Unit 4: Microscopes, Unit 4: Microscopes, Structure and Function Structure and Function

of Cellsof CellsMicroscopes -The Cell TheoryMicroscopes -The Cell Theory

HONORS BIOLOGYHONORS BIOLOGY

Monkemeier 2014Monkemeier 2014

History of KnowledgeHistory of Knowledge

1665: Robert Hooke1665: Robert Hooke 1673: van Leeuwenhoek1673: van Leeuwenhoek 1833: Schleiden and Schwann1833: Schleiden and Schwann 1855: Virchow1855: Virchow 1857: Discovery of Mitochondria1857: Discovery of Mitochondria 1897: Discovery of Golgi Apparatus1897: Discovery of Golgi Apparatus

Timeline of Events in PerspectiveTimeline of Events in Perspective

The Cell TheoryThe Cell Theory

All living things are composed of All living things are composed of one or more cells.one or more cells.

The cell is the basic unit of The cell is the basic unit of structure and function of structure and function of organisms.organisms.

Cells come from the reproduction Cells come from the reproduction of preexisting cells.of preexisting cells.

MicroscopesMicroscopes

1590:Zacharias 1590:Zacharias Jansen and the Jansen and the first compound first compound microscopemicroscope

Their first microscopes Their first microscopes were more of a novelty were more of a novelty than a scientific tool than a scientific tool since maximum since maximum magnification was only magnification was only around 9x and the around 9x and the images were somewhat images were somewhat blurry.blurry.

Van LeeuwenhoekVan Leeuwenhoek Anton van Anton van

Leeuwenhoek (1632-Leeuwenhoek (1632-1723), a Dutch draper 1723), a Dutch draper and scientist, and one and scientist, and one of the pioneers of of the pioneers of microscopy who in the microscopy who in the late 17th century late 17th century became the first man became the first man to make and use a to make and use a real microscope.real microscope.

First to view First to view Protists, Bacteria, Protists, Bacteria, Plants, Yeast.Plants, Yeast.

Modern MicroscopesModern Microscopes

Compound Compound Light Light MicroscopeMicroscope

Scanning Scanning Electron Electron MicroscopeMicroscope

Transmission Transmission Electron Electron MicroscopeMicroscope

Resolving PowerResolving Power –the ability of the –the ability of the microscope to microscope to produce separate produce separate images of two images of two closely spaced closely spaced objects. Produce objects. Produce clear, crisp imageclear, crisp image

MagnificationMagnification – – the enlargement of the enlargement of the image.the image.

Microscope ComparisonMicroscope Comparison

The Resolving Power of a microscope is The Resolving Power of a microscope is limited by the wavelength radiation used limited by the wavelength radiation used to view the sample.to view the sample.

Light used in microscopes has a Light used in microscopes has a wavelength of 400 – 600 nanometers.wavelength of 400 – 600 nanometers.

Increased resolution requires smaller Increased resolution requires smaller wavelength.wavelength.

Beam of electrons used in electron Beam of electrons used in electron microscopes has a wavelength of less than microscopes has a wavelength of less than 1 nanometer!1 nanometer!

WHY does Wavelength of WHY does Wavelength of Radiation Matter?Radiation Matter?

RefractionRefractionThe beam of electrons will not The beam of electrons will not

have as much refraction as have as much refraction as visible light.visible light.

Refraction is the bending of Refraction is the bending of “light” as it passes through a “light” as it passes through a lens (moves from one medium to lens (moves from one medium to another)another)

Comparison of Microscopes: LightComparison of Microscopes: Light

Uses beam of visible light to produce Uses beam of visible light to produce image.image.

Image produced is true to color as Image produced is true to color as the original specimen. the original specimen.

Specimen can be live.Specimen can be live. Can magnify up to 1000xCan magnify up to 1000x Can see cells.Can see cells.

Comparison of Microscopes – Comparison of Microscopes – Transmission Electron MicroscopeTransmission Electron Microscope

Uses a beam of electrons to produce Uses a beam of electrons to produce image.image.

Image produced is called micrograph and Image produced is called micrograph and it is in black and white.it is in black and white.

Can magnify up to 200,000xCan magnify up to 200,000x Specimen must be sliced extremely thin. Specimen must be sliced extremely thin.

Distortion can occur due to this.Distortion can occur due to this. Can see cross-sectional area.Can see cross-sectional area. Can see organelles.Can see organelles.

TEMTEM

Comparison of Microscopes: Comparison of Microscopes: Scanning Electron MicroscopeScanning Electron Microscope

Uses a beam of electrons to produce Uses a beam of electrons to produce image.image.

Image produced is a three-Image produced is a three-dimensional surface view.dimensional surface view.

Image produced is black and whiteImage produced is black and white Can magnify up to 100,000 xCan magnify up to 100,000 x Specimen must be coated with gold Specimen must be coated with gold

and placed in a vacuum.and placed in a vacuum.

SEMSEM

Your TurnYour Turn

Use your notes to construct a Use your notes to construct a chart which compares chart which compares Compound Light Microscopes Compound Light Microscopes to Transmission Electron to Transmission Electron Microscopes and Scanning Microscopes and Scanning Electron Microscopes!Electron Microscopes!

Comparison ChartComparison Chart

MicroscopeMicroscope Source Source of of ImageImage

Type of Type of imageimage

MagnificationMagnification Preparation of Preparation of SpecimenSpecimen

Special Special ConcernsConcerns

LimitationsLimitations

Compound Compound Light Light MicroscopeMicroscope

TransmissionTransmission

Electron Electron

MicroscopeMicroscope

Scanning Scanning Electron Electron MicroscopeMicroscope