Cell Theory

Image Cells by Filter Forge on Flickr httpflickrpePXpR5

Stephen Taylori-Biologynet

CELLS

All living things are made of

Longitudinal section of a root tip of Maize (Zea mays) by Science and Plants for Schools on Flickr (CC) httpflickrpbNNM6M

CELLS

All living things are made of

Longitudinal section of a root tip of Maize (Zea mays) by Science and Plants for Schools on Flickr (CC) httpflickrpbNNM6M

Unicellular organisms are single-celled and can carry out all of the functions of life independently

Multicellular organisms have specialized cells to carry out specific functions

CELLS

are the smallest units of life

Paramecium multimicronucleatum by Proyecto Agua on Flickr (CC) httpflickrp7W7J3y

CELLS

are the smallest units of life

Paramecium multimicronucleatum by Proyecto Agua on Flickr (CC) httpflickrp7W7J3y

Specialized structures within

cells (organelles) carry out different functions

Organelles cannot survive alone

come only from existing cells

4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) httpflickrpdaWnnS

CELLS

come only from existing cells

Cells multiply through division

All life evolved from simpler ancestors

Mitosis results in genetically identical diploid

daughter cells

Meiosis generates haploid gametes (sex cells)

Pasteur disproved the theory of spontaneous

generation with his experiments

4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) httpflickrpdaWnnS

CELLS

Hookersquos Micrographia in full httplhldigitallindahallorgcdmrefcollectionnat_histid0

1665 Hooke names ldquocellsrdquo in his bookldquoMicrographiardquo after observing cork under a lense

All living things are m

ade of cells

1676 van Leeuwenhoek a master microscope maker identifies ldquoanimalculesrdquo and becomes the father of microbiology

All l

ivin

g th

ings

are

m

ade

of c

ells

httpenwikipediaorgwikiAntonie_van_Leeuwenhoek

Robert Brown httpenwikipediaorgwikiRobert_Brown_(botanist)

1833 Robert Brown names the cell nucleus Cells are the smallest units of life

He also discovered Brownian motion

httpenwikipediaorgwikiBrownian_motion

Robert Remak httpenwikipediaorgwikiRobert_Remak

1855 Robert Remak discovers cell division and confirms the existence of the plasma membrane Cells come only from pre-existing cells

Image from Amoeba Mikersquos Blog (go read the original post) httpamoebamikewordpresscom20091006spontaneous-generation-a-brief-history-of-disproving-it

1864 Pasteur disproves the prevailing theory of ldquospontaneous generationrdquo with his swan-neck flask experiments Populations need to be seeded by existing populations cells come only from pre-existing cells

Labeling the parts of the microscope activityhttpwwwbiologyualbertacafacilitiesmultimediauploadsintro-biologymicroscopehtml

Image from wikimedia commons httpcommonswikimediaorgwikiFileMicroscope-blanksvg

MagnificationThe image we see through the light microscope has been magnified

Objective lens x eyepiece lens

Modern Microscopy

Image d2540-6 by USDA on Flickr (CC) httpflickrpdPqvvY

Modern Microscopy

Image d2540-6 by USDA on Flickr (CC) httpflickrpdPqvvY

As we develop more and more sophisticated and precise imaging tools we can see more detail of the cells and molecules that make us

Scanning electron microscopes deliver high-resolution 3D surface images of structures whereas transmission electron microscopes give us a view inside cells and organelles

Emiliana huxleyi

Image from httpearthguideucsdeduearthguideimagelibraryemilianiahuxleyihtml

Transmission electron micrograph of HIV particles

HIV-1 Transmission electron micrograph via wikimedia commons httpcommonswikimediaorgwikiFile3AHIV-1_Transmission_electron_micrograph_AIDS02bbb_loresjpg

120nm

False-coloured scanning electron micrograph of HIV (green) budding on a lymphicoyte (blue) httpenwikipediaorgwikiFileHIV-budding-Colorjpg OR httpphilcdcgovphildetailsasppid=10000

1μm

Scanning electron micrograph of HIV particles budding on a human lymphocyte

Unicellular Organismscarry out all the functions of lifeM ovementR espirationS ensitivityG rowthR eproductionE xcretionN utrition

Paramecium bursaria by Proyecto Agua on Flickr (CC) httpflickrp7WXdFz

Given the right conditions cells can survive outside their normal habitat

Art from Petri dishes_1 by Image in Science and Art on Flickr (CC) httpflickrp838xjC

VIRUSESAre they living or non-living

Hmmhellip

Image Swine Flu H1N1 virus influenza 90 by hitthatswitch on Flickr (CC) httpflickrp74e4SP

Some units that I use amp knowUnit abbr Metric equivalent

kilometer km 1000m 1 x 103m

meter m 1m 1m

centimeter cm 001m 1 x 10-2m

millimeter mm 0001m 1 x 10-3m

micrometer μm 0000 001m 1 x 10-6m

nanometer nm 0000 000 001m 1 x 10-9m

divide1000

divide1000

divide1000

X 1000

μm = micrometersWe usually use this in discussion of cells

There are 1000μm in one mm

write this correctly

Human egg cell from Grayrsquos Anatomy (1858) httpcommonswikimediaorgwikiGray27s_Anatomy_plates

50μm

Human sperm cell from Grayrsquos Anatomy (1858) httpcommonswikimediaorgwikiGray27s_Anatomy_plates

5μm

5μm

Scanning electron micrograph of human sperm and egg cells

smallest hum

an cell

largest human cell

Image from wikimedia commons httpenwikipediaorgwikiSpermatozoon

Sugar Cubes by Uwe Hermann on Flickr (CC) httpflickrpcFMMc

Which dissolves faster sugar cubes or sugar crystals Why

What will go cold faster French fries or a baked potato Why

French Fries by Ian Britton on Flickr (CC) httpflickrp6RLQ8j

Which makes green tea faster tea leaves or powder

Matcha Latte by Cupcake Murder Aftermatch on Flickr (CC) httpflickrpfCkpb5

What type of crisps delivers more flavour

regular-cut or crinkle-cut

WhySmiths Plain Chips by Penguin Cakes on Flickr (CC) httpflickrp5ygb8v

IN Oxygen Nutrients Water

OUT Carbon dioxide Waste Products (eg proteins)

The plasma membrane of a cell is the surface of exchange for materials between the inside and the outside of the cell

httpcommonswikimediaorgwikiSphere

As the cell gets larger it requires more resources to be imported and

produces more products (and waste) to be exported

Therefore a larger volume requires more exchange across the membrane

httpcommonswikimediaorgwikiSphere

httpcommonswikimediaorgwikiSphere

As the cell gets largerhellip

httpcommonswikimediaorgwikiSphere

As the cell gets largerhelliphellipthe surface area tovolume ratio actually gets smallerhellip

httpcommonswikimediaorgwikiSphere

As the cell gets largerhelliphellipthe surface area tovolume ratio actually gets smallerhelliphellipso the exchange processes become lessefficient with increasing size

httpcommonswikimediaorgwikiSphere

Diffusion Pathways

are shorter (and more efficient) in smaller cells with a larger surface are to volume ratio

DIVIDE

Surface are to volume ratio is a factor that limits the

size of cells

By dividing to make more smaller cells the efficiency of the exchange processes

across the membranes (into and out of the cells) can be

kept high

Shorter diffusion paths

More surfaces for reactions

Removal of heat and waste

4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) httpflickrpdaWnnS

CELLS

Mammalian liver mitochondria httpcommonswikimediaorgwikiFileMitochondria_mammalian_lung_-_TEM_(2)jpg

Natural selection favours adaptations that give an advantage Folded structures are everywhere in nature maximising the surface area to volume ratio for exchange of materials

StructureFunction

httpenwikipediaorgwikiCaulerpa

Big Cell Exceptions

Caulerpa species of algae are one giant cell with many

nuclei distributed throughout

Epulpoiscium by AJ Cann on Flickr (CC) httpflickrp4Nzq9t

Big Cell Exceptions

Epulopiscium is a giant species of bacteria Read more about it here NotExactlyRocketScience

100μm

E coli

Free images from Presentations ETC University of Florida httpetcusfedupresentations

Is maximising surface area to volume ratio always an advantage

Free images from Presentations ETC University of Florida httpetcusfedupresentations

Two Minute Essay

Explain the importance of surface area to volume ratio as a factor limiting cell size

Exploration which cools faster

30ml 30ml

Add 30ml hot water to a small cup and to a petri dish Predict Will one cool faster WhyRecord Take the temperature of each one every minute Describe or plot the results

Design an investigation into the effect of SAVol ratio on exchange ofhellip

Emergent Properties

Photo by Stephen Taylor httpwwwflickrcomphotosgurustip9668701965inphotostream

the whole is

more than the sum

of its parts

Design an investigation into the effect of SAVol ratio on exchange ofhellip

Emergent Properties

Photo by Stephen Taylor httpwwwflickrcomphotosgurustip9668701965inphotostream

the whole is

more than the sum

of its parts

Emergent Properties

Photo by Stephen Taylor httpwwwflickrcomphotosgurustip9668701965inphotostream

the whole is

more than the sum

of its parts

Stem Cells

A cluster of nascent retinae generated from 3D embryonic stem cell cultures by UCL News on Flickr (CC) httpflickrpffPBPT

A Stem Cell Story httpwwwyoutubecomwatchv=2-3J6JGN-_Y

Stem Cells retain the capacity to divide and can differentiate along divergent pathways

TotipotentCan differentiate into any type of cell

PluripotentCan differentiate into manytypes of cell

MultipotentCan differentiate into a few closely-related types of cell

UnipotentCan regenerate but can only differentiate into their associated cell type (eg liver stem cells can only make liver cells)

Image from httpenwikipediaorgwikiStem_cell

By Fwfu at enwikibooks [Public domain] from Wikimedia CommonshttpcommonswikimediaorgwikiFile3AStemcelldifferentiaionjpg

Stem Cells retain the capacity to divide and can differentiate along divergent pathways

Stem Cells retain the capacity to divide and can differentiate along divergent pathways

Screenshot from this excellent tutorial httpwwwnsumichedustemcells022706_Introhtml

Screenshot from this excellent tutorial httpwwwnsumichedustemcells022706_Introhtml

Differentiation (specialization) of cells All diploid (body) cells have the same chromosomes

So they carry all the same genes and allelesBUT

Not all genes are expressed (activated) in all cellsThe cell receives a signal

This signal activates or deactivates genesGenes are expressed accordingly and the cell is committed

Eventually the cell has become specialized to a function

Key Concept Structure vs FunctionHow do the structures of specialized cells reflect their

functions How does differentiation lead to this

Therapeutic Uses of Stem Cells

Animated tutorials from httpoutreachmcbharvardeduanimationsthera7cswf

Treatment for Leukemia

ProblemCancer of the blood or bone marrow resulting in abnormally high levels of poorly-functioning white blood cells

TreatmentChemotherapy and radiotherapy can be used to destroy the white blood cells but these need to be replaced with healthy cells Bone marrow transplants are often used for this

Role of Stem Cells

Hematopoetic Stem Cells (HSCs) can be harvested from bone marrow peripheral blood or umbilical cord blood As these can differentiate to form any type of white blood cell they can be used to repopulate the bone marrow and produce new healthy blood cells The use of a patientrsquos own HSCs means there is far less risk of immune rejection than with a traditional bone marrow transplant

From httpenwikipediaorgwikiPluripotential_hemopoietic_stem_cell

Animation of this process

Free images from Presentations ETC University of Florida httpetcusfedupresentations

Two Minute Essay

What is a stem cell

How do stem cells differentiate into specialized cells

Outline one therapeutic use of stem cells

For more resources amp linksincluding many on Stem Cells

This is a Creative Commons presentation It may be linked and embedded but not sold or re-hosted

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