Cytoskeleton

Question 1

Cytoskeleton

Answer 1

Supportive scaffolding in cell

Composed:

1. ) actin
2. ) microfilaments
3. ) intermediate filaments
4. ) microtubules

Complex of globular and fibrous proteins

Question 2

Actin

Answer 2

Function:
1.) regulation of physical state of cytosol- polymerization of actin

2. ) cell movement- contraction of ____
3. ) Cell division- contraction of ____

Nuclear function:

1. ) structure
2. ) gene transcription

Question 3

Polymerization of Actin

Answer 3

G-actin: globular single subunit

F-actin: filamentous, 2 long strands wound together

1. ) +end: where g-actin is added
2. )-end: where g-actin is removed

Requires energy: each g-actin requires 1 ATP

Question 4

Actin regulation

Answer 4

Function: regulation of physical state of cytosol

Cytosol can be:
1.) Gel: more firm due to longer f-actin strands that are bundled or cross-linked

2.) Soluble (sol): more liquid due to depolymerization of f-actin

Question 5

Actin binding proteins

Answer 5

Profilin: binds G-actin monomer, preventing polymerization

Cofilin: breaks f-actin into smaller segments by twisting action

Gelsolin: fragment f-actin and requires calcium

Spectrin: cross-linking protein important to structure of RBC

Dystrophin: Links actin to basement membrane fo skeletal muscles

Question 6

Intermediate filaments

Answer 6

Support structure

6 types:

1. ) type I and II: Keratins
2. ) type III: contain vimentin and most common in vivo
3. ) type IV: found in neurons

Question 7

Microtubules

Answer 7

Required for movement of chromosomes during division

Necessary for intracellular transport

Synthesis requires energy (GTP)

Regulated by centrosomes: one end is anchored to the centrosome

Question 8

Structure of microtubules

Answer 8

Protofilament

13 protofilaments join to for a hollow ring

GTP cap: where new dimers are added

Question 9

Disassembly of microtubules

Answer 9

______ occurs when dimer addition slows and cap is lost

Causes instability

Question 10

Function of Microtubules

Answer 10

Functions:
1.) chromosomal movement: organize into mitotic spindles

2. ) cilia(dynein-protein) and flagella
3. ) Intracellular movement: dynein and kinesin are called motor proteins