10.1 Disease and Immunity

Question 1

what is a pathogen

Answer 1

a disease-causing organism

Question 2

what is a transmissible disease

Answer 2

a disease in which a pathogen can be passed from one host to another

Question 3

how can a pathogen be transmitted

Answer 3

-by direct contact: sexual contact, contact with body lesions, direct body fluid from mother to child
-by indirect contact: contaminated surfaces or objects, air, contaminated food and water, vectors

Question 4

how does the body defend itself with skin

Answer 4

the skin acts as a physical barrier to prevent pathogens from entering pathogens from entering our body. if the skin gets wounded, it immediately started healing itself , forming a scab

Question 5

how does the body defend itself with hairs in the nose

Answer 5

nose hairs act as a natural filter to prevent the entry of pathogens into the lungs

Question 6

how does the body defend itself with mucus

Answer 6

it traps pathogens before they can enter the lungs

Question 7

how does the body defend itself with stomach acid

Answer 7

stomach acid contains hydrochloric acid which is strong enough to kill pathogens, that may have been consumed with food or drink

Question 8

how does the body defend itself with white blood cells

Answer 8

it defends the body against infections. they fight off infections by carrying out phagocytosis and antibody production

Question 9

how to control spread of disease

Answer 9

-clean water supply
-hygienic food preparation
-good personal hygiene
-waste disposal
-sewage treatment

Question 10

importance of clean water supply

Answer 10

contaminated water and poor sanitation are linked to transmission of diseases such as cholera, diarrhoea, dysentery and typhoid.

Question 11

importance of hygienic food preparation

Answer 11

washing hands before handling food and making sure the surfaces and utensils are clean before cooking food thoroughly at high temperatures to help kill pathogens. covering food ensures that flies cannot land on it

Question 12

importance of good personal hygiene

Answer 12

washing hands with soap, covering mouth when sneezing and washing hands after going to the toilet helps avoid the spread of disease

Question 13

importance of waste disposal

Answer 13

when rubbish is exposed, it attracts flies which may carry disease so rubbish must be covered and disposed of in a proper manner

Question 14

importance of sewage treatment

Answer 14

homes must have a proper sewage disposal methods to remove faeces from toilets safely. sewage should be treated to kill pathogens before being disposed of in the environment

Question 15

what is active immunity

Answer 15

a defence against a pathogen by antibody production in the body

Question 16

how to gain active immunity

Answer 16

-body produces antibodies after a person recovers from infection or after exposure
-body produces antibodies through vaccination using weakened, dead or non-virulent pathogens

Question 17

what is a pathogen

Answer 17

a disease-causing organism

Question 18

what is an antigen

Answer 18

each pathogen has a uniquely shaped ‘marker’ on the surface of their membranes called ‘antigens’. antigens are very specific in shape.

Question 19

what are antibodies

Answer 19

lymphocytes produce proteins called antibodies which are a complementary shape to the antigens on the surface of pathogens

Question 20

what do antibodies do

Answer 20

antibodies are proteins that bind to antigens leading to:
-direct destruction of pathogens of pathogens (lysis works by attaching to the walls of antigen to cause cell wall to be broken down)
-marking of pathogens for destruction by phagocytes (antibodies stick to antigens causing them to stop moving or dividing)

Question 21

shapes of antigens and antibodies

Answer 21

each antibody is specific to only one type of antigen as each binding site (antigen receptor) of the antibody has a particular shape that fits the specific antigen

Question 22

how do antibodies destroy the pathogen

Answer 22

-they attach themselves to the antigen and cause them to clump together
-this makes it difficult for the pathogen to move
-then they can be killed directly or
-marked for destruction by phagocytes where the antibody sends a chemical signal for phagocytes to come and engulf the pathogen

Question 23

what are memory cells

Answer 23

-lymphocytes that have made antibodies for a particular pathogen also produces memory cells
-these are cells that remain in the blood even after the infection is over
-they are able to quickly produce the original antibodies if they were to come across the same pathogen again
-therefore memory cells give long-term immunity

Question 24

what is vaccination

Answer 24

a way of protecting the body against harmful diseases, before we come into contact with them

Question 25

process of vaccination

Answer 25

-harmless forms of the pathogen or their antigens are injected into the individual’s body -the antigens stimulate an immune response by lymphocytes which produce antibodies without inducing the disease -memory cells are produced that give long-term immunity to stimulate the body’s immune response against diseases

Question 26

role of vaccination

Answer 26

-the effectiveness of a vaccine in a population depends on the proportion of people vaccinated -when majority of a population is vaccinated against a pathogen, it breaks the pathogen’s chain of infection -this means that the pathogen will have fewer places to breed and therefore it is unable to pass from person to person -hence, vaccination prevents the spread of disease. this is known as herd immunity

Question 27

what is passive immunity

Answer 27

a short-term defence against a pathogen by antibodies acquired from another individual -eg: from across the placenta and in breast milk

Question 28

importance of passive immunity

Answer 28

-breast-feeding is important for the development of passive immunity in infants -antibodies pass from mother to infant through breast milk -this is important because a baby’s immune system is not well developed and so the mother’s antibodies can protect it against any diseases to which she is immune to, for the first few months of its life until their immune system is stronger -passive immunity is a fast-acting, short term defence -memory cells are not produced in passive immunity

Question 29

what is cholera

Answer 29

a disease caused by a bacterium which is transmitted in contaminated water. it causes diarrhoea which is the loss of watery faeces from the anus

Question 30

how does cholera cause diarrhoea

Answer 30

-the cholera bacteria attach to the wall of the small intestine -they produce a toxin -the toxin causes the cells lining the intestine to secrete chloride ions into the small intestine -this causes the water potential inside the intestine to reduce -the water potential in the cells lining the intestine is higher, therefore water moves from the cells to inside the small intestine by osmosis -large quantities of water are lost from the body in watery faeces or diarrhoea -this leads to dehydration and loss of ions from blood

Question 31

how to treat cholera

Answer 31

-diarrhoea can be effectively treated by oral rehydration solution which is a drink with a small amount of salt and glucose dissolved in it