Cytoskeleton Quiz

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Questions and Answers

Which protein is most commonly associated with contractile bundles of actin?

filamin

α-actinin

talin

myosin (correct)

What type of actin bundle is primarily involved in cell migration?

Intermediate filaments

Gel-like networks

Contractile bundles (correct)

Parallel bundles

Which of the following proteins does NOT bind to actin?

Myosin

Fimbrin

Talin

Keratin (correct)

Which structure is involved in the formation of focal contacts in a cell?

Integrin Signup and view all the answers

What is the role of filamin in the cell?

Providing stiffness to gel-like networks Signup and view all the answers

Which type of actin assembly is typically associated with tightly bundled, parallel arrangements?

Stress fibers Signup and view all the answers

What cellular process is the contractile ring primarily associated with?

Cell division Signup and view all the answers

Which of these proteins is responsible for binding actin filaments to create a densely packed network?

Filamin Signup and view all the answers

What is the primary function of the cytoskeleton in animal cells?

Maintenance of cellular morphology and motion Signup and view all the answers

Which protein subunit forms the structure of thin filaments?

Globular actin (G-actin) Signup and view all the answers

Which protein regulates the polymerization of actin filaments?

Gelsolin Signup and view all the answers

What is the approximate thickness of thin filaments?

7 nm Signup and view all the answers

In non-muscle cells, what percentage of total protein content does actin represent?

15% Signup and view all the answers

What are the three classes of actin mentioned in the content?

Alpha-actin, beta-actin, gamma-actin Signup and view all the answers

What prevents the polymerization of G-actin in the cytoplasm?

Profilin and thymosin Signup and view all the answers

What is the relationship between the plus and minus ends of an actin filament?

The plus end grows more quickly than the minus end Signup and view all the answers

What is the primary function of fimbrin and villin in the cytoskeleton?

They form actin filaments into closely packed parallel bundles. Signup and view all the answers

How do intermediate filaments react to tensile forces in the extracellular matrix?

They adapt to shape and location of cellular components. Signup and view all the answers

Which of the following proteins is NOT a type of intermediate filament?

Actin Signup and view all the answers

What is the typical diameter range of intermediate filaments?

8 to 10 nm Signup and view all the answers

What is a characteristic feature of the structure of intermediate filaments?

They are made up of monomers with variable N-terminus and C-terminus. Signup and view all the answers

What role do intermediate filaments play in relation to the nucleus?

They anchor the nucleus in place and maintain its structure. Signup and view all the answers

What forms the core of microvilli?

Actin filaments bundled by villin Signup and view all the answers

What is a key function of the terminal web in the cell cortex?

It provides a network for anchoring actin filaments. Signup and view all the answers

What is the composition of a microtubule subunit?

α-tubulin and β-tubulin Signup and view all the answers

Which of the following is NOT a function of microtubules?

Transcribe genetic material Signup and view all the answers

What role do intermediate filaments of keratins primarily serve in epithelial cells?

Providing mechanical stability Signup and view all the answers

What is the primary role of motor proteins in relation to microtubules?

They aid in the intracellular transport of materials Signup and view all the answers

Epidermolysis bullosa simplex (EBS) is primarily caused by mutations in which keratin genes?

Keratin 5 and 14 Signup and view all the answers

Which type of transport do kinesins primarily facilitate?

Anterograde transport toward the plus end Signup and view all the answers

Which of the following proteins is best known for binding keratin filaments into bundles?

Filaggrin Signup and view all the answers

How do microtubule-targeted drugs affect cellular processes?

They disrupt intracellular transport by inhibiting polymerization Signup and view all the answers

Vimentin is most commonly found in which type of cells?

Mesenchymal cells Signup and view all the answers

What specific cell structures are organized by microtubules?

Centrioles Signup and view all the answers

What is the primary function of lamins within the cell nucleus?

Forming the nuclear lamina Signup and view all the answers

Disruption of which cellular structure would halt transport in neurons?

Microtubules Signup and view all the answers

Which of the following diseases is attributed to mutations in the keratin 1 and 10 genes?

Epidermolytic hyperkeratosis Signup and view all the answers

Which drug is commonly used to treat gout by affecting microtubules?

Colchicine Signup and view all the answers

What is the primary function of keratin 5 and keratin 14 proteins?

Provide mechanical stability Signup and view all the answers

Which protein is specifically associated with glial cells in the central nervous system?

GFAP Signup and view all the answers

Microtubules provide which of the following structural benefits to eukaryotic cells?

Significant rigidity for cell shape maintenance Signup and view all the answers

In which phase of the cell cycle does Taxol primarily exert its effects?

G1 phase Signup and view all the answers

What consequence does Kartagener’s syndrome have on male fertility?

Reduced sperm motility Signup and view all the answers

What is the role of microtubule polarity in cellular functions?

Influences the direction of vesicular transport Signup and view all the answers

How does Taxol function as an antitumor drug?

Stabilizes microtubules to reduce dynamicity Signup and view all the answers

What structural defect is associated with Kartagener’s syndrome?

Absence of dynein in the axoneme Signup and view all the answers

What effect does the drug vinblastine have on microtubules?

Promotes microtubule disassembly Signup and view all the answers

What is one of the key clinical uses of Taxol in cancer therapy?

Promoting mitotic arrest through stabilization Signup and view all the answers

Study Notes

Cytoskeleton

The cytoplasm of animal cells contains a three-dimensional protein filament meshwork, responsible for cellular morphology.
The cytoskeleton participates in cellular motion, including organelle and vesicle movement within the cytoplasm or the entire cell.
The cytoskeleton has three components: thin filaments (microfilaments), intermediate filaments, and microtubules.

Thin Filaments (Microfilaments)

Composed of two globular subunits (G-actin), coiled to form a filamentous protein (F-actin).
Account for about 15% of total protein in non-muscle cells.
Only about half of the total actin is in the filamentous form, as the monomeric form is bound by proteins like profilin and thymosin to prevent polymerization.
Actin molecules are highly conserved among different species.
Thin filaments are 7 nm in thickness, with a faster growing plus end (barbed end) and a slower growing minus end (pointed end).
Capping proteins attach to the plus end to terminate filament growth.
Shortening of actin filaments is regulated by ATP, ADP, and Ca2+, and capping proteins like gelsolin to prevent polymerization.

Actin Filaments (Microfilaments) Bundles, Networks, and Parallel Bundles

Actin filaments form bundles of variable lengths, depending on the cell's function.
Three types of actin filament associations include: contractile bundles, gel-like networks, and parallel bundles.
Contractile bundles are often associated with myosin.
Actin bundles are responsible for cell movement, phagocytosis, absorption of nutrients, and the formation of cellular protrusions like microvilli.

Intermediate Filaments

Electron micrographs display a category of filaments in the cytoskeleton, with diameters of 8-10 nm, between thick and thin filaments.
These filaments provide structural support for the cell, anchoring the nucleus in place, with adaptable connections between the cell membrane and cytoskeleton.
These filaments create a framework for the nuclear envelope, including its reorganization in mitosis.
Intermediate filaments are also responsible for resisting tensile forces, maintaining cellular shape, and protecting the cell from external stresses.
Different categories of intermediate filaments include keratins, desmin, vimentin, glial fibrillary acidic protein, neurofilaments, and nuclear lamins.

Microtubules

Hollow tubular structures about 25 nm in outer diameter and 5 nm in wall thickness.
Confer significant rigidity to help maintain cell shape.
Protein subunits (a-tubulin and β-tubulin heterodimers) polymerize to form the microtubules.
Tubulin heterodimers have a slight spiral organization.
Microtubule organizing centers (MTOCs) direct the polymerization of tubulin to form microtubules.
Microtubules are responsible for:
- Providing rigidity and maintaining cell shape.
- Regulating intracellular organelle and vesicle movement
- establishing intracellular compartments.
- Enabling ciliary (and flagellar) motion
Centrosomes and centrioles are important microtubule structures.
Centrioles, paired structures, approximately 0.2 µm in diameter and 0.3-0.5 µm in length are composed of nine highly organized microtubule triplets.
Microtubules are crucial to intracellular transport of vesicles and macromolecular complexes in various cell types.

Microtubule-Targeted Drugs

Some drugs inhibit microtubule polymerization (e.g., colchicine, colcemid, vincristine, vinblastine) blocking mitosis.
Other drugs stabilize microtubules (e.g., taxol), promoting mitotic arrest and cell death.

Clinical Significance

Mutations in keratin genes (e.g., keratins 5, 14, 9) can result in inherited skin disorders like epidermolysis bullosa simplex and epidermolytic hyperkeratosis.
Taxol is an anti-tumor drug that stabilizes microtubules, used to treat breast and ovarian cancers.

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Description

Test your knowledge on the cytoskeleton's structure and function, specifically focusing on thin filaments and their dynamics. This quiz covers components like microfilaments, their composition, and roles within animal cells. Discover how these protein filaments contribute to cellular morphology and movement.