Biology aqa A level common
questions And Answers Grade A+
SOLUTION
give two factors other than age and gender that would affect the
concentration of creatinine in the blood ?
muscle/ 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?
lower w.p/ more negative inside tubule cells so h2o enters by osmosis
We have an expert-written solution to this problem!
Suggest why diabetes insipidus is more common in males ?
Bc 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 ?
recessive 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
glomerulus/ 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 ?
glucagon binds to specific receptor on liver cells
activation of enzymes in liver
hydrolysis of glycogen
,F.D of glucose out of liver cells
increases blood glucose levels
Explain two ways in which the cells of the proximal convoluted tubule
are adapted for reabsorption.?
microvilli provide a large S.A for reabsorption
carrier protiens in membrane for A.T
channel proteins for F.D
many mitochondria for A.T and providing Atp
Explain the role of the loop of Henle in the absorption of water from
the flitrate ?
in the ascending limb na+ ions actively transported
ascending limb impermeable to water
in descending limb na+ ions diffuse in
descending limb h2o moves out
low w.p ( high conc of ions in medulla) the longer the loop, lower
w.p in medulla
h2o leaves collecting duct by osmosis down w.p gradient
Explain the role of ADH in the production of concentrated urine?
when w.p of blood too low it is detected by receptors in hypothalamus
pituitary secretes releases more ADH
ADH increases permeability opens channels for h2o in DCT
more h2o reabsorbed into blood by osmosis down w.p gradient
Explain how different subspecies of giraffe may have evolved from a
common ancestor ? (5)
1) no interbreeding/geographical isolation
2)variation due to mutation linked to different markings (colours)
3) survival linked to different markings different selection pressure
4) adapted organisms survive and reproduce ( different reproductive
success)
5) increase in allele frequencies
describe how crop plants use light energy during the light dependent
reaction? (5)
1) excites electrons
2) electrons move along electron transfer chain releasing energy
3) energy used to join ADP + Pi -> ATP
4) photolysis of H2O produces P, e- and O2
5) NADP reduced by hydrogen
describe how altered DNA may lead to cancer ? (6)
1. (DNA altered by) mutation;
2. (mutation) changes base sequence;
3. Of gene controlling cell growth / oncogene / that monitors cell
division;
4. Of tumour suppressor gene;
5. Change protein structure / non-functional protein / protein not
, formed;
6. (Tumour suppressor genes) produce proteins that inhibit cell
division;
7. Mitosis;
8. Uncontrolled / rapid / abnormal (cell division);
9. Malignant tumour;
why would one area ( e.g wild ower meadow) have a higher species
diversity than another e.g potato field ? (5)
1) there would be more plant species
2) hence more habitats
3) more niches
4) more food sources
5) the area is able to support more biomass
describe competitive and non-competitive inhibition of enzyme ? (6)
competitive inhibitor
1) inhibitors reduce binding of enzyme to substrate/prevent formation
of e-s complexes
2) inhibitor similar shape to substrate binds to active site of
enzyme
3) inhibition can be overcome by adding more substrate
non-competitive inhibitor
4) inhibitor binds to site on enzyme other than active site
5) prevents formation of active site/ changes shape of active site
6) cannot be overcome by adding more substrate
Meiosis
cell ÷ to form gametes
2 ÷ forming 4 haploid daughter cells
genetically non-identical due to crossing over and independent
segregation (assortment)
crossing over- creates new combination of alleles
independent assortment - creates new combination of chromosomes
Mitosis
cell divides for growth and repair
2 genetically identical daughter cells
prophase - nuclear membrane breaks down and chromosomes condense
metaphase- chromosomes line up on the equator and spindle fibres
attach to chromosome at the centromere
anaphase - centromeres split and chromatids move to opposite poles
telophase - nuclear membrane reforms, chromosomes uncoil and cell
questions And Answers Grade A+
SOLUTION
give two factors other than age and gender that would affect the
concentration of creatinine in the blood ?
muscle/ 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?
lower w.p/ more negative inside tubule cells so h2o enters by osmosis
We have an expert-written solution to this problem!
Suggest why diabetes insipidus is more common in males ?
Bc 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 ?
recessive 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
glomerulus/ 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 ?
glucagon binds to specific receptor on liver cells
activation of enzymes in liver
hydrolysis of glycogen
,F.D of glucose out of liver cells
increases blood glucose levels
Explain two ways in which the cells of the proximal convoluted tubule
are adapted for reabsorption.?
microvilli provide a large S.A for reabsorption
carrier protiens in membrane for A.T
channel proteins for F.D
many mitochondria for A.T and providing Atp
Explain the role of the loop of Henle in the absorption of water from
the flitrate ?
in the ascending limb na+ ions actively transported
ascending limb impermeable to water
in descending limb na+ ions diffuse in
descending limb h2o moves out
low w.p ( high conc of ions in medulla) the longer the loop, lower
w.p in medulla
h2o leaves collecting duct by osmosis down w.p gradient
Explain the role of ADH in the production of concentrated urine?
when w.p of blood too low it is detected by receptors in hypothalamus
pituitary secretes releases more ADH
ADH increases permeability opens channels for h2o in DCT
more h2o reabsorbed into blood by osmosis down w.p gradient
Explain how different subspecies of giraffe may have evolved from a
common ancestor ? (5)
1) no interbreeding/geographical isolation
2)variation due to mutation linked to different markings (colours)
3) survival linked to different markings different selection pressure
4) adapted organisms survive and reproduce ( different reproductive
success)
5) increase in allele frequencies
describe how crop plants use light energy during the light dependent
reaction? (5)
1) excites electrons
2) electrons move along electron transfer chain releasing energy
3) energy used to join ADP + Pi -> ATP
4) photolysis of H2O produces P, e- and O2
5) NADP reduced by hydrogen
describe how altered DNA may lead to cancer ? (6)
1. (DNA altered by) mutation;
2. (mutation) changes base sequence;
3. Of gene controlling cell growth / oncogene / that monitors cell
division;
4. Of tumour suppressor gene;
5. Change protein structure / non-functional protein / protein not
, formed;
6. (Tumour suppressor genes) produce proteins that inhibit cell
division;
7. Mitosis;
8. Uncontrolled / rapid / abnormal (cell division);
9. Malignant tumour;
why would one area ( e.g wild ower meadow) have a higher species
diversity than another e.g potato field ? (5)
1) there would be more plant species
2) hence more habitats
3) more niches
4) more food sources
5) the area is able to support more biomass
describe competitive and non-competitive inhibition of enzyme ? (6)
competitive inhibitor
1) inhibitors reduce binding of enzyme to substrate/prevent formation
of e-s complexes
2) inhibitor similar shape to substrate binds to active site of
enzyme
3) inhibition can be overcome by adding more substrate
non-competitive inhibitor
4) inhibitor binds to site on enzyme other than active site
5) prevents formation of active site/ changes shape of active site
6) cannot be overcome by adding more substrate
Meiosis
cell ÷ to form gametes
2 ÷ forming 4 haploid daughter cells
genetically non-identical due to crossing over and independent
segregation (assortment)
crossing over- creates new combination of alleles
independent assortment - creates new combination of chromosomes
Mitosis
cell divides for growth and repair
2 genetically identical daughter cells
prophase - nuclear membrane breaks down and chromosomes condense
metaphase- chromosomes line up on the equator and spindle fibres
attach to chromosome at the centromere
anaphase - centromeres split and chromatids move to opposite poles
telophase - nuclear membrane reforms, chromosomes uncoil and cell
