Download - AP BIO CH. 6.1-6.2
A Tour of the CellA Tour of the Cell
Ch. 6Ch. 6
Sections 6.1, 6.2Sections 6.1, 6.2
3 Objectives in the Section3 Objectives in the Section
1.1. Microscope types – what kind Microscope types – what kind is best for different jobsis best for different jobs
2.2. Differences between Differences between prokaryotes and eukaryotesprokaryotes and eukaryotes
3.3. Why cells need to be smallWhy cells need to be small
MicroscopesMicroscopeshow we view cellshow we view cells
Early MicroscopesEarly Microscopes
First microscopeFirst microscope Jansen (Dutch) -Jansen (Dutch) -
15951595
Christopher Cock’s Christopher Cock’s compound scopes compound scopes (1665) used by (1665) used by Robert Robert HookHook, Father of cell , Father of cell biologybiology
Leeuwenhoek’sLeeuwenhoek’s Microscopes MicroscopesBrightest, clearest lensesBrightest, clearest lensesSingle lens, Single lens, magnified over magnified over
200x200x Impressive observer Impressive observer
of protists of protists
500500 times times better than better than human eyehuman eye
Light Light MicroscopeMicroscope
Light MicroscopesLight Microscopes
Early scopes and modern scopes are light Early scopes and modern scopes are light microscopes (LMs)microscopes (LMs)Visible light passes through the specimenVisible light passes through the specimen Image magnified by a series of lensesImage magnified by a series of lenses
MagnificationMagnification
The ratio of the projected image to the real The ratio of the projected image to the real size of the objectsize of the object
LMs can effectively magnify to ~ 1000xLMs can effectively magnify to ~ 1000x
Sizes of cellsSizes of cells
One One MICROMETERMICROMETER = 1/ 1,000,000 m = 1/ 1,000,000 m One One NANOMETERNANOMETER = 1/1,000,000,000 m = 1/1,000,000,000 m
ResolutionResolutionA measure of how clear an image isA measure of how clear an image isDetermined by the minimum distance at Determined by the minimum distance at
which 2 points can still be distinguished as which 2 points can still be distinguished as 2 separate points2 separate points
LMs have resolution of ~0.2 micrometers LMs have resolution of ~0.2 micrometers at bestat best
Poor resolution
At what point can you no longer distinguish these as separate lines?
ResolutionResolution
Human eye's resolving powerHuman eye's resolving power Ability to distinguish between Ability to distinguish between
lines = lines = 1/10 mm1/10 mm If closer, lines merge into 1 lineIf closer, lines merge into 1 line
Reverses image under field of viewReverses image under field of view
Light MicroscopeLight Microscope
Dark-Field MicroscopesDark-Field Microscopes
Light comes from the sideLight comes from the side, , makes makes huge huge shadowsshadows and contrasts and contrasts
Good for LIVING CELLS
Phase-contrast MicroscopePhase-contrast Microscope
Waves of lightWaves of light are set up, are set up, bounced offbounced off the specimenthe specimen
InterferenceInterference caused caused by by shape of cells is shape of cells is plotted by plotted by computer, computer, projected projected
Electron MicroscopesElectron Microscopes
Developed in theDeveloped in the 1950s1950s
Instead of light, a Instead of light, a beam of electrons is beam of electrons is focused on specimenfocused on specimen
Transmission Electron MicroscopeTransmission Electron Microscope (T.E.M.)(T.E.M.)
Aims a Aims a beam of electronsbeam of electrons instead of instead of light waves light waves THROUGHTHROUGH a section of a section of the the specimenspecimen
200,000200,000 times better times better than the eye than the eye
T.E.M. X-secT.E.M. X-secGolgi
Actin Filament
Mitochondrion
Preparation of specimenPreparation of specimen
Since cells are mostly water, Since cells are mostly water, need dye to need dye to show up, show up, block light raysblock light rays
Hydrophobic and Hydrophobic and hydrophillic hydrophillic stainsstains will dye organelles will dye organelles different densitiesdifferent densities
Scanning Electron MicroscopeScanning Electron Microscope (S.E.M.)(S.E.M.)
Works like sonar, using Works like sonar, using electronselectrons to to bounce off specimen's surfacebounce off specimen's surface
Limited resolutionLimited resolution but but great great 3-D3-D effect effect!!
S.E.M. S.E.M.
Pollen grains
Ant
Red and white blood cells
Preparation of specimensPreparation of specimens
First embedded in waxFirst embedded in wax Sliced with a Sliced with a
MICROTOMEMICROTOME Specimens "shadowed" Specimens "shadowed"
with metal with metal, , for reflection, contrastfor reflection, contrast
ALL THESE ALL THESE PROCESSES PROCESSES KILL KILL CELLSCELLS
Pros & Cons of Microscope TypesPros & Cons of Microscope TypesLightLight Scanning Scanning
ElectronElectronTransmission Transmission ElectronElectron
ProsPros Can study Can study living cellsliving cells
Gives details on Gives details on surface of specimen; surface of specimen; resolution 0.002 resolution 0.002 micrometersmicrometers
Good for studying Good for studying internal cell internal cell structures; resolution structures; resolution 0.002 micrometers0.002 micrometers
ConsCons Magnification Magnification to only 1000x, to only 1000x, resolution resolution only 0.2 only 0.2 micrometermicrometer
Preparation of cells Preparation of cells kills them; limited kills them; limited resolutionresolution
Preparation of cells Preparation of cells kills them; need very kills them; need very thin sections of cell thin sections of cell parts (no depth)parts (no depth)
Quick ThinkQuick Think
With your neighbor, DISCUSS:With your neighbor, DISCUSS: What type of microscope would What type of microscope would
you use to study you use to study 1.1. A living white blood cell?A living white blood cell?
2.2. The details of surface texture of The details of surface texture of hair?hair?
3.3. The detailed structure of an The detailed structure of an organelle?organelle?
Separation of Organelles by Separation of Organelles by Cell Cell FractionationFractionation
Using a centrifuge to separate out successively Using a centrifuge to separate out successively smaller cell components for studysmaller cell components for study
Cell parts separated by size and densityCell parts separated by size and density
Prokaryotic Cells vs. Prokaryotic Cells vs. Eukaryotic CellsEukaryotic Cells
PROKARYOTESPROKARYOTES
They They are:are:BacteriaBacteria
Have plasma membraneHave plasma membrane (aka cell membrane) (aka cell membrane) + + cell wallcell wall
NoNo membrane-bound membrane-bound organellesorganellesNONO NUCLEAR MEMBRANE ( NUCLEAR MEMBRANE (no nucleusno nucleus))
DNA in strands in mid-cellDNA in strands in mid-cellHeterotrophic, phototrophic & chemotrophic Heterotrophic, phototrophic & chemotrophic
formsforms
ProkaryotesProkaryotes
EUKARYOTESEUKARYOTES
Much more Much more complexcomplex Contain MANYContain MANY membrane-bound membrane-bound organellesorganelles DNA DNA contained contained in a nucleusin a nucleus
membrane membrane Includes Includes ALL ALL
animals, animals, plants, protists, & plants, protists, & fungi fungi
Cell SizeCell Size
In In eukaryoteseukaryotes – cells – cells varyvary greatly, greatly, butbut basically allbasically all similar in similar in structure & sizestructure & size
10 30 micrometers‑10 30 micrometers‑Largest cell = Largest cell = eggseggs
Zygote divides rapidly to Zygote divides rapidly to get new cells to correct sizeget new cells to correct size
Critical Question:Critical Question:Why Do Cells Need to Be Why Do Cells Need to Be
ExtremelyExtremely Small? Small?
Answer:Answer: Surface to volume ratio Surface to volume ratio needs to be largeneeds to be large
LOTS of materialsLOTS of materials need to pass through plasma need to pass through plasma membrane membrane
DiffusionDiffusion only works well across very short only works well across very short distancesdistances
Nucleus Nucleus can only handle so much info at once can only handle so much info at once would “short out” if cells were much larger‑would “short out” if cells were much larger‑
Diffusion of substances across the Diffusion of substances across the plasma membraneplasma membrane
Only so much stuff can pass across the Only so much stuff can pass across the membrane at any particular locationmembrane at any particular location
Larger cells cannot move enough Larger cells cannot move enough materials in and out to support the cellmaterials in and out to support the cell
Increase Surface/Volume RatioIncrease Surface/Volume Ratio
Cell ShapeCell ShapeTend to be Tend to be sphericalspherical
because of cohesion & because of cohesion & surface tensionsurface tension Strongest structural Strongest structural
shape, stableshape, stable (like bubbles (like bubbles & balloons)& balloons)
If NOT spherical, If NOT spherical, cell needs cell needs internal internal and/or and/or external external supportsupport maintain maintain shapeshape
OrganellesOrganelles Eukaryotic cells haveEukaryotic cells have
elaborate elaborate internal internal membranesmembranes that divide the that divide the interior of the cell into interior of the cell into compartmentscompartments
These These membrane bound membrane bound compartments are called compartments are called organellesorganelles Each has a specific function Each has a specific function Each has a specific structureEach has a specific structure
Cell ComponentsCell ComponentsAnimal CellAnimal Cell
Plant CellPlant Cell
The Cell Parts ProjectThe Cell Parts Project Nucleus Nucleus NucleolusNucleolus RibosomesRibosomes Smooth ERSmooth ER Rough ER Rough ER GolgiGolgi Vacuoles (food, Vacuoles (food,
contractile, central)contractile, central) CentriolesCentrioles
Mitochondria Mitochondria ChloroplastChloroplast Cytoskeleton Cytoskeleton Cilia and flagella Cilia and flagella Cell wall Cell wall Lysosomes Lysosomes Plasma membranePlasma membrane
Do not need details of p/s or c/r
Groups and TopicsGroups and Topics
You can choose your partner, You can choose your partner, but topics will be assigned on but topics will be assigned on a first come, first served a first come, first served RANDOM basisRANDOM basis