lecture 6 - cell shape regulation Flashcards
How is the cytoskeleton dynamic?
The components of the cytoskeleton are cosntantly assembling and disassembling to rapidly change the shape of the cell.
What are the three components of the cytoskeleton that provide structure?
Microtubules, Microfilaments, Intermediate filaments
What are microtubules made up of?
Tubulin subunits (dimers) in a twisted helix tube.
What organelle do microtubules sometimes radiate out from?
Centrosomes
What are centrosomes?
An organising centre, that is sometimes surrounded by microtubules, e.g. during the formation of the mitotic spindle
What type cytoskeleton component best resists compression?
microtubules
What structures create cell motility?
Flagella and cilia
What are the cytoplasmic components of flagella and cilia?
Microtubules
What is the role of cilia in a fixed cell?
The cilia beat back and forth, moving fluid/mucous past.
How do the microtubules aid in organelle motility?
ATP powered motor proteins are able to attach to vesicles/other organelles and walk along microtubules to their targets.
What is the structure of microfilaments?
Double chains of actin subunits that twist around each other.
Actin is the component of what cytoplasmic structural component?
Microfilaments
What structures can microfilaments form?
linear strands and 3D networks
What is required to allow microfilaments to branch?
branching proteins
How do microfilaments make the cell rigid?
They form a cortical network which replaces fluid in the cytoplasm, stiffening the cell.
How do microfilaments aid in cell movement?
Actin in the microfilaments interacts with motor proteins to facilitate movement.
What interaction leads to muscle contraction?
Actin-myosin interactions.
What do Actin-Myosin interactions allow?
Muscle contraction, amoeboid movement, cytoplasmic streaming (in plants).
What are two common proteins that make up intermediate filaments?
Keratin, Lamin
How are intermediate filaments structured?
proteins are supercoiled into tight ‘cables’
What is the least dynamic cytoplasm tubule/filament?
Intermediate filaments.
What aids in maintaining structure in dead cells, such as hair and skin?
Intermediate filaments.
What are the 3 major cell junction types?
Tight junctions, desmosomes, gap junctions
What are tight junctions?
Junctions that press neighbouring cells close together, creating a continuous seal that prevents the movement of fluid between layers of cells.
What are desmosomes?
Anchoring cell junctions that attach cells in sheets.
What form of cell junctions are prevelant in muscle tissue?
Desmosomes
What connects desmosomes into the cell?
Intermediate filaments
What are gap junctions?
A point of cytoplasmic contact between two cells that allows ions and small molecules to move between cell cytoplasms via protein bridges.
What cell junction allows for rapid intercellular communication?
Gap junctions
Where do the materials of the extracellular matrix come from?
The are secreted from the cell via consituitive exocytosis.
What is the most common category of proteins in the ECM?
Glycoproteins.
What are glycoproteins?
Proteins with added carbohydrate groups.
What is the most abundant protein in the extracellular matrix?
Collagen
What are collagen fibres in the extracellular matrix embedded in?
Proteoglycans.
What are proteoglycans?
Proteins with extensive sugar additions that exist in the extracellular matrix, embedded with collagen.
What component of the ECM allows it to resist compression? And how?
Proteoglycans - They trap water, which resists breakage when compressed.
What are fibronectins?
Glycoproteins that attach cells to components of the ECM.
What are integrins?
Membrane proteins that connect the ECM to the cytoskeleton, allowing them to communicate.
What is the most dynamic cytoplasmic protein structure?
Actin (microfilaments)
