Lecture 8 Flashcards
What is the purpose of the cytoskeleton?
To help maintain cell shape and the positions of organelles.
What are the three major components of the cytoskeleton?
- microtubules
- intermediate filaments
- microfilaments
The cytoskeleton is highly _______ but still provides _______.
The cytoskeleton is highly DYNAMIC but still provides STABILITY.
How are microtubules structured?
“Tubes”
• composed of tubulin subunits
• may radiate out from an
organizing centre (centrosome)
What is the function of microtubules?
• resist compression
• provide cell motility:
- whole cell
-organelle movement
What do cilia consist of?
Microtubules
What motion do cilia make and what 2 functions does this provide?
A “rowing like” motion which can move the cell forward or move fluid past the cell when stationary.
ATP-powered motor proteins can “walk” __________ or vesicles along ____________.
ATP-powered motor proteins can “walk” ORGANELLES or vesicles along MICROTUBULES.
What is the structure of a microfilament?
"Ropes" • double chain of actin subunits • forms linear strands and threedimensional networks (with the aid of branching proteins)
What are the main functions of microfilaments?
- resist tension
- cortical network under plasma membrane helps maintain cell shape
- provide a gel-like consistency to outer cytoplasm.
What type of microfilaments support movement?
Linear actin microfilaments support movement. (eg. in muscle.)
What is the structure of intermediate filaments?
“Cables”
Coiled, less dynamic than MT or MF. Made up of various proteins.
What is the function of intermediate filaments?
• maintain cell shape
• anchor organelles
• nuclear lamina
• neuronal processes
– neurofilamentsHow are cells joined together?
- cell junctions
* the extracellular matrix
What are the 3 types of cell junctions?
- Tight junctions
- Desmosomes
- Gap junctions.
What are the functions of tight junctions?
• keep neighboring cells tightly pressed together
• may form a continuous seal
• prevent movement of fluid
across cell layers
What are the functions of desmosomes?
- anchoring junction
- attachments between sheets of cells e.g. muscle
- act like rivets (a “torn muscle” is a torn desmosome)
What are the functions of gap junctions?
- a point of cytoplasmic contact between cells
- ions and molecules may pass from cell to cell
- allow rapid intercellular communication
ECM composed of…
- material secreted by cells (fibroblasts)
- mainly glycoproteins (protein with carbohydrate)
- most abundant glycoprotein is collagen
What makes up approx. 50% of the total body protein, and exists in the ECF?
Collagen fibres
What kind of strength do collagen fibres have?
Great tensile strength.
What causes scurvy?
A lack of vitamin C results in failure of collagen synthesis. Also, hydroxyproline amino acids cannot be formed and collagen fibres can’t link correctly.
Collagen is embedded in a _______ ______
Proteoglycan matrix
What is the function of proteoglycan matrix in the ECM?
- traps water in ECM
* resists compression and retains shape
Some glycoproteins (_________) attach cells to ECM. Membrane proteins (_______) link ECM to cytoskeleton - a communication link from ECM to the cell interior
Some glycoproteins (FIBRONECTINS) attach cells to ECM. Membrane proteins (INTEGRINS) link ECM to cytoskeleton - a communication link from ECM to the cell interior.
