The Cytoskeleton...Is a supportive meshwork of fine fibers inside eukaryotic cells

Provides structural support

Is involved in cell movement and movement of organelles within cells

May help regulate cellular activities

FIGURE 1: CYTOSKELETON OF A CELL HIGHLIGHTED IN GREEN

Microfilaments

Fine, threaded protein fibers

Consists of Actin, a globular, contractile (can contract under stimuli-see next point) protein, one of the most abundant cellular proteins

Has myosin proteins (motor), activated by an ATP, causing movement along the actin fibers, causing contraction in the filament, and therefore muscle contraction

3-6 nanometers in diameter

Carry out cellular movement such as gliding, contraction, and cytokinesis (cytoplasm division of eukaryotic cells)

FIGURE 3: ATP ACTIVATED MYOSIN

MOTOR PROTEIN “WALKING” ON AN ACTIN MICROFIBER,

CAUSING IT TO CONTRACT

FIGURE 4: ARRANGEMENT OF ACTIN GLOBULAR

PROTEINS IN A MICROFILAMENT

Microtubules

Cylindrical tubes consisting of tubulin (globular protein) in subunits (two tubulin molecules per subunit)

20-25 nanometers in diameter

Determine cell shape and create pathway for cellular movement

Serve as spindle fibers for separation of chromosomes in mitosis

Constitute cilium and flagellum for cell locomotion/propulsion (see slide on flagellum and cilia)

FIGURE 5: TUBULIN

SUBUNITS FORMING A MICROTUBU

LE

FIGURE 6: PINK FIBERS ARE MICROTUBULES SERVING AS

SPINDLE FIBERS IN CYTOKINESIS

Intermediate Filaments

Consist of a variety of fibrous proteins in subunits

10 nanometers in diameter (in between microtubules and microfilaments)

Serve as anchors for organelles

Provide tensile strength and stability for the cell

Different proteins form different intermediate filaments

Keratin intermediate filaments, for example, are essential in hair and nails and epithelial cells

Vimentins give strength to muscles

FIGURE 7: VAST NETWORK OF KERATIN INTERMEDIATE FILAMENTS IN AN ANIMAL

CELL STRENGTH AND INTEGRITY

Microtubules as LocomotivesIn a cilia or flagella strand, microtubules double up

In a 9+2 pattern, 8 pairs of microtubules form a ring, and a ninth pair in the center

All nine pairs are coated with an extension of the plasma membrane of the cell

The basal body, or bottom supporting structure of the cilia/flagella, consists of 9 triplets of microtubules

Cause movement by a dynein (protein) arm on a certain microtubule grabbing an adjacent one (powered by an ATP) and “walk” on the adjacent one, causing a sliding force. Because the microtubule doublets are held together, they must bend, causing cellular propulsion

FIGURE 9: BENDING OF MICROTUBULES

FIGURE 8

The Extracellular matrix...Is a layer of glycoproteins surrounding Animal cells

Binds cells together in tissues

Has protective and supportive functions

Regulates cell behavior

AN EXTRACELLULAR MATRIX SURROUNDING A CELL

FIGURE 10

CommunicationCommunication

Four main kinds of Four main kinds of communicationcommunication-ENDOCRINE: FROM FAR

AWAY

-PARACRINE: LOCALIZED

-AUTOCRINE: SELF

-JUXTACRINE: ADJACENT-Either a hydrophilic or hydrophobic signaling molecule is sent to a

receptor in/on the cell

-If hydrophilic, the molecule must find a receptor on the membrane

-If hydrophobic, the molecule can diffuse across the membrane

FIGURE 11

Extracellular Extracellular compositioncomposition

Contains an mesh of biomoleculesContains an mesh of biomolecules

Composed of proteins and glycosaminoglycansComposed of proteins and glycosaminoglycans

Produced inside the cellProduced inside the cell

(EXAMPLE OF A GLYCOSAMINOGLYCAN)

ATTACHES TO EXTRACELLULAR JUNCTIONSTIGHT JUNCTION: TWO CELLS HELD CLOSELY TOGETHER BY JOINED

MEMBRANES

GAP JUNCTIONS: CHANNELS THAT ALLOW MOLECULE TRANSPORT

ADHERENS JUNCTIONS: MECHANICAL ATTACHMENT BETWEEN TWO CELLS

DESMOSOMES: BIND TWO CELLS TOGETHER. HELPS RESIST SHEARING FORCES

FIGURE 12

Purposes of the extracellular Purposes of the extracellular matrixmatrix

Provide structural support to animal cellsProvide structural support to animal cells

Separates different tissuesSeparates different tissues

Regulates intercellular communicationRegulates intercellular communication

Attaches to cell junctionsAttaches to cell junctions

Allows the cells to attach to each otherAllows the cells to attach to each other

(EXTRACELLULAR MATRICES IN A TISSUE)

FIGURE 13

Bibliography: (FOR PICTURES)

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4. http://www.google.com/imgres?imgurl=http://vbaulin.front.ru

5: http://www.google.com/imgres?imgurl=http://tainano.com

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12: http://www.stevens.edu/ses/ccbbme/fileadmin/ccbbme/images/pic2.png