cell motility (7.6)

cytoskeleton

dense and complex network of fibers that helps maintain cell shape by providing structural support; dynamic

actin filaments

aka microfilaments: fibrous structures made of globular protein subunits called actin

• maintain cell shape by resisting tension

• move cells via muscle contraction or cell crawling

• divide animal cells into 2

• move organelles and cytoplasm in plants, fungi, animals

intermediate filaments

fibers wound into thicker cables made up of keratins, lamins

• maintain cell shape by resisting tension

• anchor nucleus and some organelles

microtubules

hollow tubes made out of alpha and beta tubulin dimers

• maintain cell shape by resisting tension

• move cells via flagella or cilia

• move chromosomes during cell division

• assist formation of cell plate during plant cell division

• provide tracks for intracellular support

myosin

actin’s role in movement depends on protein

motor protein

myosin is a ____ ____: protein that converts the chemical energy in ATP into the kinetic energy of mechanical work

head

when myosin binds and hydrolyzes ATP to ADP, it undergoes a series of shape changes that extends the ___ region

actin, contracted

the head region of myosin, when extended after ATP hydrolysis, is attached to ___ and then ______ to pull itself along the filament

slide

changes in myosin and actin following ATP hydrolysis cause the molecules to ____ past each other

+ end

ultimately, the actin and myosin repeated rounds of interaction causes the myosin to gradually move toward the _______ of acting filament

kinesin

A class of motor proteins that uses the chemical energy of ATP to “walk” toward the plus end of a microtubule. Used to transport vesicles, particles, organelles, and chromosomes.

2

kinesin consist of __ large subunits (legs) each with 3 functional regions: head section, tail associated with small polypeptides and stalk that connects head and tail

microtubule

the head region (feet) in the kinesin binds to the

transport vesicle

the tail region (neck) of kinesin binds to the: ____ ___ (head)

cell crawling

A form of cellular movement involving actin filaments in which the cell produces bulges in the membrane that stick to the substrate and are used to pull the cell forward.