2024 BIOLOGY AQA A LEVEL
COMMON EXAM QUESTIONS
give two factors other than age and gender that would affect the
concentration of creatinine in the blood ? - CORRECT-ANSWERSmuscle/ body
mass
ethnicity
Explain how the cells of the collecting duct are able to absorb water from the
filtrate through the protein channels in their plasma membranes? -
CORRECT-ANSWERSlower w.p/ more negative inside tubule cells so h2o
enters by osmosis
structure of DNA ? - CORRECT-ANSWERSsugar phosphate backbone provides
strength and protects bases
large molecules stores lots of info
helix - compact
base sequence codes for AA
double stranded so strands act as templates - comp b.p
weak h-bonds for strand seperation
describe how dna is replicated? - CORRECT-ANSWERSstrands seperate
dna helicase breaks h bonds
both strands act as a template
free nucleotides attach by complementary b.p
dna polymerase joins nucleotides on new strand
h-bonds reform
semi conservative new dna contains 1 old and 1 new strand
starch ? - CORRECT-ANSWERSa-glucose
insoluble in h2o so doesn't affect w.p by osmosis
coiled - compact - helical shape
branched so glucose is released for respiration
Cellulose ? - CORRECT-ANSWERSb-glucosw
straight chain
1,4 glycosidic bonds
long unbranched chain
joined by h-bonding
forms microfibrils
provides rigidity
,glycogen ? - CORRECT-ANSWERSa-glucose
branched/coiled
1,4 + 1,6 glucosidic bonds
branched hydrolysed to glucose used in respiration
why are enzymes specific ? - CORRECT-ANSWERStertiary structure of
enzyme means active site is only complementary to substrate
active site changes shape to become complementary ( induced fit)
by forming e-s complexes
only substrate can bind
describe induced fit ? - CORRECT-ANSWERSactive site is not complementary
to substrate
active site changes shape as e-s complexes form
ATP ? - CORRECT-ANSWERSreleases relatively small amounts of energy
releases energy instantaneously
involves a single reaction
immediate energy source
soluble
easily hydrolysed
lock and key model? - CORRECT-ANSWERSactive site does not change shape
fixed shape
already fits substrate
xerophtic features the leaves might have ? - CORRECT-ANSWERShairs so
trap h2o vapour and w.p.g
stomata in pits decreased
thick waxy cuticle increases diffusion distance
waxy cuticle so reduces transpiration
cohesion-tension theory? - CORRECT-ANSWERSh2o lost from leaf b.c of
transpiration of h2o mol
lowers w.p of mesophyll cells
h2o pulled up xylem creates tension
h2o molecules stick together by h-bonds
forming continuous h2o column
adhesion of h2o molecules to the walls of the xylem
measurements needed for index of diversity ? - CORRECT-ANSWERSn.o of
individuals of each species
total n.o of individuals
, assumptions made when using the mark release method ? - CORRECT-
ANSWERSno immigration
no losses to predation
marking does not affect survival
birth and death rate are =
phagocytosis, t-cells and b-cells? - CORRECT-ANSWERSphagocyte recognises
antigen on bacteria as foreign
engulfs bacteria
bacteria in vacuole
lysosome fuses with enzymes in to vacuole
bacteria hydrolysed
phagocyte presents bacteria on antigen presenting cell
antigen on phagocyte activayes T-cells
T-cells destroy pathogen (t-killer cells)
t -cells present antigen and activate b-cells
clonal selection b-cell with required antibody ÷ by mitosis to form plasma
cells
antibodies are complementary to antigen form antigen-antibody complex
b cells produced from memory cells
secondary response is infected with antigen again
Suggest why diabetes insipidus is more common in males ? - CORRECT-
ANSWERSBc males only have X chromosome do not have Y chromosome
single copy of recessive allele will be expressed
A recessive allele which has harmful effects is able to reach a higher
frequency in a population than a harmful dominant allele. Explain how ? -
CORRECT-ANSWERSrecessive allele can be carried by individuals showing
effects dominant allel always expressed
organisms that are affected are more likely to reproduce therefore recessive
alleles are more likely to be passed on
In some forms of kidney disease, proteins from the blood plasma are found in
the urine. Which part of the nephron would have been damaged by the
disease to cause proteins from blood plasma to be present in the urine?
Explain your answer - CORRECT-ANSWERSglomerulus/ bowmans capsule
basement membrane
proteins are large molecules cannot normally pass through filter
can only pass through if filter damaged
Describe the role of the hormone glucagon in the control of blood sugar
concentration ? - CORRECT-ANSWERSglucagon binds to specific receptor on
liver cells
activation of enzymes in liver
COMMON EXAM QUESTIONS
give two factors other than age and gender that would affect the
concentration of creatinine in the blood ? - CORRECT-ANSWERSmuscle/ body
mass
ethnicity
Explain how the cells of the collecting duct are able to absorb water from the
filtrate through the protein channels in their plasma membranes? -
CORRECT-ANSWERSlower w.p/ more negative inside tubule cells so h2o
enters by osmosis
structure of DNA ? - CORRECT-ANSWERSsugar phosphate backbone provides
strength and protects bases
large molecules stores lots of info
helix - compact
base sequence codes for AA
double stranded so strands act as templates - comp b.p
weak h-bonds for strand seperation
describe how dna is replicated? - CORRECT-ANSWERSstrands seperate
dna helicase breaks h bonds
both strands act as a template
free nucleotides attach by complementary b.p
dna polymerase joins nucleotides on new strand
h-bonds reform
semi conservative new dna contains 1 old and 1 new strand
starch ? - CORRECT-ANSWERSa-glucose
insoluble in h2o so doesn't affect w.p by osmosis
coiled - compact - helical shape
branched so glucose is released for respiration
Cellulose ? - CORRECT-ANSWERSb-glucosw
straight chain
1,4 glycosidic bonds
long unbranched chain
joined by h-bonding
forms microfibrils
provides rigidity
,glycogen ? - CORRECT-ANSWERSa-glucose
branched/coiled
1,4 + 1,6 glucosidic bonds
branched hydrolysed to glucose used in respiration
why are enzymes specific ? - CORRECT-ANSWERStertiary structure of
enzyme means active site is only complementary to substrate
active site changes shape to become complementary ( induced fit)
by forming e-s complexes
only substrate can bind
describe induced fit ? - CORRECT-ANSWERSactive site is not complementary
to substrate
active site changes shape as e-s complexes form
ATP ? - CORRECT-ANSWERSreleases relatively small amounts of energy
releases energy instantaneously
involves a single reaction
immediate energy source
soluble
easily hydrolysed
lock and key model? - CORRECT-ANSWERSactive site does not change shape
fixed shape
already fits substrate
xerophtic features the leaves might have ? - CORRECT-ANSWERShairs so
trap h2o vapour and w.p.g
stomata in pits decreased
thick waxy cuticle increases diffusion distance
waxy cuticle so reduces transpiration
cohesion-tension theory? - CORRECT-ANSWERSh2o lost from leaf b.c of
transpiration of h2o mol
lowers w.p of mesophyll cells
h2o pulled up xylem creates tension
h2o molecules stick together by h-bonds
forming continuous h2o column
adhesion of h2o molecules to the walls of the xylem
measurements needed for index of diversity ? - CORRECT-ANSWERSn.o of
individuals of each species
total n.o of individuals
, assumptions made when using the mark release method ? - CORRECT-
ANSWERSno immigration
no losses to predation
marking does not affect survival
birth and death rate are =
phagocytosis, t-cells and b-cells? - CORRECT-ANSWERSphagocyte recognises
antigen on bacteria as foreign
engulfs bacteria
bacteria in vacuole
lysosome fuses with enzymes in to vacuole
bacteria hydrolysed
phagocyte presents bacteria on antigen presenting cell
antigen on phagocyte activayes T-cells
T-cells destroy pathogen (t-killer cells)
t -cells present antigen and activate b-cells
clonal selection b-cell with required antibody ÷ by mitosis to form plasma
cells
antibodies are complementary to antigen form antigen-antibody complex
b cells produced from memory cells
secondary response is infected with antigen again
Suggest why diabetes insipidus is more common in males ? - CORRECT-
ANSWERSBc males only have X chromosome do not have Y chromosome
single copy of recessive allele will be expressed
A recessive allele which has harmful effects is able to reach a higher
frequency in a population than a harmful dominant allele. Explain how ? -
CORRECT-ANSWERSrecessive allele can be carried by individuals showing
effects dominant allel always expressed
organisms that are affected are more likely to reproduce therefore recessive
alleles are more likely to be passed on
In some forms of kidney disease, proteins from the blood plasma are found in
the urine. Which part of the nephron would have been damaged by the
disease to cause proteins from blood plasma to be present in the urine?
Explain your answer - CORRECT-ANSWERSglomerulus/ bowmans capsule
basement membrane
proteins are large molecules cannot normally pass through filter
can only pass through if filter damaged
Describe the role of the hormone glucagon in the control of blood sugar
concentration ? - CORRECT-ANSWERSglucagon binds to specific receptor on
liver cells
activation of enzymes in liver
