Cell Bio Chapter 15

Which of the following is NOT a function of the cytoskeleton?

function in aerobic cellular respiration

Which of the following is NOT one of the three main components of the cytoskeleton?

macrofilaments

From thickest to thinnest, the three components of the cytoskeleton are:

microtubules, intermediate filaments, actin filaments.
Q:Which of the following statements about the prokaryotic cytoskeleton is TRUE?

Actin and tubulin most likely evolved before the last universal common ancestor (LUCA).

True

Without any cytoskeletal influence, cells would be shaped like:

a sphere

The structure of G‑actin is asymmetrical and therefore has polarity.

true

The polymerization and depolymerization of F‑actin are influenced by all of the following factors except:

globular F‑actin.

When bound to ATP, G‑actin adopts a conformation that promotes depolymerization.

false

If the concentration of ATP–G‑actin is high, the ATP tip at the plus end will be _ the ATP tip at the minus end.

longer than

The treadmill effect is when the rate of polymerization at the plus end exactly matches the rate of depolymerization at the minus end of an actin filament.

true

Some types of actin-binding proteins promote polymerization while others promote depolymerization.

true

Which of the following best describes the role of actin‑binding proteins that regulate the availability of actin monomers in the cell?

They either promote polymerization by increasing monomer availability or sequester monomers to prevent polymerization.

Myosin moves towards the minus end of F‑actin.

false

Each myosin heavy chain contains a globular head, a hinge, and a tail.

true

Myosin II is powered by ATP hydrolysis.

true

Which of the following lists the correct order of the four steps of myosin II movement?

attach, release, cocked, power stroke

Muscle cells, which are also called , contain many , each of which contains many _.

muscle fibers, myofibrils, sarcomeres

Muscle contraction is triggered by the release of _ from the sarcoplasmic reticulum.

Ca2+

Which of the following structures attaches fibroblasts to the substratum?

focal adhesions

Which of the following structures act as antennae to direct fibroblast migration?

filopodia

Which of the following is NOT a function of microtubules?

change the shape of the cell

Microtubule polymerization is dependent on ATP.

false

The exterior of the centrosome is covered with:

γ‑tubulin

Despite our detailed knowledge of the structure, the function of centrioles remains unknown.

True

The GTP bound to _ is hydrolyzed upon polymerization.

β‑tubulin

Polymerizing microtubules possess an ATP tip.

False

Kinesins use the energy released from _ hydrolysis to walk towards the _ end of microtubules.

ATP, plus

Which of the following is NOT a microtubule‑binding protein?

Arp2/3

Under which of the following conditions would a kinesin head be tightly bound to a microtubule?

when neither ATP, ADP, nor Pi is bound to the kinesin head

During kinesin movement, the trailing head moves forward to become the leading head upon:

ATP binding.

When not bound to cargo or walking along microtubules, kinesins are folded in half.

True

The distribution of the ER throughout the cell usually matches the distribution of:

microtubules.

Dyneins are _ than kinesins and walk towards the _ end of microtubules.

larger, minus

Which organelle do dyneins position within the cell?

Golgi

Non‑motile cilia function primarily as sensory structures, whereas motile cilia move back and forth in a whip‑like motion.

True

Which of the following is a type of MTOC?

basal body

Intermediate filament monomers do NOT possess polarity.

False

Which of the following terms best describes the structure of intermediate filaments?

rope-like

When subjected to tensile stress, intermediate filaments can be stretched to help the cell absorb the mechanical load.

True

Intermediate filaments are found in the:

nucleus and cytosol.

Hair is made from:

keratins.

Different types of intermediate filaments differ in their central rope‑like α‑helical domain.

False