Motility and Motor Proteins Flashcards
What is motility?
Movement or shortening of a cell, movement of components within a cell, or movement of environmental components past or through a cell
What is contractility?
Shortening of muscle or other cells
What are motor proteins?
Protein that uses energy derived from ATP to change shape in a way that exerts force and causes attached structures to move; includes three families of proteins (myosin, dynein, and kinesin) that interact with cytoskeleton elements (microtubules and microfilaments) to produce movements
What are some motor molecules of eukaryotic cells?
- Microfilament-associated (actin-binding) proteins
Includes Myosin I (monomer) and Myosin II (filament) - Microtubule-associated proteins
Includes cytoplasmic dynein, axonemal dynein, and kinesin
What is the function of Myosin I and II?
Myosin I: motion along actin filaments
Myosin II: thick filament of muscle cell
What is the function of cytoplasmic dynein, axonemal dynein and kinesin?
Cytoplasmic dynein: motion toward minus end of microtubule
Axonemal dynein: activation of sliding in flagellar microtubule
Kinesin: motion toward plus end of microtubule
How does kinesins move toward the plus end of microtubules?
- leading heavy chain binds ATP
- ATP binding causes conformational change; trailing heavy chain swings forward
- Trailing heavy chain finds new MT binding site
- New leading heavy chain releases ADP; new trailing head hydrolyzes ATP to ADP + Pi. Pi is released
What is cilia?
Membrane-bounded appendage on the surface of eukaryotic cell, composed of a specific arrangement of microtubules and responsible for motility of the cell or the fluids around cells; shorter and more numerous than flagella
What is flagella?
Membrane-bounded appendage on the surface of a eukaryotic cell composed of a specific arrangement of microtubules and responsible for motility of the cell; longer and less numerous than cilia
Cilia and flagella share a common structure, known as the _____ that is connected to a basal body and surrounded by an extension of the cell membrane
axoneme
What is an axoneme?
Group of interconnected microtubules that form the backbone of a eukaryotic cilium or flagellum, usually arranged as nine outer doublet microtubules surrounding a pair of central microtubules
What is the basal body?
Microtubule-containing structure located at the base of a eukaryotic cilium or flagellum, usually arranged as nine outer doublet microtubules; identical in appearance to a centriole
How are crosslinks and spokes responsible for bending?
Outer doublet microtubules and associated proteins can be isolated from cilia or flagella. When ATP is added to such preparations after treating with a protease to remove crosslinks, MTs slide apart.
In an intact axoneme, bending occurs via the coordinated action of many dyneins, which slide MTs in an organized pattern
