The Cytoskeleton

Which of the three major types of cytoskeletal filaments are described as being responsible for determining the shape of the cell’s surface and for whole-cell locomotion?

What is the approximate diameter of an actin filament, also known as a microfilament?

Which feature of actin and tubulin subunits is responsible for the structural polarity of their respective filaments?

In the context of actin polymerization, what term is used for the initial, inefficient process where small, unstable oligomers of actin are formed before rapid elongation can begin?

What is the primary function of the Arp2/3 complex in actin filament organization?

The drug Taxol, which is used in cancer treatment, affects the cytoskeleton by which mechanism?

In the structure of a sarcomere, what is the name of the enormous protein that acts as a molecular spring, positioning the thick filaments midway between the Z discs?

What is the direct trigger for the initiation of muscle contraction in a skeletal muscle cell?

How does the protein cofilin, also known as actin-depolymerizing factor, promote the disassembly of actin filaments?

What is the approximate outer diameter of a microtubule, which is constructed from 13 parallel protofilaments?

The rapid interconversion of a microtubule between a growing and a shrinking state at a uniform free tubulin concentration is known as what process?

What type of tubulin is specifically involved in the nucleation of microtubule growth and is found enriched in the microtubule-organizing center (MTOC)?

Intermediate filaments differ structurally from actin filaments and microtubules because their subunits are:

The human genetic disease epidermolysis bullosa simplex, which causes skin blistering from slight mechanical stress, is caused by mutations in the genes for which protein?

What is the primary function of the SUN-KASH protein complexes?

Which class of motor proteins generally moves toward the minus end of microtubules?

The axoneme, the core of motile cilia and flagella, has a characteristic arrangement of microtubules described as:

What is the name of the bacterial homolog of actin that is essential for maintaining the rod shape of many bacteria?

Which statement accurately describes the final assembled structure of an intermediate filament?

According to the description of the myosin II mechanochemical cycle, in what state is the myosin head when it is in the 'rigor configuration'?

In non-muscle cells, what protein family cross-links actin filaments at roughly right angles to promote the formation of a loose and highly viscous gel, like that in the cell cortex?

What is the name of the protein that binds to tubulin heterodimers, prevents their addition to microtubules, and whose activity is inhibited by phosphorylation?

During which mode of cell migration is a three-dimensional pseudopod formed by explosive actin polymerization at the leading edge, with reduced adhesion to the substratum enabling very rapid movement?

What is the approximate number of myosin heads in a single bipolar thick filament from frog muscle?

Myosin V is a two-headed myosin that is involved in organelle transport. How does its movement along actin filaments differ from that of myosin II?

Which of the following proteins are microtubule motor proteins that use ATP hydrolysis to move cargo or slide filaments?

The bacterial protein FtsZ is a homolog of which eukaryotic cytoskeletal protein and what structure does it form during cell division?

What type of cell junction anchors intermediate filaments and connects epithelial cells into a sturdy sheet?

In the process of treadmilling in an actin filament, what is occurring at the plus and minus ends of the filament when it is at steady state?

What is the role of the troponin complex in vertebrate skeletal muscle contraction?

Which of the following describes the function of formins?

How many tubulin heterodimers per second are added to a microtubule that is growing at a rate of 2 micrometers per minute, given that the length of one dimer is 8 nm?

Which myosin superfamily member is unique in that it moves toward the minus end of an actin filament?

The assembly of a centriole, which forms the core of a centrosome and a basal body, exhibits a characteristic symmetry of:

In the axon of a neuron, how are the microtubules oriented?

What is the primary role of the protein plectin?

What is the role of septin filaments in a budding yeast cell?

Which statement accurately describes the activity of profilin in relation to actin polymerization?

A single myosin II head cycles about how many times per second during the course of a rapid muscle contraction?

The motor protein kinesin-1 moves along a microtubule protofilament in discrete steps. What is the approximate length of each step?

In a migrating fibroblast, which Rho family GTPase is primarily responsible for the formation of an enormous lamellipodium extending from the entire circumference of the cell when it is constitutively activated?

How many major families of intermediate filament proteins are there in vertebrate cells, as listed in Table 16-2?

The movement of pigment granules (melanosomes) in fish melanophores is regulated by a tug-of-war between which two types of motors?

Which statement best describes the primary cilia found on the surface of most animal cells?

Familial hypertrophic cardiomyopathy, a common cause of sudden death in young athletes, is associated with subtle point mutations in the genes for which proteins?

What is the name for the weblike sheath of modified endoplasmic reticulum that surrounds each myofibril and releases Ca2+ to trigger contraction?

Which of the following cellular structures is built from actin filaments?

The motor protein that uses the energy of ATP hydrolysis to depolymerize microtubule ends, rather than to walk along them, is:

In a living cell, about 50 percent of the actin is in filaments, and 50 percent is soluble. This is possible despite the soluble monomer concentration being well above the critical concentration because:

What is the name of the protein that functions as the bacterial homolog of tubulin?