Chapter 12 Flashcards

Question

Cytokinesis

Answer 1

* Cytoplasm continues dividing * 2 daughter cells appear * Cleavage furrow forms, pinching the cell into 2

Answer 2

‘microtubule organizing center’ o region inside the cell that functions to organize the cell’s microtubules during the cell cycle o Each contain 2 centrioles (which have no role in cell division)

Answer 3

specific place on the chromosome where cell division begins in bacterial chromosome

Answer 4

- Bacterial cell division ‘division in half’ o Cell division of prokaryotes and single-celled eukaryotes (bacteria and archaea) o However, in the eukaryotes this involves mitosis o Cell grows double its size and then divides into 2

Answer 5

1) Chrom. replication occurs. Soon after, one copy of the origin moves toward the other end. 2) Replication continues. One copy of origin is now at end of each cell. Cell elongates 3) Replication finishes. PM pinches inward. New cell wall is created. 4) Result: 2 daughter cells.

Answer 6

• Prophase o Chromosomes condense (are now visible!) o Nucleoli disappear o Mitotic spindle begins to form o • Prometaphase o Chromosomes are MORE condensed o Chromosomes each have 2 aligned sister chromatids o Nuclear envelope fragments • Metaphase o Mitotic spindle formation is complete o Chromosomes are attached to microtubules at their kinetochores o Chrom. are lined up at metaphase plate • Anaphase o Chromatids of each chrom. have separated o Daughter chrom. move toward end of cell as kinet. microtubules shorten • Telophase o Daughter nuclei form o Cytokinesis has started

Answer 7

cyclically operating set of molecules in the cell that trigger and coordinate key events in the cell cycle o Subject to internal control and external adjustment o Regulated at certain checkpoints

Answer 8

control point in cell cycle where stop and go-ahead signals regulate cycle • Three checkpoints: G1, G2, and M phases

Answer 9

protein with cyclically fluctuating concentration in the cell o Level rises during S and G2 phases, and falls during M phase.

Answer 10

* Cylcin-dependent kinases * kinases of cyclin * The activity of Cdk rises and falls with changes in concen. Of cyclin partner * Ex: MPF

Answer 11

Cyclin-Cdk complex • Has peaks of concen. which correspond with peaks of cyclin concen. • It helps to think of this as the ‘M-phase promoting factor’ because it triggers cell’s passage into M phase (mitosis) past the G2 checkpoint • First discovered in eggs

Answer 12

Synthesis of cyclin begins in late S phase and continues through G2. • Cyclin is accumulating (it’s protected from degredation)

Answer 13

Cyclin combines with Cdk, producing MPF | • This checkpoint is passed when adequate MPF molecules accumulate (and mitosis begins!)

Answer 14

MPF promotes mitosis by phosphorylating different proteins. • MPF acts as a kinase by activating other kinases • MPF’s activity peaks during metaphase. • During anaphase, the cyclin part of the MPF has degraded, terminating the M phase.

Answer 15

* Degradation of cyclin continues | * CdK component of the MPF is recycled (this lasts through the S phase)

Answer 16

‘restriction point’- most important • Where cell receives the signal to complete the G1, S, G1, and M phases and divide • If cell does not receive the ‘go-ahead’ signal here, it may exit the cycle and switch into the G0 phase

Answer 17

nondividing state | • where most cells of the body exist. Esp. muscle and nerve cells.

Answer 18

protein released by certain cells that stimulates other cells to divide o Ex: Platelet-derived growth factor • Growth factor made of platelets which is required for the division of fibroblasts • The binding of PDGF molecules to PDGF receptors trigger signal transduction pathway allowing cells to pass G1 checkpoint and divide

Answer 19

phenomenon in which crowded cells stop dividing o When two cells join together, the cell surface proteins bind together, sending a cell division-inhibiting signal (Signal cell to STOP dividing) • This even occurs in the presence of growth factors. • This is why cells will divide to form a layer, but if removed will grow to fill the gap

Answer 20

when cells must be attached to an underlying surface in order to divide o Signaled via pathways involving plasma membrane proteins which are linked to the cytoskeleton

Answer 21

when cells acquire the ability to divide indefinitely | o On the other hand, all normal mammalian cells divide about 20-50 times before stopping and dying

Answer 22

abnormal cells have too few genetic and cellular changes to survive at another site o Can be removed surgically

Answer 23

abnormal cells whose genetic and cellular changes enable them to spread to new tissues and impair the functions of one or more organs = cancer o Considered transformed cells o May have unusual number of chromosomes o May have altered metabolism o May have lost attachment to neighboring cells or ECM o Secrete molecule which attract blood vessels

Answer 24

adding a phosphate group to a molecule

Answer 25

an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule