microtubules

Question 1

How do microtubules generate motility within cells?

Answer 1

Through interactions with motor proteins like kinesin and dynein, which move cargo along microtubule tracks

Question 2

What role does kinesin play in microtubule-based motility?

Answer 2

Kinesin moves cargo toward the plus end of microtubules, usually from the cell center toward the periphery.

Question 3

What role does dynein play in microtubule-based motility?

Answer 3

Dynein moves cargo toward the minus end of microtubules, typically transporting it toward the cell center.

Question 4

How do microtubules contribute to the movement of cilia and flagella?

Answer 4

By forming axonemes, structures with microtubules and dynein arms that slide to create bending motion in cilia and flagella

Question 5

What is an axoneme?

Answer 5

The core structure of cilia and flagella, consisting of a “9+2” arrangement of microtubules and dynein motors that generate movement.

Question 6

How does dynein generate motility in cilia and flagella?

Answer 6

Dynein arms attached to one microtubule doublet “walk” along an adjacent doublet, causing bending that produces ciliary or flagellar motion.

Question 7

What is the role of microtubules in mitotic spindle formation?

Answer 7

responsible for the separation and distribution of chromosomes to daughter cells

Question 8

How does microtubule polymerization and depolymerization contribute to motility?

Answer 8

By rapidly assembling and disassembling, microtubules can push or pull structures, aiding in cellular processes like mitosis and cell migration.

Question 9

What is the basic structure of cilia and flagella?

Answer 9

They have an axoneme structure with a “9+2” arrangement of microtubules: nine doublets in a ring around two central singlet microtubules.

Question 10

What role do dynein motors play in the movement of cilia and flagella?

Answer 10

Dynein motors attach to one microtubule doublet and “walk” along an adjacent doublet, creating sliding forces

Question 11

How does dynein activity result in the bending of cilia and flagella?

Answer 11

Dynein-generated sliding between microtubule doublets is constrained by linking proteins, converting sliding into bending.

Question 12

What is the role of nexin in cilia and flagella?

Answer 12

Nexin is a linking protein that connects adjacent microtubule doublets, helping to translate sliding forces into bending

Question 13

How is the beating pattern of cilia and flagella regulated?

Answer 13

The coordinated activation and inactivation of dynein arms along the axoneme generate rhythmic bending patterns.

Question 14

What is the role of the central pair of microtubules in cilia and flagella?

Answer 14

The central pair of singlet microtubules may help regulate dynein motor activity and coordinate the beating pattern.

Question 15

How do cilia and flagella differ in their beating motion?

Answer 15

cilia beat in a back and forth motion
flagella beat in a wave motion

Question 16

How does ATP influence dynein and microtubule interaction in cilia and flagella?

Answer 16

ATP provides the energy for dynein to “walk” along microtubules, which is essential for generating the sliding and bending forces.

Question 17

What role do microtubules play in mitosis?

Answer 17

They form the mitotic spindle, which organizes and separates chromosomes during cell division.

Question 18

What are the three types of microtubules in the mitotic spindle?

Answer 18

Kinetochore microtubules, polar microtubules, and astral microtubules

Question 19

What is the function of kinetochore microtubules?

Answer 19

They attach to chromosomes at the kinetochores and pull sister chromatids apart during anaphase.

Question 20

What is the function of polar microtubules?

Answer 20

They overlap with microtubules from the opposite pole, helping push the spindle poles apart during anaphase

Question 21

What is the function of astral microtubules?

Answer 21

They anchor the spindle poles to the cell cortex, helping position the spindle within the cell

Question 22

What role does the motor protein dynein play in mitosis?

Answer 22

Dynein helps anchor astral microtubules to the cell cortex and aids in pulling the spindle poles apart.

Question 23

What role does the motor protein kinesin-5 play in mitosis?

Answer 23

Kinesin-5 pushes polar microtubules from opposite spindle poles apart, assisting in spindle elongation during anaphase

Question 24

How do microtubules and motors contribute to chromosome alignment during metaphase?

Answer 24

Kinetochore microtubules, along with motor proteins, generate forces to align chromosomes at the metaphase plate

Question 25

How does depolymerization of microtubules aid in chromatid separation?

Answer 25

Depolymerization at the kinetochore microtubule ends generates force to pull sister chromatids toward opposite poles in anaphase

Question 26

What is the role of kinesin-4 and kinesin-10 in mitosis?

Answer 26

These motors help move chromosomes along microtubules toward the metaphase plate during prometaphase.

Question 27

What are the main stages of mitosis?

Answer 27

Prophase, prometaphase, metaphase, anaphase, and telophase.

Question 28

What happens to microtubules during prophase?

Answer 28

Microtubules begin to reorganize, and the mitotic spindle starts forming as centrosomes move to opposite poles

Question 29

What changes occur in microtubule organization during prometaphase?

Answer 29

The nuclear envelope breaks down, allowing spindle microtubules to attach to kinetochores on chromosomes.

Question 30

How are microtubules organized during metaphase?

Answer 30

Kinetochore microtubules align chromosomes along the metaphase plate, with polar microtubules overlapping at the spindle equator.

Question 31

What is the role of kinetochore microtubules in metaphase?

Answer 31

They attach to chromosomes at the kinetochores, holding them in place at the metaphase plate

Question 32

How does microtubule organization change during anaphase?

Answer 32

Kinetochore microtubules shorten, pulling sister chromatids to opposite poles, while polar microtubules lengthen to push the poles apart

Question 33

What is the role of astral microtubules during anaphase?

Answer 33

They interact with the cell cortex, helping position the spindle and pull the spindle poles apart.

Question 34

What happens to microtubules during telophase?

Answer 34

The spindle disassembles, and microtubules reorganize to support the reformation of the nuclear envelope around separated chromosomes

Question 35

How does cytokinesis relate to microtubule organization?

Answer 35

Although not part of mitosis, microtubules position the cell's center, helping the actin-myosin contractile ring divide the cytoplasm