Cell Biology: Centrioles and Microtubule Organization
33 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the role of ATP binding and hydrolysis in dynein movement?

  • It facilitates the cargo attachment to dynein's tail.
  • It stabilizes the dynein complex to the microtubule.
  • It causes the head domain to release from the microtubule.
  • It initiates a power stroke that propels dynein toward the microtubule minus end. (correct)

How far does dynein move along the microtubule with each cycle?

  • 12 nm
  • 8 nm (correct)
  • 4 nm
  • 10 nm

Which domain of dynein is more variable among dynein subtypes?

  • The tail domain (correct)
  • The linker domain
  • The stalk domain
  • The head domain

What structural component connects the head domain of dynein to the microtubule-binding site?

<p>The stalk (A)</p> Signup and view all the answers

What occurs after the release of ATP and phosphate during dynein movement?

<p>The linker domain undergoes a conformational change, pulling the tail toward the minus end. (C)</p> Signup and view all the answers

What role does stathmin play in microtubule dynamics?

<p>Inhibits the assembly of tubulin dimers (D)</p> Signup and view all the answers

Which protein is responsible for severing microtubules?

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

What is the primary function of kinesins and dyneins?

<p>Transporting cargo within the cell (C)</p> Signup and view all the answers

Which class of proteins stabilizes microtubules by binding along their sides?

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

What effect does kinesin-13 have on microtubules?

<p>Induces catastrophe and disassembly (A)</p> Signup and view all the answers

Which domain in microtubule dynamics is responsible for nucleating microtubule branching?

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

Which protein promotes rapid growth at the plus ends of microtubules?

<p>XMAP215 (A)</p> Signup and view all the answers

What is the role of MAP2 in relation to intermediate filaments?

<p>Links to intermediate filaments (B)</p> Signup and view all the answers

What structural feature characterizes the arrangement of microtubules in a centriole?

<p>Ninefold symmetry (B)</p> Signup and view all the answers

What is the primary role of the pericentriolar material?

<p>To assist in microtubule nucleation (D)</p> Signup and view all the answers

What occurs during the duplication of the centrosome before mitosis?

<p>Formation of a pair of centrosomes with centriole pairs (D)</p> Signup and view all the answers

Which microtubule-associated protein (MAP) is specifically confined to the cell body and dendrites in neurons?

<p>MAP2 (C)</p> Signup and view all the answers

What is the effect of catastrophe factors like kinesin-13 on microtubules?

<p>They induce depolymerization by prying microtubule ends apart (A)</p> Signup and view all the answers

In which biological system is the augmin complex primarily studied for its role in microtubule branching?

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

How do microtubule-associated proteins (MAPs) like tau and MAP2 differ in their structure?

<p>MAP2 has longer projection arms than tau (A)</p> Signup and view all the answers

What is a characteristic structural outcome of the overexpression of MAP2 in microtubule bundles?

<p>Regular spacing between microtubules (D)</p> Signup and view all the answers

What is a primary function of microtubule-based motors?

<p>To transport cargo over long distances (C)</p> Signup and view all the answers

Which kinesin is known to promote microtubule depolymerization?

<p>Kinesin-13 (A)</p> Signup and view all the answers

How do kinesin-5 motors function in relation to microtubules?

<p>They slide two microtubules past each other. (D)</p> Signup and view all the answers

What structural feature differentiates kinesin-1 from kinesin-14?

<p>Kinesin-14 moves toward the microtubule minus end. (A)</p> Signup and view all the answers

What type of molecule is cytoplasmic dynein classified as?

<p>A two-headed molecule (C)</p> Signup and view all the answers

What is a notable feature of the dynein heavy chain?

<p>It is large, containing more than 4000 amino acids. (C)</p> Signup and view all the answers

What does the tail domain of cytoplasmic dynein connect to?

<p>The motor heads and a dimerization domain (B)</p> Signup and view all the answers

Which specific domain of dynein is primarily responsible for ATPase activity?

<p>The AAA domains (A)</p> Signup and view all the answers

What happens to EB1 when a microtubule undergoes a catastrophe?

<p>EB1 is lost from the microtubule. (D)</p> Signup and view all the answers

What effect does katanin have on microtubules?

<p>It severs microtubules, creating fragments. (D)</p> Signup and view all the answers

How does incorporation of GTP-tubulin subunits affect severed microtubules?

<p>It stabilizes the severed ends and promotes rescue. (C)</p> Signup and view all the answers

What observable change occurs first after the addition of katanin to taxol-stabilized microtubules?

<p>Appearance of a few breaks in the microtubules. (D)</p> Signup and view all the answers

Flashcards

What is EB1?

A protein that binds to the plus end of growing microtubules and is lost during catastrophe events. It is regained when the microtubule starts growing again.

How does stathmin affect microtubule growth?

Stathmin binds along the side of two tubulin dimers, preventing them from incorporating into microtubules. This can decrease the pool of available tubulin for microtubule growth.

What does katanin do to microtubules?

Katanin severs microtubules. This can either decrease microtubule stability by breaking them down or increase stability by creating new ends for growth.

What happens to microtubules after being severed by katanin?

Severed microtubules create new ends for growth. The broken ends can be stabilized by incorporating GTP-tubulin subunits.

Signup and view all the flashcards

What is a microtubule catastrophe event?

A phase where microtubules shrink rapidly. This is often triggered by the loss of GTP-tubulin caps.

Signup and view all the flashcards

Centriole

A cylindrical structure composed of modified microtubules, arranged in a barrel shape with 9-fold symmetry.

Signup and view all the flashcards

Pericentriolar Material

A dense, spherical matrix surrounding the centriole, where microtubule nucleation occurs.

Signup and view all the flashcards

Centrosome Duplication

The process of copying the centrosome before cell division.

Signup and view all the flashcards

Microtubule-Associated Proteins (MAPs)

Proteins that bind to microtubule ends and influence their growth or shrinkage.

Signup and view all the flashcards

XMAP215

A MAP that promotes microtubule polymerization, increasing their growth rate by delivering tubulin dimers to the plus ends.

Signup and view all the flashcards

Catastrophe Factor

A protein that causes microtubule depolymerization, promoting their shrinkage.

Signup and view all the flashcards

Augmin

A complex composed of proteins, responsible for nucleating new microtubules with a specific angle.

Signup and view all the flashcards

Axon and Dendrite

The region of a neuron where microtubule bundles are organized.

Signup and view all the flashcards

What does dynein do?

Dynein is a motor protein that uses ATP to move along microtubules.

Signup and view all the flashcards

What are the head and tail domains of dynein?

The head domain of dynein binds to microtubules and is responsible for ATP hydrolysis, while the tail domain interacts with cargo.

Signup and view all the flashcards

How does dynein move along microtubules?

Dynein's movement is described as a "power stroke." It uses ATP to move along microtubules towards the minus end.

Signup and view all the flashcards

What are some of the functions of dynein?

Dynein is involved in various cellular processes, including transporting cargo, flagellar movement, and cell division.

Signup and view all the flashcards

What are the main types of dynein and their functions?

Cytoplasmic dynein moves cargo along microtubules, while axonemal dynein is involved in the movement of cilia and flagella.

Signup and view all the flashcards

What does +TIP stand for?

A type of microtubule-associated protein (MAP) that binds to the ends of growing microtubules, promoting rapid microtubule growth. It prevents the loss of GTP-tubulin caps, which are crucial for microtubule stability.

Signup and view all the flashcards

What is the plus end of a microtubule?

The end of a microtubule where tubulin subunits are added, and it is characterized by the presence of GTP-tubulin caps. This is the growing end.

Signup and view all the flashcards

What is the function of katanin?

A microtubule-associated protein (MAP) that severs microtubules, leading to the formation of new ends for growth or disassembly.

Signup and view all the flashcards

What is the function of MAPs?

A microtubule-associated protein (MAP) that binds to microtubules along their sides and promotes microtubule stability, preventing spontaneous disassembly.

Signup and view all the flashcards

What is the minus end of a microtubule?

The end of a microtubule where subunits are lost, and it is characterized by the loss of GTP-tubulin caps. This is the shrinking end.

Signup and view all the flashcards

What are microtubule stabilizing proteins?

Microtubule-associated proteins (MAPs) that bind to microtubules along their sides and stabilize them, preventing spontaneous disassembly. They also promote interactions with other cellular structures.

Signup and view all the flashcards

What does stathmin do?

A type of microtubule-associated protein (MAP) that binds to tubulin dimers, preventing them from incorporating into microtubules. This reduces the pool of available tubulin for assembly.

Signup and view all the flashcards

Microtubule-based motor transport

Microtubule-based motors transport cargo over longer distances than actin-based motors.

Signup and view all the flashcards

Kinesin-1 directionality

Kinesin-1, a motor protein, moves cargo towards the positive end of a microtubule, the end where it grows.

Signup and view all the flashcards

Kinesin-14 directionality

Kinesin-14, a motor protein, moves cargo towards the negative end of a microtubule, the end where it's anchored.

Signup and view all the flashcards

Kinesin-13 function

Kinesin-13 is a motor protein that depolymerizes microtubules, breaking them down.

Signup and view all the flashcards

Dynein directionality

Dynein is a motor protein that moves cargo towards the negative end of a microtubule.

Signup and view all the flashcards

Cytoplasmic dynein structure

Cytoplasmic dynein is a two-headed motor protein with a large head, which makes it different from myosin and kinesin.

Signup and view all the flashcards

Dynein heavy chain structure

The cytoplasmic dynein heavy chain is a massive polypeptide with multiple domains, including six AAA domains, for ATP binding and hydrolysis.

Signup and view all the flashcards

Kinesin-5 function

Kinesin-5 forms tetramers that slide microtubules past each other, similar to how myosin II forms thick filaments in muscle.

Signup and view all the flashcards

Study Notes

Centrioles and Centrosomes

  • Centrioles are cylindrical arrays of short, modified microtubules arranged in a barrel shape, exhibiting ninefold symmetry.
  • They are associated with accessory proteins that recruit pericentriolar material.
  • Pericentriolar material is a dense spherical matrix where microtubule nucleation occurs, believed to form through biomolecular condensation.
  • Centrosomes duplicate before mitosis, forming pairs, each containing a centriole pair.
  • During mitosis, the two centrosomes separate to create the poles of the mitotic spindle.

Microtubule Organization

  • Microtubule arrangement varies across cell types.
  • Budding yeast has an MTOC embedded within the nuclear envelope, a multilayered structure called a spindle pole body.
  • Plant cells lack centrosomes and nucleate microtubules at various sites around the nuclear envelope and the cell cortex.
  • Neither fungi nor most plant cells contain centrioles.
  • Despite differences, all cells use γ-TuRC to nucleate microtubules.

Microtubule-Associated Proteins (MAPs)

  • MAPs are proteins that bind to microtubules.
  • A subset of MAPs mediates interactions between microtubules and other cell components.
  • These MAPs have domains that bind to the microtubule surface and project outward.
  • Length of projecting domains affects closeness of microtubule packing.
  • Some MAPs, like MAP2, form stable bundles of widely spaced microtubules. Others, like tau, form tightly packed bundles.
  • Phosphorylation of MAPs alters activity and localization by disrupting electrostatic interactions with microtubules.

Microtubule-binding Proteins and Filament Dynamics

  • Microtubule polymerization dynamics are different in cells than in solutions of pure tubulin.
  • In cells, microtubules exhibit a higher polymerization rate, higher catastrophe frequency, and extended pauses in growth.
  • Different proteins bind to stabilize, depolymerize, bind along filaments, or cap filaments.
  • Examples include Taxol (stabilizes), Nocodazole (depolymerizes), and Colchicine (depolymerizes).
  • Proteins like +TIPs (plus-end tracking proteins) are enriched at microtubule plus ends and bind to actively growing plus ends, dissociating when shrinking.

Tubulin-sequestering and Severing Proteins

  • Tubulin subunits are sequestered to maintain a pool of active subunits near critical concentration.
  • Stathmin binds tubulin heterodimers, preventing addition to microtubule ends.
  • Katanin severs microtubules into fragments, impacting stability and dynamics.

Motor Proteins (Kinesins and Dyneins)

  • Kinesins and dyneins are microtubule-based motors for intracellular transport.
  • Kinesins move cargo toward the plus end of microtubules.
  • Dyneins move cargo toward the minus end of microtubules.
  • Various kinesin types (e.g., kinesin-1, kinesin-5, kinesin-13, kinesin-14) have different motor domains, mediating dimerization and cargo attachment to carry out different tasks.
  • The power stroke in dynein involves ATP binding and release causing head movement toward the minus end of the microtubule.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Cytoskeleton 80-100 PDF

Description

This quiz covers key concepts related to centrioles, centrosomes, and microtubule organization in various cell types. Explore the differences in microtubule arrangement across fungi, plant cells, and yeast. Test your understanding of the roles of centrioles and mitotic spindle formation in cell division.

More Like This

Cell Structure Components Quiz
5 questions

Cell Structure Components Quiz

BestElectricOrgan avatar
BestElectricOrgan
Cell Biology: Centrioles and Centrosomes
5 questions

Cell Biology: Centrioles and Centrosomes

ResponsiveLobster avatar
ResponsiveLobster
Cell Biology: Centrosomes and Centrioles
32 questions

Cell Biology: Centrosomes and Centrioles

AttentiveInterstellar avatar
AttentiveInterstellar
Use Quizgecko on...
Browser
Open
Browser
Browser