cytoskeleton Flashcards
cytoskeleton is a network of
fibers
cell’s internal skeleton
animal cells lack a
cell wall
cytoskeleton function
- maintenance of cell shape; resists compression and torsion
- organization of structures within the cell
- organization of processes within the cell; division, movement
- cell motility; cilia, flagella, pseudopodia
- contraction of muscle cells
cytoskeleton consists of 3 types of fibers;
- actin; microfilaments
- tubulin; microtubules
- intermediate filaments
what is most abundant intracellular protein
actin
actin is organized into
microfilaments
solid rods composed of globular actin proteins (subunits) organized into 2 intertwined strands
actin is dispersed throughout the cytoplasm but forms a dense meshwork immediately beneath the
plasma membrane
what determines and maintains the cell’s shape
actin
actin provides mechanical strength by
resisting tensive forces
actin in association w myosin filaments forms contractile structures such as
- muscle cells (sarcomeres)
- cleavage furrow of dividing cells
- pseudopodia
bundles of ___ microfilaments make up the core of microvilli
actin
tubulin is organized into
microtubules
hollow tubes composed of 13 columns of tubulin proteins with alpha and beta-tubulin protein subunits
where is tubulin
distributed throughout cytoplasm
tubulin functions to maintain cell shape via
compression resisting girders that radiate from centrosome
tubulin acts as tracks which organelles can move such as
secretory vesicles from golgi to plasma membrane
tubulin forms centrioles
- located within centrosome
- 9 sets of microtubule triplets
- involved in cell division (mitosis)
during mitosis; centrioles
- move to opposite ends of the cell, microtubules extend from one centriole to the other: spindle
- daughter chromosomes pulled towards each centriole
_____ also present in cilia and flagella
microtubules
what is the only flagellated animal cell
sperm
both cilia and flagella have a _____ microtubule arrangement and at the base is a
9+2
basal body = centriole
intermediate filaments are
fibrous proteins that are coiled to form thick cables
intermediate filaments consist of structurally related proteins including
keraitns, vimentin, demsin, neurofilaments
where are intermediate filaments
distributed throughout cell
intermediate filaments provide maintenance of cell shape by being
tension bearing, anchored to cell membrane
nucleus is enclosed within a cage of
intermediate filaments
5 major classes of intermediate filaments
1) keratin: skin epithelial cells, forms desmosomes
2) vimentin; epithelial cells, neural cells
3) desmin; muscle cells
4) glial filaments; glial cells
5) neurofilaments; neurons
Which of the following statements about the cytoskeleton is INCORRECT?
A.
Actin is dispersed throughout the cytoplasm but forms a dense meshwork beneath the plasma membrane, where it provides mechanical strength by resisting tensive forces
B.
Intermediate filaments anchor the nucleus in its characteristic position for each cell type and also provide mechanical strength to microvilli
C.
Actin is a major component of sarcomeres, the contractile ring associated with the cleavage furrow of dividing cells, and the pseudopodia of amoebae, macrophages, and neutrophils
D.
Tubulin microtubules radiate from the centrosome, forming the tracks along which secretory vesicles travel when moving from the Golgi apparatus to the plasma membrane; tubulin is also organised into centrioles
Intermediate filaments anchor the nucleus in its characteristic position for each cell type and also provide mechanical strength to microvilli
Which of the following statements about the cytoskeleton is INCORRECT?
A.
Actin is concentrated beneath the plasma membrane, where it provides mechanical strength by resisting tensive forces; it also supports the structure of microvilli
B.
Intermediate filaments are responsible for the maintenance of cell shape and anchoring of the nucleus, and are a component of desmosomes
C.
Actin forms the contractile ring associated with the cleavage furrow of dividing cells, and the pseudopodia of amoebae, macrophages, and neutrophils
D.
Tubulin microtubules form centrioles, cilia, and flagella, which consist of nine sets of microtubule doublets plus a central pair (i.e., 9 + 2 arrangement)
D.
Tubulin microtubules form centrioles, cilia, and flagella, which consist of nine sets of microtubule doublets plus a central pair (i.e., 9 + 2 arrangement)
