Cytology Flashcards
Cytoskeleton componets
- Microfilaments
- Intermediate filaments
- Microtubules
Functions of cytoskeleton
-Shaping of cells
-Important in cellular movement
Movement of vesicles and organelles in the cytoplasm
Movement of parts of the cell forming pseudopodia
Movement of the cell as a whole as in spermatozoa
- Supportive internal skeleton to the cell
Microfilaments
Synonym
Actin Filaments
Microfilaments
Size
Thin filaments of 6nm in diameter
Microfilaments
Percentage
Actin constitues 15% of total protein content of non-muscle cell
Microfilaments
Sites
In non-muscle cells: form a sheath under the cell membrane and are also present in cell extensions like pseudopodian and microvilli
In muscle cells: ACtin filaments interdigitate with thick myosin filaments in parallel arrays
Microfilaments
Structure
It is found in the cytoplasm in 2 forms:
G-actin: dispersed in the cytosol, not visible with EM, polymerize together to firm F-actin
F-actin: The filament consists of a double stranded helix. Each strand is a polymer of G-actin
Actin filaments ends
Plus end where molecules are added leading t the elongation of the filament
Minus end where actin molecules are removed leading to shortening of actin filaments
Microfilaments
Functions
-Contraction of muscle cells
-Anchorage and movement of membrane proteins
-Movement of plasma membrane as in endo and exocytosis
-Formation of pseudopodia and microvilli
-Locomotion of cells
Formation of contractile ring during cell divisionn
Intermediate filaments
Size
10 nm
Intermediate filaments
Characteristics
Stable structures with neither a plus or minus end
Keratins
Include tonofilaments
They are found in most epithelia
Desmin
In muscles
Vimentin
In fibroblasts
Neurofilaments
In neurons (axons and dendrites)
Glial filaments
In neuroglial cells
Intermediate filaments
Sites in the cytoplasm
- Keratin
- Desmin
- Vimentin
- Neurofilaments
- Glial filaments
Intermediate filaments
Sities in the nucleus
Lamins
Microtubules
Sites
Cytoplasm of all cells except RBCs
Microtubules
Size
24 nm