Cell - Cytoskeleton

F-actin, microtubule network, and intermediate filament network

The overall eukaryotic cytoskeleton can be subdivided into

F-actin

Filaments composed of repeating small globular or G-actin protein units are concentrated at the cell cortex but also found in the actinomyosin contractile arrays

Microtubules

Filaments composed of repeating small globular a and ß protein dimers arrayed throughout the cytoplasm, with all having one ned anchored to a microtubule-organizing center (MTOC) or to another molecule

G-actin

F-actin is made up of what subunits

a and B tubulin protein dimers

Microtubules are made of what subunits

Cell cortex and actinomyosin contractile arrays

F-actin is found where

F-actin

_____ ____ found in the cell cortex is anchored to the inner face of the plasma membrane and mechanically strengthens the plasma membrane and shapes its topography

Microtubule-organizing center or another molecule

Microtubules are anchored to a _____ or ______

Microtubule-associated proteins (MAPs)

Spatial organization and precise functioning of microtubules are regulated by accessory proteins known as

13 and 2

Microtubules and F-actins vary in size with microtubules being composed of _____ protofilaments and F-actin _____ protofilaments

Cortical F-actin -> Cytoplasmic intermediate filament network -> Microtubule network anchored to a centrosome/ MTOC

The distribution of cytoskeletal filaments in a "soft-bodied" eukaryotic cell (outside -> inside)

Cytoplasmic Intermediate Filaments

provides mechanical strengthening and stiffening for the cytoplasm, similar to the function of metal rebar within poured concrete

Nuclear lamins

The nuclear envelope is structurally supported along its nucleoplasmic side by a form of intermediate filaments known as

Nucleation

Process of forming a new microtubule

y-tubulin ring complex (y-TuRC)

Microtubules are mostly formed by initial nucleation at a multiprotein structure called the

Polymerization

During microtubule assesmbly, repeating tubulin dimers undergo a period of _______ growing the microtuble in length outward from the nucleating site

MTOC/ Centrosome (animal cells)

y-TuRCs are found within the ________

Anchored; free

Microtubules develop end-to-end polarity during formation with a _______ minus end and a _____ plus end

Polymerization

Net assembly

Depolymerization

Net disassembly

Net assembly and net disassbly

Microtubules are dynaomic and plastic structures that alteranative between periods of _____ and _____

G-protein

Tubulin contains a GTPase domain, making them a form of

T state ; D state

Tubulin-GTP is known as the _____ and favors assembly and maintenance while the Tubulin-GDP is known as the _______ and favors disassembly

Catastrophe and rescue

The free ends of microtubulin can undergo a _______ state and expereince rapid disassebly if the tubulins activate their GTPase domains and are hydrolyzed; usually followed by a ______ state where net assembly occurs due to the influx of fresh tubulin-GTPs from the cytosol which will regrow the plus end often in a new direction

+ / free

Microtubulins grow in what direction

Opposite

Motor proteins attach onto cargo at one end and feature two-MT domain arms at _____ ends

Actin-binding proteins (ABPs)

F-actin is concentrated at the cell cortex and regulated by