Tuesday 16 June 2026 – Morning
A Level Biology A
H420/03 Unified biology
Time allowed: 1 hour 30 minutes
You can use:
GCE
*
• a scientific or graphical calculator
• a ruler (cm/mm)
Biology A
H420/03: Unified biology
* H 4 2 0 0 3 *
*
Please write clearly in black ink. Do not write in the barcodes. A Level
Centre number Candidate number
Mark Scheme for June 2026
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 24 pages.
ADVICE
• Read each question carefully before you start your answer.
Cambridge 2026 [601/4260/1] Cambridge is an exempt Charity
DC (CJ/TC) 359628/4 Turn over
Cambridge
, 2
BLANK PAGE
Cambridge is a leading UK awarding body, providing a wide range of qualifications to
meet the needs of candidates of all ages and abilities. Cambridge qualifications include
AS/A Levels, Diplomas, GCSEs, Cambridge Nationals, Cambridge Technicals, Functional Skills,
Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT,
business, languages, teaching/training, administration and secretarial skills.
It is also responsible for developing new specifications to meet national requirements and the
needs of students and teachers. Cambridge is a not-for-profit organisation; any surplus
made is invested back into the establishment to help towards the development of qualifications
and support, which keep pace with the changing needs of today’s society.
This mark scheme is published as an aid to teachers and students, to indicate the requirements
of the examination. It shows the basis on which marks were awarded by examiners. It does not
indicate the details of the discussions which took place at an examiners’ meeting before marking
commenced.
All examiners are instructed that alternative correct answers and unexpected approaches in
candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills
demonstrated.
Mark schemes should be read in conjunction with the published question papers and the report
on the examination.
DO NOT WRITE ON THIS PAGE
Cambridge 2026
Cambridge 2026
Cambridge
, H420/03 Mark Scheme June 2026
3
1 The liver is an organ with many roles. Marking Instructions
(a) The transmission electron micrograph shows a section through liver tissue. Preparation For Marking
1. RM Assessor
An adult human liver contains millions of the blood vessel labelled B. Blood flows from an
arteriole and a hepatic portal venule into these blood vessels. • Access and complete the on-screen marking training packages: Examiner Training (RMA3).
• Read the mark scheme and question paper for this component or unit.
• The mark scheme and question paper are available in RM Assessor or on your Component Page if you use the Training Platform for
standardisation.
Hepatocyte • Log in to RM Assessor and mark the required number of practice scripts and the required number of standardisation scripts.
A
Marking
2. General Guidance
• Mark strictly to the mark scheme.
• Marks awarded must relate directly to the marking criteria.
• If you are in any doubt about applying the mark scheme, consult your Team Leader by phone, email or via the RM Assessor messaging
system.
×1800
• It is essential that you meet the RM Assessor 50% and 100% batch deadlines. For traditional marking this will be 40% and 100%. If you
B experience problems, contact your Team Leader without delay.
Name the cell labelled A and the blood vessel labelled B. • Always check the pages (and additional objects if present) at the end of the response in case any answers have been continued there. If the
candidate has continued an answer there, then add the annotation ‘SEEN’ to confirm that the work has been seen and mark any responses
A ....................................................................................................................................................... using the annotations.
B ....................................................................................................................................................... • The RM Assessor comments box is used by your Team Leader to explain the marking of the practice responses. Use these comments when
[2] checking your practice responses. Do not use the comments box for any other reason.
(b) Outline the role of the liver in carbohydrate metabolism.
2
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [2]
Cambridge 2026 Turn over
, H420/03 Mark Scheme June 2026
4
A student asks their teacher: ‘Should the liver be thought of as an organ of excretion?’
• Before the end of the marking period send a brief report on the performance of candidates to your Team Leader via email. The report should
Discuss whether or not the liver should be thought of as an organ of excretion. contain notes on strengths displayed as well as common errors or weaknesses. Constructive criticism of the question paper/mark scheme is
also appreciated.
..........................................................................................................................................................
.......................................................................................................................................................... 3. No Response and Crossed-out Answers
.......................................................................................................................................................... Using the No Response (NR) option. Only mark as NR if:
.......................................................................................................................................................... - the answer space is blank
.......................................................................................................................................................... - there is only a comment not related to the question (e.g., ‘can’t do’, ‘don’t know’)
- there is only a mark (e.g., a dash, a question mark) which is not an attempt at the question.
..........................................................................................................................................................
Note: Enter 0 marks for an attempt that earns no credit (including copying out the question). Do not use NR.
..........................................................................................................................................................
..................................................................................................................................................... [3] Crossed-out answers
If a candidate has crossed out an answer and written a clear alternative, do not mark the crossed-out answer.
(d) Catalase is an enzyme that is present in tissues throughout the body. Concentrations of catalase
are especially high in the liver. If a candidate has crossed out an answer and not written a clear alternative, mark the crossed-out answer if it is readable.
The breakdown of hydrogen peroxide (H2O2) is catalysed by the enzyme catalase.
4. Responses with more answers than needed
The diagram shows how H2O2 is broken down in the active site of catalase.
• Multiple-choice question answers
H2O2 When a multiple-choice question has only one correct answer and a candidate has written two or more answers (even if one of these answers is
H 2O O2
correct), do not award a mark.
Active site When a multiple-choice question asks candidates to select more than one option the marking guidance from your Principal Examiner will ensure
O
consistency of approach.
Fe4+
Fe3+ Fe3+ • Contradictory answers in points-based questions
Do not award any marks, even if one of the answers is correct.
Oxygen atom from H2O2 Oxygen atom reacts 3
binds to the active site with another H2O2 to
produce O2
Suggest what can be concluded from the diagram about the mechanism of action of catalase.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [2]
Cambridge 2026
A Level Biology A
H420/03 Unified biology
Time allowed: 1 hour 30 minutes
You can use:
GCE
*
• a scientific or graphical calculator
• a ruler (cm/mm)
Biology A
H420/03: Unified biology
* H 4 2 0 0 3 *
*
Please write clearly in black ink. Do not write in the barcodes. A Level
Centre number Candidate number
Mark Scheme for June 2026
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 24 pages.
ADVICE
• Read each question carefully before you start your answer.
Cambridge 2026 [601/4260/1] Cambridge is an exempt Charity
DC (CJ/TC) 359628/4 Turn over
Cambridge
, 2
BLANK PAGE
Cambridge is a leading UK awarding body, providing a wide range of qualifications to
meet the needs of candidates of all ages and abilities. Cambridge qualifications include
AS/A Levels, Diplomas, GCSEs, Cambridge Nationals, Cambridge Technicals, Functional Skills,
Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT,
business, languages, teaching/training, administration and secretarial skills.
It is also responsible for developing new specifications to meet national requirements and the
needs of students and teachers. Cambridge is a not-for-profit organisation; any surplus
made is invested back into the establishment to help towards the development of qualifications
and support, which keep pace with the changing needs of today’s society.
This mark scheme is published as an aid to teachers and students, to indicate the requirements
of the examination. It shows the basis on which marks were awarded by examiners. It does not
indicate the details of the discussions which took place at an examiners’ meeting before marking
commenced.
All examiners are instructed that alternative correct answers and unexpected approaches in
candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills
demonstrated.
Mark schemes should be read in conjunction with the published question papers and the report
on the examination.
DO NOT WRITE ON THIS PAGE
Cambridge 2026
Cambridge 2026
Cambridge
, H420/03 Mark Scheme June 2026
3
1 The liver is an organ with many roles. Marking Instructions
(a) The transmission electron micrograph shows a section through liver tissue. Preparation For Marking
1. RM Assessor
An adult human liver contains millions of the blood vessel labelled B. Blood flows from an
arteriole and a hepatic portal venule into these blood vessels. • Access and complete the on-screen marking training packages: Examiner Training (RMA3).
• Read the mark scheme and question paper for this component or unit.
• The mark scheme and question paper are available in RM Assessor or on your Component Page if you use the Training Platform for
standardisation.
Hepatocyte • Log in to RM Assessor and mark the required number of practice scripts and the required number of standardisation scripts.
A
Marking
2. General Guidance
• Mark strictly to the mark scheme.
• Marks awarded must relate directly to the marking criteria.
• If you are in any doubt about applying the mark scheme, consult your Team Leader by phone, email or via the RM Assessor messaging
system.
×1800
• It is essential that you meet the RM Assessor 50% and 100% batch deadlines. For traditional marking this will be 40% and 100%. If you
B experience problems, contact your Team Leader without delay.
Name the cell labelled A and the blood vessel labelled B. • Always check the pages (and additional objects if present) at the end of the response in case any answers have been continued there. If the
candidate has continued an answer there, then add the annotation ‘SEEN’ to confirm that the work has been seen and mark any responses
A ....................................................................................................................................................... using the annotations.
B ....................................................................................................................................................... • The RM Assessor comments box is used by your Team Leader to explain the marking of the practice responses. Use these comments when
[2] checking your practice responses. Do not use the comments box for any other reason.
(b) Outline the role of the liver in carbohydrate metabolism.
2
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [2]
Cambridge 2026 Turn over
, H420/03 Mark Scheme June 2026
4
A student asks their teacher: ‘Should the liver be thought of as an organ of excretion?’
• Before the end of the marking period send a brief report on the performance of candidates to your Team Leader via email. The report should
Discuss whether or not the liver should be thought of as an organ of excretion. contain notes on strengths displayed as well as common errors or weaknesses. Constructive criticism of the question paper/mark scheme is
also appreciated.
..........................................................................................................................................................
.......................................................................................................................................................... 3. No Response and Crossed-out Answers
.......................................................................................................................................................... Using the No Response (NR) option. Only mark as NR if:
.......................................................................................................................................................... - the answer space is blank
.......................................................................................................................................................... - there is only a comment not related to the question (e.g., ‘can’t do’, ‘don’t know’)
- there is only a mark (e.g., a dash, a question mark) which is not an attempt at the question.
..........................................................................................................................................................
Note: Enter 0 marks for an attempt that earns no credit (including copying out the question). Do not use NR.
..........................................................................................................................................................
..................................................................................................................................................... [3] Crossed-out answers
If a candidate has crossed out an answer and written a clear alternative, do not mark the crossed-out answer.
(d) Catalase is an enzyme that is present in tissues throughout the body. Concentrations of catalase
are especially high in the liver. If a candidate has crossed out an answer and not written a clear alternative, mark the crossed-out answer if it is readable.
The breakdown of hydrogen peroxide (H2O2) is catalysed by the enzyme catalase.
4. Responses with more answers than needed
The diagram shows how H2O2 is broken down in the active site of catalase.
• Multiple-choice question answers
H2O2 When a multiple-choice question has only one correct answer and a candidate has written two or more answers (even if one of these answers is
H 2O O2
correct), do not award a mark.
Active site When a multiple-choice question asks candidates to select more than one option the marking guidance from your Principal Examiner will ensure
O
consistency of approach.
Fe4+
Fe3+ Fe3+ • Contradictory answers in points-based questions
Do not award any marks, even if one of the answers is correct.
Oxygen atom from H2O2 Oxygen atom reacts 3
binds to the active site with another H2O2 to
produce O2
Suggest what can be concluded from the diagram about the mechanism of action of catalase.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [2]
Cambridge 2026
