Teacher's notes and answers to questions in the book - Hodder Plus ...

WJEC GCSE Additional Science Teacher’s Notes
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Cells and cell processes
_What are cells (pages 12–13)___________________
Note that the structure of the electron microscope does not need to be learnt.
_Are cells the same in plants and animals___________
(pages 13–15)
PRACTICAL Can you find cells (page 15)
Note that sampling your own cheek cells is perfectly acceptable on health and safety grounds.
Long ago, when HIV first became a problem, some local authorities asked schools not to do
this, but the risk is virtually insignificant and there is no reason why this technique should not
be practised.
Pupils should be allowed free investigation of the celery to discover what they can. Other
plant material may be added or substituted. Celery is particularly good for looking at xylem
cells, but is not so good for leaf epidermis (Zebrinapendula and Rhoeo discolour are good for
this).
The specification expects pupils to investigate specialisation of cells. Point 4 of the
procedure is therefore important, as the chapter text does not deal with this. No specific
specialised cells are mentioned in the specification, so it does not matter which cells the pupils
investigate.
_Can you call viruses living organisms (page 16)_____
Question
1. The cell theory says that all living organisms are made of cells. Viruses are not made of cells, yet the
cell theory is still accepted. Suggest why.
Viruses are not considered to be fully ‘living’ organisms and so the cell theory does not apply
to them.
_How are the activities of a cell controlled__________
(pages 17–18)
PRACTICAL What is the best temperature to wash your
clothes (page 18)
The answers to questions 1–3 depend upon the pupil’s experimental design and results.
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