Date post: | 11-Jan-2016 |
Category: |
Documents |
Upload: | liliana-clarke |
View: | 224 times |
Download: | 1 times |
CellsCells
The Units of LifeThe Units of Life
Mid 1600s - Robert Hooke observed Mid 1600s - Robert Hooke observed
and described cells in corkand described cells in cork
Late 1600s - Antony van Leeuwenhoek Late 1600s - Antony van Leeuwenhoek
observed sperm, microorganismsobserved sperm, microorganisms
1820s - Robert Brown observed and 1820s - Robert Brown observed and
named nucleus in plant cellsnamed nucleus in plant cells
Early DiscoveriesEarly Discoveries
Cell TheoryCell Theory
Schleiden and SchwannSchleiden and Schwann Every organism is composed of one or more Every organism is composed of one or more
cellscells
Cell is smallest unit having properties of lifeCell is smallest unit having properties of life
VirchowVirchow All exisiting cells arise from pre-existing All exisiting cells arise from pre-existing
cells.cells.
Smallest unit of lifeSmallest unit of life
Can survive on its own or has Can survive on its own or has
potential to do sopotential to do so
Is highly organized for metabolismIs highly organized for metabolism
Senses and responds to environmentSenses and responds to environment
Has potential to reproduceHas potential to reproduce
CellCell
Measuring Measuring
Cells Vary in SizeCells Vary in Size
Why Are Cells So Small?Why Are Cells So Small?
Surface-to-volume ratioSurface-to-volume ratio
The bigger a cell is, the less surface The bigger a cell is, the less surface
area there is per unit volumearea there is per unit volume
Above a certain size, material cannot be Above a certain size, material cannot be
moved in or out of cell fast enoughmoved in or out of cell fast enough
Size is Limited Size is Limited
Create detailed images of something Create detailed images of something
that is otherwise too small to seethat is otherwise too small to see
Light microscopesLight microscopes Simple or compoundSimple or compound
Electron microscopesElectron microscopes Transmission EM or Scanning EMTransmission EM or Scanning EM
Ways to Study Cells:Ways to Study Cells:MicroscopesMicroscopes
Different Types of Light Microscopy: A Different Types of Light Microscopy: A ComparisonComparison
Limitations of Light Limitations of Light MicroscopyMicroscopy
Wavelengths of light are 400-750 nmWavelengths of light are 400-750 nm
If a structure is less than one-half of a If a structure is less than one-half of a wavelength long, it will not be visiblewavelength long, it will not be visible
Light microscopes can resolve objects Light microscopes can resolve objects down to about 200 nm in sizedown to about 200 nm in size
Electron MicroscopyElectron Microscopy
Uses streams of accelerated Uses streams of accelerated electrons rather than lightelectrons rather than light
Electrons are focused by magnets Electrons are focused by magnets rather than glass lensesrather than glass lenses
Can resolve structures down to 0.5 Can resolve structures down to 0.5 nm nm
Elecrton MicroscopesElecrton Microscopes
Electron micrographsElectron micrographs
Ways to Study Cells:Ways to Study Cells:Cell FractionationCell Fractionation
Structure of CellsStructure of Cells
Two types of cellsTwo types of cells ProkaryoticProkaryotic EukaryoticEukaryotic
All cells have:All cells have: Plasma membrane Plasma membrane Region where DNA is storedRegion where DNA is stored Cytoplasm Cytoplasm
Prokaryotic CellsProkaryotic Cells No nucleusNo nucleus
Nucleoid area where DNA residesNucleoid area where DNA resides No membrane bound organelles.No membrane bound organelles. 70s ribosomes70s ribosomes Cell walls contain petidoglycan or Cell walls contain petidoglycan or
pseudomureinpseudomurein Prokaryotic OrganismsProkaryotic Organisms
ArchaeobacteriaArchaeobacteria EubacteriaEubacteria CyanobacteriaCyanobacteria
A prokaryotic cellA prokaryotic cell
E. coliE. coli
Eukaryotic CellsEukaryotic Cells
Have a nucleus and Have a nucleus and other organellesother organelles
Eukaryotic organismsEukaryotic organisms ProtistansProtistans Fungi Fungi PlantsPlants AnimalsAnimals
Overview of an animal cellOverview of an animal cell
The nucleus and its envelope The nucleus and its envelope
Keeps the DNA molecules of Keeps the DNA molecules of eukaryotic cells separated from eukaryotic cells separated from metabolic machinery of cytoplasmmetabolic machinery of cytoplasm
Makes it easier to organize DNA and Makes it easier to organize DNA and to copy it before parent cells divide to copy it before parent cells divide into daughter cells into daughter cells
Functions of NucleusFunctions of Nucleus
Group of related organelles in which lipids Group of related organelles in which lipids are assembled and new polypeptide are assembled and new polypeptide chains are modifiedchains are modified
Products are sorted and shipped to various Products are sorted and shipped to various destinationsdestinations
Components of the cytomembrane systemComponents of the cytomembrane system Endoplasmic reticulumEndoplasmic reticulum Golgi apparatusGolgi apparatus vesiclesvesicles
Cytomembrane SystemCytomembrane System
Endoplasmic ReticulumEndoplasmic Reticulum
In animal cells, continuous with In animal cells, continuous with
nuclear membranenuclear membrane
Extends throughout cytoplasmExtends throughout cytoplasm
Two regions - rough and smoothTwo regions - rough and smooth
Rough ERRough ER
Arranged into flattened sacsArranged into flattened sacs Ribosomes on surface give it a rough Ribosomes on surface give it a rough
appearanceappearance Some polypeptide chains enter rough Some polypeptide chains enter rough
ER and are modifiedER and are modified Cells that specialize in secreting Cells that specialize in secreting
proteins have lots of rough ERproteins have lots of rough ER
Smooth ERSmooth ER
A series of interconnected tubules A series of interconnected tubules No ribosomes on surfaceNo ribosomes on surface Lipids assembled inside tubulesLipids assembled inside tubules Smooth ER of liver inactivates Smooth ER of liver inactivates
wastes, drugswastes, drugs Sarcoplasmic reticulum of muscle is Sarcoplasmic reticulum of muscle is
a specialized forma specialized form
Endoplasmic reticulum (ER)Endoplasmic reticulum (ER)
Golgi BodiesGolgi Bodies
Put finishing touches on proteins and Put finishing touches on proteins and lipids that arrive from ERlipids that arrive from ER
Package finished material for Package finished material for shipment to final destinationsshipment to final destinations
Material arrives and leaves in vesiclesMaterial arrives and leaves in vesicles
The Golgi apparatusThe Golgi apparatus
VesiclesVesicles
Membranous sacs that Membranous sacs that
move through the move through the
cytoplasmcytoplasm
LysosomesLysosomes
PeroxisomesPeroxisomes
LysosomesLysosomes
Review: relationships among organelles of the Review: relationships among organelles of the endomembrane systemendomembrane system
The mitochondrion, site of cellular The mitochondrion, site of cellular respirationrespiration
Organelles with no Organelles with no MembranesMembranes
RibosomesRibosomes Function in protein synthesisFunction in protein synthesis
CytoskeletonCytoskeleton Function in maintenance of cell shape Function in maintenance of cell shape
and positioning of organellesand positioning of organelles Centrioles (animals only)Centrioles (animals only)
Function during cell divisionFunction during cell division
RibosomesRibosomes
Present in all eukaryotic cellsPresent in all eukaryotic cells
Basis for cell shape and internal Basis for cell shape and internal organizationorganization
Allows organelle movement within Allows organelle movement within cells and, in some cases, cell motilitycells and, in some cases, cell motility
CytoskeletonCytoskeleton
Cytoskeletal ElementsCytoskeletal Elements
microtubule
microfilament
intermediatefilament
MicrotubulesMicrotubules
Largest elementsLargest elements
Composed of the protein tubulinComposed of the protein tubulin
Arise from microtubule organizing Arise from microtubule organizing
centers (MTOCs)centers (MTOCs)
Polar and dynamicPolar and dynamic
Involved in shape, motility, cell Involved in shape, motility, cell
divisiondivision
MicrotubulesMicrotubules
Largest elementsLargest elements
Composed of the protein tubulinComposed of the protein tubulin
Arise from microtubule organizing Arise from microtubule organizing
centers (MTOCs)centers (MTOCs)
Polar and dynamicPolar and dynamic
Involved in shape, motility, cell Involved in shape, motility, cell
divisiondivision
MicrofilamentsMicrofilaments
Thinnest cytoskeletal elementsThinnest cytoskeletal elements
Composed of the protein actin Composed of the protein actin
Polar and dynamicPolar and dynamic
Take part in movement, formation Take part in movement, formation
and maintenance of cell shapeand maintenance of cell shape
Intermediate FilamentsIntermediate Filaments
Present only in animal cells of certain Present only in animal cells of certain tissuestissues
Most stable cytoskeletal elementsMost stable cytoskeletal elements Six known groupsSix known groups Different cell types usually have 1-2 Different cell types usually have 1-2
different kindsdifferent kinds
Cell JunctionsCell Junctions
tightjunctions
adhering junction
gapjunction
Cell MembranesCell Membranes
Structure and FunctionStructure and Function
Fig. 4.3, p. 52
one layerof lipids
one layerof lipids
lipid bilayer
fluid
fluid
Main component Main component of cell membranesof cell membranes
Gives the Gives the membrane its fluid membrane its fluid propertiesproperties
Two layers of Two layers of phospholipidsphospholipids
Lipid BilayerLipid Bilayer
Figure 8.2 Two generations of membrane modelsFigure 8.2 Two generations of membrane models
The detailed structure of an animal cell’s plasma membrane, in The detailed structure of an animal cell’s plasma membrane, in cross sectioncross section
Functions of Membrane Functions of Membrane ProteinsProteins
TransportTransport Enzymatic Enzymatic
activityactivity Receptors for Receptors for
signal signal transductiontransduction
Figure 3.4.1
Functions of Membrane Functions of Membrane ProteinsProteins
Figure 3.4.2
Intercellular Intercellular adhesionadhesion
Cell-cell Cell-cell recognitionrecognition
Attachment to Attachment to cytoskeleton cytoskeleton and and extracellular extracellular matrixmatrix
Fig. 4.4, p. 53
EXTRACELLULAR ENVIRONMENT
(cytoskeletal pro-teins beneatch the plasma membrane)
ADHESION PROTEIN
oligosaccharide groups
phospholipid
cholesterol
LIPID BILAYER
RECOGNITION PROTEIN
RECEPTOR PROTEIN
CYTOPLASM
PLASMA MEMBRANE
(area of enlargment)
TRANSPORT PROTEINS
open channel protein
gated channel proten (open)
active transport protein
gated channel proten (closed)
The fluidity of membranesThe fluidity of membranes
Cell Membranes Show Cell Membranes Show Selective PermeabilitySelective Permeability
O2, CO2, and other smallnonpolar molecules;and H2O
C6H12O6, and other large, polar(water-soluble) molecules; ions such as H+, Na+, CI-, Ca++; plus H2O hydrogen-bonded to them
X
Membrane Crossing Membrane Crossing MechanismsMechanisms
Diffusion across lipid bilayerDiffusion across lipid bilayer
Passive transportPassive transport
Active transportActive transport
EndocytosisEndocytosis
ExocytosisExocytosis
DiffusionDiffusion
The net movement of like molecules The net movement of like molecules or ions down a concentration or ions down a concentration gradientgradient
Although molecules collide randomly, Although molecules collide randomly, the net movement is away from the the net movement is away from the place with the most collisions (down place with the most collisions (down gradient)gradient)
Concentration Gradient Concentration Gradient
Means the number of molecules or Means the number of molecules or ions in one region is different than ions in one region is different than the number in another regionthe number in another region
In the absence of other forces, a In the absence of other forces, a substance moves from a region substance moves from a region where it is more concentrated to one where it is more concentrated to one one where it’s less concentrated - one where it’s less concentrated - “down” gradient“down” gradient
Factors Affecting Factors Affecting Diffusion RateDiffusion Rate
Steepness of concentration gradientSteepness of concentration gradient Steeper gradient, faster diffusionSteeper gradient, faster diffusion
Molecular sizeMolecular size Smaller molecules, faster diffusionSmaller molecules, faster diffusion
TemperatureTemperature Higher temperature, faster diffusionHigher temperature, faster diffusion
Electrical or pressure gradientsElectrical or pressure gradients
The diffusion of solutes across membranesThe diffusion of solutes across membranes
Osmosis Osmosis A Special Case of Simple DiffusionA Special Case of Simple Diffusion
Diffusion of water molecules across a Diffusion of water molecules across a selectively permeable membraneselectively permeable membrane
Direction of net flow is determined by Direction of net flow is determined by water concentration gradientwater concentration gradient
Side with the most solute molecules Side with the most solute molecules has the lowest water concentrationhas the lowest water concentration
Tonicity Tonicity
Refers to Refers to relativerelative solute solute concentration of two fluidsconcentration of two fluids
Hypertonic - having more solutes Hypertonic - having more solutes
Isotonic - having same amountIsotonic - having same amount
Hypotonic - having fewer solutesHypotonic - having fewer solutes
Tonicity and OsmosisTonicity and Osmosis
2% sucrose
water 10% sucrose 2% sucrose
The water balance of living cellsThe water balance of living cells
The contractile vacuole of The contractile vacuole of ParameciumParamecium: an evolutionary : an evolutionary adaptation for osmoregulationadaptation for osmoregulation
Increase in Fluid VolumeIncrease in Fluid Volume
compartment1
HYPOTONIC SOLUTION
membrane permeable towater but not to solutes
HYPERTONICSOLUTION
compartment2
fluid volume increasesIn compartment 2
Passive Transport Passive Transport
Faciltiated DiffusionFaciltiated Diffusion Flow of solutes through the interior of Flow of solutes through the interior of
passive transport proteins down their passive transport proteins down their concentration gradientsconcentration gradients
Passive transport proteins allow Passive transport proteins allow solutes to move both wayssolutes to move both ways
Does not require any energy inputDoes not require any energy input
Span the lipid bilayerSpan the lipid bilayer Interior is able to open to both sidesInterior is able to open to both sides Change shape when they interact Change shape when they interact
with solute with solute Play roles in active and passive Play roles in active and passive
transport transport
Transport ProteinsTransport Proteins
Two models for facilitated diffusionTwo models for facilitated diffusion
Facilitated DiffusionFacilitated Diffusion
solute
Active TransportActive Transport
Net diffusion of solute is against Net diffusion of solute is against concentration gradientconcentration gradient
Transport protein must be activatedTransport protein must be activated ATP gives up phosphate to activate ATP gives up phosphate to activate
proteinprotein Binding of ATP changes protein Binding of ATP changes protein
shape and affinity for soluteshape and affinity for solute
Active Active TransportTransport
ATP gives up ATP gives up phosphate to phosphate to activate proteinactivate protein
Binding of ATP Binding of ATP changes protein changes protein shape and affinity shape and affinity for solutefor solute
P
P
P
P
High solute concentration
Low solute concentration
ATP ADP
The sodium-potassium pump: a specific case of active The sodium-potassium pump: a specific case of active transporttransport
Review: passive and active transport comparedReview: passive and active transport compared
Bulk Transport – Another Bulk Transport – Another form of Active Transportform of Active Transport
Exocytosis
Endocytosis
The three types of endocytosis in animal cellsThe three types of endocytosis in animal cells
MitosisMitosis
How to clone a nucleusHow to clone a nucleus
Roles of MitosisRoles of Mitosis
Multicelled organismsMulticelled organisms
GrowthGrowth
Cell replacementCell replacement
Some protistans, fungi, plants, Some protistans, fungi, plants,
animalsanimals
Asexual reproductionAsexual reproduction
ChromosomeChromosome
A DNA molecule & attached proteinsA DNA molecule & attached proteins Duplicated in preparation for mitosisDuplicated in preparation for mitosis
one chromosome (unduplicated)
one chromosome (duplicated)
Cell Cycle Cell Cycle
Cycle starts when a new cell formsCycle starts when a new cell forms
During cycle, cell increases in mass During cycle, cell increases in mass and duplicates its chromosomesand duplicates its chromosomes
Cycle ends when the new cell dividesCycle ends when the new cell divides
InterphaseInterphase
Usually longest part of the cycleUsually longest part of the cycle
Cell increases in massCell increases in mass
Number of cytoplasmic components Number of cytoplasmic components
doublesdoubles
DNA is duplicatedDNA is duplicated
Mitosis Mitosis
Period of nuclear divisionPeriod of nuclear division Usually followed by cytoplasmic Usually followed by cytoplasmic
divisiondivision Four stages:Four stages:
ProphaseProphase
MetaphaseMetaphase
AnaphaseAnaphase
TelophaseTelophase
Control of the CycleControl of the Cycle
Once S begins, the cycle automatically Once S begins, the cycle automatically
runs through G2 and mitosisruns through G2 and mitosis
The cycle has a built-in molecular brake The cycle has a built-in molecular brake
in G1in G1
Cancer involves a loss of control over Cancer involves a loss of control over
the cycle, malfunction of the “brakes”the cycle, malfunction of the “brakes”
Stopping the CycleStopping the Cycle
Some cells normally stop in interphaseSome cells normally stop in interphase
Neurons in human brainNeurons in human brain
Arrested cells do not divideArrested cells do not divide
Adverse conditions can stop cycleAdverse conditions can stop cycle
Nutrient-deprived amoebas get stuck in Nutrient-deprived amoebas get stuck in
interphaseinterphase
Stages of Mitosis Stages of Mitosis
ProphaseProphase
MetaphaseMetaphase
AnaphaseAnaphase
TelophaseTelophase
Early Prophase - Early Prophase - Mitosis BeginsMitosis Begins
Duplicated chromosomes begin to Duplicated chromosomes begin to condensecondense
Late ProphaseLate Prophase
New microtubules New microtubules are assembledare assembled
One centriole pair One centriole pair is moved toward is moved toward opposite pole of opposite pole of spindlespindle
Nuclear envelope Nuclear envelope starts to break upstarts to break up
Transition to MetaphaseTransition to Metaphase
Spindle formsSpindle forms Spindle Spindle
microtubules microtubules become attached become attached to the two sister to the two sister chromatids of each chromatids of each chromosomechromosome
MetaphaseMetaphase
All chromosomes All chromosomes are lined up at are lined up at the spindle the spindle equatorequator
Chromosomes Chromosomes are maximally are maximally condensedcondensed
AnaphaseAnaphase
Sister chromatids Sister chromatids of each of each chromosome are chromosome are pulled apartpulled apart
Once separated, Once separated, each chromatid each chromatid is a chromosome is a chromosome
TelophaseTelophase
Chromosomes Chromosomes decondensedecondense
Two nuclear Two nuclear membranes form, membranes form, one around each one around each set of set of unduplicated unduplicated chromosomeschromosomes
Results of MitosisResults of Mitosis
Two daughter Two daughter nuclei nuclei
Each with same Each with same chromosome chromosome number as parent number as parent cellcell
Chromosomes in Chromosomes in unduplicated formunduplicated form
Cytoplasmic Division Cytoplasmic Division
Usually occurs between late Usually occurs between late
anaphase and end of telophaseanaphase and end of telophase
Two mechanisms Two mechanisms
Cell plate formation (plants)Cell plate formation (plants)
Cleavage (animals)Cleavage (animals)
Animal Cell DivisionAnimal Cell Division