Anne Tierney, University Teacher Cells Anne Tierney, University Teacher Room 938, Boyd Orr Building a.tierney@bio.gla.ac.uk Available through the Centre for Bioscience www.bioscience.heacademy.ac.uk/resources/projects/tierney.aspx

Intended learning outcomes Know what constitutes a cell Describe a typical cell Prokaryote Eukaryote Calibrate a light microscope Measure cells using a light microscope

What is a cell? Get into groups of two or three You have five minutes to think of everything you can that defines what a cell is Feed back to the class

Types of cell - prokaryote Simple 1-2μm No nucleus No organelles Single chromosome

The most common shapes of prokaryotes Cocci – round Bacilli – rod-shaped Spiral

Types of cell - eukaryote Complex 5-100μm Membrane-bound nucleus Several types of organelle Several chromosomes Single-celled organisms Multi-cellular organisms

A eukaryotic cell - animal

A eukaryotic cell - plant

How do we measure cells? Cells are (usually) too small to see with the naked eye Visualised with a microscope How can we measure with a microscope? Done indirectly Comparing a known scale with a scale that can be calibrated

Measuring cells eyepiece graticule stage micrometer

How do we do it? We compare the known scale (stage micrometer) to the scale that is to be calibrated

Calibrating the eyepiece graticule The eyepiece scale is UNKNOWN The stage scale is KNOWN 100 stage divisions = 10mm Calibration must be done for every magnification

Calibrating the eyepiece graticule 100 eyepiece divisions = ____ *stage divisions We know that 100 stage divisions = 10mm 1 stage division = ____mm ____ *stage divisions = ____mm 100 eyepiece divisions = ____mm 1 eyepiece division = ____ mm or ____μm Repeat this for each magnification