Froggy Jumps Centrioles, cilia, and cell junctionsOnline version - elements of the cytoskeleton (their structures and functions) - the structure and role of centrioles in the cell - types of cell junctions (their structures and functions) - pemphigus vulgaris (rare condition) by Zainab Nabeel 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. a microtubules; axoneme (central core);locomotion; surface b microtubules; flagella; axoneme; locomotion c locomotion; surface; flagella; cilia 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 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 _. a hollow cylindrical tubes; cross section; 9x5; 9x0 structure b hollow cylindrical tubes; cross section; 9x4; 9x0 structure c hollow cylindrical tubes; cross section; 9x3; 9+0 structure 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. a centrosomes b centromeres c cell junctions
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