7.4 Dynamic Cytoskeleton

yes, it moves in order to alter the cell's shape, move materials from place to place, and move the entire structure

• smallest diameter
• made of actin

individual actin molecules polymerize and coil around each other

• the strand is asymmetrical
• the two ends are different and are labeled as plus and minus ends

when filaments grow and shrink as actin subunits are added or removed from each end of the structure

myosin

a motor protein that converts ATP into mechanical energy

the ATP binds to the myosin and then is hydrolyzed into ADP

directional extension of actin filaments pushes the plasma membrane into bulges called "pseudopodia" (false-feet)

• cell division in animals
• actin filaments are arranged in a circle and must slide past each other, pinching the cell in two

directed flow of cytosol and organelles around plant and fungal cells

• defined by size
• can consist of different proteins
• each end is identical
• purely structural role

• makes up the skin
• type of intermediate filaments

• dense mesh under nuclear envelope
• type of intermediate filaments

• alpha and beta tubulin
• largest cytoskeletal components (diameter)
• each end of microtubule has different polarity
• grow from a microtubule organizing center
• help with structure and movement

microtubule organizing center in animals

• 2 bundles of microtubules within centrosome
• not needed for microtubule formation (scientists still not sure why they exist o.O)

transport material within cells

• microtubule "rail road" tracks
• movement continued as long as ATP was available
• microtubules necessary for transport

• motor protein that controls movement of vesicles
• similar to a delivery truck that carries transport vesicles along microtubule tracks
• "walks" down the microtubule

• comprised of protein called flagellin
• rotate flagella like propeller
• not surrounded by membrane

• comprised of microtubules
• whip back and forth
• surrounded by plasma membrane
• 9+2 arrangement

• location where axoneme attaches to cell
• important for growth of axoneme

• 9+2 structure of microtubules
• isolated structure

• studied cilia
• movement doesn't occur unless ATP is available

• a large, motor protein that makes up the arms of the axonemes
• when ATP attaches to dynein, the end changes shape and the dynein walks up the microtubule
• causes the flagellum to bend back and forth