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Cells - PowerPoint PPT Presentation

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Cells. Organelles. CELL. The basic unit of structure & function in living organisms. Anton Van Leeuwenhoek. 1632-1723 Was a merchant that ground up glass to make lenses. Invented microscope Made over 500 in his lifetime 1 st person to examine bacteria.

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  • The basic unit of structure & function in living organisms

Anton van leeuwenhoek
Anton Van Leeuwenhoek


Was a merchant that ground up glass to make lenses

  • Invented microscope

  • Made over 500 in his lifetime

  • 1st person to examine bacteria

Robert hooke
Robert Hooke

  • 1635-1702

  • Used Van Leeuwenhoek’s microscopes

  • Named cells after looking at cork

Robert brown
Robert Brown

  • 1773-1858

  • Discovered the nucleus in plant cells (1833)

Matthias schleiden
Matthias Schleiden

  • 1804-1881

  • Discovered all plants are made up of cells


Theodor schwann
Theodor Schwann

  • 1810-1882

  • Discovered that all animals are made up of cells(1839)

Rudolph virchow
Rudolph Virchow

  • 1821-1902

  • Proposed that all cells come from pre-existing cells (1855)

The cell theory
The Cell Theory

The cell theory states:

  • All living things are composed of cells

    B. Cells are the basic units of structure & function in living things

    C. All cells come from preexisting cells

Janet plowe
Janet Plowe

  • Demonstrated that the cell membrane is a physical structure (1931)

Lynn margoulis
Lynn Margoulis

  • Proposed that certain organelles were once free-living organisms themselves (1970)

Parts of Microscope



High Power Objective


Low Power Objective

Scanning Power Objective


Stage Clips

Course Focus

Fine Focus



Light (illumination)

Compound light Microscope Parts & Fxn’s

  • Occular – viewing eyepiece

  • Coarse adjustment – Rough focus

  • Fine adjustment – Fine focus

  • High power objective (400X)

  • Low objective (100X)

  • Scanning objective (40X)

Compound Light Microscope Parts & Fxn’s

  • Stage – holds slide up against stage clips

  • Stage clips – holds slide down on stage

  • Diaphragm – controls amount of light entering slide

  • Lamp – light source

This is an air bubble

under the microscope!!!

Power of magnification

  • The relative enlargement of the specimen when seen through the microscope.

  • The power of magnification can be calculated by multiplying the power of the eye piece lens by the power of the objective lens.


  • The reversal of the specimen image by the microscope lenses.

  • A specimen that appears upside down when being viewed is actually right-side up on the slide.

  • Moving the specimen to the right causes its image to move to the left likewise, moving it down causes it to move upward.

Working distance

  • The distance between the front of the objective and the top of the cover glass on the slide.

  • The higher the magnification the smaller the working distance.



(Resolving Power)

  • The shortest distance between two points or lines at which they are seen as two, rather than a single blur.

Depth of focus

  • The thickness of a specimen which may be seen in focus at one time.


  • Our microscopes have three objectives mounted on a revolving device known as a nosepiece.

  • Engraved on the objective is its power of magnification.

  • The longer the objective the more power of magnification.


  • A device under the stage of a microscope that can regulate the amount of light reaching a specimen.

Power of Magnification

  • Definition - The relative enlargement of the specimen when seen through the microscope.

  • Power of magnification = (Power of the eyepiece lens) X (Power of the objective lens)

Rules for Handling the Microscope

  • Always carry the microscope with one hand under the base and the other grasping the arm.

  • Keep both eyes open when looking through the eyepiece.

  • Keep the stage clean and dry.

  • Do not remove parts of the microscope.

  • Use only lens paper when cleaning lenses.

Rules for Handling the Microscope

  • Always begin focusing with the lowest power objective.

  • Always look from the side when changes lenses

  • After completing your work, place the microscope on the lowest power objective.

  • Always return the microscope where you found it & as you found it

Modern microscopes
Modern Microscopes

Electron microscopes – capable of revealing details as much as 1000 times smaller than those visible in light microscopes. (Two types -TEM & SEM)

TEM – can explore cell structure and large protein molecules.

Downside – the specimens have to be sliced thinly

Modern microscopes1
Modern Microscopes

S.E.M. – Scanning electron microscopes –

specimens do not have to be cut thinly – a beam of electrons scans over the specimen.

S e m magnification
S.E.M. Magnification