cell division
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3 reasons cell replication occurs
• replacing dead cells (repair 2. growth and maitenance
how do prokaryotes replicate
via binary fission
what is prkaryotic binary fission
each cell becomes 2 identical copies, this is asexual reproduction
3 main categories of the cell cycle
interphase, mitosis and cytokinesis
what are the phases in mitosis
prophase, metaphase, anaphase, telophase (cytokinesis)
what are the three phases in the interphase
gap 1, synthesis (gap 0), gap 2
what happens in gap 1 (interphase)
period of cell growth, normal metabolism, duplication of organelles
what happens during the synthesis stage (interphase)
near the end of interphase, chromosomes duplicate to form two chromtids that are held together at the centromere
what happens during interphase gap 2
cell grows and prepares itself for mitosis, involves increasing the volume of the cytosol and synthesising proteins in preparation for mitosis
what happens during prophase
chromosomes coil/condense and become visible, centrioles move apart to opposite poles and spindles begin to form, late prophase the nuclear membrane breaks down
what happens during metaphase
chromosomes appear as two sister chromatids joined at the centromere, chromosomes line up at the equator, microtubules of spindle attach to centromeres
what happens during anaphase
microtubules contract, pulling centromeres and chromotids apart and moving them towards centrioles at opposite poles. chromotids are now considered new chromosomes
what happens during telophase
spindle fibers breakdown, nuclear envelope forms around each group of chromosomes and chromosomes unravel to become invisible again
what happens during cytokinesis
the plasma membrane pinches in to seperate the two nuclei, cytoplasm is divided to form two new daughter cells
what is cell cycle regulation
if errors are detected at checkpoints, the cell wither repairs itself or will undergo programmed cell death - apoptosis
what does the g1 checkpoint verify
grown to correct size, synthesised enough protein for DNA replication, if DNA has been damaged during previous mitosiss and cell growth
what does the g2 checkpoint verify
dna has replicated properly during the s phase, cell has enough resources for mitosis
what does the metaphase checkpoint verify
formation of spindle fibers, choromsomes are lined up correctly
where are the three checkpoints
g1 g2 and metaphase
what can cause checkpoints to malfunction
mutagens/dna mutations or indivdual genetics
what is apoptosis
programmed cell death
what are the two pathways of apoptosis
mitochondrial and death receptor
is apoptosis the only way cells can die
no e.g necrosis, damage by oathogens, physical injury
what are capases
enzymes that digest cell contents