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111 Cards in this Set
- Front
- Back
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How many cells does a human have? (range)
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14-140 trillion cells
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Name the 3 mechanisms of the body used to keep cell # relatively constant.
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Cell division, necrosis, and programmed cell death
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what is necrosis?
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premature cell death
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name the 4 types of programmed cell death.
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apoptosis, anoikis, cornification, autophagy
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What process is important for refinement of activities to bare essentials?
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programmed cell death.
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Why are we not born with webbed fingers and toes?
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Because the cells that form the webs (as an embryo) are told to die as we mature
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Give an example of more cell division than cell death
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the bull with excessive muscle cell division; or cancer
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mitotic cell division evolved from?
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binary fission
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Which is ore complex? mitotic cell division OR binary fission
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binary fission
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How many mechanisms of cell division are there?
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many, probably about 6. they are all somewhere in between binary fission and mitosis
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The complex mitotic cell cycle is used by the organism to control: (3 things)
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cell #, cell quality, and cell type
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In order for a cell to divide it needs _______ signals
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at least 4
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In order for cell proliferation to occur it needs multiple signals that say what?
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1 from a growth horomone, 1 indicating anchorage, 1 telling it has space to divide, 1 saying there is enough nutrients
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What is a mitogen?
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a signalling molecule (ligand) that induces cell proliferation
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The growth horomone signal that tells a cell to divide is also called a _____
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mitogen
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The mitogen binds to a receptor which induces the _____ _____ _____
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MAP kinase cascade
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What does the MAP kinase cascade end with?
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the activation of a gene regulating protein, which goes into the nucleus and then activates early gene expression (which creates more proteins, preparing the cell to divide)
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Is mitosis the same as mitotic cell division?
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no, they are different
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What is the M stage of interphase?
(not a completely accurate question btw) |
mitotic cell division
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What is the 3 stages of interphase?
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Gap1 (G1), S and Gap2 (G2)
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Mitosis technically includes what steps?
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Prophase, metaphase, anaphase and telophase. (not cytokinesis or interphase)
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Mitotic cell division technically includes what steps?
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Prophase, metaphase, anaphase, telophase, & cytokinesis
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Which 3 steps of mitotic cell division occur simultaneously?
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anaphase, telophase, & cytokinesis
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What happens during G1?
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the cell gets ready for DNA synthesis (makesDNA synthase complexes, repair enzymes, histones)
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What happens during G2?
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cell gets ready for cell division (organelles, cytoskeletal proteins, molecular motors, metabolic enzymes)
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What happens during S-phase?
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DNA replication (Synthesis and error editing)
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______ ______ are lined at the metaphase plate during metaphase
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sister chromatids
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Sister chromatids are pulled toward opposite ends during______
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anaphase
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What phase are cells sometimes paused at for long periods of time?
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metaphase
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What is a kinetochore?
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the middle of the sister chromatid
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What is a centromere?
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the anchors within the cell (gold bricks)
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_______ _____ pull sister chromatids toward centromeres
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dynein motors
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how are sister chromatids pulled apart during anaphase?
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dynein motors attached to the kineochore walk along the microtubes toward the minus end (end closest to centromeres). as the motion occurs, the + end of the microtubules depolymerize
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Its not the depolymerizatio of the microtubes that pull the kinetochores, but rather...
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the dynein motors walking along the microtubules. The depolymerization merely occurs to get the + end out of the way
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contractile ring is composed of _____ and _____ ______
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actin and myosin filaments
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Cytokinesis results from the assembly of an actin-myosin ring that gets smaller and smaller as _____ pulls _____ along _____
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mysoin ,actin ,actin
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What seperates cells during cytokinesis? (2 words)
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contractile ring
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How do the microfilaments get out of the way during cytokinesis?
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severing
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Does an enzyme induce fusion during cytokinesis?
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No
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What do plants use to separate cells during division?
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They have NO contractile ring, they just form another cell wall in the middle
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What are the 6 checkpoints?
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G0/G1 ; G1/S ; S ; S/G2 ; G2/M ;
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what does the G0/G1 checkpoint decide?
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when the cell is told to enter the cell cycle or not
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Is G0 part of the cell cycle?
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no (called the quiescent stage)
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quiescent stage is?
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During G0. It's just living its life, doing its thing, not dividing
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What does the "point of no return" mean?
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After this point in the cell division cycle, it cannot go back. If for some reason it is not allowed or cant continue, it is told to die
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What are 2 other terms for the "point of no return" ?
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"go ahead" checkpoint or "start" checkpoint
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Where is the "point of no return"?
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Somewhere between the G0/G1 and the G1/S "checkpoint" (not really a checkpoint)
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how long does it take a cell to go thru the cell cycle?
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16-24 hours
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What is a CDK?
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cyclin-dependant kinase
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CDK dimerizes with what?
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cyclin
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Cyclin tells ______ to function
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CDK
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what do kinases do?
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phosphorylate things
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What does the CDK-cyclin dimer regulate?
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different checkpoints
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is there different cyclins for different checkpoints?
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yes (names are based on the checkpoint)(ex: cyclin for G0/G1 checkpoint is called G0/G1 cyclin )
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What causes the production of CDKs?
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The mitogen attaching to the receptor (causes MAP cascade, which causes genes to be expressed that produce proteins for cell division)
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The cell knows which stage of interphase it is in by the presence of what?
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specific cyclins
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If there is a peak in S cyclin, that means what?
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DNA replication will/has started
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How long is cyclin's half life? (not specific #)
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short
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Which protein is present throughout the stages? CDK or cyclin
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cyclin
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G0/G1-cdk AND the G0/G1-cyclin come together and do what?
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phosphorylate the Rb protein
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When Rb protein is unphosphorylated, what does it have a high affinity for?
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E2F
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When Rb protein is Phosphorylated, what happens?
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it loses its affinity for E2F (E2F is released)
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What is E2F?
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a strong transcription factor
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What does EF2 activate?
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E2F activates transcription of G1/s-cyclin and S-cyclin
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Is there a chance of reverting a cell back to the G0 phase if Rb is dephosphoylated?
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yes, as long as it hasnt reached the point of no return
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The production of _______ _____ marks the point of no return
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G1/S cyclin, because that is the signal to go ahead with DNA replication
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its not about 1 signal reaching a target, it's about a ______ amount reaching a target
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theshold
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What does the G2/M dimer do?
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phosphorylates histones and lamins
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When are histones phosphorylated?
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G2/M
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What happens when histones are phosphorylated?
Which checkpoint is this at? |
the histone code is changed which tells the cell to undergo chromosome condensation
G2/M |
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What is lamin?
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A subunit of the nuclear scallold (an intermediate filament)
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What happens when lamin is phosphorylated?
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the nuclear scaffold breaks down (lamins dont have an affinity for one another)
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What does lamin do when dephoshorylated?
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Has an affinity for itself, creating a nuclear scaffold
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What controls how sister chromatids line up in the middle of the cell?
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the fact that spindle fibers are formed at the same rate on either side
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M-CDK cyclin dimer regulates the cell to progress from _____ to _____
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metaphase, anaphase
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M-CDK cyclin dimer phosphorylates _____ which initiates ________
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myosin, contracting the contractile ring
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WHat is the importantance of Myc?
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It is a crucial gene regulatory proteins
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APC/C does what?
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Destroys cyclins and securin
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What does securin do?
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kjklk
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M phase checkpoint dontrols what?
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The transition from metaphase to anaphase
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A cyclosome is also called...
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APC/C
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APC/C does what?
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promotes the transition into anaphase
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When securin is destroyed by ______ it drives what?
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APC/C, anaphase (sister chromatid seperation)
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Why does APC/C destroy cyclins?
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to "clean up" or to stop the cell cycle
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apotosis is a means to control cell _______
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quality
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Name the 2 apototic pathways
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intrinsic and extrinsic
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What is the intrinsic apototic pathway?
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receiving a signal from within the cell
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What is the extrinsic apototic pathway?
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receiving a signal from outside the cell
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What are the 3 "real" characteristics of an apotitic cell?
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cell shrinkage, nuclear membrane blebbing, DNA fragmentation
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What marks the beginning of apotosis?
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Cessation of DNA repair mechanisms
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What is activated at the theshold of DNA damage?
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ATM/ATR kinase
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When the rate of DNA damage is higher than the rate of DNA repair, what happens?
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ATM/ATR kinase is activated
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When ATM/ATR kinase is activated, what is the next step in the chain?
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phosphorylation of p53
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80% of cancer cases are linked to ______ failure
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p53
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Which genes are activated by p53 depend on what 2 things?
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How many times a p53 is phosphoryated, and how many phosphoryated p53's are present
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What does hyper phosphoryated mean?
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phosphoryated more than once
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What does phosphoryated p53 do?
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Binds to the regulatory region of the p21 gene
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Why is p21 expressed? what is happening to the cell?
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the rate of DNA damage is higher than the rate of DNA repair
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does p21 have multiple binding sites?
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yes
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which protein does p21 have an affinity for?
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many! it has different affinities for different proteins
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which protein does p21 have a high affinity for?
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CDK and cyclin
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When alot of DNA repair needs to occur, what process stops? in other words, what process stops when p21 is made?
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cell division
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When does a cell arrest if it has more pressing matters to take care of, such as excessive DNA damage?
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at the checkpoints
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How does a cell get out of arrest?
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p21 has to stop being produced
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p21 has an affinity for cyclin, CDK and also _____
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PCNA
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there has to be ___ to ___% more p21 than PCNA to for binding to occur due to p21's low affinity for PCNA
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5-50%
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PCNA is important for?
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DNA replication, and DNA repair mechanisms
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What does bound PCNA signal?
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there is too much damage, it cannot be fixed (death)
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Cell death occurs when there is too much _____
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bound PCNA (too much p21), signalling DNA is beyond repair, the cell is put to death
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When cytochrome C binds to APAF-1, what happens?
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activates caspase cascade, leading to apotosis
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What is blebbing?
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When pieces start pinching off, such as pieces of the plasma membrane
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