cytoskeleton MCQs

A stress fiber contains which of the following pairs of proteins? Tubulin - Kinesin Tubulin - Cadherin Tubulin - Dynein Actin - Myosin Actin - Integrin

Actin - Myosin

A cytoskeletal component requires ATP for its polymerization and contains subunits that are observed to undergo treadmilling. That cytoskeletal component is a/an Microtubule Tubulin Intermediate filament Keratin Actin filament

Actin filament - Actin filaments require ATP for polymerization, and subunits undergo treadmilling as they make their way through an F-actin polymer. Intermediate filaments have stable structures and do not undergo dynamic assembly or disassembly processes. Keratin is a type of intermediate filament. Microtubules are composed of tubulin heterodimers. They require GTP for their polymerization. Additions and subtractions of tubulins from microtubules occur from the same end of the structure.

The stability and arrangement of actin filaments as well as their properties and functions depend on which one of the following? The structure of the actin filaments Microtubules Intermediate filament proteins Motor molecules, such as kinesin Actin-binding proteins

Actin-binding proteins - The stability, arrangement, and functions of actin filaments depend on the actin-binding proteins. The fundamental structure of the actin molecule is the same no matter what the function or arrangement in a cell. Acting-binding proteins have a variety of functions 1. tropomyosin strengthens actin filaments 2. fibrin and villin are actin-bundling proteins 3. filamin and gelsolin regulate transformation from the sol to the gel state 4. members of the myosin II family are responsible for sliding filaments 5. myosin I (minimyosin) is responsible for the movement of vesicles on filaments 6. spectrin cross-links the sides of actin filaments to the plasma membrane.

Which class of cellular adhesion molecule (CAM) is primarily used to link one cell to another cell of the same type? Integrins Immunoglobulin superfamily Filopodium Cadherins Selectins

Cadherins

A 24-year-old female patient diagnosed with Hodgkin's disease is treated with combination chemotherapy. Her drug regimen includes Velban which is known to inhibit microtubule formation. Therefore, which of the following processes will be altered/impaired by Velban? Production of filamentous actin from G-actin monomers within malignant cells. Transformation of cytosol in malignant cells from the gel to the sol states Treadmilling of filamentous tubulin monomers in an ATP-dependent process. Stabilization of malignant cell membranes and protection from stretching forces. Formation of the mitotic spindle with the arrest of malignant cells in mitosis.

Formation of the mitotic spindle with the arrest of malignant cells in mitosis - Inhibitors of microtubule formation such as Velban will prevent mitotic spindle formation with the arrest of malignant cells in mitosis. Actin is not affected so the formation of F-actin will continue and transformation from gel to sol state, regulated by actin, will also continue in the presence of the drug. Tubulin monomers are globular heterodimers, not filamentous. And GTP, not ATP, is used in the formation of microtubules. Treadmilling is usually described for actin, not for microtubules.

What is the function of the actin cytoskeleton? Forms the contractile ring during cytokinesis. Forms the mitotic spindle. Creates the 3-D structure of the Golgi. Provides tracks for kinesin motors. Provides mechanical stability for the nuclear envelope.

Forms the contractile ring during cytokinesis

Fibronectin is the ligand of a particular adhesion molecule. Therefore, that adhesion molecule most likely belongs to which family? Selectins Collagens Integrins Immunoglobulin superfamily Cadherins

Integrins - Fibronectin is a component of the ECM and integrins are the type of adhesion molecule that can mediate cell-to-ECM adhesions. Cadherins, immunoglobulin superfamily members, and selectins mediate cell-to-cell adhesion only. Collagen is not an adhesion molecule but a fibrous protein within the ECM.

A vesicle within a cell must be transported to another region of the cell along the microtubules. Which of the following proteins may be involved in catalyzing this transport? Dystrophin Spectrin Vimentin Kinesin Myosin

Kinesin - Kinesin and dynein are families of microtubule motor proteins that facilitate intracellular transport along microtubules. Dystrophin, myosin, and spectrin are actin- binding proteins. Vimentin is a type of intermediate filament.

A 13-year-old boy falls off his skateboard and scrapes his elbow on the concrete. To heal this wound, fibroblasts will migrate into the injured site to remodel the tissue. The accompanying micrograph shows a crawling fibroblast in tissue culture. The arrows point to the leading edge of the cell, which always acquires a particular shape in a crawling cell. What is the name of the structure that the leading edge of a crawling cell forms? Cilium Desmosome Flagellum Stress fiber Lamellipodium

Lamellipodium

A microtubule is observed to disassemble quickly after a period of rapid growth. Which of the following most likely occurred to this particular microtubule to stimulate its breakdown? Binding by dynein Severing by gelsolin Twisting by cofilin Loss of its GTP cap Formation of its ATP cap

Loss of its GTP cap - Loss of the GTP cap results in rapid disassembly of microtubules. Dynein is a microtubule motor protein that enables microtubules to facilitate the movement of cilia and flagella and of intracellular cargo. ATP is not part of a microtubule structure. Gelsolin and cofilin are actin-binding proteins that stimulate the breakdown of complex actin structures.

Which of the following consists of globular actin monomers linked into a double helix? Lamin A Microtubule Neurofilament Keratin Microfilament

Microfilament

A 50-year-old man attends the hottest Indianapolis 500 race in decades and sits with the sun facing him; there is no breeze. He has a history of borderline high uric acid. Dehydration during the race triggers uric acid crystal formation in his foot. The foot becomes sore, red, hot, and swollen. He drinks about 2 L of water and soda at the race and two more liters at home. However, he is anuric (complete suppression of urine formation) for 10 to 12 hours. His physician prescribes colchicine as an anti-inflammatory. Colchine acts on which intracellular structure? Centrosome Desmosome Intermediate filament Microfilament Microtubule

Microtubule

Which of the following cytoskeletal components is associated with kinesin? Neurofilament Microfilament Keratin Lamin A Microtubule

Microtubule

Inhibition of actin assembly by cytochalasins would interfere primarily with which one of the following? Vesicular transport between the Golgi apparatus and cell membrane. Phagocytic activity by macrophages Separation of chromosomes in anaphase of the cell cycle Ciliary movement The structure of centrioles

Phagocytic activity by macrophages - Cytochalasins are potent inhibitors of cell motility and other cellular events that depend on actin assembly: cytokinesis, which is conducted by the actin-containing contractile ring; phagocytosis; and formation of lamellipodia. Cytochalasins bind to the plus end of actin filaments and prevent further polymerization. The movement of chromosomes in anaphase of the cell cycle depends on the disassembly of microtubules at the kinetochore in anaphase A and addition at the plus end of the polar microtubules in anaphase B. Ciliary movement, vesicular transport, and the structure of centrioles depend on microtubules.

What is the structure of a centriole in a transmission electron micrograph (TEM)? This is a cross-section of a microtubule. This is a cross-section of an actin filament. This is a cross-section of a basal body. This is a cross-section of a cilium.

This is a cross-section of a microtubule

Which of the substances listed below is most likely to be associated with a centriole? Tubulin Actin Na+/K+ -ATPase Cholesterol Histone H2A

Tubulin

what are almost exclusively found under the plasma membrane and not deep in the cytoplasm or around the nucleus.

actin microfilaments

Which of the following properties is unique to cell adhesion mediated by cadherins? Cadherins mediate bidirectional signaling between the cytoskeleton and the ECM. Cadherins on one cell bind to the glycosylated ligands on another cell. Cadherins have homophilic binding, with other cadherins serving as their ligands. Cadherins are transmembrane proteins; other adhesion molecules are intracellular. Cadherins mediate cell-to-matrix adhesion, not cell-to-cell adhesions.

cadherins have homophilic binding, with other cadherins serving as their ligands. - Cadherins have homophilic binding, with other cadherins serving as their ligands. The unique characteristics of selectins, not cadherins, is that they bind to carbohydrate-containing ligands. All adhesion molecules are transmembrane proteins that can mediate cell-to-cell adhesions. Integrins facilitate cell-to-cell-to-ECM adhesions and have inside-out and outside-in signaling.

Actin polymerization may function to control or regulate Provide rigid structural stability to the cytoplasm. Strength within connective tissues Chromosomal movement during cell division. Changes in the physical state of the cytosol. Resilience of tissue such as cartilage.

changes in the physical state of the cytosol. - Actin polymerization controls the physical state of the cytosol and the transition from gel to sol. Microtubules, composed of tubulin, regulate chromosomal movements in cell division. Intermediate filaments provide structural stability to the cytoplasm. Unlike actin and microtubules that have dynamic changes in structure, intermediate filaments are longer-lived more permanent structures and may be likened to rigid supports. Resilience is a property attributed to proteoglycans in the extracellular matrix, not to cytoskeletal components such as actin. Collagen and elastin lend strength to the ECM in connective tissues.

What family of membrane proteins does a cell most commonly use to attach itself to its non-cellular surroundings? Lamins Integrins Cadherins Keratins Importins

integrins

what network runs throughout the nucleus and wraps completely around the nucleus.

intermediate filament

what has a bright aggregation of filaments on one side of the nucleus. This is the centrosome, or microtubule organizing center.

microtubule network

Which kind of cytoskeletal filaments are found in microvilli and cilia? Microvilli contain microtubules; cilia contain actin filaments. Microvilli contain microtubules; cilia contain intermediate filaments. Microvilli contain actin filaments; cilia contain microtubules. Microvilli contain actin filaments; cilia contain intermediate filaments. Microvilli contain intermediate filaments; cilia contain microtubules.

microvilli contain actin filaments; cilia contain microtubules.