BIOL223

223.1Introduction to Cells

THEORY OF SPONTANEOUS GENERATION

Aristotle (~340 B.C)some creatures (plants, animals)

come from parents of their own kind

others (insects, vermin) are generated spontaneously in putrefying (rotting) matter from air and “vital heat”

idea held true for 2 millenia

THEORY OF SPONTANEOUS GENERATION

17th century recipe for mice:sweaty underwearhandful of grainopen-mouth jarincubate for 21 days

DISCOVERY OF CELLS

Robert Hooke (1665)developed compound light

microscopedetailed studies of “cork”

DISCOVERY OF CELLS

“. . . I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular. . . . these pores, or cells, . . . were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this. . .”

INTERPRETATION OF GERM CELLS

Nicolaas Hartsoeker (1695)discovered “animalcules” in the

semen of humans and animalsbelieved in the theory of

Preformationism: the sperm was or contained a

“little man” with little genitals and even smaller sperm, ad infinitum

it was thus that “in Adam” (literally), all had sinned

FORMULATION OF CELL THEORY

Matthias Schleiden (1804–81)Botanist1838 detailed studies of plant cells

Theodor Schwann (1810–82)Zoologist1839 detailed studies of animal cells

FORMULATION OF CELL THEORY

Schleiden and Schwann are credited with developing

Cell Theory

THEORY vs LAW

a testable* concept used to explain observations (*disprovable)

Theory of Gravity: theory of relativity: a

consequence of the curvature of space-time

quantum field theory: gravity modulated by particles in a field

generalizations of observations, used to make predictions a

Law of Gravity: Force of gravity is

proportional by inverse square to mass of two objects separated in space

THEORY vs LAW

a testable* concept used to explain observations (*disprovable)

Theory of Eclipse sun-eating dragon

generalizations of observations, used to make predictions a

Law of Eclipse: accurate prediction

CELL THEORY1.

All living things are made up of cells and cell products.cells are the fundamental

units of structure and function in the living tissue of all of God’s creatures

cells can live separate from the rest of the organism

“Every animal appears as the sum of vital units, each of which bears in itself the complete characteristics of life.” Rudolf Virchow

CELL THEORY

Fungi

EUKARYA

Trypanosomes

Green algae

Land plants

Red algae

ForamsCiliates

Dinoflagellates Diatoms

Animals

AmoebasSlime molds

Leishmania

Euglena

Green nonsulfur bacteriaThermophiles

Halophiles

Methanobacteria

Sulfolobus

ARCHAEA

COMMONANCESTOR

BACTERIA

(Plastids, includingchloroplasts)

Greensulfur bacteria

(Mitochondrion)

Cyanobacteria

ChlamydiaSpirochetes

CELL THEORY

2.

All cells arise from pre-existing cells (Virchow, 1858)cells are autonomous and can

self-replicatecells arise from the division of

pre-existing cells“Where a cell arises, there must be a previous cell...” Rudolf Virchow

INTRODUCTION TO CELLULAR FEATURES

• Typically 5-20mm (diameter)• Limit of light microscope resolution

• 0.4-0.7mm • Can see larger organelles

• Nucleus, Mitochondria

INTRODUCTION TO CELLULAR FEATURES

a

Light Microscope Electron Microscope

Amphiuma kidney, Janus Green stain Goldfish intestine, TEM preparation

400X 50,000X

INTRODUCTION TO CELLULAR FEATURES

EukaryoticGreek…“Eu”=True or Good…“Karnon”=NutTrue/Nut - True Nucleus, Has a nucleusPlant and animal cells (multicellular)Yeast and protozoa (unicellular)

INTRODUCTION TO CELLULAR FEATURES

Prokaryotic “Pro”=Prefix, Before…“Karyon”=kernel or NucleusBefore/Nucleus - No NucleusAlludes to the idea that they are ancestors to

EukaryotesUnicellularDivision within the prokaryotes

Eubacteria Archaebacteria (1977)

Hostile environments Vastly different (Genetically)

The key to every biological problem must finally be sought in the cell, for every organism is, or at sometime has been, a cell.

- E.B. Wilson (1925)

Single Cells to Multicellular Organisms

Cell differentiationCohesion (plants vs. animals)Cell communicationDifferential gene expression