Regulation of animal cell shape Flashcards
What is the cytoskeleton?
It helps maintain cell shape and the position of organelles with in cells. It rapidly disassembles and reassembles. This allows rapid changes in cell shape. It is highly dynamic but still provides stability.
What are microtubules?
Are composed of tubulin subunits, they radiate out from the centrosome. They resist compression and thus help maintain cell shape.
What are microtubules role in cell mortality with whole cells?
Take on an arrangement called flagella which have a “snake-like” motion. As it moves will drive the cell in that direction.
Also form cilia, providing a “rowing-like” motion which is supported by the microtubules. If cells are fixed in place the cilia moves fluid past them.
What are microtubules role in cell mortality within the cell?
Forms a trackway for organelles to be moved across. ATP-powered motor proteins can “walk” organelles along microtubules allowing vesicles or other organelles to be transported to specific targets within the cell.
What are microfilaments?
A double chain of actin subunits, which resist tension. Forms structures within cells like linear strands and 3D networks using branching proteins.
Helps make the cortical network under the plasma membrane less fluid and thus maintain cell shape
What are microfilaments roles in cell motility?
Interactions between actin and myosin (a moto protein) support cell movement. This interaction allows:
- muscle contraction
- amoeboid movement (allows cells to change their shapes)
- cytoplasmic streaming in plants
What are intermediate filaments?
Are made of various proteins including: - Keratins in hair - Lamins in the nucleus - Neurofilaments in neurons They are supercoiled into "cables". Less dynamic than microtubules and microfilaments. They form relatively permanent cellular structures.
What are intermediate filaments jobs?
They help maintain cell shape and anchor organelles.
- They may also remain after the cell that made them has died, as in your hair and outer layer of skin.
How are cells joined together?
Three major types of cell junctions: - Tight junctions - Desmosomes - Gap junctions Each of these differ in structure and function
What are tight junctions? What do they do?
- Hold neighbouring cells tightly pressed together
- May form a continuous seal to prevent movement of fluid across cell layers. Wants to control what’s coming in and out.
What are desmosomes? What do they do?
Anchoring junction
- Provide attachments between sheets of cells e.g. muscle
- Act like rivets (a “torn muscle” is a torn desmosome)
- So makes permeant connections (doesn’t want to come apart)
- Connected into the cell by intermediate filaments as they are very strong.
What are gap junctions? What do they do?
A point of cytoplasmic contact between two cells (allows to cytoplasms to be in contact with each other)
- Ions and small molecules can pass from cell to cell
- Allows rapid cell to cell communication (chemical signals)
What is the extracellular matrix?
In many tissues cells do not make direct contact with other cells, cells lie within an extracellular matrix, the composition of which varies between tissues.
What is the extracellular matrix made up of?
Material secreted by cells. This secretion occurs by constitutive exocytosis. Most ECM proteins are glycoproteins (proteins with added carbohydrates).
What is the most abundant glycoprotein in the ECM? Where are these found?
Collagen - have great tensile strength. The collagen fibres are imbedded in a proteoglycan (proteins with extensive sugar additions) complex matrix.
