BIOL 201 Lecture Notes - Lecture 11: Cdc42, Formins, Buckminster Fuller
Microfilaments can assemble into a wide variety of different types of
structures within a cell, each of these diverse structures underlies
particular cellular functions
•
Cells that line inner cheek are wide and flat, in contrast to muscle tissue
are long skinny multinucleated tubes that can contract
•
Neurons have most elaborate morphology - complex dendritic arbor
and signalling axon that transmit signals
•
All have the same genome and set of proteins, so how do all these
different morphologies arise?
•
Cells come in many shapes
Ex apical side of intestine cell has microvilli that absorb
nutrients from food, and basal lining
○
Cells have to know where to build structures in relation
to other tissues
○
Have compartments with specialized protein
composition
○
Cells know which is their top and which is their bottom
•
Cells are internally organized
Cells that secrete hormones, enzymes, etc.
•
Must be transported to the surface of the cell to be released into
extracellular space
○
These are all made inside the cell, exit via Golgi apparatus
•
Must be brought to nucleus or internal cellular structure
○
Engulfment of signalling molecules secreted by other cells
•
Motor proteins that allow intracellular transport
•
Cells import and export cargo
Migration of cells towards wound essential for healing
○
Inflammatory response to attack invading pathogens
○
Cells migrate into wounds
•
Neurons migrate out into cerebral cortex in lamellar fashion
○
Also occurs in development
•
Cells move!
The cytoskeleton plays key roles in cell physiology and metabolism, like a skeleton made of bone
determines the morphology of the entire organism
•
cell arranges its cytoskeleton to determine cell shape and polarity
•
provide spatial organization and motility to its organelles (intracellular transport)
•
structural framework for processes such as cell swimming, cell crawling, contraction
•
Actin filaments are the most researched and most invested in
•
Cells construct an internal skeleton called the “cytoskeleton"
The cytoskeleton is a type of “tensegrity structure”
•
Very stiff, resistant to compression
○
Hollow tubes
○
Useful in cell division
○
Extend out from nucleus
○
Microtubules = Poles
•
High tensile strength, but flexible
○
Composed of many monomers to allow arbitrary length
○
Actin Filaments = Wires
•
Elastic and flexible
○
Intermediate Filaments = Ropes
•
Held together by tension, not compression
○
All elements being pulled apart gives structure its shape
○
“Tensegrity” was coined by Buckminster Fuller and explains
geodesic domes
•
The cytoskeleton is made of 3 major polymer systems
Discovered in 1942 by Bruno Straub, Hungarian biochemist, in the
lab of Albert Szent-Györgyi
•
Uses energy to promote motion
•
Purified from muscle where it is highly enriched
•
Have polarity: notch face towards (-) end and smooth end is
(+) end (simply fast growing, not charged)
○
Actin polymerizes into a two-stranded helical filament
•
Actin is a major component of muscle- large part of sarcomeres
that cause contraction
•
Cells control: Length, Number, Angle, Bundling, Orientation
○
Actin filaments are arranged differently at distinct intracellular
locations
•
Actin is an ATPase that drives cell motility
Lecture 11: Cell Organization and Motility
February 6, 2018
5:08 PM
Document Summary
Microfilaments can assemble into a wide variety of different types of structures within a cell, each of these diverse structures underlies particular cellular functions. Cells that line inner cheek are wide and flat, in contrast to muscle tissue are long skinny multinucleated tubes that can contract. Neurons have most elaborate morphology - complex dendritic arbor and signalling axon that transmit signals. Cells know which is their top and which is their bottom. Ex apical side of intestine cell has microvilli that absorb nutrients from food, and basal lining. Cells have to know where to build structures in relation to other tissues. These are all made inside the cell, exit via golgi apparatus. Must be transported to the surface of the cell to be released into extracellular space. Engulfment of signalling molecules secreted by other cells. Must be brought to nucleus or internal cellular structure. Migration of cells towards wound essential for healing.
