2 The Cell TheoryThe CELL THEORY, or cell doctrine, states that all organisms are composed of similar units of organization, called cells.
3 History Leading up to Cell Theory First compound microscope developedZacharias Jansen, of Middleburg, Holland, around the year 1595.
4 History Leading up to Cell Theory Robert HookeEnglish ScientistObserved cells in corkApprox. 1663
5 History Leading up to Cell Theory Antony van LeeuwenhoekFirst to observe bacteria and protozoaCalled “animacules”Approx. 1673
6 Development of Cell Theory Robert BrownBritish botanistDiscovered the nucleus of a cell1833
7 Development of Cell Theory Theodor SchwannGerman zoologistDescribed animal cells with nucleus1838
8 Development of Cell Theory Matthias SchleidenGerman botanistDescribed plant cells with a nucleus1838
9 Development of Cell Theory Rudolf VirchowGerman doctorStated “every cell originates from another cell”.About 1855
10 Tenants of Modern Cell Theory All known living things are made up of cells.The cell is structural & functional unit of all living things.All cells come from pre-existing cells by division.
11 Tenants of Modern Cell Theory Cells contains hereditary information which is passed from cell to cell during cell division.All cells are basically the same in chemical composition.All energy flow (metabolism & biochemistry) of life occurs within cells.
12 Historical Problem with the Cell Theory Flew in the face of current beliefThen, current belief was life originated from non-livingKnown as Spontaneous GenerationDisproved by Louis Pasteur
13 Pasteur’s WorkNutrient broths were heated and sterilized in a flask with a straight neck and a curved neck.
14 Pasteur’s Work Step 1 of his procedure As his control, straight-neck flaskAllowed bacteria to grow
15 Pasteur’s Work Step 2 of his procedure S-shaped necks. With such necks bacteria could not enterTherefore no bacteria grew.
17 Pasteur’s Work Straight-neck, bacteria S-shaped neck, no bacteria So, based on his observations, what can you conclude?
18 General Observations 1. All cells posess: Cell membrane Cytoplasm RibosomesHereditary Information (DNA)
19 General Observations 2. Prokaryotes 3. Eukaryotes Single celled Genetic material is a single, circular strandNo nucleusNo membrane bound organelles3. EukaryotesBegan as single-celledGenetic material – many, stringsHas a nucleusMembrane bound organellesBecame multi-celled
20 General Observations 4. Why are cells so small? Exchange sufficient amount of materialSurface area to volume ratio