Biology
REQUIRED PRACTICAL Using a light microscope to observe and record animal and plant cells
KEY WORDS ďŹ eld of view scale bar
Learning objectives: sÂŹ APPLYÂŹKNOWLEDGEÂŹTOÂŹSELECTÂŹTECHNIQUES ÂŹINSTRUMENTS ÂŹ APPARATUSÂŹANDÂŹMATERIALSÂŹTOÂŹOBSERVEÂŹCELLS sÂŹ MAKEÂŹANDÂŹRECORDÂŹOBSERVATIONSÂŹANDÂŹMEASUREMENTSÂŹ sÂŹ PRESENTÂŹOBSERVATIONSÂŹANDÂŹOTHERÂŹDATAÂŹUSINGÂŹAPPROPRIATEÂŹ METHODS
These pages are designed to help you think about aspects of the investigation rather than to guide you through it step by step.
Many scientists use electron microscopes to observe fine detail in cells. But much of the microscope work carried out – including in hospital and forensic science labs – is done with the light microscope.
Preparing cells for microscopy ,IVEÂŹCELLSÂŹCANÂŹBEÂŹMOUNTEDÂŹINÂŹAÂŹDROPÂŹOFÂŹWATERÂŹORÂŹSALINEÂŹONÂŹAÂŹ MICROSCOPEÂŹSLIDE -OSTÂŹCELLSÂŹAREÂŹCOLOURLESS ÂŹ7EÂŹMUSTÂŹSTAINÂŹTHEMÂŹTOÂŹADDÂŹCOLOURÂŹ ANDÂŹCONTRAST ÂŹ)NÂŹTHEÂŹSCHOOLÂŹLABORATORY ÂŹYOUÂŹMAYÂŹHAVEÂŹUSEDÂŹ METHYLENEÂŹBLUEÂŹTOÂŹSTAINÂŹANIMALÂŹCELLSÂŹORÂŹIODINEÂŹSOLUTIONÂŹTOÂŹSTAINÂŹ PLANTÂŹCELLS ÂŹ 1
Write an equipment list for looking at cheek cells with a microscope. State why each piece of equipment is used.
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Suggest why it’s better to mount the cells in saline than in water.
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The micrograph of the frog’s blood (Figure 1.12) shows red blood cells (the lower micrograph) and two types of white blood cell.
&IGURE A glass coverslip is carefully lowered onto the cells or tissue, taking care to avoid trapping air bubbles. The coverslip keeps the specimen at, and retains the liquid under it
a Label the different types of cell and the cell structures that are visible. Hint: use a photocopy or printout of the page. b How is the structure of the frog’s red blood cells different from that of human red blood cells?
High and low power 4HEÂŹSLIDEÂŹISÂŹlÂŹRSTÂŹVIEWEDÂŹWITHÂŹLOWÂŹPOWER ÂŹ4HISÂŹISÂŹBECAUSE sÂŹ THEÂŹlÂŹELDÂŹOFÂŹVIEWÂŹWITHÂŹHIGHÂŹPOWERÂŹISÂŹSMALL ÂŹ)TÂŹWOULDÂŹBEÂŹ DIFlÂŹCULTÂŹTOÂŹLOCATEÂŹCELLSÂŹIFÂŹSTARTINGÂŹWITHÂŹTHEÂŹHIGHÂŹPOWERÂŹ OBJECTIVE sÂŹ ITÂŹENABLESÂŹYOUÂŹTOÂŹSEEÂŹTHEÂŹLAYOUTÂŹOFÂŹCELLSÂŹWITHINÂŹTHEÂŹTISSUE sÂŹ IT SÂŹUSEFULÂŹWHENÂŹESTIMATINGÂŹTHEÂŹNUMBERSÂŹOFÂŹDIFFERENTÂŹTYPESÂŹ
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&IGUREÂŹ ÂŹCell biologists use other chemical stains. These are used to reveal or identify speciďŹ c cell structures.
AQA GCSE Biology: Student Book
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