Term
| What are the three major types of cytoskeleton in epithelial cells? |
|
Definition
1. Microtubules
2. Intermediate filaments
3. Actin filaments |
|
|
Term
| Describe the use of intermediate filaments in determining the origin of tumors |
|
Definition
| Different types of cells express different types and combinations of intermediate filaments. Examining the IF composition in a tumor can be useful in determining where it originated. |
|
|
Term
| What is the main role of intermediate filaments? |
|
Definition
| Structural support in cells |
|
|
Term
| what are the 4 sub classes of IFs and where is each found? |
|
Definition
1. Keratins - epithelia
2. Vimentin - connective tissue, muscles, neuroglial cells
3. Neurofilaments - nerve cells
4. Nuclear lamina - all nucleated cells |
|
|
Term
| Where do intermediate filaments bind to the membrane of epithelial cells and what 2 roles does this play? |
|
Definition
A) desmosomes and hemidesmosomes
B) 1. Dispersion of force 2. Mechanochemical sensing |
|
|
Term
| What are the 3 broad class of functions of actin filaments? |
|
Definition
1. Anchors
2. Stability
3. Motility |
|
|
Term
| Describe the polarity of actin thin filaments |
|
Definition
1. + and - ends
2. - end is pointed, + end is "barbed"
3. + end grows (polymerizes) faster then - end
4. Myosin motors migrate from the - toward the + end |
|
|
Term
| Describe how actin can cause movement in the absence of motor such as myosin |
|
Definition
| If the - end is anchored within a cell membrane, addition of units to the + end cause the cell to grow outward into a lemellopedia if the + end reaches and pushes on a cell membrane |
|
|
Term
| What are the 3 parts of a myosin fiber? |
|
Definition
|
|
Term
| Describe the process of myosin motors moving along actin filaments |
|
Definition
1. Nucleotide binding - Binding of ATP to a myosin head causes the head to be released from an actin subunit
2. Hydrolysis - Hydrolysis of ATP to ADP causes pivoting of the head and binding to the next subunit toward the + end
3. P release - Release of the phosphorus group causes the head to pivot and move the actin filament
4. ADP release - ADP is released from the myosin head, allowing the process to begin again |
|
|
