Cell Organization and Motility
Cells come in many shapes:
Muscles Bundle of muscle fibres multinucleated muscle cell Myofibril
Cells are highly organized structures
Muscle cells can morph into short fat cells from being long and cylindrical
• Dendrites: signal receiving part of the cell
• Axon: sends signal from one place to the other
• Different morphologies of cells that are quite similar
• Genome of all the cells are the same (have all the same DNA)
How is it that all these cells with same DNA differentiate?
Cells are internally organized Two domains:
Apical domain (sees the inside/lumen of intestine)
Basolateral makes connection with extracellular matrix.
Cells have the ability to import and export cargo
Cells can migrate into wounds – not only bacteria that can move around, but cells within
our own body can migrate.
Movement of cells is for healthy physiology/function of cell
Also prevalent in disease, metastasizing cells crawling into the body, punching
through epithelial cells
Cell constructs a cytoskeleton that shapes it just like our skeleton shapes us.
They make small building blocks that are able to self-assemble.
Key role in cell physiology
The Cytoskeleton plays a key role in cell physiology and metabolism
Shape, structure and stability
Contractility (eg: muscle) and motility
Spatial organization (apical versus basolateral domains) Microfilaments
-made of actin monomers, polymerize
-two-stranded helical structure
-play role in structure of cells because stiffer
-longer protofilament structures (13 of them form hollow tube)
-can be considered as one unit
-formation of nuclear lamina - gives nucleus mechanical structure
-huge number of diseases associated with laminothopies.
1 Microtubules = Poles Very stiff
2 Resistant to compression; - large, rigid, hollow tubes. like
plexi-glass, will not buckle under a lot of compression, resistant to
4 Actin Filaments = Wires, High tensile strength
5 But flexible; - if you pull from both ends, won't break;
Intermediate Filaments = Ropes, Elastic and flexible; if you pull
on them, they stretch, they have the ability to slide relative to one
Cytoskeleton similar to scaffold at a construction site (loose analogy) Actin is an ATPase that drives cell motility.
It was discovered in 1942 by Bruno Straub, a Hungarian biochemist.
-has ATP-binding cleft
-spend ATP by polymerizing actin
-if translocate a cell across a distance -- it takes energy/work
-the energy comes from ATP hydrolysis of actin.
-actin first purified from muscle tissue