Edexcel GCSE Combined Science: Biology: Cells and Control
6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
A person accidentally touches a very hot pan and their hand is pulled away before they consciously feel the pain. This is a reflex action controlled by a reflex arc.
Describe how the reflex arc brings about the rapid withdrawal of the hand. In your answer you should refer to the receptor, the neurones involved, the synapse, and the effector. (6 marks)
A health visitor uses a percentile growth chart to monitor a baby boy's mass. The chart shows three reference percentile lines. The table below gives the baby's mass and the values of the percentile lines at each age.
| Age / months | Baby's mass / kg | 25th percentile / kg | 50th percentile / kg | 75th percentile / kg |
|---|---|---|---|---|
| 0 | 3.5 | 3.2 | 3.5 | 3.9 |
| 3 | 6.4 | 5.7 | 6.4 | 7.1 |
| 6 | 8.0 | 7.1 | 7.9 | 8.7 |
| 9 | 9.0 | 8.0 | 8.9 | 9.8 |
(a) State which percentile the baby's mass is closest to across the whole period, and what this means. (2 marks)
(b) A different baby was on the 50th percentile at birth but had dropped to below the 25th percentile by 9 months. Explain why this pattern might concern the health visitor. (2 marks)
Stem cells can be obtained from human embryos and from a patient's own bone marrow.
(a) Give one way in which an embryonic stem cell differs from an adult stem cell in terms of the range of cell types it can form. (1 mark)
(b) Describe one potential medical use of stem cells. (1 mark)
(c) Suggest one risk or objection associated with using embryonic stem cells. (1 mark)
The human eye detects light and allows us to see clearly at different distances and in different light levels.
(a) When a person moves from a dark room into bright sunlight, the pupil gets smaller. Explain why this change is useful. (2 marks)
(b) Name the part of the eye that changes shape to focus light from objects at different distances onto the retina. (1 mark)
Before a cell divides by mitosis, the cell cycle includes a stage in which the DNA is copied (replicated).
Explain why it is important that the DNA is copied before the cell divides by mitosis. (2 marks)
The central nervous system (CNS) coordinates the body's response to stimuli.
Name the two organs that make up the central nervous system. (1 mark)