Lecture 15 - The Cytoskeleton I - Structure Flashcards
What are the functions of the cytoskeleton (7)?
- maintains cell shape
- helps with internal organization
- allows for cell movement
- support plasma membrane
- provides mechanical strength
- separates chromosomes
- assists in cell division
What is hereditary spherocytosis?
- defect in RBC cytoskeleton causing RBC’s to be fragile
- results in hemolytic anemia
__________ consist of linear strings of protein subunits which are thermally (stable/unstable) __________.
Protofilaments; unstable
What are the types of filaments found in the cytoskeleton?
- actin filaments
- microtubules
- intermediate filaments
What are the functions of actin filaments? (4)
- cell surface shape
- cell locomotion
- secretion
- endocytosis
Describe the structure and characteristics of actin filaments.
- two stranded, helical polymer
- actin subunits
- 5-9nm in diameter
- flexible
Describe the structure and characteristics of microtubules.
- hollow cylinders
- tubulin monomers
- 25nm diameter
- rigid
- one end attached to centrosome
What are the functions of microtubules? (3)
- make centrioles and mitotic spindle
- make cilia and flagella
- directed intracellular transport
Describe the structure and characteristics of intermediate filaments.
- 10nm diameter
- rope-like
- large, heterogenous family of monomers
- strong
What are the functions of intermediate filaments?
-span from cell junction to cell junction strengthening epithelial sheets
What is the structure of polymerized actin?
- two actin filaments arranged in a helical manner
- plus ends oriented in the same direction
What conditions are conducive to actin growth?
-high concentrations of ATP-actin
What is the structure of polymerized microtubules?
- 13 filaments arranged in a staggered cylindrical fashion
- filaments consist of alternating α-tubulin and β-tubulin
- held together by α-β, α-α, and β-β interactions
What is nucleation?
-initial aggregation of subunits required for formation of of actin or microtubule polymers
What are the stages of filament formation?
- nucleation
- elongation
- steady state
