AQA AS Biology 7401/1 Paper 1 June 2024 Question Paper and Mark Scheme STUDY BUNDLE PACKAGE WITH COMPLETE SOLUTIONS

AQA AS Biology 7401/1 Paper 1 June 2024 Question
Paper and Mark Scheme STUDY BUNDLE PACKAGE
WITH COMPLETE SOLUTIONS
The nucleus and a chloroplast of a plant cell both contain DNA.
Give three ways in which the DNA in a chloroplast is different from DNA in the
nucleus.
[3 marks] - ANSWERIn chloroplasts
-DNA shorter;
-Fewer genes;
-DNA circular not linear;
-Not associated with protein/histones, unlike nuclear DNA;
-Introns absent but present in nuclear DNA;

Some DNA nucleotides have the organic base thymine, but RNA nucleotides do not
have thymine. RNA nucleotides have uracil instead of thymine.
Give one other difference between the structure of a DNA nucleotide and the
structure of an RNA nucleotide.
[1 mark] - ANSWERDeoxyribose in DNA and Ribose in RNA

Not all mutations in the nucleotide sequence of a gene cause a change in the
structure of a polypeptide.
Give two reasons why.
[2 marks] - ANSWER1. Triplets code for same amino acid2. Occurs in introns /non-
coding sequence;

What is a monoclonal antibody?
[1 mark] - ANSWER(Antibodies with the) same tertiary structure
OR
(Antibody produced from) identical/cloned plasma cells/B cells/B lymphocytes;

After a disease is diagnosed, monoclonal antibodies are used in some medical
treatments.
Give one example of using monoclonal antibodies in a medical treatment.
[1 mark] - ANSWERAccept any one suitable use, eg Targets/binds/carries
drug/medicine to specific
cells/antigens/receptors
OR
Block antigens/receptors on cells;

Describe the role of antibodies in producing a positive result in an ELISA test.
[4 marks] - ANSWER1. (First) antibody binds/attaches /complementary (in shape) to
antigen;
2. (Second) antibody with enzyme attached is added;
3. (Second) antibody attaches to antigen;4. (Substrate/solution added) and colour
changes;

,Write the chemical group in each glucose molecule used to form a glycosidic bond.
[1 mark] - ANSWEROH, HO

A precipitate is produced in a positive result for reducing sugar in a Benedict's test. A
precipitate is solid matter suspended in solution.
A student carried out the Benedict's test. Suggest a method, other than using a
colorimeter, that this student could use to measure the quantity of reducing sugar in
a
solution.
[2 marks] - ANSWER1. Filter and dry (the precipitate);
2. Find mass/weight;

In an investigation, a student wanted to identify the solutions in two beakers, A and
B. She knew one beaker contained maltose solution and the other beaker contained
glucose solution. Both solutions had the same concentration.
She did two separate biochemical tests on a sample from each beaker.
Test 1 - used Benedict's solution to test for reducing sugar.
Test 2 - added the enzyme maltase, heated the mixture at 30 °C for 5 minutes, and
then used Benedict's solution to test for reducing sugar.
Maltose is hydrolysed by maltase.The student's results are shown in Table 1:
Beaker A- Red (Test 1), Red (Test 2)
Beaker B- Red (Test 1), Dark red (Test 2)
Explain the results for beakers A and B in Table 1.
[2 marks] - ANSWERA = glucose and B = maltose;
Because more sugar/precipitate after hydrolysis/maltase action;

Use of a colorimeter in this investigation would improve the repeatability of the
student's results.
Give one reason why.
[1 mark] - ANSWER1. Quantitative
OR
(Colour change is) subjective; 2. Standardises (the) method;

Explain why it is more useful to calculate an index of diversity than to record species
richness.
[2 marks] - ANSWER1. (Index of diversity also) measures abundance / number /
population (size) of each species;
2. (So useful because) may be many of some species
OR
(So useful because) may be few of other species;

Suggest how the scientist measured the rate of water flow in the river.
[1 mark] - ANSWER1. Movement of (floating) object over known distance and over
given timeORTime to fill container of known volume OR
Use of data logging device;

, explain a reason for the
difference in the numbers of Slate Drake mayfly at these sites in this river.
[2 marks]
Hint: Site 1 has less mayfly than Site 2 - ANSWER1. Less food/prey at site 1; 2. (So
more) mayfly starve;
OR
3. Less oxygen at site 1;4. (So) less respiration/ATP/energy (for mayflies);
OR
5. More predators/Anglers' Curse at site 1; 6. (So more) mayfly
killed/eaten/removed;
OR
7. More competition at site 1; 8. (So more) mayfly starve;

It was important that the sampling procedure was standardised when collecting the
Slate Drake mayflies from the two sites.
Give one way in which the sampling procedure could be standardised.
[1 mark] - ANSWERSame size of area (sampled)
OR
Same size net/mesh
OR
Same sampling time
OR
Samples taken at same time of day/on same day;

The detail shown in an organelle would not be seen using an optical microscope.
Explain why.
[2 marks] - ANSWER1. Light has long(er) wavelength;
2. (So) low(er) resolution;

Name an organelle found in both a chloroplast and a prokaryotic cell.
[1 mark] - ANSWER(70S) Ribosome;

A biologist separated cell components to investigate organelle activity. She prepared
a suspension of the organelles in a solution that prevented damage to the
organelles.
Describe three properties of this solution and explain how each property prevented
damage to the organelles.
[3 marks] - ANSWER-(Ice) cold to prevent/reduce enzyme activity;
-Buffered to prevent denaturing of enzyme/protein;
-Same water potential/Ψ to prevent lysis/bursting (of organelle);

Describe and explain the advantage of the counter-current principle in gas exchange
across a fish gill.
[3 marks] - ANSWERWater and blood flow in opposite directions;
Maintains diffusion/concentration gradient of oxygen
OR
Oxygen concentration always higher (in water);