Cell Bio Exam 3 - Cytoskeletal Systems and Cellular Movement

Cells can either be a part of a stationary and tight brick-like layer of cells known as the ____________, or are highly mobile

epithelium

________________ are the smallest cytoskeletal element, and are mainly comprised of __________ fibers

Microfilaments, actin

___________________ are the largest cytoskeletal filament and are mainly comprised of ____________ dimers

Microtubules, tubulin

____________________ pathways affect the cytoskeleton, causing organelles to be moved or organized, to changes in cell shape, movement, and contraction to occur

Signal transduction

Cytoskeletal defects can contribute to _____________, which causes issues with heart contractility

cardiomyopathy

_______________ increase surface area of the intestinal lumen

Microvilli

________________/_____________ aid in cell movement

Lamellipoduim, Filopodia

__________ Fibers facilitate contractility

Stress

_____________ provides support and organization for membrane proteins

Cell cortex

______________ belt provides strength to epithelium

Adherens

______________ ring helps to constrict and generate two daughter cells during cytokinesis

Contractile

Microfilaments are ___________, with dynamic ___________, and are integral for cellular functions

Polar, instability

___-Actin is a _____________, that contains Mg2+ complexed with ATP/ADP, and is an ATPase. When polymerized forms ____-Actin

G, monomer, F

The ___________ end of F-Actin is favored for addition of actin

The ____________ end of F-Actin is favored for removal of actin

positive, negative

___________________ refers to the fact that F-actin filaments are modifiable and constantly changing

Dynamic instability

________________ must first happen for G-Actin monomers to come together to create F-Actin filaments

Nucleation

ATP-bound G-Actin is bound at both ends of the F-Actin molecule, and ADP-bound G-Actin is lost around the same rate at both ends, but due to ________________, ATP-bound G-Actin is added 10x faster to the ___________ end, which creates a larger net gain on that end.

Treadmilling, positive

_______________, added to the positive end, and ________________, added to the negative end of the F-actin filament, are used to stabilize the filament in order to prevent growth and disassembly from occurring in an uncontrolled manner

Cap Z, Tropomodulin

Microtubules are comprised of dimers of alpha and beta ___________, which stack to make ________________. 13 of those associate to form a ________________ tube.

Dimers, Protofilaments, hollow

Key functions of microtubules are related to _______________ separation and establishment of __________________

Chromosomal, centrosomes

___________________ filaments are the most diverse group of cytoskeletal elements, but play no role in cell movement, only structural. Comprised of _________ like monomers, that dimerize to _________-_______, which then aggregate to form tetramers and larger filament bundles

Intermediate, rope, coiled-coil

Cell _________ involves movement of a cell or organism through the __________________, movement of the environment past or through the ________, and movement of ___________ in the cell.

Motility, environment, cell, components

The two eukaryotic motility systems are interactions between ________ proteins and _____________, and the interactions between __________ and ____________ motor proteins

motor, microtubules, actin, myosin

__________________ is a specialized form of motility, used to describe shortening of muscle cells

Contractility

The two major families of microtubule motor proteins are ____________ and ___________

Kinesins, Dyneins

Kinesin ___ moves cargo towards the positive end of microtubules

1

Kinesin ___ moves synaptic vesicles in neurons

3

Kinesin ___ facilities bidirectional sliding of microtubules during anaphase

5

Kinesin ___ is involved in destabilization of positive ends of microtubules

13

Kinesin ___ is involved in spindle dynamics in meiosis and mitosis, moves towards negative end

14

____________ dynein moves cargo towards the positive end of microtubules

Cytoplasmic

____________ dynein activates sliding in flagellar microtubules

Axonemal

Motor proteins “walk” along microtubules by

hydrolyzing ATP

Kinesins consist of 3 parts: __________ head, __________ __________ region, and _________ chain

globular, coiled helical, light

The ___________ head in kinesics, and ____________ chain in dyneins, attach to microtubules and involved in ________________

Globular, heavy, ATP hydrolysis

The __________ chain, in both kinesins and dyneins, attach to other proteins and organelles

light

Dyneins consist of _________ chain, _________ chain, and _________ chain

heavy, intermediate, light

You can tell which end of a microtubule is which because __________ will be moving towards the positive end and _________ will be moving towards the negative end

Kinesins, dyneins

_____________ dynein associates with the Dynactin complex, which binds ____________ in the membrane of the cargo vesicle

Cytoplasmic, spectrin

Vesicles from the ER or plasma membrane move toward the Golgi via ___________

Vesicles from Golgi move toward ER or cell periphery via _____________

Dynein, Kinesin

_________ occurs both in unicellular and multicellular eukaryotes, with unicellular organisms using them for ____________ and food collection, and multicellular organisms using them for moving ________ across cells

Cilia, locomotion, media

Cilia moves _____________ to the cell, and flagella moves ____________ to the cell

Perpendicular, parallel

_____________ move cells through fluid environments, similar in diameter but _________ than cilia

Flagella, longer

______________ elements provide ciliary motor powered by ATP hydrolysis

Axonemal

The ______________ anchors cilia and flagella in the cell

Basal body

_____________ are ATP-dependent motors that exert force on actin filaments, and are made up of a heavy chain, globular head, and tail

Myosins

There are _____ types of myosin, with type ___ being the most understood

24, 2

Myosins function in a wide range of cellular events, including ____________ contraction, cell _____________, _______________, and _____________ transport

muscle, movement, phagocytosis, vesicle

Type II myosin use ATP hydrolysis to cause actin filaments to slide past myosin molecules, resulting in _____________ of a cell or group of cells

contraction

Each muscle fiber contains multiple _____________, which are subdivided into units called _______________, which are the fundamental unit of the muscle cell. Each of those units contains bundles of thick (___________) and thin (___________) filaments

myofibrils, sarcomeres, myosin, actin

____________ and ___________ attach thick and thin filaments to Z line

Titin, nebulin

______-Actin and ______________ provide structural support for thick and thin filaments

alpha, myomesin

____ bands remain consistent in length, whereas ___ bands shorten progressively and virtually disappear in the fully contracted state.

Thin filaments are drawn into the spaces between thick filaments, and do not change in _____________

A, I, length

Process of Muscle Contraction:

1. Cross-bridge formation, release of Pi

2. Power stroke, ADP is released, myosin undergoes a conformational change

3. ATP binds myosin, causing detachment of myosin fro actin, cross-bridge dissociates

4. ATP hydrolysis occurs, cocking myosin head

(x)

x

Binds Ca2+, causing a conformational change that removes tropomyosin from its binding sites

Troponin

Covers actin binding sites preventing myosin from forming cross-bridges and muscle

Tropomyosin

Binds to the thin filament providing structural support

Nebulin

Membrane depolarization spreads throughout the sacrolemma via the ________ __________ _______

transverse tubule system

T tubule system comes into contact with

Sacroplasmic reticulum

The sarcoplasmic reticulum releases and removes Ca2+, causing contraction and relaxation (x)

x

Cardiac muscle is similar to skeletal muscle, but has actin and myosin joined end to end, with _____ junctions that are electrically coupled to neighboring cells, which facilities depolarizing _________

gap, waves

Smooth muscle is responsible for _____________ contractions, which much __________ contractions but also _____________ in duration

involuntary, slower, greater

Smooth muscle cells are line, thin, and pointed, with no ___________ like skeletal and muscle

striations

Smooth muscle cells contain ____________, plaque like structures than contain intermediate filaments

dense bodies

Cascade of events that takes place due to Ca2+ enters smooth muscle

1. Activates myosin light chain

2. MLCK phosphorylates myosin light chain (regulatory)

3. Light chain uncurls and becomes capable of assembly

4. Active myosin interacts with actin to cause contractions

(x)

x