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30 Flashcards

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Biology 101 flashcards
1
Q

what are the 2 ways cells die?

A

killed by injurious agents

induced to commit suicide

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2
Q

how do cells die from injury?

A

mechanical damage

exposure to toxic chemicals

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3
Q

what are the characteristic changes that cells experience when undergoing death by injury?

A

cell & organelles swell - lose their osmotic balance

cell contents leak out, leading to inflammation of surrounded tissues - burst

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4
Q

what occurs when cells are induced to commit suicide?

A

shrink

develop blebs

DNA degraded

mitochondria break down

break into membrane-wrapped fragments

phospholipid phosphatidylserine is exposed on the surface (usually embedded in the PM)

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5
Q

what effect does phospholipid phosphatidylserine exposed on the surface of the PM have?

A

triggers the receptors on phagocytes

receptors bind to it & engulf fragments

phagocytes secrete cytokines & inhibit inflammation

PM asymmetry & bilayer diffs signify apoptosis

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6
Q

what are the 2 reasons why a cell commits suicide?

A

proper development

destroy cells that pose a threat to the integrity of the organism

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7
Q

what are exs of cell death for proper development?

A

tadpole tail

removal of webbing b/w fingers & toes (lysosomal)

menstruation - removal of the inner lining of the uterus, removal of capillary bed that was formed to support a fertilized egg

nerual innervations - removal of surplus neurons when tissues are formed during development

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8
Q

what are exs when cells that pose a threat to the integrity of the organism are destroyed?

A

cytotoxic T lymphocytes (CTLs) kill viruses - viruses are trapped in a vesicle & CTLs phagocytose the vesicle to destroy the virus

destruction of CTLs post a heightened immune response (defaults in apoptosis machinery leads is assoc to autoimmune diseases like allergies)

cells with DNA damage - when DNA damage is detected p53 PRO is produced & induces apoptosis

cancer cells - radiation & chemotherapy is used to induce apoptosis of cancer cells

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9
Q

how does apoptosis contribute to elderly fragility?

A

aren’t receiving full recovery of stem cells post regulatory apoptosis

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10
Q

what are the diseases that defects in apoptosis lead to?

A

excessive apoptosis causes atrophy (tissue wasting)

insufficient apoptosis results in uncontrolled proliferation (cancer)

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11
Q

how does the rate of apoptosis differ among youth & elderly?

A

it doesn’t

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12
Q

what makes a cell decide to commit suicide?

A

the balance b/w:

the withdrawal of positive signals (required for survival) - require continuous stimulation from other cells through contact & adhesion to other cells or substrates
Growth factors & cytokines

received of negative signals - incres oxidants, DNA damage (UV, cytotoxic compounds etc.), accumulation of mis-folded PRO, death activators

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13
Q

what are the 2 general mechanisms to induce apoptosis?

A

intrinsic factors & extrinsic factors

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14
Q

intrinsic factors

A

signals arising from within the cell itself often as a result of some damage to key organelles, like mitochondria

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15
Q

extrinsic factors

A

death activators binding to receptors at PM

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16
Q

intrinsic pathway of apoptosis

A
  1. The outer membranes of mitochondria display the PRO Bcl-2 on their surface
  2. Internal damage to the cell (ex: from reactive oxygen species) causes Bcl-2 to activate a related PRO, Bax, which punches holes in the outer & inner mitochondrial membrane, causing cytochrome c to leak out

o Targets ETC

  1. The released cytochrome c binds to apoptosis-promoting PROs (Apaf-1 & procaspase-9)
    o Pro = doesn’t mean its active, active when protease (caspase) causes it to lose some AAs
  2. These PROs aggregate to form apoptosomes
    o Contains: Cty c & other apoptosis PROs
  3. The apoptosomes activate executioner caspases (which are proteases)
    o Targets macromolecules within the cell
  4. There is an expanding cascade of many caspases, which digest structural PROs in the cytoplasm, degrade DNA, etc.
  5. Phagocytes are recruited to destroy the dying cell
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17
Q

what are the apoptosis-promoting PROs in the intrinsic pathway of apoptosis?

A

Apaf-1 & procaspase-9

18
Q

what do apoptosomes activate?

A

executioner caspases, proteases

19
Q

what do apoptosomes consist of?

A

cyt c & apoptosis PROs

20
Q

what activates the Bax PRO?

A

p53 & Bcl-2

21
Q

what factors induce intrinsic apoptosis?

A

p53 - activates Bax

viral dsRNA - detected by a PKR, PRO that stops the cell’s translational machinery (by inhibiting an eIF) & then by inducing caspases (this pathway may also be considered an extrinsic pathway)

22
Q

extrinsic pathway of apoptosis

A
  1. TNF receptors (ex: TNFR1) are integral PROs that detect death factors
  2. TNFR1 cytoplasmic domains then bind to other PROs, which recruit Procaspase 8
  3. This leads to activation of caspase 8
  4. Caspase 8 (like caspase 9) initiates a cascade of caspase activation
  5. This leads to phagocytosis of the cell
23
Q

what is the diff b/w intrinsic & extrinsic pathways of apoptosis?

A

intrinsic - caspase 9

extrinsic - caspase 8

24
Q

where does a cell receive an extrinsic death activator?

A

immune sys cells - natural defense against viruses

25
Q

what is a FasL?

A

a TNF

26
Q

what induces the anchor pathway of apoptosis?

A

the mitochondria

27
Q

why is the anchor pathway not an intrinsic factor?

A

doesn’t use caspases, induced by the mitochondria

28
Q

what mediates the anchor pathway of apoptosis?

A

AIF - apoptosis-inducing factor

29
Q

what is the role of AIFs?

A

located in the intermembrane space of the mitochondria, when there’s oxidative damage, the AIF move from the mitochondria to the nucleus & induce degradation of DNA

30
Q

what is the role of AIFs?

A

located in the intermembrane space of the mitochondria, when there’s oxidative damage, the AIF move from the mitochondria to the nucleus & induce degradation of DNA

31
Q

AIF

A

nuclease

32
Q

when is the anchor pathway of apoptosis triggered?

A

when the cell receives an extrinsic signal or senses reactive oxygen species

33
Q

what are the visible signs of a cell undergoing apoptosis?

A

shrinkage & rounding due to the breakdown of the cytoskeleton by caspases

chromatin condenses

nuclear membrane breaks

fragmented DNA & nucleus

PM has blebs

34
Q

what does the cell change into when apoptosis is triggered? & what happens to them?

A

apoptotic bodies

phagocytosed

35
Q

what balances the cells lost by apoptosis?

A

replacement of cells by stem cells

36
Q

stem cells

A

self-renewing: can divide while maintaining an undifferentiated state

immortal b/c they contain telomerase

37
Q

why are stem cells potent?

A

capacity to differentiate into specialized cell types

38
Q

totipotent or pluripotent & exs

A

can give rise to any mature cell type
can produce the entire organism

exs: oocytes

39
Q

multipotent or unipotent

A

make many cell types but only of certain categories

can’t make the entire organism but can produce many tissue types

unipotent - can make one kind of tissue (ex: skin cells)

40
Q

describe stem cells of the intestines

A

renewed by stem cells at the base & migrate upwards

41
Q

describe stem cells of skin

A

renewed from stem cells in the basal layer

42
Q

what are the applications of stem cells?

A

replacement of damage or lost cells (ex: replace damage cells of someone who had a heart attack)

generating new eggs

grow organs - 3D printing

C Bio (30 decks)

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