Lecture 20- Intermediate Filaments

Question 1

Two important things to note in intermediate filaments

Answer 1

1. Because there’s so many of them joined together, there’s no (+) or (-) end.
2. They are all or none (either subunits form into filament or not)

Question 2

Structure of intermediate filaments. What are they made of?

Answer 2

Made of 2 polypeptide come together to form a homodimer

Question 3

Where can you find intermediate filaments?

Answer 3

Found only in vertebrates and in a number of soft-bodied animals.

Found in animal cells that require a lot of strength (such as the epithelial cells of the skin).

Question 4

Assembly and disassembly of intermediate filaments

A. Treadmillling
B. Dynamic instability
C. Both A & B
D. Neither A nor B

Answer 4

Neither A nor B

Question 5

Intermediate filaments are made of ___ proteins

Answer 5

Cytokeratin

Question 6

Why is intermediate filament stability desirable?

Answer 6

1. IFs are made of cytokeratin proteins
2. IFs with nuclear lamin proteins line the inside of the nuclear envelope
3. IFs with extracellular keratin proteins form hair, nails, claws, horns, feathers, etc.

Question 7

What are the three protein subunits of intermediate filaments?

Answer 7

1. Cytokeratins- found in cytoskeleton
2. Nuclear lamins- found in nuclear lamina
3. Extracellular keratins- found in hair, nails, etc.