A-LEVEL BIOLOGY MARK SCHEME
Practice Paper 3 Maximum marks: 78
View detailed guidance on the conclusions you can draw from your students' performance in
these papers on the MERiT welcome page. Understand how your students compare with
others and target revision effectively by entering marks into MERiT.
1 (a) Introns; 1
(b) Ile Gly Val Ser; 1
(c) (i) Has no effect / same amino acid (sequence) / same 1
primary structure;
Reject same amino acid formed or produced.
Glycine named as same amino acid; 1
It still codes for glycine = two marks.
(ii) Leu replaces Val / change in amino acid (sequence) / primary structure;
Change in hydrogen / ionic bonds which alters tertiary structure / active site;
Different amino acid formed or produced negates first marking
point.
Substrate cannot bind / no longer complementary / 3
no enzyme-substrate complexes form;
Active site changed must be clear for third marking point but
does not need reference to shape.
(d) (i) Interphase / S / synthesis (phase); 1
(ii) DNA / gene replication / synthesis occurs / longest stage; 1
Allow ‘genetic information’ = DNA.
Allow ‘copied’ or ‘formed’ = replication / synthesis
[Total 9 marks]
2 (a) (i) where mitosis / division / growing / occurs 1
(reject growing cells)
(ii) to distinguish chromosomes / chromosomes not visible without stain; 1
(iii) to let light through / thin layer; 1
to make a single layer of cells
(b) (i) 74 + ; 2
= 9.4% / 9%;
(allow 1 mark for identifying prophase & metaphase i.e.92 or
correct method using wrong figures)
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, (ii) genetic differences / different types of garlic; 2 max
time of day;
chance;
age of root tip;
water availability;
temperature;
nutrient availability;
(environmental factors = 1 but cannot be awarded in addition to
a named environmental factor)
[Total 7 marks]
3 (a) Aorta; 1
(b) 1. Left ventricle pumps to whole body (except lungs) / pumps blood further; 2
Accept converse for right ventricle
Reject ‘push’
2 Left ventricle does most work / produces a greater pressure /
produces a greater force;
(c) 1. (Valve A) atrioventricular valve; 2
Accept bicuspid / mitral
2. Semi-lunar valve;
Accept aortic valve
Ignore references to left and right
(d) X because (no mark) 3
Accept other valid calculations - probabilities
1 52% survived without replacement compared to 12% / difference of 40%;
If correct figures written in table, award marks
2. 11% required repair or replacement of artificial heart compared to 41% /
difference of 30%;
Max 2 if incorrect rounding of values
3. 37% died compared to 46% / difference of 9%;
OR (X / Y = 119 divided by 58 = 2.05)
14.4; 49.2; 55.4;
Note that this ratio could be reversed i.e. 58 divided by 119
multiplied by numbers in top row
Accept rounded to 14; 49; and 55;
[Total 8 marks]
4 (a) 1. (Phosphate) changes shape of TK / changes shape of enzyme / 2
changes the active site;
It = phosphate
Accept ‘alters’ for changes
Reject that phosphate is an inhibitor
Accept adding energy / affecting charged / affects polar groups
(on amino acids)
2. Active site forms / becomes the right shape / can bind to substrate /
complementary to substrate / E-S complex can form;
Reject similar / same shape as substrate
(b) 1. Faulty TK has functional active site without phosphate; 2
Accept ‘works without phosphate’
2. (So, faulty) TK functional all the time / TK not controlled (by phosphate);
This document is licensed to Haggerston School - MB260045
Practice Paper 3 Maximum marks: 78
View detailed guidance on the conclusions you can draw from your students' performance in
these papers on the MERiT welcome page. Understand how your students compare with
others and target revision effectively by entering marks into MERiT.
1 (a) Introns; 1
(b) Ile Gly Val Ser; 1
(c) (i) Has no effect / same amino acid (sequence) / same 1
primary structure;
Reject same amino acid formed or produced.
Glycine named as same amino acid; 1
It still codes for glycine = two marks.
(ii) Leu replaces Val / change in amino acid (sequence) / primary structure;
Change in hydrogen / ionic bonds which alters tertiary structure / active site;
Different amino acid formed or produced negates first marking
point.
Substrate cannot bind / no longer complementary / 3
no enzyme-substrate complexes form;
Active site changed must be clear for third marking point but
does not need reference to shape.
(d) (i) Interphase / S / synthesis (phase); 1
(ii) DNA / gene replication / synthesis occurs / longest stage; 1
Allow ‘genetic information’ = DNA.
Allow ‘copied’ or ‘formed’ = replication / synthesis
[Total 9 marks]
2 (a) (i) where mitosis / division / growing / occurs 1
(reject growing cells)
(ii) to distinguish chromosomes / chromosomes not visible without stain; 1
(iii) to let light through / thin layer; 1
to make a single layer of cells
(b) (i) 74 + ; 2
= 9.4% / 9%;
(allow 1 mark for identifying prophase & metaphase i.e.92 or
correct method using wrong figures)
This document is licensed to Haggerston School - MB260045
, (ii) genetic differences / different types of garlic; 2 max
time of day;
chance;
age of root tip;
water availability;
temperature;
nutrient availability;
(environmental factors = 1 but cannot be awarded in addition to
a named environmental factor)
[Total 7 marks]
3 (a) Aorta; 1
(b) 1. Left ventricle pumps to whole body (except lungs) / pumps blood further; 2
Accept converse for right ventricle
Reject ‘push’
2 Left ventricle does most work / produces a greater pressure /
produces a greater force;
(c) 1. (Valve A) atrioventricular valve; 2
Accept bicuspid / mitral
2. Semi-lunar valve;
Accept aortic valve
Ignore references to left and right
(d) X because (no mark) 3
Accept other valid calculations - probabilities
1 52% survived without replacement compared to 12% / difference of 40%;
If correct figures written in table, award marks
2. 11% required repair or replacement of artificial heart compared to 41% /
difference of 30%;
Max 2 if incorrect rounding of values
3. 37% died compared to 46% / difference of 9%;
OR (X / Y = 119 divided by 58 = 2.05)
14.4; 49.2; 55.4;
Note that this ratio could be reversed i.e. 58 divided by 119
multiplied by numbers in top row
Accept rounded to 14; 49; and 55;
[Total 8 marks]
4 (a) 1. (Phosphate) changes shape of TK / changes shape of enzyme / 2
changes the active site;
It = phosphate
Accept ‘alters’ for changes
Reject that phosphate is an inhibitor
Accept adding energy / affecting charged / affects polar groups
(on amino acids)
2. Active site forms / becomes the right shape / can bind to substrate /
complementary to substrate / E-S complex can form;
Reject similar / same shape as substrate
(b) 1. Faulty TK has functional active site without phosphate; 2
Accept ‘works without phosphate’
2. (So, faulty) TK functional all the time / TK not controlled (by phosphate);
This document is licensed to Haggerston School - MB260045
