Cytoskeletal Microtubules & Microfilaments
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Questions and Answers

What is the average half-life of a microtubule?

  • 10 minutes (correct)
  • 60 minutes
  • 30 minutes
  • 2 minutes

Which of the following accurately describes the composition of a microtubule?

  • Made solely of actin filaments
  • Made of heterodimers of α- and β-tubulin subunits (correct)
  • Formed by lipid bilayers
  • Composed of 13 filamentous proteins

What role do microtubules play during cell division?

  • They form the mitotic spindle (correct)
  • They store genetic information
  • They stabilize the cell membrane
  • They create energy for cellular functions

Which component of the cytoskeleton is responsible for providing rigidity and maintaining cell shape?

<p>Microtubules (C)</p> Signup and view all the answers

Which motor proteins are relevant to cell trafficking associated with microtubules?

<p>Kinesin and Dynein (C)</p> Signup and view all the answers

What is the primary function of the centrosome in relation to microtubules?

<p>It serves as a nucleation site for microtubules (D)</p> Signup and view all the answers

How do microtubules contribute to ciliary and flagellar motion?

<p>By facilitating wave-like movements via dynein activity (B)</p> Signup and view all the answers

What is a key feature of the dynamic nature of microtubules?

<p>They frequently change length through growth and shortening (C)</p> Signup and view all the answers

What is the primary effect of colchicine on microtubule formation?

<p>It prevents the polymerization of tubulin into microtubules. (B)</p> Signup and view all the answers

Which family of microtubule motor proteins is responsible for moving vesicles toward the minus end of the microtubule?

<p>Dynein (D)</p> Signup and view all the answers

During cell division, what is the role of centrioles?

<p>They help in the formation of the spindle apparatus. (A)</p> Signup and view all the answers

Microtubule-associated proteins (MAPs) primarily function to:

<p>Assist in the movement of organelles and prevent microtubule depolymerization. (A)</p> Signup and view all the answers

What component is primarily found in the structure of centrioles?

<p>Microtubule triplets (B)</p> Signup and view all the answers

The movement of organelles along microtubules occurs in what direction?

<p>In both directions, toward plus and minus ends. (C)</p> Signup and view all the answers

Which of the following is NOT a function of centrioles?

<p>Preventing microtubule depolymerization. (D)</p> Signup and view all the answers

What type of protein makes up the thin filaments known as actin filaments?

<p>Globular subunits (G-actin) (B)</p> Signup and view all the answers

Flashcards

Colchicine's effect on microtubules

Colchicine prevents microtubule polymerization by binding to tubulin molecules.

Microtubule-associated proteins (MAPs)

Motor proteins that move organelles and vesicles along microtubules.

Dynein's movement

Moves vesicles towards the minus end of a microtubule.

Kinesin's movement

Moves vesicles towards the plus end of a microtubule.

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Centrioles composition

Cylindrical structures composed of nine microtubule triplets.

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Centrosome's function

Organizes microtubules and assists in their self-duplication. Also organizes cellular spindle apparatus for cell division.

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Centrioles in cell division

Form the spindle apparatus during cell division.

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Actin filaments (microfilaments)

Thin filaments formed by two chains of G-actin coiled together.

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Microtubules (MTs)

Long, hollow structures in cells that act as intracellular pathways, maintaining cell shape and enabling movement of organelles and vesicles.

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Centrosome

A region near the nucleus that contains centrioles and γ-tubulin ring complexes, acting as nucleation sites for microtubule growth.

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Microtubule Dynamics

Microtubules constantly grow and shrink at their plus ends, resulting in a short average life span of about 10 minutes.

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Protofilaments

Parallel strands that form microtubules, composed of α- and β-tubulin subunits and heterodimers

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Cytoskeleton Function

Maintains cell shape and enables both intracellular and cellular motion, acting as an intracellular framework.

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Cell Shape Maintenance

The cytoskeleton helps cells maintain their shape, offering structural support.

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Motor Proteins

Proteins that facilitate movement along microtubules during cellular transport.

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Microtubules and Cell Division

Microtubules form the mitotic spindle during cell division, allowing chromosome separation.

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Study Notes

Cytoskeletal Microtubules & Microfilaments & Motility

  • Microtubules (MTs) are hollow, straight structures acting as intracellular pathways
  • Centrosome, located near the nucleus, houses centrioles and y-tubulin ring complexes, which nucleate microtubules
  • Microtubules are dynamic, changing length by growth spurts and shortening at the plus end (away from the nucleus). Average half-life is about 10 minutes.
  • Microtubules are composed of 13 parallel protofilaments made of α and β-tubulin heterodimers
  • Microtubules provide rigidity, maintain cell shape, regulate organelle and vesicle movement, and establish intracellular compartments. They are involved in cilia/flagella movement and mitotic spindle formation.
  • Colchicine disrupts microtubule formation, impacting leukocyte migration, phagocytosis and inflammatory mediator release
  • Microtubule-associated proteins are motor proteins facilitating organelle and vesicle transport. Dynein moves toward the minus end (and kinesin toward the plus end) of the microtubule in the presence of ATP.

Microfilaments (Actin Filaments)

  • Actin filaments (microfilaments) are thin, composed of G-actin subunits forming F-actin
  • Actin filaments have a faster-growing plus end and a slower-growing minus end
  • Contractile bundles of actin filaments are arranged loosely, parallel to each other, plus/minus ends alternating, forming cleavage furrows during mitosis
  • Gel-like networks of actin filaments provide structural support in the cell cortex
  • Actin bundles form the core of microvilli (apical cell projections)
  • Focal points are actin-based structures at contact points between the cell and extracellular matrix

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Description

Explore the structures and functions of microtubules and microfilaments in cellular motility. Learn about their dynamic nature, roles in cell shape maintenance, and involvement in processes such as mitosis. This quiz will also cover the impact of colchicine on microtubule formation and related motor proteins.

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