Lecture 9

Question 1

Cytoskeleton

Answer 1

It’s the structure of all cells. Without cyto, every cell would be spherical, with organelles floating around randomly.

Question 2

What are the three major types of filaments that make up the cytoskeleton?

Answer 2

Microtubules, actin filaments, and intermediate filaments.

Filaments are polar and dynamic structures, and are made of many smaller subunits and require energy to assemble.

Question 3

How are actin and tubulin structures are nucleated?

Answer 3

Nucleation of a microtubule is relatively slow. α and β-tubulin in a test tube form microtubules spontaneously, but only very slowly. However, in a cell, this nucleation takes place on, and is accelerated by, a specialized third form of tubulin called γ-tubulin.

Question 4

What is treadmilling?

Answer 4

loss of actin from - end, addition of actin to + end

Question 5

What is dynamic instability?

Answer 5

elongation/shrinkage can be regulated by cell. Can be controlled.

Question 6

What are some molecular motors and what do they do?

Answer 6

Kinesins- use ATP to move cargo proteins; typically
the majority of kinesins move from - to + ends of microtubules.
cytoplasmic dyneins- use ATP to move cargo proteins
from + to - ends of microtubules