Organisms and evolution - 5

Question 1

what is a microbe?

Answer 1

parasite with only one host species and are transmitted by direct contact

Question 2

what are the three main components of a virus?

Answer 2

nucleic acid, protein coat, antigen

Question 3

what are antigens?

Answer 3

proteins coded for by viral genes

Question 4

what are the 5 stages of virus replication?

Answer 4

• attachment
• penetration
• synthesis of new components
• assembly
• release
  (APSAR)

Question 5

what happens once the virus DNA has been replicated?

Answer 5

virus genes are transcribed to RNA which is translated to make viral protein coats

Question 6

what is an RNA retrovirus?

Answer 6

use enzyme reverse transcriptase to form DNA copy of virus genome

Question 7

what are the body’s first-line defences?

Answer 7

physical barriers and chemical secretions

Question 8

what occurs in an inflammatory response?

Answer 8

• histamine released from infected cells
• blood vessels dilate to increase blood flow
• permeability of blood vessels increases
• swelling stimulates phagocytes

Question 9

what are non-specific defences?

Answer 9

• first line defences

- second line defences, eg inflammation, phagocytes, natural killer cells

Question 10

what are phagocytes?

Answer 10

white blood cells that engulf and digest foreign objects

Question 11

what are natural killer cells?

Answer 11

detect abnormal cell-surface proteins and cause apoptosis

Question 12

what are the third line of defence?

Answer 12

specific cellular response

Question 13

what is the specific cellular response triggered by?

Answer 13

triggered by antigens on surface of parasite

Question 14

what is they type of white blood cell involved in specific cellular defences?

Answer 14

lymphocytes

Question 15

what do each lymphocyte present on the surface of cell?

Answer 15

one type of antigen-receptor protein

Question 16

what do lymphocytes carry out?

Answer 16

carry out immune surveillance, checking for specific antigens

Question 17

what are lymphocytes part of?

Answer 17

part of a clone

Question 18

when are B lymphocytes selected?

Answer 18

selected when antigen-receptor protein binds to specific antigen

Question 19

what is activated if phagocytes present the correct antigen fragments?

Answer 19

T lymphocytes

Question 20

what is the role of helper T lymphocytes?

Answer 20

target immune response cells and stimulate to rapidly divide

Question 21

what produces the antibodies which bind to antigens on parasite?

Answer 21

B lymphocytes

Question 22

what does a B lymphocyte do to a parasite?

Answer 22

neutralises parasite to make it easier for phagocytes to engulf

Question 23

what do cytotoxic T lymphocytes do?

Answer 23

destroy infected cells by inducing apoptosis

Question 24

why is immunological memory important?

Answer 24

quicker and larger response if specific antigen is detected again. Ensures long-term survival of larger population

Question 25

what is epidemiology?

Answer 25

study of the outbreak and spread of infectious disease

Question 26

what is herd immunity?

Answer 26

results if high proportion of population are immune to disease

Question 27

what is the herd immunity threshold?

Answer 27

the density of resistant hosts required in a population to prevent an epidemic

Question 28

what does the herd immunity threshold depend on?

Answer 28

- the disease - effectiveness of vaccine - contact parameters for the population

Question 29

what are some difficulties of developing a vaccine?

Answer 29

- some parasites hard to culture in lab | - parasite may use rapid antigen change

Question 30

if there are similarities between host and parasite metabolism, what difficulties can this cause?

Answer 30

if drug kills parasite it could have other negative effects on host

Question 31

what can be done to help control parasites?

Answer 31

- civil engineering projects to improve sanitation | - coordinated vector controlled strategy, eg mosquito nets

Question 32

in what type of places is is difficult to control parasites?

Answer 32

overcrowded and tropical climates

Question 33

what are three benefits of controlling parasites?

Answer 33

- reduce child mortality - general health improves - improvements in child development and intelligence