cell biology lecture 1 & 2 sem i 2011-2012 introduction to cell biology, cell as the basic unit...
TRANSCRIPT
STBP STBP 1023 1023
Cell Cell BiologyBiology
Assoc. Prof. Dr. Hasidah Mohd. Assoc. Prof. Dr. Hasidah Mohd. SidekSidek
School of Biosciences & Biotechnology
Faculty of Science & Technology(Level 1 Biological Science Building)
Course ObjectivesCourse Objectives
At the end of the course, At the end of the course, students will :students will :
• understand understand the biochemical the biochemical basisbasis of the living system of the living system
• understand the concept of the understand the concept of the cell as the basic unit of lifecell as the basic unit of life and and appreciate the structure & appreciate the structure & function of cell componentsfunction of cell components
Course Objectives (continued)Course Objectives (continued)
• understand the understand the principles of principles of bioenergeticsbioenergetics in order to in order to appreciate how intermediary appreciate how intermediary metabolism though complex is metabolism though complex is very systematic and orderlyvery systematic and orderly
• understand the concept of understand the concept of energy utilisation and energy utilisation and productionproduction of energy (ATP) in of energy (ATP) in the cellthe cell
Course StructureCourse Structure
•Lectures Lectures
•TutorialsTutorials
EvaluationEvaluation
• Mid-semester Examination (30-Mid-semester Examination (30-40%) 40%)
• Final Examination (60-70%)Final Examination (60-70%)
Course FacilitatorsCourse Facilitators
• Assoc. Prof. Dr. Hasidah Mohd. Assoc. Prof. Dr. Hasidah Mohd. Sidek (HMS)Sidek (HMS)
• Dr. Izyanti Ibrahim (II)Dr. Izyanti Ibrahim (II)
• Dr. Sharom Md. Yusof (SMY) Dr. Sharom Md. Yusof (SMY) **
** Coordinator Coordinator ([email protected])([email protected])
Lecture ScheduleLecture Schedule
One SetOne Set
Monday Monday 11:00-12:00 11:00-12:00 DKG129BBDKG129BB Tuesday 08:00-09:00Tuesday 08:00-09:00 DKG129BBDKG129BB ThursdayThursday 08:00-09:0008:00-09:00 DKG130BBDKG130BB
Course OutlineCourse Outline
1. Cell as the basic unit of life (2 1. Cell as the basic unit of life (2 h)h)
- Overview of cell structure & function- Overview of cell structure & function
- Techniques to study cell structure &- Techniques to study cell structure &
function (microscopy, cell function (microscopy, cell
fractionation)fractionation)
2. Structure & function of cells 2. Structure & function of cells (3h)(3h) - Organelles (mitochondria, chloroplasts,- Organelles (mitochondria, chloroplasts,
ribosomes, nucleus, Golgi complex,ribosomes, nucleus, Golgi complex,
endoplasmic reticulum, bacterial &endoplasmic reticulum, bacterial &
plant cell walls, cytoskeleton)plant cell walls, cytoskeleton)
3. Cell buffering system (4 h)3. Cell buffering system (4 h) - Characteristics of water, acids,- Characteristics of water, acids,
bases & properties of buffersbases & properties of buffers
- Physiological buffers- Physiological buffers
4. Macromolecules in cells (5 h)4. Macromolecules in cells (5 h) - Proteins- Proteins
- Polysaccharides- Polysaccharides
- Lipids- Lipids
5. Membrane Biology (4 h)5. Membrane Biology (4 h) - Structure, composition & models of- Structure, composition & models of
membranesmembranes
- Transport across membranes- Transport across membranes
6. Enzymatic reactions in cells 6. Enzymatic reactions in cells (5h)(5h)
- - Types & functions of enzymesTypes & functions of enzymes
- Catalytic characteristics- Catalytic characteristics
- Factors influencing enzyme reactions- Factors influencing enzyme reactions
- Isoenzymes & coenzymes- Isoenzymes & coenzymes
7. Bioenergetics (2 h)7. Bioenergetics (2 h) - Principles of thermodynamics- Principles of thermodynamics
- Involvement of ATP in coupled reactions- Involvement of ATP in coupled reactions
8. Energy metabolism & ATP 8. Energy metabolism & ATP
synthesis (7 h)synthesis (7 h) - Glycolysis- Glycolysis
- TCA cycle- TCA cycle
- Respiratory chain & synthesis of ATP- Respiratory chain & synthesis of ATP
- - -oxidation of fatty acids-oxidation of fatty acids
- Shuttle systems- Shuttle systems
Campbell N.A. & Reece J.B. 2005. Campbell N.A. & Reece J.B. 2005. Biology. 7Biology. 7thth Edition. San Francisco: Edition. San Francisco: Pearson Benjamin Cummings.Pearson Benjamin Cummings.
Campbell M.K. & Farrell S.O. 2006. Campbell M.K. & Farrell S.O. 2006. Biochemistry. 5 Biochemistry. 5thth Edition. Edition. Belmont: Thomson Brooks / Cole.Belmont: Thomson Brooks / Cole.
Nelson, D.L. & Cox, M.M. 2008 Nelson, D.L. & Cox, M.M. 2008 or or 20062006. . Lehninger Principles of Lehninger Principles of Biochemistry. 5Biochemistry. 5thth or 4or 4thth EditionEdition. . New York: W.H. Freeman.New York: W.H. Freeman.
Recommended TextRecommended Text
First 2 lectures…
Cell as the basic unit of life (2 h)Cell as the basic unit of life (2 h)
- Overview of cell structure & function- Overview of cell structure & function
- Techniques to study cell structure &- Techniques to study cell structure &
function (microscopy, cell fractionation)function (microscopy, cell fractionation)
All Living Things are Composed All Living Things are Composed of Cellsof Cells
CellCell• Mass of protoplasmMass of protoplasm• Bound by Bound by
membranemembrane• Smallest Smallest livingliving unit unit
In other words, the cell isIn other words, the cell is
the basic unit of lifethe basic unit of life Anything lower than the cellAnything lower than the cell
is considered non-living is considered non-living
• Cells comprise of Cells comprise of :: - molecules- molecules - atoms- atoms (organised into(organised into macromoleculesmacromolecules))
• Individually, Individually, molecules and molecules and atomsatoms are non-livingare non-living componentscomponents
• molecules and molecules and atomsatoms are not able to are not able to carrycarry out life out life processesprocesses
We will review later on whatWe will review later on what
properties make the cell properties make the cell
‘ ‘living’ as compared to its living’ as compared to its
‘ ‘non-living’ constituentsnon-living’ constituents ((molecules and atoms)molecules and atoms)
http://www.sinauer.com/cooper/4e/chapter01.html July 5th 2009
All present-day cells (both prokaryotes & eukaryotes) All present-day cells (both prokaryotes & eukaryotes)
are descended from a single ancestorare descended from a single ancestor
The first cell arose at least 3.8 billion years ago as a The first cell arose at least 3.8 billion years ago as a
result of enclosure of self-replicating RNA in a result of enclosure of self-replicating RNA in a
phospholipid membrane phospholipid membrane
Present-day prokaryotes are divided Present-day prokaryotes are divided into two groups : into two groups : the archaebacteriathe archaebacteria the eubacteria the eubacteria
Eukaryotic cells:Eukaryotic cells: are larger and more complex than prokaryotic cellsare larger and more complex than prokaryotic cells contain a nucleuscontain a nucleus consist of cytoplasmic organelles consist of cytoplasmic organelles
and a cytoskeletonand a cytoskeleton
The simplest eukaryotes are The simplest eukaryotes are unicellular organismsunicellular organisms (e.g. yeasts & (e.g. yeasts & amoebas)amoebas)
Multicellular organisms Multicellular organisms evolved from evolved from associations between such unicellular associations between such unicellular eukaryoteseukaryotes
Division of labor led to the Division of labor led to the development of the many kinds of development of the many kinds of specialised cells specialised cells that make up that make up present-day plants & animals present-day plants & animals
In research, cells have been In research, cells have been used as experimental modelsused as experimental models
Examples of cells as Examples of cells as experimental modelsexperimental models
The The bacteria, bacteria, E. coliE. coli is useful is useful for investigating fundamental for investigating fundamental aspects of biochemistry & aspects of biochemistry & molecular biology (related to molecular biology (related to the genetic simplicity of the the genetic simplicity of the bacteria thus easily studied)bacteria thus easily studied)
science.howstuffworks.com 12 Sept 2011 en.wikipedia.org 12 Sept 2011
• some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls
• the harmless strains are part of the normal flora of the gut
• E. coli is the most widely studied prokaryotic model organism
• an important species in the fields of biotechnology and microbiology (it has served as the host organism for the majority of work with recombinant DNA)
senescence.info 12 Sept 2011
More examples of cells More examples of cells (and organisms) as(and organisms) as
experimental modelsexperimental models
YeastsYeasts, as the simplest , as the simplest eukaryotic cells, are important eukaryotic cells, are important models for studying various models for studying various aspects of eukaryotic cell aspects of eukaryotic cell biologybiology
The The nematode, nematode, Caenorhabditis Caenorhabditis eleganselegans is a simple is a simple multicellular organism that multicellular organism that serves as an important model serves as an important model in developmental biologyin developmental biology
The The fruitfly, fruitfly, Drosophila Drosophila melanogaster melanogaster has been has been extensively studied in terms of its extensively studied in terms of its genetics and contribute to major genetics and contribute to major advances in understanding advances in understanding animal developmentanimal development
Also the Also the small flowering plant, small flowering plant, Arabidopsis thalianaArabidopsis thaliana is widely used is widely used as a model for studies of plant as a model for studies of plant molecular biology & developmentmolecular biology & development
genotyping.wordpress.com Sept 12 2011
- Its small stature and short generation time facilitates rapid genetic studies
- Arabidopsis was the first plant to have its genome sequenced
In addition, many kinds of In addition, many kinds of vertebrate cells vertebrate cells can be grown in can be grown in culture where they can be culture where they can be studied under controlled studied under controlled laboratory conditionslaboratory conditions
Specialised cell types, such as Specialised cell types, such as neurons & muscle cells, provide neurons & muscle cells, provide useful models for investigating useful models for investigating particular aspects of cell biologyparticular aspects of cell biology
Epithelial cells in culture, stained for keratin (red) and DNA (green)
Growth of Animal Cells in Culture:Growth of Animal Cells in Culture: The propagation of animal cells in The propagation of animal cells in culture has allowed studies of the culture has allowed studies of the mechanisms that control cell mechanisms that control cell growth & differentiationgrowth & differentiation
Culture of Plant Cells:Culture of Plant Cells: Cultured Cultured plant cells can differentiate to form plant cells can differentiate to form specialised cell types &, in some specialised cell types &, in some cases, can regenerate entire plants cases, can regenerate entire plants
Viruses:Viruses: Viruses provide simple Viruses provide simple models for studies of cell functionmodels for studies of cell function
The The frog frog Xenopus laevisXenopus laevis & & zebrafishzebrafish are important models are important models for studies of early vertebrate for studies of early vertebrate development development
The The mousemouse is a mammalian is a mammalian species suitable for genetic species suitable for genetic analysis and also for analysis and also for in vivo in vivo trialstrials
At the level of organisms…
The ease of manipulation in amphibian embryos has given them an important place in modern developmental biology.
- Fully-sequenced genome - Well understood, easily observable and testable developmental behaviors
- relatively easy to maintain and handle- reproduce quickly- share a high degree of homology with humans (mouse genome already sequenced)
Tools which have Tools which have facilitated studies in facilitated studies in cell biology include… cell biology include…
Light Microscopy allows for:Light Microscopy allows for: - - visualisation of cells & subcellularvisualisation of cells & subcellular structuresstructures - determination of intracellular- determination of intracellular localisation of specific moleculeslocalisation of specific molecules
Electron Microscopy (with a Electron Microscopy (with a resolution resolution 100 fold greater 100 fold greater than light microscopy) allows:than light microscopy) allows:
- - detailed analysis of cell structure detailed analysis of cell structure
Subcellular Fractionation:Subcellular Fractionation: allows organelle isolation allows organelle isolation from eukaryotic cells for from eukaryotic cells for further biochemical further biochemical analysisanalysis
(via (via differential centrifugation)differential centrifugation)
thin slices of cork thin slices of cork as observed by as observed by Robert HookeRobert Hooke
internal ultrastructure
of cells-transmission electron microscope
surface details of cilia- scanning electron microscope
Blood components (surface details)
– scanning electron microscope
The early microscope!The early microscope!
SEM
Development of Development of microscopy microscopy
contributed to the contributed to the formulation offormulation of
the cell theorythe cell theory
Cell theory historical timelineCell theory historical timeline
Basic tenets of the Cell Basic tenets of the Cell TheoryTheory
1.1. All organisms consist of All organisms consist of one or more cellsone or more cells
2.2. The cell is the basic unit of The cell is the basic unit of structure for all organismsstructure for all organisms
3.3. All cells arise only from All cells arise only from pre-existing cellspre-existing cells
The combined work of The combined work of Schleiden, Schwann & Schleiden, Schwann & VirchowVirchow led to the Cell Theory led to the Cell Theory
This would not have been This would not have been possible without the possible without the
contribution of contribution of ‘microscopists’‘microscopists’
Robert Hooke
Anton van LeeuwenhoekAnton van Leeuwenhoek
Cells are the basic Cells are the basic structural units of all structural units of all livingliving organisms organisms
Organisms may be Organisms may be made up of singlemade up of single
or multiple cellsor multiple cells
in other words, in other words,
organisms are unicellular organisms are unicellular or multicellularor multicellular
The cell is the lowest level of The cell is the lowest level of organisation that can perform all organisation that can perform all activities required for lifeactivities required for life
25 µmFigure 1.5
Therefore…Therefore…
Any lower level of organisation is non-living
General General characteristicscharacteristics
of cellsof cells
Cell structure is diverse but all cells Cell structure is diverse but all cells share common characteristicsshare common characteristics
The chemical composition of all The chemical composition of all cells are basically the samecells are basically the same
Basic elements in cells – C, H, N, O, P, SBasic elements in cells – C, H, N, O, P, S
‘‘Non-living’ elements form cellular Non-living’ elements form cellular macromoleculesmacromolecules - proteins, nucleic - proteins, nucleic acids, carbohydrates & lipidsacids, carbohydrates & lipids
Activities carried out by cells depend Activities carried out by cells depend on properties & functions of on properties & functions of macromoleculesmacromolecules
All cells are bounded by a All cells are bounded by a plasma membraneplasma membrane
The plasma membrane :The plasma membrane :
• separates activities occurring in separates activities occurring in neighboring cellsneighboring cells
• gives each cell an independent gives each cell an independent entityentity
Lateral movement(~107 times per second)
Flip-flop(~ once per month)
(a) Movement of phospholipids
Lipid bilayer of the plasma membraneLipid bilayer of the plasma membrane
Hydrophillic head exposed to aqueous environmentHydrophillic head exposed to aqueous environmentHydrophobic tail hidden from the environmentHydrophobic tail hidden from the environment
Cells are highly complexedCells are highly complexed & organised& organised
Organisation of Organisation of LifeLife• CellCell
• TissueTissue• OrganOrgan• Organ SystemOrgan System• OrganismOrganism• PopulationPopulation• CommunityCommunity• EcosystemEcosystem• BiosphereBiosphere
Smallest Smallest LevelLevel
Largest LevelLargest Level
Cells possess a Cells possess a genetic program genetic program & the means to & the means to use ituse it
Genetic information is contained in genes
Genes constitute blueprints for cell structure, activities & multiplication
The Cell’s Heritable Information Cells contain chromosomes made partly of DNA Cells contain chromosomes made partly of DNA
(the substance of genes)(the substance of genes)
DNA programs the cellular production of proteins DNA programs the cellular production of proteins and transmit information from parents to offspringand transmit information from parents to offspring
Egg cell
Sperm cell
NucleicontainingDNA
Fertilized eggwith DNA fromboth parents
Embyro’s cells with copies of inherited DNA Offspring with traits
inherited fromboth parentsFigure 1.6
Cells are capable Cells are capable of producing more of producing more of themselvesof themselves
Reproduce by Reproduce by division (mitosis)division (mitosis)
Developing and maintaining complexity Developing and maintaining complexity requires requires energy from the sunenergy from the sun
Photosynthesis converts light energy Photosynthesis converts light energy into into chemical energy – sucrose and chemical energy – sucrose and starchstarch
Animal cells – contains Animal cells – contains prepackaged prepackaged energy in the form of glucoseenergy in the form of glucose
Glucose metabolism produces ATPGlucose metabolism produces ATP
Cells acquire and utilise energy
Cells perform a variety of Cells perform a variety of chemical reactionschemical reactions
Cell processes based on Cell processes based on biochemical reactionsbiochemical reactions
Require enzymesRequire enzymes
Biological catalysts increase Biological catalysts increase reaction rate without increase in reaction rate without increase in temperaturetemperature
Cells engage in numerous Cells engage in numerous mechanical activitiesmechanical activities
Transport, assembly and Transport, assembly and degradationdegradation
These activities are based on These activities are based on dynamic changes in protein dynamic changes in protein structurestructure
Cells are able to respond to Cells are able to respond to stimulistimuli
Visible responses – cilliate moves away Visible responses – cilliate moves away from object or moves towards a source of from object or moves towards a source of nutrientsnutrients
Less obvious for multicellular organismLess obvious for multicellular organism Receptors on cell surface interact with Receptors on cell surface interact with
substances – hormones, growth factors substances – hormones, growth factors etcetc
Respond by altering metabolic Respond by altering metabolic activities, preparing for cell division, activities, preparing for cell division, committing suicide(!)committing suicide(!)
Cells are capable of self-regulationCells are capable of self-regulation
To maintain constant ordered stateTo maintain constant ordered state
Failure to correct mistake during DNA Failure to correct mistake during DNA replication may cause mutation leading replication may cause mutation leading to diseases e.g. cancerto diseases e.g. cancer
SummarySummaryThe chemical composition of all cells are basically the same
Cells acquire and utilize energy
All cells are bounded by a plasma membrane
Cells perform a variety of chemical reactions
Cells are highly complexed & organized
Cells engage in numerous mechanical activities
Cells possess a genetic program & the means to use it
Cells are able to respond to stimuli
Cells are capable of producing more of themselves
Cells are capable of self-regulation
Thus far, we have looked at Thus far, we have looked at common characteristics of common characteristics of cellscells
There are differences too…There are differences too…
Cells vary in sizeCells vary in size smallest bacteria - 0.2 smallest bacteria - 0.2 m in m in
diameterdiameter
longest in mammalslongest in mammals (nerve cells, giraffe neck)(nerve cells, giraffe neck)
largest volumelargest volume (yolk of ostrich egg-also the (yolk of ostrich egg-also the
largest single cell in the world)largest single cell in the world)
Animal and plant cells large Animal and plant cells large enough to be seen with a light enough to be seen with a light microscopemicroscope
Smaller molecules only Smaller molecules only observed with an electron observed with an electron microscopemicroscope
Cells vary in shape & Cells vary in shape & functionfunction
Nerve cells are enormously Nerve cells are enormously extended to allow transmission extended to allow transmission of electrical signalsof electrical signals
Human red blood cells are Human red blood cells are flattened to allow transport of flattened to allow transport of OO22
Cell Cell classificationclassification Based on the presence or Based on the presence or
absence of a nucleusabsence of a nucleus
Two basic types of cellsTwo basic types of cells Eukaryotes (from the Greek word Eukaryotes (from the Greek word
eueu meaning ‘truly’ and meaning ‘truly’ and karyonkaryon, a , a ‘nucleus’)‘nucleus’)
Prokaryotes (from Prokaryotes (from propro, meaning , meaning ‘before’)‘before’)
Prokaryotes evolved Prokaryotes evolved earlier than eukaryotesearlier than eukaryotes
A Brief History of Life on EarthA Brief History of Life on Earth
Earth formedEarth formed4.5 billion 4.5 billion yearsyears ago ago
3.5 billion years ago3.5 billion years ago
1.5 billion years ago1.5 billion years ago
0.5 billion years ago0.5 billion years ago
First life - prokaryoticFirst life - prokaryoticbacteria dominatebacteria dominate
Nucleated cells arise - eukaryoticNucleated cells arise - eukaryotic
Cambrian explosionCambrian explosionmulticellular eukaryotes arisemulticellular eukaryotes arise
Two basic types of cells
Diagrams:
Prokaryotic & Eukaryotic Cell, Mariana Ruiz
__________________________________________
http://cellbiologypowerpoints.googlepages.com/home July 5th. 2009
Prokaryote Eukaryote
Generally,…Generally,… Prokaryotes are almost always single-Prokaryotes are almost always single- celledcelled (except for prokaryote colonies) (except for prokaryote colonies)
Prokaryotes do not contain any cell Prokaryotes do not contain any cell nucleus or any other membrane-nucleus or any other membrane-
boundbound organellesorganelles ((DNA travels openly around the cell)DNA travels openly around the cell)
Prokaryotes reproduce by Prokaryotes reproduce by binary fissionbinary fission
(generation of another copy by dividing)(generation of another copy by dividing)
BinarBinaryyFissiFissionon
All bacteria All bacteria (Kingdom=Monera)(Kingdom=Monera)
are prokaryotesare prokaryotes
Eukaryotic vs prokaryotic Eukaryotic vs prokaryotic cellscells
Also to put things in perspective in terms of size
Thiomargarita (Sulfur Pearl of Namibia)
Atypically-sized prokaryote
>100 X bacterial size (typical size 1-5
m)
large nitrate-storing vacuole contributes
to the size
When compared to prokaryoticWhen compared to prokaryotic cells, eukaryotic cells are morecells, eukaryotic cells are more complex complex
containing membrane-enclosedcontaining membrane-enclosed organelles absent in prokaryotes organelles absent in prokaryotes
Eukaryotes are 10-20 X Eukaryotes are 10-20 X largerlarger
than prokaryotes (~10-than prokaryotes (~10-100 100 m)m)
Multicellular eukaryotes Multicellular eukaryotes (human, animal, plant, fungus, (human, animal, plant, fungus,
protist)protist) Unicellular eukaryotes Unicellular eukaryotes (yeast, Paramecium)(yeast, Paramecium)
YeastYeast
ParameciParameciumum
Candida albicans
Acetabularia Acetabularia (Mermaid's (Mermaid's wineglass algae)wineglass algae)
Atypically-sized eukaryotic Atypically-sized eukaryotic cellcell
A single giant cell ~5-7 cm in A single giant cell ~5-7 cm in length length
The nucleus is in holdfast The nucleus is in holdfast (root)(root)
Red blood cell is a Red blood cell is a eukaryoticeukaryoticcell without nucleuscell without nucleus Unable to undergo mitosisUnable to undergo mitosis
Some eukaryotic cells Some eukaryotic cells have more than one have more than one nucleinuclei
Fungi - fused cells,Fungi - fused cells,
multinucleatemultinucleate
Human skeletal muscle cells -Human skeletal muscle cells -
multinucleatemultinucleate
Cross section of Cross section of skeletal muscle :skeletal muscle : with with peripheral nuclei and large amounts of peripheral nuclei and large amounts of cytoplasm / small extracelluarcytoplasm / small extracelluar spacespace
Figure 4 - Skeletal muscle transverse section (Bright field illumination). Bar is 30 microns
www.bris.ac.uk/.../m1_index/histprac/page3.htm 7 July 2007
Multinucleatedeukaryotic cells
Different methods forDifferent methods for
enhancing visualisationenhancing visualisation of of
cellular structures in cellular structures in microscopymicroscopy
EUnstained versus stained human cheekUnstained versus stained human cheekepithelial cellsepithelial cells Brightfield microscopy : light Brightfield microscopy : light passes directly through specimenpasses directly through specimen
Image has little contrast unless Image has little contrast unless cell is naturally pigmented orcell is naturally pigmented orartificially stainedartificially stained
(a)
Staining with various dyesStaining with various dyes enhances contrastenhances contrast
Most staining proceduresMost staining proceduresrequire that cells be fixedrequire that cells be fixed(preserved)(preserved)
(b)
Phase-contrast. Enhances contrast in unstained cells by amplifying variations in density within specimen; especially useful for examining living, unpigmented cells.
50 µm
Brightfield (stained specimen). Staining with various dyes enhances contrast, but most staining procedures require that cells be fixed (preserved).
(b)
In phase-contrast microscopy, In phase-contrast microscopy, contrast of unstained cellscontrast of unstained cellsmay be enhanced by may be enhanced by optical modificationoptical modification
For differential-interference-contrast For differential-interference-contrast (Nomarski) microscopy, (Nomarski) microscopy, image appearsimage appears 3 D through optical modification3 D through optical modification
In fluorescence microscopy,In fluorescence microscopy, the locations the locations of specific molecules in the cell of specific molecules in the cell are shown by tagging the moleculesare shown by tagging the molecules with fluorescent dyes or antibodieswith fluorescent dyes or antibodies
These fluorescent substances absorbThese fluorescent substances absorb ultraviolet radiation and emit visible light, ultraviolet radiation and emit visible light, as shown here in a cell from an arteryas shown here in a cell from an artery
Confocal. Uses lasers and special optics for “optical sectioning” of fluorescently-stained specimens. Only a single plane of focus is illuminated; out-of-focus fluorescence above and below the plane is subtracted by a computer. A sharp image results, as seen in stained nervous tissue (top), where nerve cells are green, support cells are red, and regions of overlap are yellow. A standard fluorescence micrograph (bottom) of this relatively thick tissue is blurry.
50 µm
In electron microscopy,In electron microscopy,
a beam of electrons is a beam of electrons is
focusedfocused
throughthrough a specimen (TEM) or a specimen (TEM) or
ontoonto its surface (SEM) its surface (SEM)
Transmission electron micrograph allows for detailed study of the
internal ultrastructure of cells
Transmission electron micro-scopy (TEM). A transmission electron microscope profiles a thin section of a specimen. Here we see a section through a tracheal cell, revealing its ultrastructure. In preparing the TEM, some cilia were cut along their lengths, creating longitudinal sections, while other cilia were cut straight across, creating cross sections.
Figure 6.4 (b)
In contrast, scanning electronIn contrast, scanning electron
micrograph…. micrograph…. allows for detailed study of the allows for detailed study of the
surface of a specimensurface of a specimenTECHNIQUE
Scanning electron micro-scopy (SEM). Micrographs takenwith a scanning electron micro-scope show a 3D image of the surface of a specimen. This SEM shows the surface of a cell from a rabbit trachea (windpipe) covered with motile organelles called cilia. Beating of the cilia helps moveinhaled debris upward toward the throat.
Figure 6.4 (a)
RESULTS
Importance of cellular Importance of cellular fractionationfractionation
for the study of for the study of cell structure & cell structure &
functionfunction
Cell FractionationCell Fractionation• A combination of A combination of
various methods used to various methods used to separate cell organelles & separate cell organelles & componentscomponents
• Consists of two phases :Consists of two phases :― homogenisationhomogenisation― centrifugation centrifugation
http://www.freewebs.com/ltaing/ july 9 2008
HomogenisationHomogenisation• The process of breaking open cellsThe process of breaking open cells• Accomplished with the use of : Accomplished with the use of :
― chemicals― chemicals ― ― enzymesenzymes
― ― sound wavessound waves• Forcing cells through small spaces Forcing cells through small spaces
at high pressure may also break at high pressure may also break cells apartcells apart
CentrifugationCentrifugation• Isolation of cell organellesIsolation of cell organelles• Results in the isolation of Results in the isolation of mitochondria, nucleus, mitochondria, nucleus, chloroplast etc.chloroplast etc.
Generally…Generally…• Applications for centrifugation Applications for centrifugation are many including :are many including :― sedimentation of cells & virusessedimentation of cells & viruses― isolation of macromolecules (e.g.isolation of macromolecules (e.g.
DNA, RNA, proteins, or lipids)DNA, RNA, proteins, or lipids) ― separation of sub-cellularseparation of sub-cellular
organellesorganelles
In cell biology, cell In cell biology, cell fractionation…fractionation…
• increases knowledge on increases knowledge on organelle functionsorganelle functions― isolate organelles into pure groups isolate organelles into pure groups
i.e.i.e.
specific cell components specific cell components • e.g. by centrifugation, a specific e.g. by centrifugation, a specific
cell fraction was determined to cell fraction was determined to have enzymes that function in have enzymes that function in cellular respirationcellular respiration
• Because this cell fraction is rich inBecause this cell fraction is rich in mitochondria, this is evidence that mitochondria, this is evidence that thethe mitochondria is the site for mitochondria is the site for cellularcellular respirationrespiration
Microscopy is used to identify the Microscopy is used to identify the organelles in each pelletorganelles in each pellet
Biochemical methods are then used Biochemical methods are then used to determine the metabolic functions to determine the metabolic functions associated with each type of associated with each type of organelleorganelle Cell fractionation is now widely used Cell fractionation is now widely used to isolate particular organelles in to isolate particular organelles in order to study further details of their order to study further details of their functionfunction
Subcellular
Fraction
Marker Enzyme
MitochondriMitochondriaa
Succinate Succinate DehydrogenasDehydrogenas
ee
Lysosomes Acid Phosphatase
MicrosomesMicrosomes Glucose-6-Glucose-6-PhosphatasePhosphatase
CytosolLactate
Dehydrogenase
http://www.wpi.edu/Academics/Depts/Chemistry/Courses/General/fractionation.html9 July 2007
Uses of centrifugationUses of centrifugation• separation of blood components ― plasma mostly H2O content ― erythrocytes (red blood cells) ― buffy coat (white blood cells & platelets)
Uses of differential Uses of differential centrifugationcentrifugation• sperm separation (fertility sperm separation (fertility
clinic)clinic)
― sperm with an X chromosome (for sperm with an X chromosome (for girls) weigh a little more than girls) weigh a little more than sperm with a Y chromosome (for sperm with a Y chromosome (for boys)boys)
― sperms can be sorted out & sperms can be sorted out & prepared for insemination prepared for insemination
Course Outline Course Outline (revisited)(revisited) 1. Cell as the basic unit of life (2h)1. Cell as the basic unit of life (2h)
- Overview of cell structure & function- Overview of cell structure & function
- Techniques to study cell structure &- Techniques to study cell structure &
function (microscopy, cell function (microscopy, cell
fractionation)fractionation)
2. Structure and function of cells (2h)2. Structure and function of cells (2h)
- Organelles (mitochondria, - Organelles (mitochondria, chloroplasts,chloroplasts,
ribosomes, nucleus, Golgi complex,ribosomes, nucleus, Golgi complex,
endoplasmic reticulum, bacterial &endoplasmic reticulum, bacterial &
plant cell walls, cytoskeleton)plant cell walls, cytoskeleton)
Course Outline Course Outline (continued)(continued) 3. Cell buffering system (4 h)3. Cell buffering system (4 h)
- Characteristics of water, acids,- Characteristics of water, acids,
bases & properties of buffersbases & properties of buffers
- Physiological buffers- Physiological buffers
4. Macromolecules in cells (6 h)4. Macromolecules in cells (6 h)
- Proteins- Proteins
- Polysaccharides- Polysaccharides
- Lipids- Lipids