cell movement

cell motility

• move cell or organism thru environment

• movement of environment past or thru cell

• move components in cell

contractility

describe shortening of muscle cells, is a specialized form of motility

_______involved in ATP-dependent transport toward the plus ends (away from the centrosome).

anterograde axonal transport

_________ associate with a protein complex called dynactin, which helps link dynein to cargo2.

cytoplasmic dynein

________ activate microtubule sliding in cilia/flagella2.

Dyneins

basal body looks like a centriole, with ________________ structure around the circumference

nine sets of triplets (three MTs)

Each outer doublet of the axoneme consists of one complete MT (the A tubule) and one _____ MT (the B tubule)

incomplete

At regular intervals, _______ project inward toward the central pair

radial spokes

•

In intraflagellar transport (IFT), ________ motor proteins move material to the tips of the flagella

plus-end-directed

In intraflagellar transport (IFT), ______ brings material back toward the base

dynein

Cell motility and intracellular movements are driven by motor

proteins, which couple _____ hydrolysis to movements.

ATP

_________ are important for shaping and transport of endomembrane system, and for intraflagellar transport

Microtubule (MT) motors

Kinesins move toward the ________ of MTs. There are many families of kinesins, which can travel great distances along MTs

plus ends

Dyneins move toward the___________. There are relatively few

dyneins, which can be (1) cytoplasmic or (2) axonemal.

minus ends

Cytoplasmic dyneins carry their cargo through the adapter called

the ____________

dynactin complex.

_______ ________ mediate the bending of cilia and eukaryotic

flagella.

Axonemal dyneins

Cilia and flagella consist of an axoneme connected to a basal body. ___________within the axoneme leads to bending of cilia and

flagella

Doublet sliding

Microfilament-based motility

Example: muscle contraction

Microtubules (MTs) and microfilaments (MFs)

provide a scaffold for motor proteins that

produce motion at the molecular level

MOLECULAR MOTORS

couple ATP hydrolysis to changes in

shape and attachment of the motor protein

They undergo cycles of ATP hydrolysis, ADP

release, and acquisition of new ATP

They have common structural features

They can move along a cytoskeletal filament

for significant distances

1. Microtubule-based motility – dyneins and

kinesins

2. Microfilament-based motility – myosins

ICROTUBULE-BASED

MOVEMENT INSIDE CELLS:

KINESINS AND DYNEINS

MTs provide a rigid set of tracks for

transport of a variety of organelles

and vesicles

Traffic toward minus ends of MTs

is considered “inbound”; toward the

plus end is “outbound”

Microtubule-associated motor

proteins—kinesins and dyneins—

walk along the MTs and provide the

force needed for movement

MOTOR PROTEINS MOVE CARGOES ALONG MTS DURING AXONAL TRANSPORT. ______ is involved in ATP-dependent transport toward the plus ends (away from the centrosome), called anterograde axonal transport. While ______ moves particles (cargo) toward the minus ends, called retrograde axonal transport

• Kinesin

• Cytoplasmic dynein

Kinesins consist of 2 dimerized heavy chains and 2 light chains

The _______ chains contain globular domains that attach to

microtubules, a coiled-coil stalk, a lever-like neck that connects the two, and a tail

The ______ are associated with the tail

heavy; light chains

Kinesin movement looks like “_______,” with the two

globular head domains taking turns as the front foot

Each kinesin molecule exhibits ______

walking; processivity

processivity

it can move long distances along an MT before detaching

from it by releasing bound ADP and acquiring a new

ATP, so that the cycle repeats

• Each kinesin molecule exhibits processivity

________ dyneins – associate with a protein complex called

dynactin, which helps link dynein to cargo. ______ dyneins – activate microtubule sliding in cilia/flagella

cytoplasmic; axonemal

cilia

• microtubule-based motility

About 2–10 μm long and occur in large

numbers on the surface of ciliated cells

Occur in both unicellular and multicellular

eukaryotes

Display an oarlike pattern of beating,

generating a force parallel to the cell

surface

flage

Move cells through a fluid environment

Same diameter as cilia, but usually much

longer (up to 200 μm)

Limited to one or a few per cell and

move with a propagated bending motion,

which generates a force parallel to the

flagellum

cilia and flagella

share a common

structure, the axoneme

It is connected to a basal body and

surrounded by an extension of the

cell membrane

• basal body looks like a centriole, with nine sets of triplets (three

MTs) structure around the circumference

Between the axoneme and basal

body is a transition zone in which the

MTs take on the pattern

characteristic of the axoneme

axonemes (cilia and flagella)

• “9 + 2” pattern, with 9 outer doublets

and 2 MTs in the center, the central pair

Each outer doublet of the axoneme consists of one complete MT (the A

tubule) and one incomplete MT (the B tubule)

The A tubule has 13 protofilaments, whereas the B tubule has 10 or 11

The tubules of the central pair are both complete