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Biochem BLOCK 3 > Cell Cycle > Flashcards

Flashcards in Cell Cycle Deck (52):
1

What part of the cell cycle is the cell in most of the time

Interphase (G1, S, G2)

2

G1

Active metabolism and accumulation of building blocks and energy

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S phase

Synthesis of DNA: DNA replication occurs-each DNA molecule produce identical copy; centrosome is duplicated

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G2

Active metabolism and protein synthesis; duplication of organization

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Cells undergo normal growth and metabolism while also preparing for cell division

Interphase

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Prophase

-chromosomes and condense and become visible
-spindle fibers emerge from the centrosomes
-nuclear envelope breaks down
-nucleus disappears

7

Prometaphase

-chromosomes continue to condense
-kinetochores appear at the centromeres
-mitotic spindle microtubules attach to kinetochores
-centrosomes move toward opposite poles

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Metaphase

-mitotic spindle is fully developed, centrosomes are opposite poles of the cell
-chromosomes are lined up at the metaphase plate
-each sister chromatid is attached to a spindle fiber originatin from opposite poles

9

Anaphase

-cohesion proteins binding the sister chromatids together break down
-sister chromatids (now called chromosomes) are pulled toward opposite poles
-non-kinetechore spindle fibers lengthen, elongating the cell

10

Telophase

-chromosomes arrive at opposite poles and begin to decondense
-nuclear envelope material surrounds each set of chromosomes
-the mitotic spindle breaks down

11

Cytokinesis

-animal cells: a cleavage furrow separates the daughter cells
-plant cells: a cell plate separates the daughter cells

12

Majority of the cells in th human body have withdrawn from the cell cycle into:

-A terminally differentiated state (neurons, myocytes)-DO NOT renter the cell cycle
-a reversible quiescent G0 phase (stem cells, glial cells)-capable to return to the cell cycle

13

G0-rest in

A period in the cell cycle in which cells exist in a quiescent state

14

Quiescent state

The cell is neither dividing not preparing to divide

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G2 checkpoint

Check for:
-cell size
-accurate DNA replication

16

M checkpoint

Check for:
-chromosome attachment to the spindle

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G1 checkpoint (restriction)

Check for:
-cell size
-nutrients
-growth factors
-DNA damage

18

What is the point of the regulation at internal checkpoints?

Avoid producing mutated cells

19

Regulatory molecules in the control of the cell cycle

1. Positive regulation
2. Negative regulation

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Positive regulation

Cycling and Cdk

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Cyclins and Cdks

-changes of different cyclins throughout the cell cylce
-direct correlation between cycling accumulation and the three major cell cycle checkpoints

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What happens to the cylin following each checkpoint

Sharp decline of cyclin levels following each checkpoint as cyclin is degraded by cytoplasmic enzymes

23

When are cyclins active?

Only when bond to the respective cyclin-dependent kinase (CDK)

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Rib, p53, p21

Negative regulation

25

What prevents initiation of the cell cycle in G1 phase

Rib-retinoblastoma protein

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What is p53?

Transcriptional repressor

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What does p53 do?

Has the ability to repress transcription and to promote apoptosis through direct interaction with apoptotic regulators in the cytosol

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What does p53 induce?

Cell cycle arrest

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What does p53 check for?

DNA damage, cell cycle abnormalities, hypoxia

30

What prevents cell cycle progression

p21

31

How does p21 prevent cell-cycle progression?

-by inhibiting the activity of cyclin E-associated CDK2
-therefore preventing E2F-mediated gene transcription and cell cycle progression

32

External stimuli that cause cells to proliferate (return to G1 if in G0)

Mitogens

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Mitogen sources

-can be provided by extracellular matrix (integrins)
-can be extracellular signals from more distant sources

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Cell-matrix contact of mitogens

Mitogenic

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Cell-to-cell contact

Antimitogenic (contact inhibition)
-no more space, stop dividing

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Extracellular signals from more distant sources of mitogens

-growth factors
-cytokines

37

Mitogen growth factors

-EGF
-VEGF
-NGF
-FGF

Tissue/cell specific

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Mitogen cytokines

-IL-1
-IL-6

39

Platelet derived growth factor (PDGF)

Present in the a-granules of platelets from which it is releases during activation- participates in wound healing

40

What participates in wound healing

Platelet derived growth factor (PDGF)

41

Epidermal growth factors (EGF)

Stimulates the proliferation of epithelial cells and some other cells. It acts primarily in its tissues of origin (local)

42

Fibroblast growth factors (FGFs)

Are a family of at least 22 proteins that act on four different tyrosine kinase receptors. They stimulate notionally fibroblasts by also many other cells

43

Insulin-like growth factor 1 (IGF-1)

Releases from the liver in response to growth hormone

44

Vascular endothelial growth factor (VEGF)

Produced by cells that stimulates vasculogenesis and angiogenesis (new blood vessel formation) wet AMD

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Nerve growth factor (NGF)

Stimulates the growth and differentiation (but not mitosis) of postganglionic sympathetic neurons

46

Neoplasms

Abnormal uncontrolled cell cylce over period of time can lead to the development of this

47

Group of cells that have undergone unregulated growth and will often form a mass or lump, but may be distributed diffusely

Tumors

48

6 hallmarks of cancer, which are required to produce a malignant tumor:

-cell growth and division absent the proper signals
-continuous growth and division even given contrary signals
-avoidance of programmed cell death
-limitless number of cell divisions
-promoting blood vessel construction
-invasion of tissue and formation of metastases

49

Mutated normal genes that encode positive cell cycle regulators that cause a cell to become cancerous

Oncogenes

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Genes that encode for negative regulator proteins that will suppress uncontrolled cell division

Tumor suppressor genes
-put a break on the cell cycle if possible

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Example of tumor suppressor genes

Rib; p53; p21

52

Mutated p53

Cell cycle continues instead of programmed cell death