microtubules Flashcards
How do microtubules generate motility within cells?
Through interactions with motor proteins like kinesin and dynein, which move cargo along microtubule tracks
What role does kinesin play in microtubule-based motility?
Kinesin moves cargo toward the plus end of microtubules, usually from the cell center toward the periphery.
What role does dynein play in microtubule-based motility?
Dynein moves cargo toward the minus end of microtubules, typically transporting it toward the cell center.
How do microtubules contribute to the movement of cilia and flagella?
By forming axonemes, structures with microtubules and dynein arms that slide to create bending motion in cilia and flagella
What is an axoneme?
The core structure of cilia and flagella, consisting of a “9+2” arrangement of microtubules and dynein motors that generate movement.
How does dynein generate motility in cilia and flagella?
Dynein arms attached to one microtubule doublet “walk” along an adjacent doublet, causing bending that produces ciliary or flagellar motion.
What is the role of microtubules in mitotic spindle formation?
responsible for the separation and distribution of chromosomes to daughter cells
How does microtubule polymerization and depolymerization contribute to motility?
By rapidly assembling and disassembling, microtubules can push or pull structures, aiding in cellular processes like mitosis and cell migration.
What is the basic structure of cilia and flagella?
They have an axoneme structure with a “9+2” arrangement of microtubules: nine doublets in a ring around two central singlet microtubules.
What role do dynein motors play in the movement of cilia and flagella?
Dynein motors attach to one microtubule doublet and “walk” along an adjacent doublet, creating sliding forces
How does dynein activity result in the bending of cilia and flagella?
Dynein-generated sliding between microtubule doublets is constrained by linking proteins, converting sliding into bending.
What is the role of nexin in cilia and flagella?
Nexin is a linking protein that connects adjacent microtubule doublets, helping to translate sliding forces into bending
How is the beating pattern of cilia and flagella regulated?
The coordinated activation and inactivation of dynein arms along the axoneme generate rhythmic bending patterns.
What is the role of the central pair of microtubules in cilia and flagella?
The central pair of singlet microtubules may help regulate dynein motor activity and coordinate the beating pattern.
How do cilia and flagella differ in their beating motion?
cilia beat in a back and forth motion
flagella beat in a wave motion
How does ATP influence dynein and microtubule interaction in cilia and flagella?
ATP provides the energy for dynein to “walk” along microtubules, which is essential for generating the sliding and bending forces.
What role do microtubules play in mitosis?
They form the mitotic spindle, which organizes and separates chromosomes during cell division.
What are the three types of microtubules in the mitotic spindle?
Kinetochore microtubules, polar microtubules, and astral microtubules
What is the function of kinetochore microtubules?
They attach to chromosomes at the kinetochores and pull sister chromatids apart during anaphase.
What is the function of polar microtubules?
They overlap with microtubules from the opposite pole, helping push the spindle poles apart during anaphase
What is the function of astral microtubules?
They anchor the spindle poles to the cell cortex, helping position the spindle within the cell
What role does the motor protein dynein play in mitosis?
Dynein helps anchor astral microtubules to the cell cortex and aids in pulling the spindle poles apart.
What role does the motor protein kinesin-5 play in mitosis?
Kinesin-5 pushes polar microtubules from opposite spindle poles apart, assisting in spindle elongation during anaphase
How do microtubules and motors contribute to chromosome alignment during metaphase?
Kinetochore microtubules, along with motor proteins, generate forces to align chromosomes at the metaphase plate
How does depolymerization of microtubules aid in chromatid separation?
Depolymerization at the kinetochore microtubule ends generates force to pull sister chromatids toward opposite poles in anaphase
What is the role of kinesin-4 and kinesin-10 in mitosis?
These motors help move chromosomes along microtubules toward the metaphase plate during prometaphase.
What are the main stages of mitosis?
Prophase, prometaphase, metaphase, anaphase, and telophase.
What happens to microtubules during prophase?
Microtubules begin to reorganize, and the mitotic spindle starts forming as centrosomes move to opposite poles
What changes occur in microtubule organization during prometaphase?
The nuclear envelope breaks down, allowing spindle microtubules to attach to kinetochores on chromosomes.
How are microtubules organized during metaphase?
Kinetochore microtubules align chromosomes along the metaphase plate, with polar microtubules overlapping at the spindle equator.
What is the role of kinetochore microtubules in metaphase?
They attach to chromosomes at the kinetochores, holding them in place at the metaphase plate
How does microtubule organization change during anaphase?
Kinetochore microtubules shorten, pulling sister chromatids to opposite poles, while polar microtubules lengthen to push the poles apart
What is the role of astral microtubules during anaphase?
They interact with the cell cortex, helping position the spindle and pull the spindle poles apart.
What happens to microtubules during telophase?
The spindle disassembles, and microtubules reorganize to support the reformation of the nuclear envelope around separated chromosomes
How does cytokinesis relate to microtubule organization?
Although not part of mitosis, microtubules position the cell’s center, helping the actin-myosin contractile ring divide the cytoplasm
