Cell Biology and Signalling: Cytoskeleton Quiz

Questions and Answers

What represents the fundamental unit of intermediate filaments?

Tetramer (correct)

Protofilament

Monomer

Helical dimer

Which of the following statements regarding the interaction of intermediate filaments is true?

They cannot interact with other cytoskeletal components.

They link exclusively through plectin.

They can link actin microfilaments and microtubules. (correct)

They only link to actin microfilaments.

Which of the following mutations is associated with epidermolysis bullosa simplex?

Mutations in actin

Mutations in keratins (correct)

Abnormal microtubule expression

Heterodimer mutations in tubulin

What is true about the exchange of subunits in intermediate filaments?

Subunit exchange is slow but occurs throughout the length of the filament. Signup and view all the answers

How many protofilaments are arranged in a typical microtubule structure?

13 Signup and view all the answers

What characterizes a tubulin monomer?

It is a heterodimer consisting of α-tubulin and β-tubulin. Signup and view all the answers

What is the primary defect associated with Situs inversus?

Defect in cilia-mediated movement of growth factors Signup and view all the answers

Which of the following agents is known to interfere with microtubule formation?

Colchicine Signup and view all the answers

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is primarily associated with defects in which cellular structure?

Primary cilia Signup and view all the answers

Which type of junctions are most directly connected to the actin microfilaments in the cytoskeleton?

Adherens junctions Signup and view all the answers

What is the possible outcome of disrupting the mitotic spindle during cell division?

Improper chromosome segregation Signup and view all the answers

What term describes the ECM connections that attach to the cell cytoskeleton?

Focal adhesions Signup and view all the answers

Which actin binding protein is responsible for inhibiting polymerisation?

Thymosin β4 Signup and view all the answers

What is the primary role of villin in microvilli?

Create parallel bundles Signup and view all the answers

What process involves the contraction of a ring of actin in the center of the cell, anchoring to the plasma membrane?

Cytokinesis Signup and view all the answers

Which actin binding protein is known to sever actin filaments and bind to the plus end?

Gelsolin Signup and view all the answers

What structure do lamellipodia primarily rely on for cell movement?

Actin networks Signup and view all the answers

What type of filaments provide physical support and structure in epithelial cells?

Intermediate filaments Signup and view all the answers

Which statement accurately describes the assembly process of actin microfilaments?

The polymerization process involves the hydrolysis of ATP. Signup and view all the answers

Which intermediate filament proteins are found specifically in axons?

Neurofilamin(s) Signup and view all the answers

What is the primary role of intermediate filaments in the cytoskeleton?

Providing tissue-specific structural support. Signup and view all the answers

What key function do lamins A, B, and C serve in the cell?

Support nuclear structure Signup and view all the answers

Which of the following functions is NOT associated with the cytoskeleton?

Synthesis of ATP. Signup and view all the answers

How does the diameter of microtubules compare to that of actin microfilaments?

Microtubules are larger in diameter than actin microfilaments. Signup and view all the answers

Which of the following statements regarding the dynamic structure of actin microfilaments is true?

Length changes based on the rate of G-actin monomer loss and gain. Signup and view all the answers

What is a major role of the cytoskeleton in cell movement?

Aiding in chromosome separation during mitosis. Signup and view all the answers

Which type of cytoskeletal component is primarily involved in cytokinesis?

Actin microfilaments. Signup and view all the answers

What can be inferred about diseases related to the cytoskeleton?

They often involve structural abnormalities in cytoskeletal components. Signup and view all the answers

What role do microtubules play in mitosis?

They serve as a scaffold for spindle formation. Signup and view all the answers

Which motor protein moves cargo towards the cell periphery along microtubules?

Kinesin Signup and view all the answers

What are centrioles primarily composed of?

Stable fused microtubules. Signup and view all the answers

What is the function of the microtubule-organizing centre (MTOC)?

It serves as the primary site for microtubule assembly. Signup and view all the answers

How do cilia differ from primary cilia?

Cilia are motile and facilitate movement of fluids. Signup and view all the answers

What happens to microtubules during cellular mitosis?

They disassemble but then reform post-mitosis. Signup and view all the answers

What is the primary component that maintains the structure of stereocilia?

Actin filaments. Signup and view all the answers

What is the role of Aster microtubules during cell division?

They connect the centrosome to the cell membrane. Signup and view all the answers

Study Notes

Cytoskeleton Overview

Composed of a network of protein filaments within cells, serving multiple functions.
Vital roles include maintaining cell shape, intracellular transport, cytokinesis, and cell movement.
Connects with the extracellular matrix (ECM).

Three Major Components of the Cytoskeleton

Actin Microfilaments
- Polymers of actin with a diameter of 7-9 nm; involved in muscle contraction and maintaining cell shape.
- Monomer (G-actin) binds ATP, polymerizes to form filament (F-actin), with dynamic growth at both ends.
- Constitutes about 5% of cellular protein.
Intermediate Filaments (IF)
- Composed of various tissue-specific proteins; approximately 10 nm in diameter.
- Examples include keratins in epithelial cells and neurofilaments in axons.
- Generally stable, providing structural support to cells.
Microtubules
- Composed of tubulin heterodimers; approximately 25 nm in diameter.
- Formed by 13 protofilaments creating a hollow tube, critical for cell organization and mitotic spindle formation.

Actin Microfilaments Details

Actin microfilament structure features a dynamic assembly that includes a (+) end for growth and a (-) end for depolymerization.
Important actin-binding proteins regulate filament dynamics:
- Thymosin β4 inhibits polymerization.
- Gelsolin severs and regulates filament stability.
Plays crucial roles in non-muscle cell movement and cytokinesis.

Intermediate Filaments Functions

Connects with actin microfilaments and microtubules, offering structural stability.
Clinical relevance includes diseases like epidermolysis bullosa simplex from keratin mutations and amyotrophic lateral sclerosis related to neurofilamin abnormalities.

Microtubules Functionality

Dynamic elements in cells providing a scaffold for organelle organization and cargo movement.
Involved in chromosome separation during mitosis, with centrosomes acting as microtubule-organizing centers (MTOC).
Motor proteins (kinesin and dynein) facilitate transport along microtubules using ATP.

Cilia and Their Functions

Hair-like membrane extensions supported by microtubules, crucial for various movements.
Types include primary cilia and motile cilia, with functions ranging from sensory detection to fluid movement in respiratory epithelium.

Clinical Considerations of the Cytoskeleton

Disruption of microtubules can affect cell division, influencing cancer treatment strategies.
Chemotherapeutics like colchicine and taxol target microtubule dynamics.

Cell-Adhering Structures

The cytoskeleton is essential in forming junctions between cells (like desmosomes and gap junctions) and adhering to the ECM (through hemidesmosomes and focal adhesions).

Summary Points

The cytoskeleton consists of actin microfilaments, intermediate filaments, and microtubules, each with distinct structures and functions.
Regulation and dynamics of these components are critical for cellular integrity, movement, and functionality.
Dysfunctional cytoskeletal components can lead to various diseases, highlighting their importance in health and disease mechanisms.

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Description

Test your knowledge on the cytoskeleton's major structural components, their assembly and disassembly, and associated proteins. This quiz will help you understand the integral role of the cytoskeleton in cell structure and intracellular motility.