Cellular filaments and Cellular Junctions Flashcards
the structure and motility of the cell is determined by a network of filaments known as the?
cytoskeleton
what does the cytoskeleton do?
it anchors some membrane proteins, and other cellular components , moves components within the cell and moves the cell itself.
what are the 2 major types of filaments in the cytoskeleton?
microtubules and the microfilaments
what are the microtubules?
these are larger then microfilaments, they are rigid hollow tubes made from a protein called tubulin (tubulin is a globular protein)
what causes the spiral appearance of the microtubules?
two types of tubulin are used alpha and the beta in the synthesis.
what two special structures are made from microtubules?
cilia and flagella. the major portion of each flagellum and cilium called axoneme , contains 9 parts of microtubules forming a circle around two lone microtubules in an arrangement known as 9+2.
how does dynein play role in microtubule formation?
cross bridges made from dynein connect each of the outer pairs of microtubules to their neighbour. the cross bridges cause the microtubule pairs to slide along their neighbours creating a whip like action in cilia causing fluid to move laterally or a wiggle action in flagella causing fluid to move directly away from the cell.
what does the - (minus) end of the microtubule do?
it attaches to the microtubule organizing centre of the cell . the microtubule grows away from an MTOC at its + end. the major MTOC in animal cells is the centrosome.
what are microfilaments?
these are smaller than microtubules. protein actin forms a major component of the microfilaments. microfilaments produce the contracting force in muscles and microvilli. they squeeze the membrane together in phagocytosis and cytokinesis.
what are intermediate filaments?
primarily serve to impart structural rigidity to the cell. keratin is an intermediate filament found in epithelial cels and is associated with hair and skin
what is the difference in euykparyotic flagella and the prokaryotic flagella?
eukaryotic flagella is made from a 9+2 microtubule configuration
prokaryotic flagella is a thin strand of single protein called flagellin.
eukaryotic flagella undergo a whip like action , while prokaryotic flagella rotate.
what are the three types of junctions or attachments that connect animal cells?
tight junctions, desmosomes and gap junctions.
what are tight junctions?
watertight seal from cell to cell. they can block water, ions and other molecules from moving around and past cells. tissue held together by tight junctions may act as a complete fluid barrier.
epithelial tissue in organs like bladder, intestines, and kidney are held together by tight junctions in order to prevent waste materials from seeping around the cells and into the body.
what are desmosomes?
join two cells at a single point. they attach directly to the cytoskeleton of each cell. found in tissues that experience a lot of stress like skin or intestinal epithelium. they often accompany tight junctions.
what are gap junctions?
these are small tunnels connecting cells, they allow small molecules or grins to move between cells.
they are in cardiac cells and provide for the spread of action potential from cell to cell
