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First Microscope• Zacharias Janssen

– in 1595 he and father Hans created the first compound microscope by placing two lens in a tube.

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Early Discoveries• Robert Hooke– In 1665 wrote book

Micrographia which detailed things he had seen under microscope

– In mid 1600’s first person to call a cell a “cell”

Looked at sample of cork, was reminded of monk’s cell, or room

– Also further developed Janssen’s microscope into more practical device

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Early Discoveries• Anton van Leeuwenhoek

– In late 1600’s observed sperm, microorganisms

– 1st person to observe single celled organisms in pond water

– Used hand lenses (magnifying glasses) which he made

– Made first accurate description of red blood cells

• 1820s - Robert Brown observed/named nucleus in plant cells

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Early Discoveries

• Mathias Schleiden & Theodor Schwann– In 1838 Schleiden recognized that all plants

are made up of cells.– In 1839 Schwann recognized that all animals

are made up of cells– Together the two articulated the cell theory

• Rudolf Virchow– In 1855 Virchow proposed that all cells come

from existing cells.– This provided the last piece of the cell theory

Video Clip

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Cell Theory

• All organisms are composed of one or more cells.

• Cells are the smallest living units of all living organisms.

• Cells arise only by division of a previously existing cell.

BrainPop on Cells, login & password: masonhs

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• Create detailed images of something that is otherwise too

small to see

• Light microscopes

– Simple or compound

• Electron microscopes

– Transmission EM

electrons transmitted through specimen

– Scanning EM

electrons beamed onto surface of the specimen

– They have better Resolution

minimum distance two points can be apart and still

be distinguished as two separate points

Microscopes

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light TEM SEM microscope

source of light light electrons electrons

specimen living(moving)/nonliving nonliving nonliving

max resolution 200 nm 1 nm 10 nm

max magnify 1,500x 250,000x 100,000x

stains colored dye heavy metal coated C, Au

type of image colored black/white black/white

Comparison between Microscopes

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animal cell EM

What type of microscope was used for each image?

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Light Microscopy• Wavelengths of

light are 400-750 nm

• If a structure is less than one-half of a wavelength long, it will not be visible

• Light microscopes can resolve objects down to about 200 nm in size

ocular lens

objective lens

stage

condenser

illuminator

prism

source of illumination

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Electron Microscopy

• Uses streams of accelerated electrons rather than light

• Electrons are focused by magnets rather than glass lenses

• Can resolve structures down to 0.5 nm

viewing screen

projector lens

intermediate lens

objective lens

specimencondenser lens

accelerated electron flow (top to bottom)

You Tube Video Clip

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Visualizing Cells

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Cell Characteristics/Groups• All cells start out life with:

– cell membrane a thin, flexible barrier around the

cell– Cytoplasm

material inside the cell membrane

– Ribosomes location of protein synthesis

– DNA Genetic instructions for making

proteins• Two major types of cells:

– Prokaryotic– Eukaryotic

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Prokaryotic Cells

• Common name:

– BACTERIA• Archaebacteria

and Eubacteria• DNA is not

enclosed in nucleus

• Generally the smallest, simplest cells

• No organelles except ribosomes

Video Clip

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Slime

Plasma Membrane

Pili

Plasmid

Know the functions of all these parts of a Prokaryotic Cell

•Increases surface area for cell respiration•Helps form cell walls

•Strands of DNA

•Circular ring of DNA

•Helps connect cell to other cells, aids in movement

•Protection & helps cell stick to surfaces

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Eukaryotic Cells• Have a nucleus and

many other organelles

• Complex – many cell parts

– Learn the structure/function of the parts in the chart provided in class

• Eukaryotic organisms have Eukaryotic cells:

– Plants– Animals– Protists– Fungi

BrainPop on Cell TypesLogin & Password: masonhs Video Clip