2024_OCR: A Level Biology A H420/01 Biological Processes (Merged Question Paper & Marking Scheme) (2025)

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• Course 2024_OCR: A Level Biology A H420/01 Biological Pro

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2024_OCR: A Level Biology A H420/01 Biological Processes
(Merged Question Paper & Marking Scheme)

Key Areas to Revise:

1. Cell Recognition and the Immune System
o Phagocytosis and Antigen Presentation: Study the process by which phagocytes engulf
pathogens and present their antigens to trigger an immune response, leading to the activation
of T-cells.
o The Role of T-cells and B-cells: Understand how T-cells aid in identifying infected cells,
while B-cells produce antibodies that neutralize pathogens, forming the basis of the immune
response.
2. Bioenergetics (Energy Transfers)
o ATP Production in Cellular Respiration: Review the steps of aerobic respiration
(Glycolysis, Krebs Cycle, Electron Transport Chain) and how they generate ATP, the energy
currency of the cell.
o Anaerobic Respiration: Compare anaerobic respiration in humans (lactic acid fermentation)
and yeast (ethanol fermentation), focusing on how these processes differ from aerobic
respiration and their efficiency in ATP production.
3. Photosynthesis
o The Light-dependent and Light-independent Reactions: Study the stages of
photosynthesis, focusing on how light energy is captured in the thylakoid membranes (light-
dependent reactions) and how carbon fixation occurs in the stroma (Calvin Cycle).
o Factors Affecting Photosynthesis: Understand how environmental factors such as light
intensity, temperature, and CO2 concentration affect the rate of photosynthesis.
4. Cell Division
o Mitosis and Meiosis: Review the stages of mitosis (prophase, metaphase, anaphase,
telophase) and meiosis (meiosis I and II), and how these processes contribute to genetic
stability (mitosis) and genetic diversity (meiosis).
o Chromosome Segregation and Genetic Variation: Understand how independent assortment
and crossing over during meiosis contribute to genetic variation, and how errors in these
processes can lead to disorders.
5. The Nervous System
o Structure and Function of Neurons: Study the structure of neurons (dendrites, axon, myelin
sheath) and how electrical impulses are transmitted along nerve fibers.
o Synaptic Transmission: Explore how neurotransmitters are released at synapses to transmit
signals between neurons, focusing on the roles of excitatory and inhibitory neurotransmitters.
6. Homeostasis
o Thermoregulation: Review the mechanisms of temperature regulation in humans, such as
vasodilation, vasoconstriction, sweating, and shivering, which help maintain a stable internal
environment.
o Blood Glucose Regulation: Understand the hormonal control of blood glucose levels,
focusing on the roles of insulin and glucagon in maintaining homeostasis.

, o Kidney Function and Osmoregulation: Study the processes involved in water and ion
balance in the kidneys, including filtration, reabsorption, and secretion, and how the kidneys
help to maintain homeostasis.
7. Genetics and Genetic Variation
o DNA Structure and Replication: Understand the structure of DNA and the process of DNA
replication, including the roles of enzymes like helicase, DNA polymerase, and ligase.
o Gene Expression and Protein Synthesis: Study the processes of transcription and translation
that convert genetic information from DNA into functional proteins.
o Mutations and Genetic Disorders: Review the impact of mutations in DNA on protein
synthesis and the potential for mutations to lead to genetic diseases.
8. Circulatory Systems
o Structure of the Heart and Blood Vessels: Examine the structure and function of the heart,
arteries, veins, and capillaries in the human circulatory system, and understand how blood
flow is regulated.
o Cardiac Cycle and Heart Rate: Understand the events of the cardiac cycle (diastole and
systole), and how heart rate is controlled through autonomic regulation and feedback
mechanisms.
9. The Role of Enzymes
o Enzyme Catalysis: Study how enzymes lower the activation energy of biochemical reactions
and their specificity due to the lock-and-key model or induced fit model.
o Factors Affecting Enzyme Activity: Explore how temperature, pH, and substrate
concentration affect enzyme activity and the concept of enzyme inhibition.
10. Biodiversity and Conservation

 Species Diversity: Study the importance of species diversity and the ways it is measured, including
Simpson's diversity index.
 Conservation Methods: Explore conservation strategies such as habitat preservation, captive
breeding, and seed banks to protect biodiversity and prevent species extinction.

, Oxford Cambridge and RSA

Wednesday 5 June 2024 – Afternoon
A Level Biology A
H420/01 Biological processes
Time allowed: 2 hours 15 minutes

You can use:
*1345735268*

• a scientific or graphical calculator
• a ruler (cm/mm)

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 36 pages.

ADVICE
• Read each question carefully before you start your answer.

© OCR 2024 [601/4260/1] OCR is an exempt Charity
DC (SK/SG) 330031/7 Turn over

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