01the Cell Theory

7/31/2019 01the Cell Theory

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THE CELL

THEORY


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What level of complexity is

necessary for life? Aristotle (384 322BC)

Matter

Organisedmaterial (living)

Unorganisedmaterial

(non-living)

Heterogeneous

(organs)

Homogeneous(tissues)

2010 Paul Billiet ODWS
http://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.html


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Tissues and Organs

Image Credit Muscle tissue (surloin

steak)Image Credit Kidney longitudinal section
http://www.beefretail.org/cmimages/beefretail/recipeimages/1422TopSirloinSteak01.jpghttp://www.beefretail.org/cmimages/beefretail/recipeimages/1422TopSirloinSteak01.jpghttp://www.nephrology-hypertension.com/http://www.nephrology-hypertension.com/http://www.beefretail.org/cmimages/beefretail/recipeimages/1422TopSirloinSteak01.jpghttp://www.beefretail.org/cmimages/beefretail/recipeimages/1422TopSirloinSteak01.jpg


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necessary for life?C17th microscopists discovered tissues

were made ofcells (Hooke 1665 and

Leeuwenhoek 1677)

Image Credit Cork cells 2010 Paul Billiet ODWS
http://lensonleeuwenhoek.net/microscopes.htmhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://lensonleeuwenhoek.net/microscopes.htm


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Cells

C18th and C19thshowed that

tissues weremade ofcells

The cells of aparticular tissuehad a commonstructure.

Image Credit Liver cells
http://biologyofdrugs.blogspot.com/http://biologyofdrugs.blogspot.com/


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What is a cell?

Taken to its simplest form

A plasma membrane

Surrounding cytoplasm

Containing hereditary material.



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necessary for life? Xavier Bichat (1771-

1802): An organ iscomposed of differenttissues

Several organs can begrouped together as anorgan system (e.g. thedigestive system)

An idea of hierarchy ofstructure developed:

Organism

Organ-system

Organ

Tissue

Cell



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necessary for life? Purkinje (1835) Observed a fertilised hen's

egg (a single cell) could develop into an

embryo (many specialised cells in acompact mass)

C19th botanists showed that plant tissues

consist of many different types of cells.



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THE CELL THEORY

Matthias Schleiden (1838) & Theodor

Schwann (1839)

The cell is the basic unit of livingtissue

The cell is an autonomous unit (a citizen)

grouped together to form an organism(the society).



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Omnis cellula e cellula

Rudolf Virchow (1858)

noted that:

all cells come frompre-existing cells

Image Credit Cell division
http://www.sciencecentric.com/news/07091003-mystery-behind-how-nuclear-membrane-forms-during-mitosis-solved.htmlhttp://www.sciencecentric.com/news/07091003-mystery-behind-how-nuclear-membrane-forms-during-mitosis-solved.html


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THE ORGANISMAL THEORY

The counter arguments:

Reichert a morphologist: Argued that an

organism has a structured plan

Image Credit Frog embryo Image Credit Frog embryo fate map
http://www.treknature.com/gallery/photo76251.htmhttp://scienceblogs.com/pharyngula/2006/07/ancient_rules_for_bilaterian_d.phphttp://scienceblogs.com/pharyngula/2006/07/ancient_rules_for_bilaterian_d.phphttp://www.treknature.com/gallery/photo76251.htm


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Plasmodesmata

Strasberger a cytologist:

Cells are connected in

an organism sometimesby cytoplasmicbridges

Image Credit Black sapote (Diospyros) fruit
http://www.doctortee.com/dsu/tiftickjian/cse-img/botany/plant-anat/fruit-seed/diospyros-endosperm.jpghttp://www.doctortee.com/dsu/tiftickjian/cse-img/botany/plant-anat/fruit-seed/diospyros-endosperm.jpghttp://www.doctortee.com/dsu/tiftickjian/cse-img/botany/plant-anat/fruit-seed/diospyros-endosperm.jpghttp://www.doctortee.com/dsu/tiftickjian/cse-img/botany/plant-anat/fruit-seed/diospyros-endosperm.jpghttp://www.doctortee.com/dsu/tiftickjian/cse-img/botany/plant-anat/fruit-seed/diospyros-endosperm.jpghttp://www.doctortee.com/dsu/tiftickjian/cse-img/botany/plant-anat/fruit-seed/diospyros-endosperm.jpg


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Acellular organisms

Some organisms do

not have cellular

compartments

Image Credit Common field mushroom (Agaricus bisporus)

Image Credit Fungal hyphae
http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artdec00/fixation2.htmlhttp://bugs.bio.usyd.edu.au/learning/resources/Mycology/StructureFunction/hyphalStructure.shtmlhttp://bugs.bio.usyd.edu.au/learning/resources/Mycology/StructureFunction/hyphalStructure.shtmlhttp://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artdec00/fixation2.html


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Homeostasis

Sherrington andPavlov

neurophysiologists:Cells communicatewith one another andthey are co-ordinated

in their actions

Image Credit Spiney dendrites of the hippocampus

region of the brain. Red dots show the spines

associated with synapses.
http://biology.ucsd.edu/labs/halpain/images.htmlhttp://biology.ucsd.edu/labs/halpain/images.htmlhttp://biology.ucsd.edu/labs/halpain/images.htmlhttp://biology.ucsd.edu/labs/halpain/images.htmlhttp://biology.ucsd.edu/labs/halpain/images.htmlhttp://biology.ucsd.edu/labs/halpain/images.html


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Unicellular organisms

Some organisms only consist of a single

cell

But these do usually have the componentsof cells (nucleus, membrane etc)

Image Credit Paramecium
http://biology.unm.edu/ccouncil/Biology_203/Summaries/Protists.htmhttp://biology.unm.edu/ccouncil/Biology_203/Summaries/Protists.htm


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Cellular components

Some cells lack the basic components

But as a result their functions are affected.

Image Credit Red blood cells
http://embryology.med.unsw.edu.au/Notes/heart20.htmhttp://embryology.med.unsw.edu.au/Notes/heart20.htm


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Tissue culture

Cells can be cultured away from a body

But this often requires elaborate support

systems

Image Credit Tissue culture hood U of Wisconsin
http://www.bmolchem.wisc.edu/labs/denu/lab.htmlhttp://www.bmolchem.wisc.edu/labs/denu/lab.html


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SUMMARY

2. Certain cells lack the basic

components

Cells in multicellular organisms are

highly specialisedUnicellular organisms have a

cytoplasm that is not subdivided

Should be considered as acellular

2. The basic components of the cell

are repeated in every cell

1. Some organisms are not divided

into cellular compartments

= non-cellular

1. Multicellular organisms develop

from a single fertilised germ cell (the

zygote)

THE ORGANISMALTHEORY

THE CELL THEORY



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SUMMARY

4. Homeostatic control and co-

ordination is required to maintain the

whole organism whether it is

unicellular or multicellular.

3. Remove cells from complete

multicellular organisms requires

elaborate life support systems to keepthem alive

3. All cells come from cells

Cells can be taken from organismsand cultured away from the body

New individuals can be cultured from

isolated cells

Regeneration capacity = totipotence

THE ORGANISMALTHEORY

THE CELL THEORY



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Cell theory or organismal

theory? That the cell is the basic unit of living

organisms is accepted

That unicellular organisms carry out all thefunctions of life is accepted

BUT multicellular organisms are not simply

a mass of similar building blocks



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More is different!

As a multicellular organism grows and

develops it follows a structured plan

The cells specialise (differentiate

)

The whole organism shows homeostaticcontrol

A developing multicellular organism showsemergent properties

It is not just the sum of the parts


01the Cell Theory

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