summary of virusesviruses maybe considered either living or non-living. give one reason to support...

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



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




-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




-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”




-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.




-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. ______________________________________




-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.

__________________________________________________________________________________




-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.

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_________________________________________________________________________



Week: Week 22

Title: Human Defence

1

Summary of Human Defence System

Antibody:

Antibiotic:

Immunity:

Active Immunity:

Passive Immunity:

Vaccine:



Week: Week 22


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



Week: Week 22


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



Week: Week 22


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



Week: Week 22


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.



Week: Week 22


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



Week: Week 22


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.________________________________________________________________________________



Week: Week 22


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.

_____________________________________________________________________________________

_____________________________________________________________________________________

____________________________________________



Week: Week 22


9

DEB 2013

summary of virusesviruses maybe considered either living or non-living. give one reason to support...

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