A student measured his reaction time. His partner held a ruler with the 0 cm mark level with the top of the student's thumb, then dropped it without warning. The student caught it as quickly as possible, and the partner read the distance fallen.
Conversion table from distance fallen to reaction time: 10 cm, 0.143 s; 11 cm, 0.150 s; 12 cm, 0.156 s; 13 cm, 0.163 s; 14 cm, 0.169 s; 15 cm, 0.175 s.
Distance fallen (cm)
10
11
12
13
14
15
Reaction time (s)
0.143
0.150
0.156
0.163
0.169
0.175
.1
In five trials the ruler fell 15 cm, 12 cm, 14 cm, 11 cm and 13 cm.
Calculate the mean distance.
[2 marks]
.2
Use the conversion table to give the student's mean reaction time.
[1 mark]
.3
Give two variables the student should control to make his results valid.
[2 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Some strains of bacteria are resistant to antibiotics. MRSA is resistant to several antibiotics.
.1
Explain how a population of bacteria becomes resistant to an antibiotic.
[4 marks]
.2
Give two ways to reduce the rate at which antibiotic-resistant strains develop.
[2 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A student investigated the effect of pH on the time taken for amylase to break down starch.
She mixed amylase, starch and a buffer solution in a water bath at 35 °C. Every 30 seconds she put a drop of the mixture onto iodine solution on a spotting tile. She recorded the time when the iodine no longer turned blue-black.
Time for starch to be broken down: pH 5, 150 s; pH 6, 90 s; pH 7, 60 s; pH 8, 120 s; pH 9, 240 s.
pH
Time for starch to be broken down (s)
5
150
6
90
7
60
8
120
9
240
.1
The rate of reaction can be found with:
rate =time1000
Calculate the rate of reaction at pH 7.
[1 mark]
.2
Explain why the starch took much longer to break down at pH 9.
[2 marks]
.3
Suggest how the student could find the optimum pH of amylase more precisely.
[1 mark]
.4
Sampling every 30 seconds limits the accuracy of the times.
Explain why.
[1 mark]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Scientists compared two ways of growing new bone cells to repair a damaged bone.
Method A uses adult stem cells from the patient's own bone marrow.
Method B uses stem cells from an embryo.
The table shows their results.
Table comparing method A (bone marrow stem cells) and method B (embryonic stem cells): cells after 14 days, 18 million and 45 million; percentage becoming bone cells, 85 and 55.
Measurement
Method A: bone marrow
Method B: embryo
Cells after 14 days (millions)
18
45
Cells that became bone cells (%)
85
55
.1
Compare the results of method A and method B.
[2 marks]
.2
Calculate how many bone cells method B produced. Give your answer in millions.
[1 mark]
.3
Suggest one advantage of method A for the patient that is not shown in the table.
[1 mark]
4 marksFoundation
Spec and skills
Original practice question
Answer and supported method checks
Animal cells, plant cells and bacterial cells contain different structures.
.1
What is the function of mitochondria?
[1 mark]
.2
Name the structure in a plant cell that absorbs light for photosynthesis.
[1 mark]
.3
Which two structures are found in a bacterial cell? Tick two boxes.
