1.
A microtubule is one of the ___ elements of the cytoskeleton that are present in the cytoplasm.
A
three
B
four
C
two
2.
A microtubule is a left-handed helix that consists of 13 vertical protofilaments assembled together. Each protofilament is a ______ that is composed of a-tubulin and B-tubulin protein units. In simpler terms, a microtubule is a hollow cylinder.
A
heterodimer
B
dimer
C
polymer
3.
Cell locomotion is driven by _. Essentially, microtubules form the _ of cilia and flagella. Both are structures that cells depend on for _. Cilia are hair-like structures found on the _ of many cells, while flagella are only found in sperm cells.
4.
__ are cylindrical structures made up of microtubules.
A
Centrioles
B
golgi apparatus
C
proteins
5.
__ also form the spindle fibers that extend from the centrioles to attach to sister chromatids during cell division.
A
Microtubules
B
Microfilaments
C
Intermediate filaments
6.
Microtubules are also the routes through which neurotransmitters coming from the cell body travel along to reach the end of __.
A
axons
B
dendrites
C
axon terminals
7.
Out of all three elements of the cytoskeleton, __ are the narrowest, with a diameter of 7 nm.
A
microfilaments
B
microtubules
C
centrioles
8.
__ are made up of two intertwined strands of actin molecules.
A
Microfilaments
B
Microtubules
C
Centrioles
9.
In cross section, microfilaments can be confused with small __, though microfilaments have a diameter that is only 33% of the diameter of these small ribosomes.
A
ribosomes
B
centrioles
C
microvilli
10.
Microfilaments make up microvilli, which are finger-like __ that are found along the inner surface of the small intestine. Microvilli increase the surface area of the small intestine, thereby facilitating more absorption of nutrients.
A
cavities
B
dents
C
protrusions
11.
Microfilaments are concentrated in networks or bundles in an area just beneath the cell membrane called the __.
A
cell cortex
B
cilia
C
centrioles
12.
__ get their name because they are intermediate in size, between microtubules and microfilaments.
A
Intermediate filaments
B
microtubules
C
microfilaments
13.
Intermediate filaments are __ in composition, so there is more than one type of intermediate filaments in a cell. However, usually one type predominates.
A
homogeneous
B
heterogenous
C
hetero
14.
There are four main types of __ based on the protein involved: Type I, Type II, Type III, and Type V.
A
intermediate filaments
B
microfilaments
C
microtubules
15.
An intermediate filament has a rope-like conformation.
A
B
C
16.
Essentially, two _ coil around each other to form a parallel dimer, which is the basic building block of an intermediate filament. Two parallel dimers come together to form what we call a tetramer. An _ is basically made up of tetramers that are _.
A
monomers; intermediate filament; packed together
B
polymers; microfilament; packed together
C
monomer; intermediate filament; coiled together
17.
In a parallel dimer of an intermediate filament, each monomer consists of a central _ and one C-terminus at one end and one N-terminus at the other end.
A
a-helical domain
B
beta-helical domain
C
alpha rod
18.
Intermediate filaments are found directly under _ in a cell.
A
microfilaments
B
microtubules
C
tubules
19.
Type I intermediate filaments are keratins divided into acidic and basic types. Type II are vimentin-like proteins, which are found in cells of mesodermal origin. Type III are neurofilaments found in nerve axons. Type V are nuclear lamins (____).
A
form the nuclear lamina, which is a layer under the nuclear envelope
B
form the nucleus
C
form the nuclear envelope
20.
_ provide stability for the cell by allowing it to maintain its shape and structure.
A
microfilaments
B
Intermediate filaments
C
microtubules
21.
In simple terms, centrioles are _. Every centriole consists of 9 long tubes and every tube consists of 3 parts, which can be clearly seen in a _. That is why a centriole is called a _ structure. Since a centriole is hollow, it's also called a _.
22.
_ are always found in pairs and at right angles to each other because of the fibrous structures that connect and hold them in place. Usually _ are found in the cytoplasm in an area near the nucleus called the microtubular organizing center.
A
centrioles ; centrioles
B
ribosomes ; centrioles
C
microtubules ; ribosomes
23.
As mentioned, every tube in a centriole has 3 parts or sets. Set A is the closest to the center. It's a complete microtubule, so it has 13 _ that form a _. The middle set is B and C is the one _ from the center. Sets B and C are incomplete.
A
protofilaments; left-handed helix; farthest away
B
microfilaments; right-handed helix; farthest away
C
microtubules; left-handed helix; farthest away
24.
At the _ end of a centriole, there is a cartwheel structure from which fibrous structures come out.
A
proximal
B
distal
C
posterior
25.
Centrioles are components of _, which are the structures that microtubules (spindle fibers) extend from to attach to sister chromatids during cell division.
