Introduction to cell biology.pdf

7/22/2019 Introduction to cell biology.pdf

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Reference Textbooks

Cell BiologyCell Biology2002by Thomas D. Pollard and William C. Earnshaw

Molecular Biology of The CellMolecular Biology of The Cell 4th Ed.2002by Bruce Alberts, Dennis Bray, Julian Lewis

Martin Raff, Keith Roberts, James D. Watson

Molecular Cell BiologyMolecular Cell Biology 6th Ed. 2008by Harvey Lodish, Arnikd Berk, Paul Matsudaira,

Chris A. Kaiser, Monty Krieger, Matthew P.Scott, Lawrence Zipursky, James Darnell

BiologyBiology 6th Ed. 2002by George B. Johnson and Peter H. Raven


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Biology

Historical event

chemistry physics

Origin and evolution of life on earth


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The Central dogma of living Cells-1


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Cells come in an astounding assortment of shapes and sizes.c d

(c) Blood cells; (d) Fossilized dinosaur eggs.

Molecular Cell Biology, Ch 1, 2004


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A single cell, the human egg (~200 m), with sperm, which arealso single cells. From the union of an egg and sperm will arisethe 10 trillion cells of a human body.


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Basic cellular architecture.A. A section through a eukaryoticcell showing the internal components.B and C. Comparing cells

from the major branches of the phylogenetic tree with color-

coded components.Cell Biology, Ch 1, by Pollard and Earnshaw, 2002


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The biological universe consistsof two types of cells:

prokaryotic cells

eukaryotic cells


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12Molecular Cell Biology, Ch 1, 2004


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many proteins are preciselylocalized in their aqueous

interior, orcytosol, indicatingthe presence of internalorganization.



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cytoplasm, comprising thecytosol(aqueous phase)

and theorganelles.



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Prokaryotic cells consist of a single closedcompartment that is surrounded by theplasmamembrane, lacks a definednucleus, and has arelatively simple internal organization.

Eukaryotic cells contain a defined membrane-boundnucleus and extensive internal membranes thatenclose other compartments, theorganelles.

Prokaryotic cells have a simpler internal organization

than eukaryotic cells.


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Cell

NOYESCytoskeleton

NOYESCompartmentalized

Prokaryotic cellsEukaryotic cells


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18Cell Biology, Ch 1, by Pollard and Earnshaw, 2002

Electron micrograph of a liver cell showing organelles.


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Nuclear envelopeNuclear envelope

Endoplasmic reticulumEndoplasmic reticulum

GolgiGolgiapparatusapparatus

LysosomesLysosomes

PeroxisomesPeroxisomes

Nucleoplasm and cytoplasm

The site of protein and phospholipid synthesis

An organelle that adds sugars to proteins(membrane, lysosomal and secretory proteins)

A compartment for digestive enzymes

Containers for enzymes involved in oxidative reaction

Structures that convert energy stored in thechemical bonds of nutrients into ATP

MitochondriaMitochondria


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Membranes

Allow cells to create an internal environment

Divide into compartments-organelles

Impermeableto macromolecules andselectively permeableto ions

Biological membranes are generally:


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Biological Membranes

A bilayer of lipids

Integral proteins crossing the bilayer

Peripheral proteins associated with the

surfaces


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Development of ideas about membrane structure

1920s

Cellular membranes consist of lipid bilayers

1930sA surface coating of proteins to reinforce the bilayer

Electron micrographs: a pair of dark linesElectron micrographs: a pair of dark lines

separated by a lucent areaseparated by a lucent area

1970sProteins cross the lipid bilayer

Electron micrographs with freezeElectron micrographs with freeze--fracturingfracturing

technique:technique: protein particles embedded in the lipidbilayer

Chemical labeling of membrane proteins:Chemical labeling of membrane proteins:proteins traverse the bilayer


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23Cell Biology, Ch 6, by Pollard and Earnshaw, 2002

Development of concepts

in membrane structure.

A.A. GorderGorderandandGrendelGrendelmodelmodel

from 1926.from 1926.

B.B. DavsonDavsonandandDanielliDanielli modelmodel

from 1943.from 1943.

C.C. Singer and NicholsonSinger and Nicholson fluidfluid

mosaic modelmosaic model fromfrom1972.1972.


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Development of concepts in membrane structure.

D.D. Contemporary model with peripheral and integral membraneContemporary model with peripheral and integral membrane

proteins.proteins.Cell Biology, Ch 6, by Pollard and Earnshaw, 2002


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Fluid mosaic model of the plasma membrane.

Most membrane: 50% protein : 50% lipid (5-10% of mass is glycoproteinsand glycopeptides)

1 molecule of protein v.s. 50-100 molecules

* Dissociated from the

membrane following

treatments with

polar reagents;

* Soluble in aqueous

buffers;

* Not inserted intothe hydrophobic

interior of the lipid

bilayer

* Released by treatments that disrupt

the phospholipid bilayer;

* Inserted into the lipid bilayer


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Mobility of membrane proteins

Not all proteins are able to diffuse freely

through the membrane; restricted by

* association with the c y t o s k e l et o n ;* other m e m b r a n e p r o t e i n s ;

* proteins ont h e s u r f a c e o f a d j ac e n t c e l l s

* proteins on t he ext r acel lular mat r ix


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Drawing of the lipid composition of a plasma membrane illustrating

the heterogeneity of the lipids and the asymmetrical distribution ofthe lipids between the two halves of the bilayer.

Cell Biology, Ch 6, by Pollard and Earnshaw, 2002

SM: sphingomyelin; GS: glycosphingolipid; PC: phosphatidylcholine;

PE: phosphatidylethanolamine; PS: phosphatidylserine.


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Some membrane lipids and proteins colocalize in lipidrafts.


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Membrane Proteins

In t e g r al m em b r a n e p r o t e in s

cross the lipid bilayer

L i p i d a n c h o r ed m em b r a n e p r o t ei n s

bound covalently to one or more

lipid molecules.

P er i p h e r al m em b r a n e p r o t ei n s associate with the inside or outside

surface of the bilayer


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Diagram of how various classes of proteins associate

with the lipid bilayer.


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All Cells

Signals

Receive Respond

Gases to proteins


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Temperature, Osmotic stress, Light,Mechanical force, Gases, Nutrients,

Attractants, Hormones, Cells, ECMECM: extracellular matrix

Cellular activitiesProtein synthesis, Mobility, Proliferation,

Energy metabolism...

Environmental conditions


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An inducing signal can be transmitted from one

cell to another in three main ways

(Wolpert, Ch1, 2002)


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Cell communication.

Ligands and receptors.


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External signals commonly cause a change in the activity of

preexisting proteins or in the amounts and types of proteins thatcells produce.



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During growth, eukaryotic cells continually progress through the

four stages of the cell cycle, generating new daughter cells.



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Dad made you a boy or girl.



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Apoptotic cells break apart without spewing forth cell constituents

that might harm neighboring cells.Molecular Cell Biology, Ch 1, 2004


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Definitions and General Concepts About

Stem Cells

Totipotent: Able to give rise to all embryonic and extra-embryonic cell types, i.e.a cell that can producean entire organism.In the mouse, only a zygote and a blastomere from a 2-cell stage embryowould be considered totipotent.

Pluripotent:Able to give rise to all cell types of the embryoproper, i.e.the derivatives of all three germ layers; that is, essentiallyall cell types that are found in the adult organism. An embryonic stem cellwould be a typical example of a pluripotent cell and it is not the the onlypluripotent cell type.

Cell 116:639-648, 2004.


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Definitions and General Concepts About

Stem Cells

Multipotent: Able to give rise to a subset of cell lineages, i.e.angive rise to multiple cell types, but these would nevertheless berestricted to derivatives of a single germ layer (for example, amesenchymal cell that is able to differentiate into fibroblasts, adipocytes,chondrocytes, muscle cells and so on) or to a specific sublineage (forexample, haematopoietic stem cells that give rise to erythrocytes,

leucocytes and lymphocytes).

Oligopotent: Able to give rise to a more restricted subset of celllineages than multipotent stem cells.

Unipotent: Able to contribute to only one mature cell type.


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It might one day be possible to manipulate ES cells so that theyand their derivatives form a complete conceptus without any

contribution from an embryo. At that point ES cells could be

called totipotent, but until then this term is best avoided whendescribing ES cells.

Nullipotent:Mouse embryonal carcinoma cells are usually able to

differentiate into several cell types. However, some embryonalcarcinoma cell lines lose the capacity for differentiation on

prolonged in vitroculture and are then termed as nullipotent.

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Introduction to cell biology.pdf