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OCR AS/A Level Biology Exam Questions > module 4.1: communicable diseases, disease prevention and the immune system > Flashcards

module 4.1: communicable diseases, disease prevention and the immune system Flashcards

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1
Q

define the term parasite

A

lives in host
gains nutrition from host
at the expense of/ harms host

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2
Q

explain why the human body’s primary defences do not prevent the entry of Plasmodium into the body

A

mosquito feeds on blood
breaks skin so skin cannot act as a barrier

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3
Q

suggest why malaria is much more common in tropical areas than in other parts of the world

A

suitable climate for Anopheles
more mosquitos live there
relatively poor so methods of prevention less effective

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4
Q

suggest two reasons why government in parts of the world other than tropical areas, are also becoming increasingly concerned about malaria

A

climate change/global warming may result in spread to other parts of the world
increased movement of infected people
non - malaria countries fund anti malaria measures via international trade
resistance of parasite to drugs / mosquito to insecticides

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5
Q

suggest why erythrocytes that contain Plasmodium are more likely to be destroyed by phagocytosis than healthy erythrocytes

A

different chemicals that are attract phagocytes released from infected erythrocytes

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6
Q

describe the difference between globular and fibrous proteins using haemoglobin and collagen as examples

A

Globular
spherical
hydrophilic r-groups on the outside of 3D structure
form H bonds with water
examples: hormone, antibody, channel, carrier
haemoglobin transports oxygen
contains prosthetic group Fe2+
polypeptide chains within haemoglobin have tertiary structure in a ball shape
fibrous
insoluble / few hydrophilic groups
strong
have structural role
collagen has a high proportion of glycine so chains can lie close together
forms crosslinks between molecules
crosslinks are staggered to avoid weak points
collagen forms part of tendon/ cartilage/ skin/ bronchi/ trachea/ ligament

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7
Q

describe how antibodies allows them to perform their function

A
  • 2 light chains and 2 heavy chains/ 4 polypeptide chains
  • variable region allows binding to antigen
  • 2 variable regions allow binding of more than one of the same antigen
  • variable region on different antibodies allows specificity to different antigens
  • constant region allows attachment to phagocytes
  • hinge region allows flexibility
  • disulfide bonds hold polypeptides/ light and heavy chains together
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8
Q

outline the mode of action of antibodies in defending the body against pathogens by describing the processes of neutralisation and agglutination

A

neutralisation
- cover binding site
- bind to toxins
- prevent binding to host cell
agglutination
- clump together many pathogens
- clumps too large to enter host cell/ cross membrane
- increase likelihood of being consumed by phagocyte

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9
Q

“bacteria can evolve quickly and many are now immune to antibiotics”
explain why the student’s use of the word immune was incorrect

A
  • immunity involves bacteria not having lymphocytes
  • correct term is resistance
  • bacteria is unicellular / only multicellular organisms can have have an immune response
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10
Q

why are phagocytes described as a secondary defence against pathogens

A

involved after pathogen has entered the body

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11
Q

why is the response involving phagocytes regarded as non specific

A

phagocytes able to engulf a range of different pathogens

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12
Q

explain how phagocytes are able to pass from the blood into the tissue fluid

A
  • lobed/ narrow nucleus
  • cells change shape
  • can squeeze between cells/ through pores in wall of capillaries
  • histamines makes capillary walls/ endothelium leaky
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13
Q

describe the process by which a pathogen is destroyed after it has become attached to the surface of a phagocytes

A

pathogen is engulfed by endocytosis
formation of phagosome
phagolysosomes form when lysosomes and phagosomes fuses with each other
lysins/ hydrogen peroxide/ free radicals in lysosomes aids pathogens being hydrolysed into amino acids/ sugar/ glucose/ fatty acids/ glycerol
break down products absorbed into cytoplasm
cytoskeleton involved in movement of vesicles

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14
Q

name the infective agent that cause TB

A

mycobacterium

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15
Q

describe how the infective agent that causes TB is transmitted from one individual to another

A

droplets containing pathogen
released by coughing or sneezing
inhaled by uninfected individual

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16
Q

suggest three reasons why the incidence of TB is higher in the low income group

A

overcrowding
poor ventilated
poor diet
poor health
homelessness
more likely to consume meat from infected cattle
medication is more difficult to acccesd

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17
Q

state two features of the malarial parasite that indicate that this is not a prokaryote

A

nucleus
mitochondria
linear chromosomes
DNA associated with histones
80s large ribosomes
large cells
no cell wall

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18
Q

describe how the mosquito transmits the malarial parasite to a human

A

mosquito is vector
Plasmodium present in the mosquito’s
salivary gland
infected mosquito feeds on humans
Plasmodium passes from saliva to blood

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19
Q

suggest reasons why some people might be concerned about using insecticides

A

destruction of species is ethically wrong
might cause unintended heath problems in humans
might harm other species
bioaccumulation

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20
Q

suggest how the effects of insecticide use on a population of Anopheles mosquitoes could be measured and state the steps that should be taken in order to produce valid and reliable results

A

sampling before and after insecticide treatment
unbiased/ random sampling of population
example of sampling technique: sweep net, pond net, light trap
sampling in different times/ weather
standardised sampling procedure
large number of samples taken
prevent counting same individual more than once
capture - recapture
calculate standard deviation
OR
laboratory investigation
with and without insecticides exposure
measuring mosquito survival
control:
exposure time
species of mosquito
stage of mosquito life cycle
sex if mosquito
number of mosquito
insecticide type
insecticide concentration
volume of insecticide
temperature

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21
Q

matured in thymus ………
secrete substances which kill infected cells……..
manufactured antibodies……..
undergo clonal expansion……..
activate other lymphocytes……..

A

t
t
b
both
t

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22
Q

describe the changes in antibody concentration that occur in the patient’s blood during the primary response

A

no antibodies detected before 4 days
increase then decrease
figures for peak with time and antibody concentration
decrease less steep than increase
antibody concentration returns to 0 at 27 days

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23
Q

what are the functions of the following
hinge region
constant region
variable region

A

flexibility
attachment to phagocytes
attachment to antigens

24
Q

state groups of people that the government would consider as being vulnerable

A

the elderly
at trish children
pregnant women
those with compromised immune systems
those with chronic diseases
health workers
poultry workers

25
Q

suggest why the influenza vaccine has to be changed each year

A

different strains of the virus
new strains have different antigens
antibody produced needs to match new strain/ antigen

26
Q

state differences between the primary and secondary immune responses

A

secondary response starts earlier
secondary response more rapid
secondary response produces more antibodies

27
Q

describe the role of these memory cells when the influenza virus enters the body

A

recognise pathogen
produce a clone
can change to form plasma cells
make antibodies
responsible for secondary response
can change to form named T- cell ( helpers, killer)

28
Q

state why a doctor would not prescribe antibiotics to treat influenza

A

effective only against bacteria
antibiotics are not effective against viruses

29
Q

this enzyme is used to break down the host cell membrane and allow the influenza viruses to leave cell. tamiflu is a neuraminidase inhibitor.
suggest how tamiflu could inhibit neuraminidase

A

tamiflu is competitive/ non-competitive inhibitor
complementary shape to active site / fits to allorestic site or site other than active site and changes shape of active site
prevents the formation of ESC

30
Q

suggest how tamiflu could help to reduce the spread of influenza

A

fewer pathogens produced
fewer pathogens when sneezing and coughing
as pathogens cannot leave cell
so cannot spread to other cells
treating large population

31
Q

suggest why researchers in Nepal concentrated their research on plants that had been used in traditional medicine

A

plants already identified as likely to have to have medicinal properties
reduces time in finding plants
possibly reduces cost

32
Q

identify the infective agent that causes AIDS

A

human immunodeficiency virus

33
Q

the government has introduced needle exchange programmes for drug users. explain how this may help reduce the transmission of AIDS

A
  • (infective agent), in blood / body fluids
  • idea of: used needles are contaminated
  • reduces chance of sharing needles
34
Q

name the monomers that make up:
proteins ……………..
RNA …………..

A

amino acids
nucleotides

35
Q

using the information in Fig. 1.1, suggest why the infective agent (HIV) is able to ‘take control’ once it has entered the T lymphocytes

A
  • reverse transcriptase in (host) nucleus
  • viral DNA, (inserted) in (host), chromosome / DNA
  • idea of: (viral) RNA / mRNA produced / transcribed
  • (to) code for / make / translate, viral proteins
36
Q

state three factors that increase the chance of infection with TB

A

not vaccinated against TB
weakened immune system
(lifestyle) e.g. poor diet / lack of protein / malnourished / smoking / alcoholism
homelessness
poor ventilation (of housing) / AW
overcrowding
close contact with people from / visiting, area where TB is common
close / prolonged, contact with individual(s) with TB
consumption of milk or beef, from infected cattle / in developing countries

37
Q

when an infection occurs, some T lymphocytes produce cell signalling molecules called
cytokines. these cytokines stimulate specific groups of B lymphocytes to divide. describe how cytokine molecules can stimulate specific groups of B lymphocytes to divide

A
  • cytokine / interleukin / receptor has, specific / unique, shape
    (cytokine / interleukin), binds / attaches / bonds to / fits into, receptor
  • receptor on (cell surface) membrane (of B lymphocyte)
  • (receptor and cytokine have) complementary shapes
  • activates / stimulates, clonal expansion / mitosis
38
Q

what is meant by the term health?

A
  • free from, disease / illness
  • physical and mental and social wellbeing
  • good nutrition
  • suitably housed
39
Q

state two features of the body that form part of the primary defence. for each feature, explain how it helps to prevent the entry of pathogens and parasites into the body

A
  • skin - idea of: physical barrier to prevent entry of microorganisms
  • mucus - traps pathogens
  • cilia / ciliated epithelium - remove, pathogen / parasite, laden
  • blood clotting - prevents, pathogens / parasite, entering bloodstream
  • ear wax / nasal hairs - traps, pathogens / parasite
  • lysozyme / tears - kills bacteria / contains antibacterial agent
  • gastric juice / stomach acid - kills, pathogens / parasite
40
Q

define the term parasite and suggest how the threadworm benefits from this relationship

A
  • lives, on / in / in contact with, and harms host
  • takes nutrition from / feeds on (host)
  • warmth
  • protection / safe place
  • allows transmission / spread, to a new host
41
Q

Name the parasite that causes malaria

A

Plasmodium

42
Q

Name the vector for the malarial parasite

A

female Anopheles

43
Q

Name a human cell in which the malarial parasite reproduces

A

hepatocyte / liver (cell) ;
erythrocyte / red blood (cell)

44
Q

Describe the actions of the B lymphocytes in the immune response

A

Humoral response
(B) cell / lymphocytes ,has antigen receptor / carries antibody on its surface which specific to / matches / complementary to , only one antigen
Clonal selection
selection / activation , of , appropriate / specific , B lymphocyte / B cell by , macrophages
Clonal expansion
(selected cell) divides by mitosis
- (B) cells , differentiate / specialise .(B cells) form , plasma / effector , cells (which) secrete / produce ,antibodies which are , specific / complementary , to antigens
(B cells) form memory cells
Either (memory cells) long-lived / remain in circulation /
provide immunological memory

45
Q

Suggest why adults who have survived malaria may lose their immunity when they leave a malarial area

A
  • no repeat infections (to antigen / pathogen / parasite)
  • no booster / lose immunological memory
  • limited life for memory cells so no , secondary response / secondary response described
46
Q

State three biological reasons why it has not been possible to produce an effective vaccine for malaria

A
  • different , strains / species / types (of Plasmodium) so different antigens due to , mutation / variation
  • more than one stage in the life cycle (within human). different stages have different antigens so will need , a different vaccine / components of vaccine ,for each , strain / stage
    (parasite) concealed / hidden , in cells and only , exposed / in circulation , for short time
47
Q

characteristics are passed on to the next generation ….
there is a struggle for existence…..
individuals with beneficial characteristics are among the few who survive…..

A

W
Y and Z
X and Y and Z

48
Q

suggest why the resistance of MRSA to existing antibiotics is of major concern to humans

A
  • MRSA may become untreatable
  • potential for, disease outbreak
  • developing new / more powerful, antibiotics, is expensive
49
Q

the evolution of antibiotic resistance in bacteria is evidence to support the theory of evolution. how does fossil evidence support the idea that evolution has taken place

A
  • fossils show that organisms have changed over time
  • idea that fossils or rocks can be dated
  • idea of fossils showing intermediate forms / sequences
50
Q

state the two different causes of variation

A

genetic
environmental

51
Q

the growth rate of the chickens in Fig. 6.1 shows continuous variation. describe three characteristics of this type of variation

A
  • no defined categories
  • range of values
  • influenced by, environment / many genes / genes and
    environment
  • quantitative
52
Q

state which group of chickens, A, B, C or D, he should use to breed from in order to improve the growth and productivity of the flock

A

B

53
Q

suggest two undesirable consequences of selective breeding in chickens

A
  • growth too rapid
  • increased susceptibility to, disease
  • reduces gene pool / genetic variation
54
Q

the wild ancestor of the domestic chicken is the red jungle fowl found in the rainforests of South East Asia. explain why it is important to preserve the population of the red jungle fowl

A
  • maintain biodiversity
  • aesthetic (reasons) / tourism
  • ethical (reasons)
  • part of a food chain / web
  • maintain / increase gene pool
  • genetic resource / availability to breed with domestic chickens
55
Q

suggest two further benefits of using antibiotics

A
  • reduces / prevents (infectious) disease
  • prevent, problems with gut
  • digest food more, efficiently
  • greater proportion of, food / energy, can contribute to growth
  • reduce risk of transmitting, pathogens to humans
56
Q
A

OCR AS/A Level Biology Exam Questions (13 decks)

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