Discovering Cells…Discovering Cells…

Anton van LeenwenhoekAnton van LeenwenhoekDutch scientistDutch scientistThe first person to look at water using a The first person to look at water using a

single-lens microscope in the mid-1600’s. single-lens microscope in the mid-1600’s. He was surprised to see He was surprised to see the water was full of the water was full of living things:living things:

““animalcules” animalcules”

van Leenwenhoek Microscopevan Leenwenhoek Microscope

Robert HookeRobert Hooke

English scientistEnglish scientistStudied cork using Studied cork using

a compound light a compound light microscope. microscope.

Hooke MicroscopeHooke Microscope

CELLSCELLSHe observed tiny He observed tiny

geometric shapes geometric shapes and named them and named them “cells” because “cells” because they reminded him they reminded him of the small rooms of the small rooms monks lived in at monks lived in at the monastery.the monastery.

Robert Hooke Robert Hooke published published 'Micrographia' in 'Micrographia' in 1665. It is his 1665. It is his most famous most famous work, and is work, and is notable for the notable for the stunning stunning illustrations, illustrations, drawn by Hooke drawn by Hooke himself. himself.

The picture of The picture of the flea shown the flea shown is one of his is one of his most famous most famous images; the images; the original is 18 original is 18 inches across. inches across.

Additional Hooke drawingsAdditional Hooke drawings

Matthias Schleiden Matthias Schleiden German scientistGerman scientistObserved different Observed different

plants and plants and concluded that all concluded that all plantsplants are are composed of cells composed of cells in the 1830’s.in the 1830’s.

Theodore Schwann Theodore Schwann German German

scientistscientistMade Made

observations observations that all that all animalsanimals are composed are composed of cells.of cells.

Robert BrownRobert BrownScottish scientistScottish scientistObserved that all Observed that all

cells contained a cells contained a prominent structure prominent structure that appeared to be that appeared to be a “blob” in the a “blob” in the center of the cell…center of the cell…the the nucleusnucleus..

Rudolf VirchowRudolf VirchowConcluded that the Concluded that the

nucleus was the nucleus was the structure structure responsible for cell responsible for cell division.division.

Together, these men Together, these men developed developed The Cell TheoryThe Cell Theory::

The Cell TheoryThe Cell Theory

1. All organisms are composed 1. All organisms are composed of one or more cells.of one or more cells.

2. The cell is the basic unit of 2. The cell is the basic unit of organization of organisms.organization of organisms.

3. All cells come from 3. All cells come from preexisting cells.preexisting cells.

Compound Light MicroscopesCompound Light Microscopes

Uses 2 or more glass lenses to Uses 2 or more glass lenses to magnify objects.magnify objects.

Can magnify up to 1500 times.Can magnify up to 1500 times.

Compound Light MicroscopesCompound Light Microscopes

Scanning Electron MicroscopeScanning Electron MicroscopeSweeps a beam of electrons over the Sweeps a beam of electrons over the

surface of a specimen causing surface of a specimen causing electrons to be emitted from the electrons to be emitted from the specimen.specimen.

Produce a realistic, 3D image…but Produce a realistic, 3D image…but only on the surface.only on the surface.

Can magnify about 60,000 times.Can magnify about 60,000 times.

Scanning Electron MicroscopeScanning Electron Microscope

Transmission Electron MicroscopeTransmission Electron MicroscopeAims a beam of electrons through Aims a beam of electrons through

a specimena specimenTwo-dimensional images are Two-dimensional images are

used to study details of cellsused to study details of cellsCan magnify hundreds of Can magnify hundreds of

thousands of times.thousands of times.

Transmission Electron MicroscopeTransmission Electron Microscope

Blood CellsBlood Cells

Compound Microscope

TEM

SEM

LOOKING AT CELLSLOOKING AT CELLS

FORM DEFINES FUNCTIONFORM DEFINES FUNCTIONA cell’s shape reflects its function.A cell’s shape reflects its function.

VARIOUS SHAPESVARIOUS SHAPESBranchedBranchedFlatFlatRoundRound

RectangularRectangularIrregularIrregularChange shapesChange shapes

CELL SIZECELL SIZECell size is limited by a cell’s Cell size is limited by a cell’s

surface area-to-volume ratiosurface area-to-volume ratioCells get larger…need more Cells get larger…need more

nutrients…release more waste.nutrients…release more waste.The substances have to move The substances have to move

farther to reach their destinationfarther to reach their destination

CELL FEATURESCELL FEATURES(Venn Diagram?)(Venn Diagram?)ALL cells share common ALL cells share common

structural features:structural features:Cell membraneCell membraneCytoplasmCytoplasmRibosomesRibosomesDNADNA

Two Types of CellsTwo Types of Cells

ProkaryotesProkaryotesLacks a nucleusLacks a nucleusPro = beforePro = beforeKaryon = Karyon =

nucleusnucleus

EukaryotesEukaryotesHas a nucleusHas a nucleusEu = trueEu = trueKaryon = Karyon =

nucleusnucleus

Two Types of CellsTwo Types of Cells

ProkaryotesProkaryotesSmall, Small,

simple, simple, single-celled single-celled organismsorganismsBACTERIBACTERIAA

EukaryotesEukaryotesComplex, Complex,

multi-celled multi-celled organismsorganismsPLANTS & PLANTS & ANIMALSANIMALS

Two Types of CellsTwo Types of Cells

ProkaryotesProkaryotesDo NOT have:Do NOT have:

EukaryotesEukaryotesDO have:DO have:

Internal compartments Internal compartments (membrane-bound organelles)(membrane-bound organelles)

Eukaryotic cells can carry out Eukaryotic cells can carry out more specialized functions more specialized functions because of their complex because of their complex organization (organelles).organization (organelles).

DNA

Cell Division

Cell Membrane

Ribosomes

Small, simple, Small, simple, single-celled single-celled organismsorganisms

NucleusNo Nucleus

Complex, multi-Complex, multi-celled celled

organismsorganisms

No Internal No Internal Compartments—Compartments—membrane-bound membrane-bound

organellesorganelles

Has Internal Has Internal Compartments—Compartments—membrane-bound membrane-bound

organellesorganelles

Earliest cellsEarliest cells

Smaller Smaller ribosomesribosomes

Larger Larger ribosomesribosomes

Cells evolved laterCells evolved later

Cell Division—Cell Division—Binary FissionBinary Fission

Cell Division—Cell Division—MitosisMitosis