AQA AS Biology 7401/1 Paper 1 June 2024 Question
Paper and Mark Scheme STUDY BUNDLE PACKAGE
WITH COMPLETE SOLUTIONS
Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells -
ANSWERComparisons
1. Nucleotide structure is identical; 2. Nucleotides joined by phosphodiester bond;
OR Deoxyribose joined to phosphate (in sugar, phosphate backbone); 3. DNA in
mitochondria / chloroplasts same / similar (structure) to DNA in prokaryotes
Contrasts
4. Eukaryotic DNA is longer; 5. Eukaryotic DNA contain introns, prokaryotic DNA does
not; 6. Eukaryotic DNA is linear, prokaryotic DNA is circular; 7. Eukaryotic DNA is
associated with / bound to protein / histones, prokaryotic DNA is not
Haemoglobins are chemically similar molecules found in many different species.
Differences in the primary structure of haemoglobin molecules can provide evidence
of phylogenetic (evolutionary) relationships between species. Explain how -
ANSWER1. Mutations change base / nucleotide (sequence); 2. (Causing) change in
amino acid sequence; 3. Mutations build up over time; 4. More mutations / more
differences (in amino acid / base / nucleotide sequence / primary structure) between
distantly related species; OR Few(er) mutations / differences (in amino acid / base /
nucleotide sequence / primary structure) in closely related species; 5. Distantly
related species have earlier common ancestor; OR Closely related species have
recent common ancestor
Explain why students were unable to make a conclusion from the table? - ANSWER-
missing information -so cannot compare all stages -no statistical comparison of
standard deviations given or no measure of significant differences
Why do we press down firmly on the cover slip? - ANSWERTo form a thin layer of
cells so light passes through making cells visible
Describe and explain what the student should have done when counting cells to
make sure that the mitotic index he obtained for this root tip was accurate -
ANSWER• Examine large number of fields of view to ensure representative sample
• Repeat count to ensure figures are correct
• Count only whole cells to standardise counting
Where do hydrogen bonds form? - ANSWERHydrogen bonds form between NH and
C=O groups in a protein's secondary structure
Scientists looking for extra-terrestrial life are looking for planets with evidence of
free water. Explain why water is considered so important for life to occur. -
ANSWERLife evolved in water. Water provides support (for bodies of organisms).
Water is a major component of cytoplasm. Metabolic reactions occur in aqueous
, solutions (solvent). Water is a metabolite/reactant is many cell reactions. Water
stabilises temperature (high specific heat capacity). Important in cooling (high latent
heat).
Limiting water loss in insects - ANSWER-Small surface area to volume ratio, to
minimise the area over which water is lost.
-Exoskeleton covered with a waterproof cuticle.
-Spiracles remain closed to minimise water loss.
Describe the difference between the structure of a triglyceride molecule and the
structure of a phospholipid molecule (1 mark) - ANSWERIn phospholipids, one of the
fatty acid chains are *replaced* by a phosphate group
Explain why it is more useful to calculate an index of diversity than to record species
richness. - ANSWERMeasures abundance of each species because there may be
many of 1 species or very few of one species.
Suggest how scientists measured the rate of water flow in the river. -
ANSWERmeasured time to fill a container of a known volume.
slow water flow leads to... - ANSWERless oxygen dissolved in water so less
respiration for aquatic life
How to standardise a sampling procedure. - ANSWERuse same size measuring object
same size of area sampled
same sampling time
Not all mutations in the nucleotide sequence of a gene cause a change in the
structure of a polypeptide. Give two reasons why. - ANSWERdegenerate code
could happen in introns/non coding
Suggest a method that could be used to measure the quantity of reducing sugar in a
solution. - ANSWERFilter and dry the precipitate
Weigh/find mass
Why using a colorimeter improves the repeatability of the student's results. -
ANSWERquantitative
colour change is subjective
standardises values
Explain how the active site of an enzyme causes a high rate of reaction. -
ANSWEREnzyme lowers the activation energy.
Induced fit causes the active site of the enzyme to change shape.
Enzyme-Substrate complex causes the bonds to break.
Why anti HIV drugs do not destroy HIV in the body but stops or slows the
development of AIDS. - ANSWERInitially the person still has HIV DNA in their DNA.
Paper and Mark Scheme STUDY BUNDLE PACKAGE
WITH COMPLETE SOLUTIONS
Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells -
ANSWERComparisons
1. Nucleotide structure is identical; 2. Nucleotides joined by phosphodiester bond;
OR Deoxyribose joined to phosphate (in sugar, phosphate backbone); 3. DNA in
mitochondria / chloroplasts same / similar (structure) to DNA in prokaryotes
Contrasts
4. Eukaryotic DNA is longer; 5. Eukaryotic DNA contain introns, prokaryotic DNA does
not; 6. Eukaryotic DNA is linear, prokaryotic DNA is circular; 7. Eukaryotic DNA is
associated with / bound to protein / histones, prokaryotic DNA is not
Haemoglobins are chemically similar molecules found in many different species.
Differences in the primary structure of haemoglobin molecules can provide evidence
of phylogenetic (evolutionary) relationships between species. Explain how -
ANSWER1. Mutations change base / nucleotide (sequence); 2. (Causing) change in
amino acid sequence; 3. Mutations build up over time; 4. More mutations / more
differences (in amino acid / base / nucleotide sequence / primary structure) between
distantly related species; OR Few(er) mutations / differences (in amino acid / base /
nucleotide sequence / primary structure) in closely related species; 5. Distantly
related species have earlier common ancestor; OR Closely related species have
recent common ancestor
Explain why students were unable to make a conclusion from the table? - ANSWER-
missing information -so cannot compare all stages -no statistical comparison of
standard deviations given or no measure of significant differences
Why do we press down firmly on the cover slip? - ANSWERTo form a thin layer of
cells so light passes through making cells visible
Describe and explain what the student should have done when counting cells to
make sure that the mitotic index he obtained for this root tip was accurate -
ANSWER• Examine large number of fields of view to ensure representative sample
• Repeat count to ensure figures are correct
• Count only whole cells to standardise counting
Where do hydrogen bonds form? - ANSWERHydrogen bonds form between NH and
C=O groups in a protein's secondary structure
Scientists looking for extra-terrestrial life are looking for planets with evidence of
free water. Explain why water is considered so important for life to occur. -
ANSWERLife evolved in water. Water provides support (for bodies of organisms).
Water is a major component of cytoplasm. Metabolic reactions occur in aqueous
, solutions (solvent). Water is a metabolite/reactant is many cell reactions. Water
stabilises temperature (high specific heat capacity). Important in cooling (high latent
heat).
Limiting water loss in insects - ANSWER-Small surface area to volume ratio, to
minimise the area over which water is lost.
-Exoskeleton covered with a waterproof cuticle.
-Spiracles remain closed to minimise water loss.
Describe the difference between the structure of a triglyceride molecule and the
structure of a phospholipid molecule (1 mark) - ANSWERIn phospholipids, one of the
fatty acid chains are *replaced* by a phosphate group
Explain why it is more useful to calculate an index of diversity than to record species
richness. - ANSWERMeasures abundance of each species because there may be
many of 1 species or very few of one species.
Suggest how scientists measured the rate of water flow in the river. -
ANSWERmeasured time to fill a container of a known volume.
slow water flow leads to... - ANSWERless oxygen dissolved in water so less
respiration for aquatic life
How to standardise a sampling procedure. - ANSWERuse same size measuring object
same size of area sampled
same sampling time
Not all mutations in the nucleotide sequence of a gene cause a change in the
structure of a polypeptide. Give two reasons why. - ANSWERdegenerate code
could happen in introns/non coding
Suggest a method that could be used to measure the quantity of reducing sugar in a
solution. - ANSWERFilter and dry the precipitate
Weigh/find mass
Why using a colorimeter improves the repeatability of the student's results. -
ANSWERquantitative
colour change is subjective
standardises values
Explain how the active site of an enzyme causes a high rate of reaction. -
ANSWEREnzyme lowers the activation energy.
Induced fit causes the active site of the enzyme to change shape.
Enzyme-Substrate complex causes the bonds to break.
Why anti HIV drugs do not destroy HIV in the body but stops or slows the
development of AIDS. - ANSWERInitially the person still has HIV DNA in their DNA.
