10 Questions
What are the major structural elements of the cytoskeleton?
Microfilaments, microtubules, intermediate filaments
What are the functions of the cytoskeleton?
Cell movement and division
What are the bacterial cytoskeletal elements structurally similar to those in eukaryotes?
Actin-like MreB and tubulin-like FtsZ
Which proteins use ATP to drive vesicle or organelle transport or to generate sliding forces between microtubules?
Microtubule-binding proteins
Which proteins bind at regular intervals along a microtubule wall, allowing for interaction with other cellular structures and filaments?
Microtubule-stabilizing/bundling proteins
Which proteins promote depolarization of microtubules?
Catastrophins
Which proteins bind to tubulin heterodimers and prevent their polymerization?
Stathmin/Op18
What gives microtubules inherent polarity with plus and minus ends?
Protofilaments made of α and β tubulin heterodimers
What contributes to the dynamic instability of microtubules, leading to periods of growth, shrinkage, catastrophe, and rescue?
GTP hydrolysis
What nucleates the assembly of new microtubules?
γ-tubulin
Study Notes
Microtubules: Structure, Assembly, and Function
- Microtubules are the largest structural elements of the cytoskeleton, involved in various cellular functions.
- There are two types of microtubules: cytoplasmic and nuclear, responsible for different functions such as maintaining axons and cell shape, and forming spindles.
- Microtubules are composed of tubulin heterodimers, forming straight, hollow cylinders of varied lengths.
- Protofilaments, made of α and β tubulin heterodimers, give microtubules inherent polarity with plus and minus ends.
- Microtubules form through the reversible polymerization of tubulin dimers in the presence of GTP and Mg2+, with distinct lag and elongation phases.
- Microtubule assembly depends on the concentration of tubulin dimers and the critical concentration, leading to growth or disassembly.
- The plus end of microtubules grows faster due to the addition of tubulin dimers, while treadmilling occurs when free tubulin concentration varies at the plus and minus ends.
- GTP hydrolysis contributes to the dynamic instability of microtubules, leading to periods of growth, shrinkage, catastrophe, and rescue.
- Microtubules originate from microtubule-organizing centers (MTOCs) containing γ-tubulin, which nucleates the assembly of new microtubules.
- MTOCs organize and polarize microtubules within cells, with the minus ends anchored in the MTOC, leading to dynamic growth and shrinkage at the plus ends.
- Centrosomes, containing γ-tubulin ring complexes, are MTOCs that nucleate the assembly of new microtubules away from the centrosome.
- Loss of γ-TuRCs prevents a cell from nucleating microtubules, impacting cellular functions.
Test your knowledge of microtubules with this quiz on their structure, assembly, and function. Explore the composition of microtubules, their polymerization process, and the impact of GTP hydrolysis. Dive into the role of microtubule-organizing centers (MTOCs) and centrosomes in nucleating and organizing microtubules within cells.
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