AS
BIOLOGY
Paper 1
2020 - scan
Materials
For this paper you must have:
a ruler with millimetre measurements
a scientific calculator, which you are expected to use where appropriate.
Instructions
Use black
...
AS
BIOLOGY
Paper 1
2020 - scan
Materials
For this paper you must have:
a ruler with millimetre measurements
a scientific calculator, which you are expected to use where appropriate.
Instructions
Use black ink or black ball-point pen.
Fill in the boxes at the top of this page.
Answer all questions.
You must answer the questions in the spaces provided. Do not write
outside the box around each page or on blank pages.
All working must be shown.
Do all rough work in this book. Cross through any work you do not want
to be marked.
Information
The marks for questions are shown in brackets.
The maximum mark for this paper is 75.
For Examiner’s Use
Question Mark
1
2
3
4
5
6
7
8
9
10
TOTAL
Do not write
outside the
box
2
*02*
1
2
Answer all questions in the spaces provided.
0 1 Figure 1 shows part of a DNA molecule.
Figure 1
. How many nucleotides are shown in Figure 1?
[1 mark]
. Name the type of bond labelled X in Figure 1.
[1 mark]
0 1
0 1
Do not write
outside the
box
3
*03*
6
0 1 . 3 The enzymes DNA helicase and DNA polymerase are involved in DNA
replication.
Describe the function of each of these enzymes.
[2 marks]
DNA helicase
DNA polymerase
0 1
. 4 Adenosine triphosphate (ATP) is a nucleotide derivative.
Contrast the structures of ATP and a nucleotide found in DNA to give two
differences.
[2 marks]
1
2
Turn over ►
Do not write
outside the
box
4
*04*
A student investigated the effect of three types of disinfectant on the growth of
Lactobacillus bacteria.
During the investigation, the student:
boiled the agar before pouring the agar plates
transferred 0.5 cm3
of a diluted liquid culture of Lactobacillus onto each agar
plate
left some agar plates as controls
added to other agar plates different concentrations of the disinfectants as
shown in Table 1 on page 5.
After 2 days, she counted the number of colonies of bacteria on each agar plate.
0 2
. 1 Explain the purpose of:
[2 marks]
boiling the agar
transferring the same volume of liquid culture onto each agar plate.
0 2
Do not write
outside the
box
5
*05*
2
The three disinfectants used by the student were Lysol, propan-2-ol and
ammonia.
Table 1 shows the student’s results.
Table 1
Concentration of
disinfectant /
arbitrary units
Number of colonies of bacteria
Lysol Propan-2-ol Ammonia
0 300 300 300
5 0 290 300
10 0 195 295
15 0 0 275
20 0 0 240
. The liquid culture the student transferred was diluted by 1 in 10 000 (10–4
).
Use information in this question to calculate how many bacteria were present in
1 cm3
of undiluted liquid culture.
[2 marks]
Answer =
Question 2 continues on the next page
Turn over ►
0 2
Do not write
outside the
box
6
*06*
3
6
. The student concluded that the minimum concentration of propan-2-ol needed to
stop the growth of Lactobacillus was 15 units. This conclusion is incorrect.
Describe how you could obtain a more accurate estimate of the minimum
concentration of propan-2-ol needed to stop the growth of this species of
bacterium.
[2 marks]
0 2
Do not write
outside the
box
7
Turn over for the next question
DO NOT WRITE ON THIS PAGE
ANSWER IN THE SPACES PROVIDED
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