Unit 10 Diseases and immunity Flashcards
Describe: a pathogen
a disease-causing
organism
a transmissible disease
examples of diseases not transmissible
a disease in which the pathogen can be passed from one host to another
e.g., cancer, diabetes
How is a pathogen transmitted?
2 ways
(a) by direct contact, including through blood & other body fluids e.g. semen
(b) indirectly, including from contaminated surfaces, food, animals and air [pathogen leaves host & is carried in some way to another, uninfected individual]
Ways of transmission, examples - FOUR
1) droplets in air - common cold, influenza
2) food or water - cholera, typhoid, dysentery
3) touching contaminated surfaces - athletes foot, common cold, sal.
4) insect bites - malaria, dengue fever
Describe the body defences
- Mechanical barrier:
define ; structures that make it difficult for pathogens to get past them and into the body
- Skin - covers almost all parts of your body to prevent infection from pathogens. If it is cut or grazed, it immediately begins to heal itself, often by forming a scab
- Mechanical barrier:
Hairs in the nose - make it difficult for pathogens to get past them further up the nose so they are not inhaled into the lungs
- Chemical barrier:
substances produced by the body cells that trap / kill pathogens before they can get further into the body & cause disease
- Mucus - made in various places in the body, pathogens get trapped in the mucus and can then be removed from the body (by coughing, blowing the nose, swallowing etc), prevents it reaching the respiratory system
- Chemical barrier:
+ Chemical barrier:
Stomach acid - contains hydrochloric acid which is strong enough to kill any pathogens that have been caught in mucus in the airways and then swallowed or have been consumed in food or water
Another: antibacterial tears
Cellular barrier?
Enhanced by…?
- White blood cells - work to prevent pathogens reaching areas of the body they can replicate in
Phagocytosis (engulfing & digesting pathogenic cells), &
antibody production by lymphocytes [which clump pathogenic cells together so they can’t move as easily (known as agglutination) and releasing chemicals that signal to other cells that they must be destroyed]
Enhanced by vaccination
Functions
Lymphocytes
Cells that tag foreign material, antigens, with antibodies, targeting the material for destruction
Phagocytes
Engulf foreign material, pathogen, through phagocytosis, digesting it by releasing digestive enzymes
Explain the importance of the following in controlling the spread of disease:
How is this done?
(a) a clean water supply
(b) hygienic food preparation
(c) good personal hygiene
(d) waste disposal
(e) sewage treatment
;; It stops pathogens from spreading!
Examples of hygienic food preparation
🔗 Keep food cold so bacteria & fungi produce more slowly
🔗 Prepare food hygienically to avoid contamination from pathogens by washing hands well with soap and cleaning work surfaces with products such as bleach to kill pathogens
🔗 Cook food well (long enough at high temp) to kill bacteria & fungi
🔗 Cover food to prevent flies landing on it before eating
🔗 Use separate chopping boards/utensils for cutting uncooked meat
🔗 Wash hands after using the bathroom before handling food
Examples of personal hygiene
🔗 Washing w/ soap removes substances which trap pathogens & pathogens themselves from skin
🔗 Use tissues to catch sneezes & coughs
🔗 Dispose of used tissue as soon as possible bc pathogens can still be alive
🔗 Wash hands after using the bathroom
Examples of waste disposal
🔗 Waste food = food source for flies that can act as vectors for transmissible diseases & should be disposed of in a sealed container
🔗 Rubbish bins should be covered & removed to the landfill for disposal/burning regularly
🔗 All rubbish should be stored before collection away from human habitation
Examples of sanitation
- clean water supply
🔗 Homes & public places should have plumbing & drains to safely remove faeces & waste which can carry pathogens
- sewage treatment
🔗 Raw sewage should be treated to remove solid waste and kill pathogens before being released into the environment
Do pathogens have a specific shape?
each pathogen has its own antigens, which have specific shapes
What are antigens?
Antigens are any structure that can be identified by an immune system (usually proteins)
Each organism has its own unique antigens. The shape is…
Organism = own antigens.
The shape of the antigen is COMPLEMENTARY to the binding groove on the antibody.
What happens next?
Once the ANTIBODY-ANTIGEN COMPLEX is formed, it marks the foreign material/antigens for destruction
by PHAGOCYTES
Why do our bodies need to create an antibody that fits the antigen?
specific antibodies have complementary shapes which fit specific antigens
Each pathogen has its own unique antigens.
Describe: antibodies
proteins that bind to antigens leading to direct destruction of pathogens
or marking of pathogens for destruction by phagocytes
Outline:
Process of vaccination ➡
(a) weakened pathogens or their [specific] antigens are put into the body
(b) the antigens stimulate an immune response by lymphocytes which produce antibodies
Complementary antibody binds to the antigen, tagging it for destruction by phagocytes
(c) memory cells are produced that give long-term immunity, allowing for the antibody to be produced rapidly in the future
Explain the role of vaccination in controlling the spread of diseases
🔗 Vaccinations give protection against specific diseases & boost the body’s defence against infection from pathogens without the need to be exposed to dangerous diseases that can lead to death
The level of protection in a population depends on the proportion of people vaccinated
The pathogen in vaccine cannot cause illness but can provoke an immune response
As memory cells have been produced due to vaccine, this immunity is long-lasting
Preventing the Spread of Disease:
Explain herd immunity & higher proportion of vaccinated people providing more protection.
If a large enough percentage of the population is vaccinated, it provides protection for the entire population because there are very few places for the pathogen to breed - it can only do so if it enters the body of an unvaccinated person = herd immunity
Spread of contagious disease is contained.
What happens otherwise?
If the number of people vaccinated against a specific disease drops in a population, it leaves the rest of the population at risk of mass infection
bc more likely to come across people who are infected and contagious, increases:
🔗 the number of infections
🔗 the number of people who could die from a specific infectious disease
What does herd immunity do?
prevents epidemics and pandemics from occurring in populations = the reason that many vaccinations are given to children
Is the goal of a vaccination programme always just to control the disease?
Example?
No; sometimes, its aim is to eradicate certain dangerous diseases
Like smallpox in 1980 [by WHO since 1950s]
Describe: active immunity
defence against a pathogen by antibody production in the body
How is active immunity gained?
What ways? With what cells?
after an infection by a pathogen
or by vaccination
Memory cells are produced.
Describe: Passive immunity
Example?
passive immunity: a [fast-acting,] short-term
defence against a pathogen by antibodies acquired from another individual,
including mother to infant, across the placenta [through blood] and in breast milk
Explain the importance of breast-feeding for the
development of passive immunity in infants
Importance for newborns:
get all antibodies from the mother; it helps the very young to fight off infections until they are older and stronger and their immune system is more responsive
Are memory cells produced in passive immunity?
memory cells are NOT produced in passive immunity
Describe: cholera
a disease caused by a
bacterium which is transmitted in contaminated water
What does the cholera bacterium do?
Explain
The cholera bacterium produces a toxin
that causes secretion of chloride ions into the small intestine,
causing osmotic movement
of water into the gut,
causing diarrhoea, dehydration and loss of ions from the blood
Why do we always feel more sick from first infections?
It takes our body many days to create antibodies that will fit an antigen if we have never been exposed to it [& if any, it’s slow]
The second time our body is exposed to it, it recognises the antigen much faster & can start producing antibodies
[First infection w/ new pathogen: more risky, symptom causing]
Explain how cholera causes diarrhoea (4)
cholera releases toxin
toxin causes more chloride released into small intestine
lowering water potential in lumen
osmosis into the lumen
diarrhoea is loss of watery faeces
can lead to death due to loss of salts and dehydration
Describe how diarrhoea is treated (2)
oral rehydration therapy
drink mixture of sugar and salt
replace lost water
(b) Explain what would happen if a kidney from a person with blood group A was
transferred into the body of a person with blood group O.
kidney would be rejected ;
(lymphocytes produce anti-A) antibodies ;
(antibodies) attach to blood vessels ;
Describe how antibodies provide protection from diseases caused by viruses and
bacteria.
attach to virus / bacteria / antigens ;
prevent movement around the body and entry into cells ;
stop division ;
neutralise, toxins ;
clumping bacteria tgt to help phagocytes engulf virus / bacteria ;
Explain what is meant by the term antibiotic. [2]
drug / chemical / substance ;
produced by microorganisms ;
that kills / stops, growth of, bacteria
Explain why
(i) only a few bacteria grew in dish B compared with dish A, [1]
(ii) more bacteria grew in C than in B. [1]
i) (most) were killed by the antibiotic
ii) (only) resistant bacteria in C
Fig. 4.1 shows the effect of an antibiotic on a species of disease-causing bacterium.
Suggest why antibiotics should not be used too often.
resistant bacteria survive / not killed ;
eventually, all / many, become resistant ;
antibiotic no longer effective ;
Explain the possible effect of the X-rays on the bacteria. [3]
X-rays caused mutations ;
change in DNA ;
ref to, gene / allele ;
mutation causes antibiotic resistance
State two ways in which the structure of a bacterium differs from the structure of a
virus.
cell wall
flagellum
Human Immunodeficiency Virus (HIV) infects cells of the immune system.
Describe the effects of HIV on the immune system. [4]
Outline how the human immunodeficiency virus (HIV) affects the immune system. [3]
HIV infects lymphocytes ;
[[T helper (lymphocytes / cells) ;]]
fewer antibodies produced ;
infected cells not killed (by immune system) ;
phagocytes less effective ;
increased susceptibility to / longer recovery time for, (infectious)
diseases
///// ref. to invasion of lymphocytes ;
so no production of antibodies ;
ref. to decrease in body’s ability to fight infection ;
Explain why it is important for newborn babies to have antibodies. [3]
📍 any 3 from:
provides (passive) immunity;
protects against illness and pathogens ;
immune system of babies not yet developed;
bc antibodies stop pathogens entering cells ;
Some mothers bottle-feed their newborn babies with formula milk rather than breast-feed.
Describe four advantages of breast-feeding, other than providing antibodies. [4]
bonding/AW, with mother;
it’s free/‘cheap’;
sterile/no risk of infection;
body temperature;
no preparation/easily available;
