cytoskeleton

intermediate filaments, microtubules, and actin filaments (micro filament)

the types of cytoskeleton

intermediate filaments

what type of cytoskeleton is ropelike that can form a meshwork around the nucleus called the nuclear lamina?

microtubules

what type of cytoskeleton is hollow and are made up of tubulin to help organize a centrosome.

actin filament (micro filament)

what type of cytoskeleton are helical polymers with flexible structures that are highly concentrated at the cortex, the layer of cytoplasm that is just beneath the plasma membrane?

nucleus

where does the intermediate filaments form a network around through the cytoplasm?

desmosomes

what anchors at cell-cell junctions?

nuclear lamina

intermediate filament network found in the nucleus

to enable cells to withstand mechanical stress; ex: stretching

what is the main function of intermediate filaments?

it is very thick and durable

what makes intermediate filaments be able to withstand against concentrated salt solutions and detergents?

forms a coiled dimer

what forms when alpha-helical monomers are coming together?

central rod domain

what is the alpha helical region of a monomer?

staggered tetramer

2 coil dimers that run in opposite directions for what?

generates a final ropelike intermediate filament

what happens when the tetramer associates with each other side-by-side?

2 dimers point in opposite directions and two ends of the tetramer are the same

what can distinguish cytoskeleton from actin and microtubules?

keratin filaments

what is the most diverse class of intermediate filaments?

ends of keratin filaments

what anchors to desmosome?

plectin

accessory protein that reinforces intermediate filaments' cross links the filaments into bundles

microtubules and actin

what can plectin link to?

can die within a few days with blistered skin and abnormal skeletal and heart muscle?

what happens when there is a lack of plectin?

epidermolysis bullosa simplex

what disease has mutation in keratin genes where the skin becomes highly vulnerable to mechanical injury which is a blistering phenotype?

lamins

filament proteins that makes up the nuclear lamina and allows to disassemble and reforms at each cell division

phosphorylation

what causes conformational change where it can weaken binding between lamin tetramer to cause the filaments to fall apart?

progeria

mutation in lamin gene where this disorder can

microtubules

what can create tracks within the cell, mitosis, and forms stable structures such as cilia and flagella?

cilia and flagella

hairlike structures that extend from the surface of the cells to help swim or sweep fluid over the surface of the cells

flagella

what type of hairlike structure helps sperm move around?

create tracks within the cell

what do microtubules do to transport cell components and position membrane enclosed organelles with the cell?

microtubules disassemble and reassemble into the mitotic spindle

what happens to microtubules during mitosis to provide machinery that will segregate chromosomes?

cilia and flagella

what stable structures do microtubules form that are hair-like to help swim or sweep fluid over the surface of the cell?

tubulin

what kind of protein are microtubules built from?

alpha-tubulin and beta-tubulin

what are 2 globular proteins are dimers composed of?

through noncovalent interactions

how is the dimer bounded tightly?

13

how many parallel protofilaments are there?

alpha and beta

what is alternated in the parallel protofilaments?

structural polarity

what is it when the alpha exposed to one end and beta exposed to the end?

plus end

what is the polarity of the beta tubulin end?

minus end

what is the polarity of the alpha tubulin end?

plus end ( beta tubulin side)

what polarity end will the microtubule grow rapidly at which is why they name the ends this way?

dynamic stability

what is it when microtubules switch back and forth between polymerization and depolymerization

grows outwards from the organizing center by the addition on alpha/beta-tubulin dimers to its plus end

what happens when the microtubules are nucleated?

transitioning and shrinking

what can microtubules undergo?

they are replaced with new microtubules that grows from the same gamma tubulin ring complex

what happens when microtubules disappear completely?

GTP hydrolysis

what are microtubules driven by?

tubulin dimers

what carries a GTP to hydrolyze in microtubules?

shortly after the dimer is added to a growing microtubule

when does the gtp hydrolysis occur on the tubulin dimer?

polymerization

what is it when tubulin dimers add to the plus end faster than they can go through GTP hydrolysis?

growing microtubule will be composed with GTP forming a GTP cap where those dimers bind more strongly to the dimers bearing GTP

what occurs during polymerization in relation to GTP?

if GTP cap can hydrolyze before the next dimer is added, there are free ends that are composed of GDP that causes rapid shrinking

what occurs during depolymerization?

shrinking

does depolymerization cause growing or shrinking?

the centrosome where microtubules extend from

where is the gamma tubulin ring created around?

by attachment to capping proteins with GTP

how can microtubules be stabilized?

during mitosis

when are microtubules more dynamic?

taxol, vinblastine, and vincristine

what types of chemotherapy can stop mitosis?

by other proteins

how is dynamic instability suppressed to generate more stable microtubules?

axon terminals

in the cell polarity, where do the plus ends point to?

axon on one end, dendrites on the other end of the cell body

what is part of cell polarity?

secretion

where is the golgi apparatus positioned towards?

helps position organelles in their required location

how does microtubule help generate polarity?

motor proteins

what microtubule-associated proteins use energy derived from repeated cycles of ATP hydrolysis to travel steadily along microtubule or actin filaments in a single direction?

kinesin

protein that moves toward the plus ends of microtubules

dynein

protein that moves toward the minus end of microtubules

dimers

what do dynein and kinesin act as?

have 2 globular ATP binding heads an a single tail

what do both kinesin and dynein have?

pull the ER outward along microtubule stretching it like a net

what do kinesins do when attached to the outside of the ER membrane?

pull the golgi along the microtubule in the opposite direction inward toward the nucleus

what do dyneins do when attach to the golgi?

cilia

hair-like structure that extend from the surface of many kind of eukaryotic cells

9 + 2 array

there is a 9 doublet MT arranged in a ring around a pair of single MT. what is this known as?

flagella

what propels sperm

actin

what is essential for cell's movement

actin binding proteins

what enable the filaments to serve a variety of functions for the cell?

microvilli on epithelial cells where there will be contractile bundles within each cell

what helps form still structures with actin?

forming dynamic structure

what is it when there is a leading edge of crawling cell where the contractile ring pinches off the cytoplasm at the end of mitosis?

myosin

actin-dependent movements require what?

to form a twisted chain of identical globular actin monomers to allow structural polarity

why is it good for actin to be thin and flexible?

thinner, more flexible, and more abundant

how is actin in comparison to microtubules?

plus end

where is it faster for actin to grow from?

more unstable and can disassemble at both ends

what is it when there is naked actin, meaning no caps?

ATP

what do free actin monomers carry?

it hydrolyzes

what happens when ATP is incorporated into the filament?

reduces the strength of binding between monomers like in microtubules

what does hydrolysis of ATP allow in actin?

treadmilling

what is it when ADP actin destabilizes the structure where the filament loses subunits from the minus end at the same time as it adds them to the plus end

treadmilling

what involves rate of addition and loss are equal?

dynamic instability

what is it when there is a rapid switch from growth where there in shrinkage on the minus end of growth on the positive end?

dynamic instability

what undergoes more drastic changes in length: dynamic instability or treadmilling?

cortical actin

what proteins are cross-link actin under the cell cortex that supports the PM, gives mechanical strength to the cell, and have chemoreceptors on cell surface that can trigger change sin actin filament assembly?

cell crawling

what is it when the cell pushes out protrusions at its front/leading edge?

lamellipodia

what is a protrusion from the cell that contains dense meshwork of actin filament where the plus ends is close to the PM?

filopodia

thinner stiff protrusion at the leading edge and other places where it can contain a loose bundle of actin filaments and has the plus end pointing outward

other proteins, such as integrins, will adhere the cell to that extracellular matrix (ECM)

what happens where the protrusions locate a favorable surface?

link to internal actin network to anchor the cell and attach to the ECM (adaptor proteins)

what can integrins do?

Myosin II

subfamily of myosin that is found in muscle, exists as dimer, and has a single-coiled tail

Two globular ATPase Heads

what does Myosin II contain that point as a double headed arrow and point in different directions?

form bipolar myosin filament from which the head projects on either end.

what happens when clusters bind to each other through coiled tails?

one end bind to actin to move it in one direction and the other set binds other actin filament to move in the opposite direction

what do the two sets bind two in myosin II?

the myosin slides the opposite actin filaments away from each other which causes a contraction

what happens when the myosin moves in both directions?

cytosolic Ca

what is contraction triggered by?

causes action potential in the muscle cell of the PM

what happens when the neurotransmitter is released from the nerve terminal?

membranous tubes extend inward from PM around each myofibril to relay sarcoplasmic reticulum and trigger the release of Ca

what happens when electrical excitation spreads to transverse tubules (T tubules)?

muscle

where is sarcoplasmic reticulum found?