Introduction to the Microscope

9.1 - Microscopy and

Cell Theory

Genova

Lesson Objectives

●Introduction to microscopes, how they work, and the different types:
brightfield microscopy, fluorescence microscopy, and electron microscopy.

●Learn about the events that led to the development of the cell theory.

Vocabulary Terms

●Microscope

●Micrographs

●Simple microscope

●Compound microscope

●Light microscope

●Fluorescent microscopy

●Electron microscopy

●Cell

●Cell theory

Scale of Cells

Poll

Which one do you think is bigger in size?

• Red Blood Cells

• White Blood Cells

Poll

Which cell do you think is bigger in size?

• Animal Cell

• Plant Cell

Microscopy

What is a microscope and how are they used?

●Cells vary in sizes but all still generally too small to see.

●Scientists use microscopes.

○Micro → small

○Scope → to look at

●Microscope → an instrument that magnifies objects otherwise too small to
be seen, producing an image in which the object appears larger

●Micrograph → photograph or digital image taken through a microscope

Open Ended

What are microscopes used for?

Open Ended

How has the invention of the microscope change science?

Open Ended

What kind of cell do you think this is?

Microscope Lenses

●Simple Microscopes → Microscopes that
only have one lens.

●Compound Microscopes → Microscopes
that have two or more lenses.

●Depending on the arrangement of its
lenses, it’s able to bend light to further
magnify the image.

○Fancier microscopes.

●Images may be “flipped”

Open Ended

What is the biggest difference between a simple and a compound microscope?

Poll

Would you consider a magnifying glass as a microscope?

• Yes

• No

Types of Microscopes

●Brightfield microscopy

○Also known as Light microscopy

●Fluorescence microscopy

●Electron microscopy

What is light microscopy and how does it work?

●Light Microscopy → an
ordinary microscope that uses
light through the specimen.

●How does it work?

○Visible light passes through the
specimen

○Light is bent through the lens
system, allowing the user to see a
magnified image

Light Microscopes

Advantages:

●Can be used on living cells

●Can see organelles at work!

Disadvantages:

●Low resolving power

○Clarity and detail of the
image

What is fluorescent microscopy and how does it work?

●Fluorescent microscopy → same as a
conventional light microscope but absorbs
one wavelength and emits another to
enhance the image.

○A variation of a light microscope

●How does it work?

○Light of one wavelength is used to excite the
fluorescent molecules

○The light of a different wavelength that they emit is
collected and used to form a picture

Fluorescent Microscopes

Advantages:

●Live cell observations

●Higher resolution

●High sensitivity allowing it to detect low
concentrations of fluorescently labeled
molecules.

Disadvantage:

●Dependent on fluorescent probes

●Only structures labeled with fluorophores are
visible, and non-fluorescent components
remain undetected.

What is an electron microscopy?

●Electron microscope → an instrument in which a beam of electrons is used
to produce an enlarged image of a very small object

○Does not use light to produce an image.

○Electrons have much a shorter wavelength than visible light, and this allows electron
microscopes to produce higher-resolution images

●Two types:

○Scanning electron microscopy (SEM)

○Transmission electron microscopy (TEM)

Scanning electron microscopy (SEM)

●A beam of electrons moves back
and forth across the surface of a cell
or tissue, creating a detailed image
of the 3D surface

Transmission electron microscopy (TEM)

●The sample is cut into extremely
thin slices before imaging, and the
electron beam passes through the
slice rather than skimming over its
surface

●TEM is often used to obtain
detailed images of the internal
structures of cells.

Electron Microscopes

Advantages:

●Very high resolution

●Detailed

○Not just whole cells, but also the subcellular
structures and compartments within them.

Disadvantages:

●Electron microscopy samples must be
placed under vacuum

●This means that live cells cannot be
imaged.

●Significantly bulkier and more expensive
than standard light microscopes

Categorize

Options (11)

Can be used at see organelles at work

Low Resolutions

Relies on fluorescent probes

Higher resolution

Uses visible light to emit different waves

Most common microscope

Highest resolution

Uses electron instead of light

Detailed images

Simple Microscope

Compound Microscope

Organize these options into the right categories

Light Microscope

Fluorescent Microscope

Electron Microscope

Types of Lenses

Multiple Choice

What type of microscope do you expect this micrograph to be from?

• Light Microscopy

• Scanning Electron Microscopy

• Transmission Electron Microscopy

• Fluorescent Microscopy

Multiple Choice

What type of microscope do you expect this micrograph to be from?

• electron microscopy

• light micrscopy

• fluorescent microscopy

• TEM microscopy

Multiple Choice

What type of microscope do you expect this micrograph to be from?

• Fluorescent Microscopy

• Transmission Electronic Microscopy

• Light Microscopy

• Scanning Electronic Microscopy

Multiple Choice

What type of microscope do you expect this micrograph to be from?

• Electron Microscopy

• Scanning Electron Microscope (SEM)
• Light Microscope

• Fluorescent microscopy

Word Bank #6-10

• Compound Microscope

• Simple Microscope

• Electron Microscopy

• Light Microscopy

• Fluorescent Microscopy

• Brightfield Microscopy

• Micrograph

• Lens

• Mirror

Cell Theory

Robert Hooke

●People never knew the cellular world existed!

●Robert Hooke created a primitive
microscope to look at the cellular world.

●Published a book Micrographiain 1665

○Draws observations from his microscope

○Lice, fleas, and cork.

●Compared the structure of cork to the living
quarters of monks called “cells” therefore
calling them cells

●Cells → The smallest living unit of life

Newton vs. Hooke feud

●Theory suggests that Newton burned the only painting of Robert Hooke.

○Hooke accused Newton for stealing his ideas on optics, published a book on 1665.

○Newton published his own works on optics, in 1672, and refused to acknowledge Hooke’s
work.

Hooke’s Observations

●Only observed dead cells

●Was not able to see living cells with
his microscopes

●From the cork, only saw the cell
wall and that was it!

Open Ended

How did Hooke discover cells?

Antonie van Leeuwenhoek

●Dutch lenscrafters, was inspired by Hooke.

○Created a better microscope for a better observation.

●Observed unicellular organisms

○Directly observed living cells, see them move in real time.

○Observed protists and bacteria, called them
“animalcules”

●Starting to develop a theory that all living things
are composed of tiny animalcules.

Open Ended

Why do you think Leeuwenhoek called them "animalcules"?

Matthias Schleiden and Theodor Schwann

●1830s → modern cell theory:

●Cell theory → The explanation of the
relationship between cells and all living
organisms

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

2. Cell is a basic unit of life.

●Where do cells come from?

Robert Remak or Rudolph Virchow

●Mid 1800s → Remak updated cell
theory

3. All cells come from other cells.

●There are some evidence that Virchow
plagiarist Remak’s work!

Open Ended

How does the cell theory help scientist understand living organisms?

Time

Event

Early

1600s

Robert Hooke discovered dead cells using early microscope.

Late

1600s

Anton van Leeuwenhoek develops a more powerful microscope that allows him

to see living cells like bacteria.

Early

1800s

Matthias Schleiden and Theodor Schwann conclude that all living organisms are

made of cells, and that cells can be produced from other cells.

Mid

1800s

Rudolf Virchow confirms that all cells must come from pre-existing cells. (There

is some evidence that this idea was stolen from Polish scientist Robert Remak.)

Cell discovery and cell theory

Open Ended

What is the cell theory? (There are three statements)

Multiple Choice

Which scientist created the first microscope and coined the term "cells"?

• Isaac Newton
• Antonie van Leeuwenhoek

• Matthias Schleiden

• Robert Hooke

Multiple Choice

Which scientist(s) stated that "all cells come from other cells"

• Remak/Virchow

• Robert Hooke

• Schleiden/Schwann

• Antonie van Leeuwenhoek

Multiple Choice

Which scientists hated each other?

• Newton and Hooke

• Hooke and Leeuwenhoek

• Remak and Schwann

• Virchow and Schleiden

Multiple Choice

Which scientist created a better microscope to view living cells and called them "animalcules"?

• Rudolph Virchow

• Robert Hooke
• Theodor Scwann

• Antonie van Leeuwenhoek

Multiple Choice

Which scientist(s) stated that "all living things are made up of cells" and "cells are basic building blocks of life"

• Remak/Virchow

• Hooke/Newton

• Schleiden/Schwann

• Leeuwenhoek/Hooke

Word Bank #7-10

• Dead

• Cells

• Cell theory

• Microscope

• Lenscrafter

• Leeuwenhoek

• Animalcules

• Hooke

Poll

Have we achieved our objectives?

• Yes

• No

• I'm confused

Vocab Recap

●Microscope → an instrument that magnifies objects otherwise too small to be seen,
producing an image in which the object appears larger

●Micrograph → photograph or digital image taken through a microscope

●Simple microscope → Microscopes that only have one lens.

●Compound microscope → Microscopes that have two or more lenses.

●Light microscope → an ordinary microscope that uses light through the specimen.

●Fluorescent microscopy→ same as a conventional light microscope but absorbs one
wavelength and emits another to enhance the image.

●Electron microscopy → an instrument in which a beam of electrons is used to
produce an enlarged image of a very small object

●Cell → The smallest living unit of life

●Cell theory → The explanation of the relationship between cells and all living
organisms