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Cell Proliferation / Cell Death Flashcards

1
Q

what is cell proliferation?

A

a process that results in an increase in the number of cells

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2
Q

what is cell proliferation characterised by?

A

by balance between cell division and cell death/differentiation

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3
Q

when is cell proliferation increased?

A

in tumours

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4
Q

when does cell death occur?

A

in response to injury

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5
Q

what is cell death essential for?

A

essential part of development

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6
Q

what are the 2 forms of cell death?

A

apoptosis

necrosis

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7
Q

what is increased proliferation achieved by?

A

Shortening cell cycle

Recruiting quiescent cells into cell cycle

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8
Q

what is cell proliferation controlled by?

A

Controlled by cell contact or soluble signals

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9
Q

what are the stimuli for cell proliferation?

A

May involve physiological or pathological stimuli

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10
Q

what are labile cells?

A

cells that are constantly dividing, regenerate rapidly

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11
Q

what are examples of labile cells?

A

skin cells

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12
Q

what are stable cells?

A

cells that have low level of replication; can rapidly divide in response to stimuli

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13
Q

what are examples of stable cells?

A

hepatocytes

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14
Q

what are permanent cells?

A

non-dividing cells, terminally differentiated; unable to re-enter cell cycle

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15
Q

what are examples of permanent cells?

A

neurons

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16
Q

what controls organ/tissue growth?

A

Balance between increase cell number due to proliferation

& decrease in cell numbers due to cell death

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17
Q

what is cell growth?

A

Response of cells to increased functional demands

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18
Q

what are examples of physiological hypertrophy?

A

skeletal muscles in athletes

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19
Q

what are examples of pathological hypertrophy?

A

myocardium - outflow obstruction, hypertension

Arterial smooth muscle - hypertension

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20
Q

what are physiological examples of hyperplasia?

A

Bone Marrow: RBC at altitude

Breast: puberty, pregnancy

Thyroid: puberty, pregnancy

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21
Q

what are pathological examples of hyperplasia?

A

Prostate: epithelial & connective tissue

Thyroid: Grave’s Disease

Adrenal cortex: ACTH secreting pituitary tumour

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22
Q

what are physiological examples of combined hypertrophy and hyperplasia?

A

Uterine smooth muscle: puberty, pregnancy

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23
Q

what is hyperplasia?

A

Increase in number of cells

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24
Q

what is hypertrophy?

A

Increase in size of cells

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25
what is cell cycle?
A series of highly regulated steps that governs cell proliferation
26
what part of the cell cycle are in interphase?
G1, S, G2
27
what is G1?
pre-synthesis gap | cells differentiate, perform specialist function as part of tissue
28
what is the duration of G1?
10 hours - | highly variable duration – several days/weeks
29
what is the S stage?
“synthesis” – DNA replication
30
how long does the S phase last?
9 hours
31
what is the G2 phase?
post-synthesis gap | cells prepare for mitosis
32
how long does G2 last?
4 hours
33
how long does mitosis last?
1 hour
34
what is G0?
Differentiated cells | Continuous differentiated function
35
when do chromosomes first become visible in nucleus?
prophase
36
what happens in prophase?
- Chromosomes first become visible in nucleus & become condensed - Nucleoli disappear - Dissolution of nuclear envelope - Microfilaments & microtubules disaggregate into protein subunits - Centrioles migrate to opposite poles of cells - Spindle of microtubules forms between centrioles
37
what happens in metaphase?
- Mitotic spindle moves into nuclear area - Duplicated chromosomes attached at kinetochore (AKA chromosome microtubule) - Chromosomes aligned along metaphase plate - Mitosis cannot progress until all chromatid pairs aligned (metaphase checkpoint)
38
what happens in anaphase?
- Splitting of centromere which bind chromatids of duplicated chromosomes - Mitotic spindle lengthened - Centrioles pulled apart - Chromatids of each duplicated chromosome pulled to opposite ends of spindle - Two groups of identical chromosomes at opposite ends of cell
39
what is the final phase of mitosis?
telophase
40
what happens in telophase?
Chromosomes uncoil Nuclear membrane reassembles & nucleoli become apparent Cytokinesis Plasma membrane around spindle equator indents – cleavage furrow Cells cleave
41
how is the cell cycle controlled?
- check points - cyclins & cyclin dependent kinases (CDK) - promote cell cycle progression - CDK inhibitors - stop cell cycle progression
42
what happens at the G2 checkpoint?
if DNA synthesis has been done correctly
43
what happens at the metaphase checkpoint?
if the sister chromatids can separate correctly
44
what happens at G1 checkpoint?
if DNA synthesis can begin
45
what do cyclin and CDK control?
transition from | G1-S and G2-M
46
what are the cyclin-CDK complexes do?
Phosphorylate protein substrates
47
what do Cyclin-CDK complexes do at S-phase?
proteins that initiate DNA replication
48
what do Cyclin-CDK complexes do at M-phase?
proteins needed for chromosomal condensation; nuclear membrane stabilisation
49
what is the objective of Cyclin & Cyclin Dependent Kinases?
Correct DNA synthesis & mitosis
50
what is the M-phase Cyclin*/CDK complex phosphorylated by?
CAK
51
when is the M-phase Cyclin*/CDK complex activated?
Activated at end of G2 by phosphatase - Cdc25 (removes inhibitory phosphates)
52
what is p53?
multifunctional protein
53
what is the function of p53?
regulates cell-cycle & apoptosis
54
what does p53 do?
Recognises & binds damaged DNA
55
what is the transcription factor for p21?
p53
56
what is p21?
CDK inhibitor
57
where is a p53 mutation found?
Mutation found in Li-Fraumeni Syndrome
58
when are cyclins degraded?
Cyclins are degraded after mitotic division
59
what are active CDK complexes regulated by?
CDKIs Kinases Phosphatases
60
when are checkpoints activated?
Problems with DNA replication, repair
61
what do cell cycle checkpoints allow?
Allowing time for repair
62
what is pRb?
Retinoblastoma protein
63
what does pRb do?
Recognises damaged DNA Prevents progression from G1-S Binds & inhibits E2F (transcription factor)
64
what does pRb mutation lead to?
Mutation leads to retinoblastoma
65
what can lead to increased cell proliferation?
``` high growth factors high oncogenes low tumour suppressors high ECM stiffness low cell density ```
66
what can lead to increased cell cycle arrest?
``` low growth factors low oncogenes high tumour suppressors low ECM stiffness high cell density ```
67
what is necrosis?
collapse of membrane integrity & death of a cell or tissue
68
what can lead to necrosis?
cell death by injury
69
how does necrosis occur?
Swelling of cells & organelles Release of lysosomal enzymes Membrane breaks down Nuclear changes
70
what is karyolysis?
loss of staining
71
what is karyorrhexis?
fragmentation
72
true or false necrosis is associated with inflammation?
true
73
is necrosis active or passive cell death?
passive cell death
74
what is apoptosis?
programmed cell death
75
what is meant by active process?
Requires energy | RNA & protein synthesis
76
what is the characteristic morphology of apoptosis?
Chromatin condenses Cells shrinks Formation of apoptotic bodies Cleared by phagocytosis
77
is apoptosis associated with inflammation?
apoptosis has no inflammatory response
78
is apoptosis or necrosis part of normal homeostasis?
apoptosis
79
how is apoptosis induced?
Physiological or pathological stimuli
80
how is necrosis induced?
usually due to pathological injury
81
to what extent does apoptosis effect cells?
only affects single cells
82
what extent does necrosis effect cells?
usually affects cell groups
83
what are the biochemical events in apoptosis?
Engergy-dependent fragmentation of DNA by endogenous endonucleases Lysosomes intact
84
what are the biological events in necrosis?
Energy failure Impairment/cessation of homeostasis Lysosomes leak lytic enzymes
85
what happens to cell membrane integrity in apoptosis?
it is maintained
86
what happens to cell membrane integrity in necrosis?
it is lost
87
what is the morphology of apoptosis?
Cell shrinkage & fragmentation to form apoptotic bodies
88
what is the morphology of necrosis?
Cell swelling and lysis
89
what is the fate of dead cells in apoptosis?
Ingested by neighbouring cells
90
what is the fate of dead cells in necrosis?
Ingested by neutrophils & macrophages
91
what is the outcome of apoptosis?
cell elimination
92
what is the outcome of necrosis?
defence & preparation for repair

Pathology (17 decks)

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