AQA A-level Biology paper 1
A vaccine can be used to produce immunity. Describe how memory cells are important
in this process. (3) - ANSimportant because when individual is in contact with virus
again, antibodies can be produced at a faster rate in a secondary immune response,
and so the pathogen can be destroyed faster.
abiotic - ANSnon-living
artery structure - ANSthick muscle layer so that they can dilate and contract to smooth
blood flow.
thick elastic layer so artery can stretch and recoil with systole and diastole, smoothing
blood flow.
overall thickness of wall is large so that it doesn't burst under pressure.
artificial active immunity - ANSinvolves inducing an immune response in an individual
WITHOUT them suffering the symptoms of the disease.
e.g. vaccinations
memory cells produced
Attaching lactase to the beads is a more efficient use of lactase than adding the lactase
directly to cow's milk.
Suggest three reasons why it is more efficient to attach lactase to the beads. -
ANSlactase bead can be reused
continuous process
lactase not present in milk
before cell fractionation, why is the tissue placed in a cold, isotonic buffer? - ANScold:
reduce enzyme activity that may break down the organelles
isotonic: same water potential as tissue, this prevents organelles shrinking/bursting due
to osmotic loss/gain of water
buffered: so the pH doesn't fluctuate, so that nothing alters the organelle structures or
affects enzyme functioning
biotic - ANSliving
capillary structure - ANSone cell thick endothelium. allows rapid diffusion.
numerous, highly branched, so provides a larger surface area.
narrow lumen and diameter.
spaces in lining to allow tissue fluid to form.
courtship behaviour results in reproductive success by... - ANS1. allowing recognition of
own species
2. identifying those capable of breeding
,AQA A-level Biology paper 1
3. forming a pair bond
4. synchronising mating
define community - ANSall the populations of different species living and interacting in a
particular place at the same time.
define ecological niche - ANSThe position occupied by an organism in a particular
ecosystem, dependent upon the resources it uses. The more resources that are taken
into account then the more carefully defined the organism's niche will be, the organism
will become more specialised.
define ecology - ANSthe study of the inter-relationships between organisms and their
environment, including abiotic and biotic factors.
define ecosystem - ANSdynamic systems made up of a community and all the non-
living factors of its environment. It includes all the living organisms that interact with one
another and also with the physical and non-physical factors present.
define genome - ANSthe complete set of genes in a cell
define habitat - ANSthe place where an organism normally lives
define population - ANSa group of individuals that occupy the same habitat at the same
time and are potentially able to interbreed.
define proteome - ANSthe full range of proteins that a cell is able to produce
describe and explain the countercurrent exchange principle - ANS-the blood and the
water flow in opposite directions
-blood that is loaded with O2 meets water, which already has maximum O2
-blood with little O2 meets with water with O2 removed
-so, diffusion concentration gradient established and maintained across the entire width
of the gill lamellae
-so, 80% of O2 in water absorbed into fish blood
describe and explain why plant stomata links to gas exchange and its benefits -
ANSstomata are like minute pores, on the underside of leaves.
each has guard cells, which control the rate of gas exchange
guard cells close when water loss is excessive
describe benedicts test for reducing sugars - ANSadd equal volumes of the sugar
sample and benedicts reagent.
heat the mixture in a water bath for 5 minutes.
, AQA A-level Biology paper 1
brick red precipitate will form.
describe binary fission - ANSthe circular DNA molecule replicates and both copies
attach to the cell membrane.
plasmids also replicate
cell membrane grows between the two DNA molecules, dividing the cytoplasm into two.
a new cell wall forms between the two DNA molecules.
two daughter cells are produced, each with a single copy of circular DNA and a variable
number of plasmids.
describe cell mediated immunity - ANS1. phagocytes injest pathogens.
2. the phagocyte places antigens from pathogen on its cell surface membrane, so it
becomes an antigen presenting cell.
3. receptors of T-helper cells have a complimentary fit to these antigens.
4. this attachment activates T cells to divide rapidly by mitosis and form a clone of
genetically identical cells.
5. the cloned T cells:
a. develop into memory cells
b. stimulate phagocytosis
c. stimulate B cells to divide and secret their antibody
d. activate cytotoxic T cells.
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the
leaf (3) - ANSit enters via stomata, which are opened as guard cells open. if diffuses
down a concentration gradient through the air spaces.
Describe how oxygen in air in the alveoli enters the blood in capillaries. - ANSdiffusion
across alveoli epithelium
describe humoral immunity - ANS1. the surface antigen of a pathogen is taken up by B
cell
2. the B cell processes it and presents the antigen on its surface
3. T-helper cells attach to the processed antigens, thus activating the B cell
4. B cells divide by mitosis to produce a clone of plasma cells
5. these secrete the specific antibody that can bind to the pathogens antigen
6. the antigens destroy the pathogen
7. some B cells develop into memory cells
describe semi conservative replication - ANS- DNA helicase unwinds separates the two
strands of DNA into single strands by breaking the H bonds between the bases
- this therefore forms 2 base templates (the bases on each strand are exposed)
- free complimentary nucleotides align with the bases according to complimentary base
pairing
A vaccine can be used to produce immunity. Describe how memory cells are important
in this process. (3) - ANSimportant because when individual is in contact with virus
again, antibodies can be produced at a faster rate in a secondary immune response,
and so the pathogen can be destroyed faster.
abiotic - ANSnon-living
artery structure - ANSthick muscle layer so that they can dilate and contract to smooth
blood flow.
thick elastic layer so artery can stretch and recoil with systole and diastole, smoothing
blood flow.
overall thickness of wall is large so that it doesn't burst under pressure.
artificial active immunity - ANSinvolves inducing an immune response in an individual
WITHOUT them suffering the symptoms of the disease.
e.g. vaccinations
memory cells produced
Attaching lactase to the beads is a more efficient use of lactase than adding the lactase
directly to cow's milk.
Suggest three reasons why it is more efficient to attach lactase to the beads. -
ANSlactase bead can be reused
continuous process
lactase not present in milk
before cell fractionation, why is the tissue placed in a cold, isotonic buffer? - ANScold:
reduce enzyme activity that may break down the organelles
isotonic: same water potential as tissue, this prevents organelles shrinking/bursting due
to osmotic loss/gain of water
buffered: so the pH doesn't fluctuate, so that nothing alters the organelle structures or
affects enzyme functioning
biotic - ANSliving
capillary structure - ANSone cell thick endothelium. allows rapid diffusion.
numerous, highly branched, so provides a larger surface area.
narrow lumen and diameter.
spaces in lining to allow tissue fluid to form.
courtship behaviour results in reproductive success by... - ANS1. allowing recognition of
own species
2. identifying those capable of breeding
,AQA A-level Biology paper 1
3. forming a pair bond
4. synchronising mating
define community - ANSall the populations of different species living and interacting in a
particular place at the same time.
define ecological niche - ANSThe position occupied by an organism in a particular
ecosystem, dependent upon the resources it uses. The more resources that are taken
into account then the more carefully defined the organism's niche will be, the organism
will become more specialised.
define ecology - ANSthe study of the inter-relationships between organisms and their
environment, including abiotic and biotic factors.
define ecosystem - ANSdynamic systems made up of a community and all the non-
living factors of its environment. It includes all the living organisms that interact with one
another and also with the physical and non-physical factors present.
define genome - ANSthe complete set of genes in a cell
define habitat - ANSthe place where an organism normally lives
define population - ANSa group of individuals that occupy the same habitat at the same
time and are potentially able to interbreed.
define proteome - ANSthe full range of proteins that a cell is able to produce
describe and explain the countercurrent exchange principle - ANS-the blood and the
water flow in opposite directions
-blood that is loaded with O2 meets water, which already has maximum O2
-blood with little O2 meets with water with O2 removed
-so, diffusion concentration gradient established and maintained across the entire width
of the gill lamellae
-so, 80% of O2 in water absorbed into fish blood
describe and explain why plant stomata links to gas exchange and its benefits -
ANSstomata are like minute pores, on the underside of leaves.
each has guard cells, which control the rate of gas exchange
guard cells close when water loss is excessive
describe benedicts test for reducing sugars - ANSadd equal volumes of the sugar
sample and benedicts reagent.
heat the mixture in a water bath for 5 minutes.
, AQA A-level Biology paper 1
brick red precipitate will form.
describe binary fission - ANSthe circular DNA molecule replicates and both copies
attach to the cell membrane.
plasmids also replicate
cell membrane grows between the two DNA molecules, dividing the cytoplasm into two.
a new cell wall forms between the two DNA molecules.
two daughter cells are produced, each with a single copy of circular DNA and a variable
number of plasmids.
describe cell mediated immunity - ANS1. phagocytes injest pathogens.
2. the phagocyte places antigens from pathogen on its cell surface membrane, so it
becomes an antigen presenting cell.
3. receptors of T-helper cells have a complimentary fit to these antigens.
4. this attachment activates T cells to divide rapidly by mitosis and form a clone of
genetically identical cells.
5. the cloned T cells:
a. develop into memory cells
b. stimulate phagocytosis
c. stimulate B cells to divide and secret their antibody
d. activate cytotoxic T cells.
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the
leaf (3) - ANSit enters via stomata, which are opened as guard cells open. if diffuses
down a concentration gradient through the air spaces.
Describe how oxygen in air in the alveoli enters the blood in capillaries. - ANSdiffusion
across alveoli epithelium
describe humoral immunity - ANS1. the surface antigen of a pathogen is taken up by B
cell
2. the B cell processes it and presents the antigen on its surface
3. T-helper cells attach to the processed antigens, thus activating the B cell
4. B cells divide by mitosis to produce a clone of plasma cells
5. these secrete the specific antibody that can bind to the pathogens antigen
6. the antigens destroy the pathogen
7. some B cells develop into memory cells
describe semi conservative replication - ANS- DNA helicase unwinds separates the two
strands of DNA into single strands by breaking the H bonds between the bases
- this therefore forms 2 base templates (the bases on each strand are exposed)
- free complimentary nucleotides align with the bases according to complimentary base
pairing
