Cytoskeleton and Cell Division Flashcards
what are the functions of the cytoskeleton
- provide support for plasma membrane and organelles
- intracellular movement/ transport of substances
- cell locomotion
- Mm contractions
what are the 3 main elements of the cytoskeleton
microfilaments, intermediate filaments, and microtubules
-what is the function of microfilaments
maintain cell shape and facilitates shape changes during movement
what are actin strands made of
G-actin subunits
what are protofilaments
when G-actin polymerizes
what makes up F-actin
2 protfilaments twisting together
what does filamin do
forms support meshwork under plasma membrane call cell cortex
what does the cell cortex do
prevents cell from deformaition
what are microfilaments made of
actin and myosin
what is required for movement of microfilaments with myosin
Ca and ATP
what cell types are intermediate filaments found in
- (cyto)keratin
- vimentin
- desmin
- neurofilament proteins
- GFAP
- lamin
where are keratin cells found
epithelial cells, forms tonofibrils
where is vimentin found
mesodermal cells of mesenchymal origin (endothelial cells, muscle, and neuroectodermal cells)
where is desmin found
unique to muscle cells, mesodermal origin
where are neurofilament proteins found
present in nerve cells
where are GFAP proteins found and what does it stand for
- glial fibrillary acidic protein
- found in glial cells of nervous system
where is lamin found
forms layer of inside of nuclear membrane
what are microtubules made of
alpha and beta tubulin
what are the functions of microtubules
- cell movement
- maintenance of cell shape
- intracellular transport of substances
how do microtubules move
via addition or subtraction of tubulin subunits from microtubules
what molecules attach microtubules to organelles
dynein and kynsein
how are microtubules stabilized
capping proteins
what inhibits microtubule polymerization and cell division
colchicine, vincristine and vinblastin
where are microtubules found
- cilia and flagella
- centrioles
- basal bodies of cilia
- mitotic spindles
what are axoneme
9 pairs of microtubules containing dynein arms arranged in a circle with central doublet in the middle
how is the central doublet connected to peripheral doublet
radial spokes
how are peripheral doublets connected to each other
nexin
where are axonemes found
cilia and flagella
where are centrioles located
in the centrosome near the nucleus and functions in cell division
what is a diplosome
centrioles orient at right angles to make a “T” shape
what is a centriole made of
9 triplets of microtubules arranged in a cylinder
how do movement of chromosomes occur in cell division
addition and subtraction of tubulin subunits and attachment of proteins to chromatids at the kinetochore
what are the phases of mitosis
interphase, prophase, metaphase, anaphase, telophase
what is interphase and what are the parts in it
time between divisions, G1, S, G2
what occurs in G1
longest of cell phase, hypertrophy
what happens in the S phase of interphase
- replication of DNA prior to division
- at beginning chromosome # is 2n at end it is 4n
- following replication in S phase, each chromosome contains 2 chromatids connected by centromere
- 2 diplosomes
what happens in G2
- preparation for mitosis
- synthesis of ATP and tubulin for mitotic spindle
what happens in the M phase of the cell cycle
mitosis
- 2 daughter cells form
- nucleus divides (karyokinesis) followed by cytoplasmic division (cytokinesis)
what do chromosomes look like during the S and M phases
chromosomes condense, become visible, look like coiled snakes
what do chromosomes look like during G1 and G0
chromosomes exist in an unraveled mass
what are facultative dividers
cells that retain capacity for division with proper stimulus
what are terminally differentiated cells
cells that have lost the capacity to divide
what happens in prophase
chromosomes visibly condense
- microfilaments and microtubules of cytoskeleton disaggregate
- centrioles migrate to poles of cell, form spindle apparatus with interpolar microtubules between them
what happens in prometaphase/ late prophase
nuclear membrane and nucleoli disappear at end of prophase
- mitotic spindle attached to chromosomes at kinetochore
what is the major distinction between prophase and prometaphase
the nuclear membrane does not exist in prometaphase
what happens during metaphase
chromosomes line up along the equator
what happens during anaphase
centromeres split apart, chromosomes migrate to opposite ends of the cell
- pulled by microtubules connecting centriole and kinetochore
what happens in telophase
- mitotic spindle disaggregates
- nuclear envelope reassembles, nucleoli reappear,
- plasma membrane forms either cleavage furrow (animal cell) or cytokinesis ( plants)
what is the mitotic index
a tool used to describe proportion of cells in a tissue in mitosis at any given time
what is a normal mitotic index
1 or less
what happens in meiosis
chromosomal duplication followed by two consecutive cell divisions
what are the phases of the first meiotic division
prophase, metaphase, anaphase, and telophase
what does the first meiotic division result in
two daughter cells
how does meiosis differ from mitosis
- in prophase I, homologous pairs of chromosomes form tetrads, with exchange of chromatin via crossing over. it results in hybrid chromatids different from parents
- centromeres do not split during anaphase I
when does crossing over occur
only in prophase I
what happens before the second meiotic division
brief interphase II with no replication of DNA
what happens in each phase of the second meiotic division
prophase II- no crossing over
anaphase II- centromeres split
telophase II- cytokinesis yields four haploid gametes
how many viable gametes does spermatogenesis produce
3 or 4
how many viable gametes does oogenesis create
1
what are the non-functional gametes in oogenesis called
polar bodies
when does spermatogenesis begin
at puberty
when does oogenesis begin
during fetal development
when do female germ cells enter prophase I
about 5th month of gestation during fetal development then they stop
what are the triggers for apoptosis
- programmed cell death
- some cells have finite life spans
- growth and regression of ovarian follices
- destruction of virus or tumor cells
- clonal deletion
what is clonal deletion
in thymus it is the removal of t-cells that react to self molecules
describe what happens in apoptosis
- begins with condensation of nuclear chromatin and shrinkage of nucleus
- cell swells
- lysosomes release catalytic enzymes into cytoplasm
- autolysis
- cell becomes bright pink
- caspace cascade
what is pyknosis
shrinkage of nucleus
why does the cell swell in apoptosis
because the mitochondrial membrane is disrupted so it cannot produce ATP for the sodium potassium pump and sodium gets stuck inside the cell and water rushes in
why does the cytoplasm of the cell become pink in apoptosis
because the enzymes from lysosomes decrease the pH and denature proteins
how can you decipher a pyknotic nucleus
its very dark black from condensation of chromatin
what is the caspace cascade
enzymes that trigger the activation of the next to destroy the cell in apoptosis
what is karyolysis
chromatin in nucleus begins to degenerate
what is karyorhexis
nuclear material begins to fragment and nuclear membrane disintegrates
what are apoptotic bodies
fragmented nuclear debris
