocytes are types of what kind of blood cells
4. Lymphocytes are part of the specific line of defence. Explain the underlined term
5. Lymphocytes are made up of two types of cells. What are the names of these cells
6. where are B- cells produced and where do they mature
7. what is the role of B-cells
8. what is the correct term for a “foreign body” which enters the body
9. name the cells which stimulate the B-cells to produce antibodies
10. when the anti-bodies attach themselves to the antigen, what does this structure become known
as
11. what is perforin and what is its role in the body
12. name the cells that produce perforin
13. what is the role of suppressor T-cells
14. where are t-cells produced and where do they mature
15. what is the role of memory T-cells
16. state the difference between active and passive immunity
17. What is the role of phagocytes
18. Immunity obtained through vaccination is the same as immunity obtained through suffering
from the illness/virus is the same. justify this statement based on your knowledge of active
immunity
19. State the difference between anti-bodies and antibiotics
20. What are antibiotics
21. What group of biomolecules are antibiotics made from
22. What is the issue with giving antibiotics to treat a viral infection
23. Give an example of a passive form of immunity
24. Is passive immunity a long or short term form of immunity and give a reason for your answer
25. Why might a doctor prescribe an anti-biotic to treat a bacterial infection considering our body is
supposed to produce antibodies to fight a bacterial infection
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
7
Human Defence System Exam Paper Questions
2013-Q12 (c)
(i) Distinguish clearly between antibodies and antibiotics by writing a note about each.
Antibiotics
_____________________________________________________________________________________
_____________________________________________________________________________________
____________________________________________________________________________
Antibodies
_____________________________________________________________________________________
_____________________________________________________________________________________
____________________________________________________________________________
(ii) In relation to antibodies, distinguish between active and passive immunity.
Active Immunity
__________________________________________________________________________________
Passive Immunity
__________________________________________________________________________________
(iii) Using your knowledge of antibiotics and bacteria, suggest why a person is more likely to pick up an
infection in hospital than at home.
______________________________________________________________________________
______________________________________________________________________________
___________________________________________________________________
2012 Q15 (b)
(i) State two ways, other than colour, in which red blood cells differ from white blood cells.
1. ___________________________________________________________________________
2. ___________________________________________________________________________
(ii) Name a group of white blood cells, other than lymphocytes. _________________________________
(iii) Lymphocytes may be divided into B cells and T cells. B cells produce antibodies.
1. What is the role of antibodies in the body?
__________________________________________________________________________________
2. Name any three types of T cell.
1. ___________________ 2.____________________________ 3._____________________________
3. State a role of each of the T cell types that you named in part 2.
1. _________________________________________________________________________________
2.________________________________________________________________________________
3.________________________________________________________________________________
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
8
2009 Q15 (c)
Write notes on the following topics:
(i) The role of lymphocytes.
_________________________________________________________________________________
_________________________________________________________________________________
________________________________________________________________________
2007 Q14 (c)
(i) What is meant by the term immunity?
_____________________________________________________________________________________
_______________________________________________________________________________
(ii) Outline briefly the role of B lymphocytes in the human immune system.
_____________________________________________________________________________________
_____________________________________________________________________________________
____________________________________________________________________________
(iii) Distinguish between active and passive immunity.
Active _______________________________________________________________________________
Passive ______________________________________________________________________________
(iv) “Vaccination gives rise to active immunity”. Explain this statement.
_____________________________________________________________________________________
_______________________________________________________________________________
(v) In certain situations a person is given a specific antibody rather than being vaccinated.
1. Is this an example of active or passive immunity? __________________________________________
2. Under what circumstances might an antibody, rather than a vaccination, be given?
_________________________________________________________________________________
3. Comment on the duration of immunity that follows the administration of an antibody.
__________________________________________________________________________________
2005 Q15(a)
(iii) Name two types of lymphocyte and state a role of each when viruses or other microorganisms
enter the blood.
1. _______________________ 2. __________________________
Role of 1._____________________________________________________________________________
Role of 2. ____________________________________________________________________________
(iv) “Immunity that results from vaccination is effectively the same as the immunity that develops
following an infection”. Do you agree with this statement? Explain your answer.
_____________________________________________________________________________________
_____________________________________________________________________________________
____________________________________________
Subject: Leaving Certificate Biology Higher Level
Teacher: Ms. R. Doyle
Week: Week 22
Title: Human Defence
9
DEB 2013