Question 1

In a normal microtubule,how many protofilaments make up its cylindrical wall?

Accepted Answer

A normal microtubule consists of 13 protofilaments arranged in a cylindrical shape, with alpha and beta tubulin dimers forming the walls.

Question 2

TIRF works by _________________.

Accepted Answer

TIRF (Total Internal Reflection Fluorescence) microscopy works by focusing on a very thin plane just above the surface on which microtubules are lying, and by using a special technique that prevents light rays emanating from individual motor proteins being monitored from being obscured by light rays from other areas. This allows for high-resolution imaging of the microtubules and their associated proteins at the cell membrane.

Question 3

A new field of mechanical engineering that involves the development of tiny machines capable of performing specific activities in a submicroscopic world is called ________.

Accepted Answer

The new field of mechanical engineering that involves the development of tiny machines capable of performing specific activities in a submicroscopic world is called nanotechnology. The other options do not accurately describe this field of engineering.

Question 4

What kinds of forces are thought to hold microtubular structure together?

Accepted Answer

Microtubules are held together by noncovalent interactions, such as electrostatic attractions and hydrogen bonding, between the subunits that make up the structure. These interactions are weaker than covalent bonds and allow for the dynamic behavior of microtubules, including their ability to grow and shrink as needed. Strong interactions and covalent interactions do not play a significant role in holding microtubules together. Magnetism is not a relevant force for this structure.

Question 5

Which of the following appears to be the most extensible?

Accepted Answer

The answer of Which of the following appears to be...

Question 6

The microtubule wall is composed of globular proteins arranged in longitudinal rows called _________.

Accepted Answer

The term "protofilaments" refers specifically to the longitudinal rows of globular proteins that make up the wall of a microtubule. The other answer choices are either incorrect or not specific to microtubules.

Question 7

Which type of cytoskeletal element is described as tough,ropelike fibers composed of a variety of related proteins like keratin?

Accepted Answer

Intermediate filaments are tough, ropelike fibers composed of a variety of related proteins like keratin. Microfilaments are thin, flexible fibers composed of actin that provide mechanical support and help with cellular movement, while microtubules are hollow tubes composed of tubulin that play a role in cell division and intracellular transport. Macrofilaments are not a type of cytoskeletal element.

Question 8

In cell biology and with respect to microtubules and microfilaments,the word "dynamic" means ________.

Accepted Answer

When referring to microtubules and microfilaments, "dynamic" means that they are in a constant state of change, constantly growing, shrinking, and relocating. This is important for their functioning in processes such as cell division and cell movement.

Question 9

Which of the following could be a method used to label microtubules with a fluorescent dye?

Accepted Answer

The answer of Which of the following could be a...

Question 10

A microscope is equipped with a laser that can be focused on a small region of the cell.The laser beam is used to bleach fluorescent tubulin in a small region of the cell.The specimen is then followed over time and the recovery of the fluorescent signal into the bleached zone is then measured.What is the name of this technique?

Accepted Answer

The answer of A microscope is equipped with a laser...

Question 11

If the FRAP technique is used to bleach a small zone of fluorescent microtubules in a cell,which of the following is a possible explanation for the recovery of fluorescence in the region of the cell previously bleached?

Accepted Answer

The recovery of fluorescence in the bleached zone could be due to any combination of the three options listed: the dynamics of the microtubules turning over, the growth of new microtubules into the bleached zone, and movement of microtubules through the bleached zone. Therefore, option D, "all of these choices," is the best choice.

Question 12

You use a nonionic detergent to extract a cell.When you do,much of the mRNA stays behind with the cytoskeleton,which is not solubilized by this treatment.What do these results mean?

Accepted Answer

The fact that much of the mRNA stays behind with the cytoskeleton suggests that the mRNA is anchored to the cytoskeleton and therefore not solubilized by the nonionic detergent. This indicates a physical association between the two components, rather than a denaturation or destabilization of the cytoskeleton. The options B and E are incorrect based on this observation, while options A and D are not supported by the information given.

Question 13

In stretching an intermediate filament with an atomic force microscope,what properties of an intermediate filament can be tested?

Accepted Answer

In stretching an intermediate filament with an atomic force microscope, the two main properties that can be tested are tensile strength and extensibility. Tensile strength refers to the ability of the filament to resist being pulled apart, while extensibility refers to the ability of the filament to stretch without breaking. Therefore, the best choice is E, which includes both tensile strength and extensibility.

Question 14

In an attempt to monitor the movement of individual kinesin molecules labeled with GFP along microtubules labeled with a red fluorescent dye using an in vitro motility assay,what specialized type of laser-based fluorescence microscopy would be most likely to be employed?

Accepted Answer

TIRF (Total Internal Reflection Fluorescence) microscopy is specifically designed to observe events at or near the cell surface, such as the movement of molecules along microtubules, by exciting fluorophores in a very thin region. Total internal reflection microscopy is another name for TIRF, so both terms refer to the same technique.

Question 15

When laser beams are shone through the objective lens of a microscope,a weak attractive force is generated near the point of focus.This allows the grasping of microscopic objects.Such a device is called a(n)______.

Accepted Answer

The description matches with that of optical tweezers, which generates an attractive force near the point of focus and enables the grasping of microscopic objects. The other options are not relevant to the given description.

Question 16

Fluorescence microscopy allows investigators to view things _________ of regular light microscopes.

Accepted Answer

The answer of Fluorescence microscopy allows investigators to view things...

Question 17

Which type of cytoskeletal element is characterized as a hollow,rigid cylindrical tube with walls composed of tubulin subunits?

Accepted Answer

Microtubules are characterized as hollow, rigid cylindrical tubes with walls composed of tubulin subunits. Microfilaments are composed of actin subunits and are not hollow. Intermediate filaments are composed of various types of proteins and do not form hollow tubes. Minitubules are not a recognized type of cytoskeletal element.

Question 18

Which technique below can be used to measure the mechanical properties of the cytoskeletal elements themselves?

Accepted Answer

Atomic force microscopy can be used to directly probe and measure the mechanical properties of the cytoskeletal elements themselves, such as their stiffness and elasticity, by applying a small amount of force and measuring the resulting deformation. Laser beams and electron microscopies can provide imaging and structural information but do not directly measure mechanical properties. SDS-PAGE is a biochemical technique for separating and analyzing proteins and does not provide mechanical information.

Question 19

Using TIRF,scientists have been able to _________________.

Accepted Answer

TIRF (Total Internal Reflection Fluorescence) microscopy is a powerful imaging technique used to visualize single molecules at the cellular level. By using TIRF, scientists can observe the movement of individual motor proteins, allowing them to measure their properties under different experimental conditions, compare the properties of different motor proteins, and ask how specific mutations affect their motility properties. Therefore, all the options given are correct, and the best choice is E, which includes all of them.

Question 20

An intermediate filament can stretch up to _____ its normal length before it breaks into two pieces.

Accepted Answer

According to research, intermediate filaments can stretch up to 3.5 times their normal length before breaking into two pieces. This property allows the intermediate filament to provide structural support and protect the cell's integrity during mechanical stress.

Quiz 9: The Cytoskeleton and Cell Motility