Lecture 5 Flashcards
What is the role of the cytoskeleton?
To help maintain cell shape.
How does the cytoskeleton allow rapid changes in cell shape
This is due to the cytoskeletons ability to disassemble and reassemble.
The cytoskeleton is highly dynamic but still provides stability
What are the three main components that make up the cytoskeleton
Microtubules, Microfilaments, Intermediate filaments
What are microtubules composed of?
Tubulin subunits
What is the function of microtubules
Microtubules resist compression and thus help maintain cell shape
What is motility
the ability of an organism to move independently.
What kind of motion is flagella
Snake-like motion. eg. sperm cells
What kind of motion is cilia
rowing-like motion
How are microtubules also involved with organelle motility within the cell
Because ATP-powered motor proteins can walk organelles along microtubules.
This allows vesicles or other organelles to be transported to specific targets within the cell
What are microfilaments composed of
Microfilaments are a double chain of actin subunits
What do microfilaments form
They form linear strands and 3-dimenstional networks using branching proteins
What is the function of microfilaments
Microfilaments resist tension
How does the cortical network of Microfilaments (underneath the plasma membrane) help maintain cell shape
The dense cortical network makes the reigon less fluid, thus maintains cell shape
What are intermediate proteins made up of
Various proteins such as Keratins in the hair, lamins in the nucleus, neurofilaments in neurons
How are intermediate filaments structured
They are coiled into cables
What is the function of Intermediate filaments
They maintain cell shape and anchor organelles
How come intermediate filaments are able to stay behind after the cell has died?
This is because intermediate filaments are relatively permanent cellular stuctures
What are the three major types of cell junctions
Tight Junctions, Desmosomes, Gap junctions
What is the function of tight junctions
They hold neighboring cells tightly pressed together
May form continuous seal
Prevents movement of fluid across cell layers
What is the function of Desmosomes
They are an anchoring junction. They provide attatchments between sheets of cells eg. muscle
When you have torn your muscle, what cell juction has been torn
You have a torn desmosome
How are desmosomes connected into the cell
Desmosomes are connected into the cell by intermediate filaments.
What is the function of Gap junctions
To allow ions and small molecules to pass from cell to cell.
This allows rapid intercellular communitcaion
What are gap junctions
A point of cytoplasmic contact between two cells
What is ECM composed of
Material secreted by cells
By what process does secretion of ECM material occur
Constitutive Exocytosis
What are proteoglycans
Proteins with extensive sugar additions
What is the functions of proteoglycans in the EXM
Proteoglycans trap water. Water resists compression and thus helps retain tissue shape
What attatches the cells to the ECM
Fibronectins (these are glycoproteins)
What attaches the ECM to the cytoskeleton
Integrins
Define the ECM
The extracellular matrix (ECM) is the non-cellular part of tissues and is
secreted via constitutive exocytosis
