Original questions for every area of study, with worked explanations.
Multiple choice
Section A style, worked or timed
Section B
Short and extended answers, scenarios and investigations
Written answers
Read against the mark points, with your next step
Practice papers
Two 40-question Section A papers
Try 4 questions
Question 1
Oxygen used by isolated mitochondria with different additions.
Tube
Substrate added
Cytosol extract added
Oxygen used / µmol per minute
1
Glucose
No
0.1
2
Pyruvate
No
4.8
3
Glucose
Yes
4.5
In a hypothetical experiment, mitochondria were separated from liver cells and placed in a buffer with plenty of oxygen, ADP and phosphate. Each tube was given one substrate, and some tubes also received an extract of cytosol with no mitochondria. The table shows the oxygen used. Which explanation fits all three results?
Question 2
Antibody level against the toxin in persons X and Y on five days after day 0.
Day
Person X / arbitrary units
Person Y / arbitrary units
0
100
0
7
70
5
14
45
40
28
15
60
56
2
50
On day 0, person X and person Y were each protected against a bacterial toxin. One was injected with antibodies against the toxin; the other was given a vaccine of inactivated toxin. The table shows the hypothetical antibody level in each person. Both meet the toxin again on day 120. Which prediction is best supported?
Question 3
Amino acid differences in one protein between four hypothetical species.
Species
W
X
Y
Z
W
0
2
9
14
X
2
0
8
15
Y
9
8
0
13
Z
14
15
13
0
The table gives the number of amino acid differences in one protein between four hypothetical mammal species, W, X, Y and Z. Which phylogenetic tree is best supported by these data?
Question 4
To make human insulin in E. coli, the inserted DNA is made from mature mRNA (or synthesised from the known sequence) rather than cut from a human chromosome. Why?