Treating, curing and preventing disease

Question 1

what are the physical barriers of the body? (3)
-identify which ones are first and second line defences

Answer 1

skin (1st)
cilia (1st)
mucus (1st)

Question 2

how does the ‘skin’ act as a physical barrier? (2)

Answer 2

prevents pathogens from entering
forms scabs if cut which prevent infection

Question 3

how does mucus act as a physical barrier?

Answer 3

traps pathogens before they can enter the lungs

Question 4

how do ciliated cells act as a physical barrier?

Answer 4

move mucus and pathogens upwards towards the throat where it is swallowed into your stomach.

Question 5

what are the chemical barriers of the body? (4)
-identify which ones are first and second line defences

Answer 5

stomach acid (1st)
lysozymes (1st)

lymphocytes (2nd)
phagocytes (2nd)

Question 6

how does stomach acid act as a chemical barrier?

Answer 6

strong hydrochloric acid which kills pathogens

Question 7

how do lysozymes act as chemical barries?

Answer 7

contain enzymes that destroy bacterial cells by breaking down their cell walls

Question 8

what are phagocytes?
how do phagocytes act as chemical barriers/?

Answer 8

non specific white blood cells which engulf pathogens

phagocytes’ membrane surrounds the pathogen and the enzymes found inside the cell, then break down the pathogen in order to destroy

Question 9

what is the only specific form of defence?

Answer 9

lymphocytes

Question 10

what are lymphocytes and what do they do?

Answer 10

specific white blood cells which have antibodies on their surface that attach to antigens and destroys its accompanying pathogen

Question 11

what can a memory lymphocyte do?
and what will it result in if a second exposure to an antigen occurs?

Answer 11

-‘remember’ the antigens from an infection by a previous pathogen.
-Antibodies will be produced much quicker, resulting in a much faster immune response.

Question 12

describe a graph of ‘antibody concentration’ and ‘days after infection’ (2)

Answer 12

During the primary infection the antibodies slowly increase, peak and then gradually decrease.
A second exposure to the same pathogen causes the white blood cells to respond quickly in order to produce lots of the relevant antibodies, which prevents infection.

Question 13

what can lymphocytes do in response to the toxins that are produced by pathogens?

Answer 13

produce antitoxins to neutralise these toxins.

Question 14

describe the process of immunisation: (4)
-what is the last step of this process called?

Answer 14

-inactive form of the disease causing pathogen is injected into the body
-white blood cells (lymphocytes) release antibodies which are complementary to the antigen
-antibodies attach and clump pathogens together
-pathogens are engulfed by phagocytes

-phagocytosis

Question 15

what is meant by herd immunity? (2)

Answer 15

-majority of the population are immunised against serious diseases,
-people who have not been immunised will still be protected because they are less likely to come into contact with an infected person

Question 16

describe herd immunity when no one is vaccinated, some of the population is vaccinated, and when all of the population is vaccinated: (3)

Answer 16

-no one is vaccinated = contagious disease spreads throughout the population
-some of the population is vaccination = contagious disease spreads to some of the population
-most of the population is vaccinated = spread of contagious disease is contained

Question 17

what happens If the number of people immunised against a specific disease drops in a population?

-what does this lead to an increase of, and how could this affect people?

Answer 17

it leaves the rest of the population at risk of mass infection, as they are more likely to come across people who are infected and contagious

increases the number of infections, as well as the number of people who could die from a specific infectious disease.

Question 18

what are the (rather obvious) advantages of immunisation? (3)

Answer 18

-when fewer people are immunised, the number of cases of the disease increases
-the chance of falling seriously ill or dying from the disease may be far greater than the chance of experiencing a serious side-effect
-using a vaccine may be much cheaper than treating a very ill person

Question 19

how do antibiotics work?

Answer 19

damage the bacterial cells by inhibiting their cellular processes, but do not damage the host cells

Question 20

what do we need to treat bacterial infections if different bacteria cause different diseases?

Answer 20

a range of different antibiotics is needed for the treatment of the whole range of bacterial diseases.

Question 21

why can viral diseases NOT be treated by antibiotics?

Answer 21

as they reproduce inside the host cells

Question 22

why is it difficult to develop anti-viral drugs?

Answer 22

as they might damage the host cell whist killing the virus

Question 23

why can we not depend on anti-viral drugs for the treatment of viral diseases? (2)

Answer 23

-they only slow down viral development of the virus
-viruses change their antigens quickly which means new drugs have to be generated regularly.

Question 24

describe the process of a virus infecting a cell: (6)

Answer 24

1- virus enters cells
2- substances in the cell begin to strip virus’ outer coat of protein
3- nucleic acid in the centre of the virus is released
4- nucleic acid gets into the cell’s chemical manufacturing system
5- cell ignore its own chemical needs and switches to making new viruses
6- cell is destroyed in process and viruses are released to infect other cells

Question 25

what is the future of antibiotics like?

Answer 25

development of new antibiotics has slowed down as it becomes difficult to find new versions to tackle different bacterial infections

Question 26

how quickly can bacteria replicate?

Answer 26

approximately every 20 minutes by binary fission

Question 27

what does the level of replication will depend on for bacteria?

Answer 27

availability of nutrients and other suitable conditions such as temperature.

Question 28

what are the two ways of culturing bacteria?

Answer 28

nutrient broth solution in a culture vial
colonies on an agar plate

Question 29

what is a nutrient broth solution?
-what must it contain?

Answer 29

a liquid or gel that provides all the nutrients needed for bacteria to grow successfully.
-carbohydrates for energy, nitrogen for protein synthesis, plus other minerals.

Question 30

how are agar plates created?

Answer 30

pouring hot molten agar into sterile Petri dishes, which are then allowed to set

Question 31

what needs to happen to Nutrient broth solutions, culture vials, agar solution and Petri dishes before they can culture bacteria?

-what are these and what do they use?

Answer 31

sterilisation to stop any other microorganisms growing on or in them.

-autoclave. strong containers which use high temperatures and pressures to kill microorganisms.

Question 32

why is it important to ensure that the bacteria culture is uncontaminated? (2)

Answer 32

-contaminating bacteria would compete for nutrients in the broth or agar.
-bacteria could be harmful (such as pathogens) and would complicate the results of experiments when testing the efficiency of antibiotics or other anti-microbial compounds.

Question 33

what do aseptic techniques include? (3)

Answer 33

-killing all microorganisms on equipment such as inoculating loops by flaming equipment in a Bunsen burner or dipping them in alcohol
-keeping all lids on equipment when not in use
-wearing gloves, eye goggles, lab coats or other protective equipment

Question 34

equation for ‘Bacteria at the end of the growth period’ :

Answer 34

Bacteria at the end of the growth period = bacteria at the beginning × 2^number of divisions of the growth period