Edexcel GCSE Combined Science CB2 Cells and control: a complete overview of the cell cycle, mitosis, stem cells and the nervous system
A deep-dive Edexcel GCSE Combined Science guide to Topic 2 (CB2) Cells and control. Covers the cell cycle and mitosis, growth in animals and plants, percentile charts, stem cells and their uses, the structure of the nervous system, the reflex arc, and the three types of neurone, with exam patterns Edexcel repeats.
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What CB2 actually demands
Cells and control builds directly on Key concepts in biology. It looks at how cells divide to make a whole organism, how undifferentiated stem cells can be put to use, and how the nervous system carries fast signals to coordinate the body. The examiners test the order of events in the cell cycle and the reflex arc, and reward precise links between structure and function.
This guide walks through the two halves of the topic and ties together the matching dot-point pages, each with its own practice questions.
The cell cycle, mitosis and growth
The cell cycle produces two genetically identical daughter cells. During the long stage (interphase) the cell grows and replicates its DNA; during mitosis the chromosomes line up, separate, and the cell divides. Mitosis is used for growth, repair and asexual reproduction.
Animals grow by cell division and differentiation; plants grow by cell division at meristems followed by cell elongation, and keep the ability to differentiate for life. A baby's growth is monitored with percentile charts, which compare it against a large population of the same age and sex.
Stem cells
Stem cells are undifferentiated. Embryonic stem cells can form any cell type; adult stem cells form a limited range; plant meristem cells stay versatile for life. They could treat diabetes or paralysis and are used in plants to clone useful crops, with ethical concerns and risks of rejection or infection weighed against the benefits.
The nervous system and the reflex arc
The nervous system uses fast electrical impulses carried by neurones. The central nervous system (brain and spinal cord) coordinates responses. A reflex is fast and automatic, following a reflex arc:
A relay neurone in the CNS links the sensory and motor neurones. Between neurones are synapses, where a chemical (neurotransmitter) diffuses across the gap to pass the signal on.
The three neurones are the sensory neurone (receptor to CNS), the relay neurone (within the CNS), and the motor neurone (CNS to effector). A myelin sheath insulates the axon and speeds up the impulse.
How CB2 is examined
- Sequencing. Putting the stages of the cell cycle or the parts of a reflex arc in the correct order.
- Structure to function. Explaining how neurones are adapted to carry impulses quickly.
- Data interpretation. Reading percentile charts and judging whether growth is normal.
- Evaluation. Weighing the benefits and risks of using stem cells.
Check your knowledge
A mix of recall and application questions covering CB2. Attempt them under timed conditions, then check against the solutions.
- Name the type of cell division used for growth and repair. (1 mark)
- State two uses of mitosis. (2 marks)
- Define a stem cell. (2 marks)
- Give one use of stem cells in plants. (1 mark)
- Name the two parts of the central nervous system. (1 mark)
- Put these in the correct order for a reflex: motor neurone, receptor, effector, sensory neurone, relay neurone. (2 marks)
- State the function of a myelin sheath. (1 mark)
- Explain what the 50th percentile on a growth chart means. (2 marks)
Sources & how we know this
- Edexcel GCSE (9-1) Combined Science (1SC0) specification — Pearson (2016)