worked solutions
model answers
, Oxford Cambridge and RSA
Thursday 5 June 2025 – Afternoon
A Level Biology A
H420/01 Biological processes
Time allowed: 2 hours 15 minutes
You can use:
* 1 8 4 7 3 5 9 7 5 2 *
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 4 2 0 0 1 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
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 100.
• 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 32 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2025 [601/4260/1] OCR is an exempt Charity
DC (PQ/FC) 346176/6 Turn over
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, 2
Section A
You should spend a maximum of 20 minutes on this section.
Write your answer to each question in the box provided.
1 Which option describes a function of inorganic ions?
A Ca2+ is pumped across the membrane of a neurone to establish the resting potential.
B Cl – and HCO3– are involved in transport of oxygen in the blood.
C Plants need NO3– for synthesis of amino acids.
D PO43− is a component of triglycerides.
Your answer [1]
2 Which option describes a conjugated protein?
A A globular protein with a prosthetic group
B A protein with an inorganic ion
C A protein with more than one polypeptide chain
D An enzyme with an inorganic ion
Your answer [1]
3 Which statement about the function of enzymes is not correct?
A Enzymes affect the structure of whole organisms.
B Enzymes build larger molecules from smaller molecules.
C Enzymes carry signals from one part of the body to another.
D Enzymes catalyse reactions that affect cellular metabolism.
Your answer [1]
© OCR 2025
for more: tyrionpapers.com
, 3
4 Which option describes the structure of biological molecules?
A Carbohydrates contain only C, H and O, usually with an H to O ratio of 2 : 1.
B Nucleic acids contain only C, H, O, N, P and S in variable ratios.
C Proteins contain only C, H, O and N in variable ratios.
D Triglycerides contain only C, H and O, usually with an H to O ratio of 2 : 1.
Your answer [1]
5 Which option describes endocrine communication?
A Endocrine glands release hormones into ducts such as the pancreatic duct.
B Hormones are all lipid soluble and bind to receptors in the cytoplasm.
C Hormones are released from exocrine glands and taken by the blood to specific target cells.
D Target cells have specific receptors for the hormones that act upon them.
Your answer [1]
6 Which option describes a role of the adrenal glands within the endocrine system?
A Adrenaline is produced by the adrenal cortex.
B Glucocorticoids help to regulate the balance of salt and water concentrations in the body.
C Mineralocorticoids are produced in the adrenal medulla.
D The adrenal cortex secretes steroid hormones.
Your answer [1]
© OCR 2025 Turn over
for more: tyrionpapers.com
model answers
, Oxford Cambridge and RSA
Thursday 5 June 2025 – Afternoon
A Level Biology A
H420/01 Biological processes
Time allowed: 2 hours 15 minutes
You can use:
* 1 8 4 7 3 5 9 7 5 2 *
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 4 2 0 0 1 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
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 100.
• 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 32 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2025 [601/4260/1] OCR is an exempt Charity
DC (PQ/FC) 346176/6 Turn over
for more: tyrionpapers.com
, 2
Section A
You should spend a maximum of 20 minutes on this section.
Write your answer to each question in the box provided.
1 Which option describes a function of inorganic ions?
A Ca2+ is pumped across the membrane of a neurone to establish the resting potential.
B Cl – and HCO3– are involved in transport of oxygen in the blood.
C Plants need NO3– for synthesis of amino acids.
D PO43− is a component of triglycerides.
Your answer [1]
2 Which option describes a conjugated protein?
A A globular protein with a prosthetic group
B A protein with an inorganic ion
C A protein with more than one polypeptide chain
D An enzyme with an inorganic ion
Your answer [1]
3 Which statement about the function of enzymes is not correct?
A Enzymes affect the structure of whole organisms.
B Enzymes build larger molecules from smaller molecules.
C Enzymes carry signals from one part of the body to another.
D Enzymes catalyse reactions that affect cellular metabolism.
Your answer [1]
© OCR 2025
for more: tyrionpapers.com
, 3
4 Which option describes the structure of biological molecules?
A Carbohydrates contain only C, H and O, usually with an H to O ratio of 2 : 1.
B Nucleic acids contain only C, H, O, N, P and S in variable ratios.
C Proteins contain only C, H, O and N in variable ratios.
D Triglycerides contain only C, H and O, usually with an H to O ratio of 2 : 1.
Your answer [1]
5 Which option describes endocrine communication?
A Endocrine glands release hormones into ducts such as the pancreatic duct.
B Hormones are all lipid soluble and bind to receptors in the cytoplasm.
C Hormones are released from exocrine glands and taken by the blood to specific target cells.
D Target cells have specific receptors for the hormones that act upon them.
Your answer [1]
6 Which option describes a role of the adrenal glands within the endocrine system?
A Adrenaline is produced by the adrenal cortex.
B Glucocorticoids help to regulate the balance of salt and water concentrations in the body.
C Mineralocorticoids are produced in the adrenal medulla.
D The adrenal cortex secretes steroid hormones.
Your answer [1]
© OCR 2025 Turn over
for more: tyrionpapers.com
