C3.2 - medical defences against diseases (3s)

Question 1

what is stimulated by antigens on erythrocytes?

Answer 1

the antigens on erythrocytes of a blood donor may stimulate antibody production in the recipient

Question 2

what occurs when an incompatible blood transfusion occurs?

Answer 2

following incompatible blood transfusions, antibodies cause clumping of the blood cells in a process called agglutination

Question 3

what determines our blood groups?

Answer 3

the presence of the absence of three antigens proteins determines our blood groups

Question 4

what criterion must be met in order for a blood transfusion to be successful?

Answer 4

for a blood transfusion to be successful, a person must not receive a protein that they do not already have
- during blood transfusions, red blood cells are placed into the recipients body
- if complementary shaped antibodies are present, no agglutination occurs

Question 5

what does ABO blood groups involve?

Answer 5

• a person with group A blood has A antigens
• a person with group B blood has B antigens
• a person with blood group AB has both A and B antigens on their erythrocytes
• a person with blood group O has neither A nor B antigens on their erythrocytes

Question 6

what blood group does Rhesus (RH) blood group involve?

Answer 6

• a person with a positive blood group has Rh antigens on their erythrocytes
• a person with a negative blood group does not have Rh antigens on their erythrocytes

Question 7

why is AB known as a universal recipient?

Answer 7

AB is a universal recipient as it can receive blood from any blood group as they have all three proteins in their blood so will not agglutinate

Question 8

why is O known as a universal donor?

Answer 8

O is a universal donor as their blood doesn’t contain any of the three proteins that could trigger agglutination

Question 9

why can a person with blood group A- not donate to someone with blood group B-?

Answer 9

a person with A- cannot donate to someone with B- as the recipient does not have the B antigen on their cells, so will agglutinate

Question 10

why can a person with blood group A- not donate to someone with blood group A+?

Answer 10

a person with A- cannot donate to someone with A+ as the recipient does not have the Rh antigen on their cells, so agglutination could occur

Question 11

what is HIV?

Answer 11

HIV (human immunodeficiency virus) is a type of retrovirus

Question 12

how can HIV be transmitted?

Answer 12

• bodily fluids
• blood transfusions
• from mother to fetus
• from mother to fetus
• breastfeeding or saliva

Question 13

how can AIDS be a consequence of HIV infection?

Answer 13

• HIV affects lymphocytes (helper T-cells), and when the new HIV viruses bud off, the helper T-cell lymphocytes die
• there is a progressive reduction in the number of active lymphocytes which limits the ability to produce antibodies and fight opportunistic infections
• this is because helper T-cells normally activate B-lymphocytes, which differentiate to produce plasma cells
• when the number of lymphocytes falls so low that opportunistic infections cannot be cleared, the person is said to have AIDS

Question 14

what is the cause of AIDS?

Answer 14

AIDS is caused by infection with HIV which is a retrovirus that enters lymphocytes and weakens the immune system, leading to increased chance of opportunistic infections

Question 15

what are the social implications of AIDS?

Answer 15

when HIV is not managed, AIDS can develop widely and the cost of treatment can impact the health system and reduce populations and workforce as well as discrimination

Question 16

what are antibiotics?

Answer 16

chemicals that are used to prevent or treat bacterial infections

Question 17

how do antibiotics work?

Answer 17

kill or inhibit the growth of bacteria, or work by blocking processes that occur in prokaryotic cells, but not eukaryotic cells as their metabolism is different

Question 18

why are all antibiotics not effective for all species?

Answer 18

not all pathogenic bacteria have the same metabolism, so not all antibiotics are effective for every bacterial species

Question 19

why can antibiotics not treat viruses?

Answer 19

antibiotic have no direct contact on viruses as they are not alive and do not have their own metabolism, but use the host cell’s metabolism, but have no antibiotic targets

Question 20

what is antibiotic resistance?

Answer 20

bacterial strains evolve resistance to antibiotics via natural selection

Question 21

what causes antibiotic resistance?

Answer 21

problem resulting from excessive use of antibiotics by doctors or in livestock due to low doses or not finishing the course

Question 22

how does antibiotic resistance occur?

Answer 22

1. variation exists in a bacterial population with some bacteria being naturally resistant to a particular bacteria
2. the presence of the antibiotic means there is selection pressure
3. bacteria without the resistant gene die while those who have the gene reproduce
4. the offspring inherits the gene for the resistance and the frequency in the bacterial population will increase
5. overtime the resistant population replace the non-resistant population

Question 23

what does antibiotic resistance involve?

Answer 23

bacterial strains evolve resistance to antibiotics by natural selection

Question 24

why is antibiotic resistance harmful?

Answer 24

population will be exposed to antibiotic resistance bacteria but will not have the antibiotic to kill the bacteria

Question 25

how can antibiotic resistance be reduced?

Answer 25

careful, restricted use of antibiotics to slow the emergence of multiresistant bacteria as less use of antibiotics means less antibiotic resistance evolves in pathogens

Question 26

what is an example of how the technique of searching chemical libraries yielded a new antibiotic?

Answer 26

searching chemical libraries to yield new antibiotics
- a computer model used AI to analyse molecular structures of compounds in a few days and link this to particular properties to create an antibiotic (Halicin)
- this was then followed up by testing in mouse which determined that the drug has a broad specificity with many drug-resistant species of bacteria being killed