Cells

Anne Tierney, University TeacherRoom 938, Boyd Orr Building

a.tierney@bio.gla.ac.ukAvailable through the Centre for Biosciencewww.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

• Prokaryote– Simple

– 1-2μm

– No nucleus

– No organelles

– Single chromosome

The most common shapes of prokaryotes

a. Cocci – round

b. Bacilli – rod-shaped

c. Spiral

Types of cell - eukaryote

• 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