The Cytoskeleton. Objectives 1. Define cytoskeleton. 2. Explain the general functions of the cytoskeleton.…

The CytoskeletonThe Cytoskeleton

ObjectivesObjectives1.1. Define cytoskeleton.Define cytoskeleton.

2.2. Explain the general functions of the cytoskeleton.Explain the general functions of the cytoskeleton.

3.3. List the 3 types of cytoskeletal elements and their respective functions.List the 3 types of cytoskeletal elements and their respective functions.

4.4. Describe the structure and function of the centrosome.Describe the structure and function of the centrosome.

5.5. Describe the structure and functions of centriolesDescribe the structure and functions of centrioles

6.6. List and describe the similarities and differences between cilia and flagella.List and describe the similarities and differences between cilia and flagella.

The CytoskeletonThe Cytoskeleton

Prior to 1970’s cytosol thought to be unorganized mix Prior to 1970’s cytosol thought to be unorganized mix of organic molecules. of organic molecules.

Electron microscopy reveals organized cytosolElectron microscopy reveals organized cytosol

Immunoflourescence microscopy identified protein Immunoflourescence microscopy identified protein fibers.fibers.

The CytoskeletonThe CytoskeletonCharacteristicsCharacteristics

Found in eukaryotesFound in eukaryotes

Network of connected filaments and tubulesNetwork of connected filaments and tubules

Extends from nucleus to plasma membraneExtends from nucleus to plasma membrane

Elements can disassemble and reassembleElements can disassemble and reassemble

The CytoskeletonThe Cytoskeleton

FunctionFunction Maintains cell shapeMaintains cell shape

Allows organelles to moveAllows organelles to move

The CytoskeletonThe Cytoskeleton

Composed of 3 Types of FilamentsActin

Intermediate

Microtubules

Actin FilamentsActin Filaments

CharacteristicsCharacteristics

Long, thin about 7 micrometers in diameterLong, thin about 7 micrometers in diameter

Occur in bundles or meshlike networks.Occur in bundles or meshlike networks.

Consist of two chains of globular actin monomers Consist of two chains of globular actin monomers twisted to form a helix.twisted to form a helix.

Actin FilamentsActin FilamentsFunctionsFunctions

StructuralStructural

Form dense complex web just under the Form dense complex web just under the plasma membrane.plasma membrane.

In microvilli of intestinal cells likely shorten or In microvilli of intestinal cells likely shorten or extend cell into intestine.extend cell into intestine.

In plant cells, they form tracks along with In plant cells, they form tracks along with chloroplasts circulate.chloroplasts circulate.

Actin FilamentsActin Filaments

FunctionsFunctions

MovementMovement

Iinteracts with motor molecule myosinIinteracts with motor molecule myosin

Similar action accounts for pinching off cells Similar action accounts for pinching off cells during division and for amoeboid movement.during division and for amoeboid movement.

Intermediate FilamentsIntermediate Filaments

CharacteristicsCharacteristics

8-11nm in diameter8-11nm in diameter

Rope-likeRope-like

Fibrous polypeptidesFibrous polypeptides

Intermediate FilamentsIntermediate Filaments

FunctionsFunctions

SupportSupportNuclear envelopeNuclear envelopePlasma membranePlasma membrane Form cell-to-cell Form cell-to-cell junctions.junctions.

MicrotubulesMicrotubules

DescriptionDescription

Ropelike, hollow cylinders (25nm in Ropelike, hollow cylinders (25nm in diameter, 0.2 micrometers in length).diameter, 0.2 micrometers in length).

Composed of protein (Composed of protein (Tubulin)Tubulin); ; alpha and betaalpha and beta

Associated with motor molecules Associated with motor molecules (kinesins) kinesin and dynein(kinesins) kinesin and dynein

MicrotubulesMicrotubules

FunctionsFunctions Maintain shape of cellsMaintain shape of cells Tracks for vesicle and Tracks for vesicle and

organelle movementorganelle movement Different kinesins move Different kinesins move

different vesicles or organelles.different vesicles or organelles.

CentriolesCentrioles Short cylinders with a 9+0 pattern of microtubules Short cylinders with a 9+0 pattern of microtubules

triplets. triplets.

Animals cells and most protista, two centrioles Animals cells and most protista, two centrioles lying at right angleslying at right angles

Plant and fungal cells have equivalent of a Plant and fungal cells have equivalent of a centrosome but does not contain centrioles.centrosome but does not contain centrioles.

Centrioles serve as basal bodies for cilia and Centrioles serve as basal bodies for cilia and flagella.flagella.

CentriolesCentrioles

Serve as basal bodies for cilia and flagella.Serve as basal bodies for cilia and flagella.

Cilia and FlagellaCilia and FlagellaFlagella (L. Flagella (L. flagello,flagello, whip) whip) Cilia (L. Cilia (L. ciliumcilium, eyelash, hair), eyelash, hair)

Short, usually numerous hair like Short, usually numerous hair like projections that can move in an undulating projections that can move in an undulating fashion. fashion.

Flagella longer than cilia, usually fewerFlagella longer than cilia, usually fewer

Flagella are whip-like projectionsFlagella are whip-like projections

Flagella move whip-like (e.g. Sperm cells), cilia move Flagella move whip-like (e.g. Sperm cells), cilia move swimmer-like/oar-likeswimmer-like/oar-like

DifferencesDifferences

ConstructionConstructionMembrane-bounded cylindersMembrane-bounded cylinders(9+2 pattern of micortubules).(9+2 pattern of micortubules).

Basal bodiesBasal bodies

MovementMovementMicrotubules slide past one another.Microtubules slide past one another.

SimilaritiesSimilarities

GrowthGrowthBy addition of tubulin to tipsBy addition of tubulin to tips

Movement MechanismMovement MechanismMicrotubules slide past one another.Microtubules slide past one another.

SimilaritiesSimilarities(Cont’d)(Cont’d)

ReviewReview1.1. Define cytoskeleton.Define cytoskeleton.

2.2. Explain the general functions of the cytoskeleton.Explain the general functions of the cytoskeleton.

3.3. List the 3 types of cytoskeletal elements and their respective functions.List the 3 types of cytoskeletal elements and their respective functions.

4.4. Describe the structure and function of the centrosome.Describe the structure and function of the centrosome.

5.5. Describe the structure and functions of centriolesDescribe the structure and functions of centrioles

6.6. List and describe the similarities and differences between cilia and flagella.List and describe the similarities and differences between cilia and flagella.