Cytoskeleton

Question 1

What are the three components of the Cytoskeleton?

Answer 1

-Intermediate Filaments
-Microtubules
-Actin Filaments

Question 2

Why are Intermediate Filaments Important?

Answer 2

-Important for managing cellular mechanical stress In Nerve, Muscle, and Epithelial cells

> Stretch and Distribute the force applied to them
rope-like structure

Question 3

What is the Monomer of an Intermediate Filament?

Answer 3

A single protein made from a single polypeptide

-N and C terminus have globular heads
-alpha-helical domain region
-Surface is exposed to allow for interactions

Question 4

What is the Intermediate coiled-coil heterodimer?

Answer 4

Forms from two monomers (single protein polypeptides)

-Intermediate filament monomers wrap around each other at the alpha-helical domain
-Held together by hydrophobic non-covalent bonds

Question 5

How is the Intermediate Filament rope built?

Answer 5

• two coiled homodimers associate in a staggered position
  -run anti-parallel to one another
  -no directionality to the molecule

Question 6

How many tetramers pack together to form Intermediate Filaments?

Answer 6

Eight
-bind side by side and then twist together
-> creates the rope structure

Question 7

What do Intermediate Filaments Provide to the Cell?

Answer 7

Strength
-stretch and distribute the force applied to them.

Question 8

What happens if cells didn’t have Intermediate Filaments?

Answer 8

They would stretch and rupture the cell. basically tear in half from mechanical stress

Question 9

How do Intermediate Filaments maintain Cellular Stress?

Answer 9

Switch between Alpha-Helical form and Beta Sheets.
-When there is no mechanical stress the IF’s are alpha helical, but when stretching/mechanical stress is occurring the alpha-helical domains form into beta sheets.

THINK OF A SLINKY

Question 10

Three types of Cytoplasmic Intermediate Filaments

Answer 10

1. Keratin Filaments: Epithelial Cells
2. Vimentin: Muscle/ Connective tissue
3. Neurofilaments: Nerve cells

Question 11

One type of Nuclear Intermediate Filament

Answer 11

Nuclear Lamins

-Inside the nucleus, in all animal cells not red blood cells)

Question 12

What do Intermediate filaments need for stability?

Answer 12

Accessory Proteins
- Hold IF’s together
-Link IF’s to desmosomes
-required to help cells withstand mechanical stress

Question 13

EX. of an Intermediate Filament Accessory Protein

Answer 13

Plectin

Question 14

Keratin Filaments

Answer 14

Provide strength and resilience to Hair, Skin, and Nail cells
-All epithelial tissues contain keratin proteins
-humans have at least 54 keratin genes

Question 15

Rare Human Genetic Disease in Keratin Filaments

Answer 15

Epidermolysis bullosa simplex

Question 16

Keratin Filaments span the entire cytoplasm of epithelial cells and link to neighboring cells by

Answer 16

Desmosomes

Question 17

Vimentin

Answer 17

Found in Connective tissues/ Bone and Muscles
MAJOR ROLE: provide support and anchor the nucleus, mitochondria, and ER

Question 18

Neurofilaments

Answer 18

Found in the cytoplasm of neurons, especially the axons
MAJOR ROLE: help support the axons and provide space-filled properties to provide diameter.
–> diameter increases by electrochemical inpulses

Question 19

Nuclear Lamins

Answer 19

form a meshwork, found beneath the nuclear envelope that provides mechanical support

Question 20

How to Nuclear Lamins Disassemble?

Answer 20

when phosphorylated in the early stages of mitosis as the nuclear envelope breaks down

Question 21

How do Lamins assemble

Answer 21

reassemble by dephosphorylation in late mitosis to form nuclei in daughter cells