Apoptosis Flashcards
1)How do cancer cells evade apoptosis;
In normal cells there is a P-53 gene which is a tumour suppressor gene that activates apoptosis. In cancer cells there is a mutation in the p53 gene which means apoptosis is not activated causing the cancer cells to thrive.
Purpose of apoptosis:
destroyCell infected by virus,cells is no longer needed, Mutations or cancer cells
To sculpt body into its final form- webbing between digits, eyelids and tadpole tails
Problems with apoptosis:
-Rapid and irreversible, hence may remove healthy cells from the body
When does apoptosis begin:
●Begins when a signal is received which activates caspase enzymes to cause cell death
Cascape:
Is a signalling molecule that activates other caspases leading to apoptosis.
MAJOR STEPS OF APOPTOSIS:
1.Caspase enzymes are activated
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2.Organelles begin to breakdown
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3.The cell and nucleus shrinks and chromatic condesnses●
4.Blebbing of the plasma membrane occurs forming apoptotic bodies
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5.Apoptotic bodies are engulfed by phagocytes (immune cells).
2 pathways of apoptosis
mictohdonrial pathway
death receptor pathway
Mitochondria(intrinsic) pathway-
Process:
When DNA is damaged (radiation), the mitochondria releases a protein known as cytochrome c
Cytochrome c binds with proteins in the cytosol to activate caspase enzymes
When caspases are active, apoptosis begins.
Death receptor pathway what is
Signalling molecules called death ligands bind to death receptors on the plasma membrane, this causes capsace enxymes to become activated to start apoptosis
What initiates apoptosis via the mitochondrial pathway?
DNA damage, UV radiation, hypoxia (lack of oxygen), viral infection act as stress signals for the cell to initiate apoptosis via the intrinsic pathway
Differences between mitochondria and death receptor pathway:
Intrinsic pathway occurs due to stress signals inside the cell such as hypoxia and uv radiation whereas extrinsic pathway occurs due to external signals/death ligands
intrinsic pathway involves cytochrome c and apoptosome whereas extrinsic pathway does not
intrinsic pathway involves caspase 9 whereas extrinsic involves caspase 8
SIMILARITIES BETWEEN BOTH THE mitochodniral and death receptor PATHWAYS
- both result in apoptosis
both end up activating caspase 3
How is apoptosis related to cancer?
Apotosiswill occur the cancer cell to destruct
Inhibited apoptosis:
May result in unnecessary body parts after development eg. webbed feet and hands
Excessive apoptosis:
may result in diseases and disorders such as Huntington’s disease, Alzheimer’s disease and Parkinson’s disease.
What does apoptosis in neurons result in:
●Apoptosis in neurons resulting in changes in mood, difficulty in movement and decreased cognitive ability.
What happens if DNA repair is not possible?
P-53 gene activates apoptosis
Tumours and Cancer occur when?:
when damaged cells replicate exponentially. Apoptosis does not occur enough
when are erros in tumours detected
the G1 and G2 checkpoint
Decreased rate of apoptosis can result:
: tumours
Types of tumours
Benign tumours:
slowing growing masses that arent spread to other tissues and orgnas
malignant tumours:
cells that have invaded nearby tiusse and ohter parts of the body. these are cancerous cells
malignant tumours:
cells that have invaded nearby tiusse and ohter parts of the body. these are cancerous cells
Benign tumours:
slowing growing masses that arent spread to other tissues and orgnas
Characteristics of cancer cells:
-Able to invade and spread
-resist cell death
-good blood supply
-evade tumours suppressors such as p53 gene
-able to replicate(immortal)
Necrosis and example of it
unregulated death of a cell due to injury
can spread to neihouring tissue and often reuslts in inflammation
the heart would be an example of necrosis
FACTORS THAT IMPACT APOPTOSIS:
●Inherited genes –
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●Mutations in genes
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●Tumour supressing genes
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●Chemical factors – tobacco, air pollutants
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●Physical factors – x-rays, UV rays
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●Biological factors – viruses which cause cancer
apoptosis and example
regulated/controlled programmed cell death
example would be apotposis removing flesh between webbed hands in the womb
main reasons for apoptosis
cells that are damaged or defective (because they have become cancerous ro infceted by a virus) must be eliminateed.
During fetal development, aptosis scuplts the body from its tissues. eg. webbing between fingers is removed by aptopsos
What are the two major stages of apoptosis and what dothey iinclude
initiation-involves intrinsic and extrinsic pathway
execution-
**list whathappens in apoptoisis
what are cancer cells, how do they form and how do cancer cells spread
unspecalised cells that divide and grow rapidly unctrollable to form a tumour
cancer cells form to genetic changes when a normal cell is transformed into a malignant cell
cancer cells spread by dividing uncontrollably and spreading to surrounding tissues.
An example of an essiental change that causes magliancy
failure in apoptosis
a cell infected by a virus can be secreted by
apoptosis if a natural killer cell finds it early enough to destroy and necrosis if the cell goes unchecked for a while
reason for a defect in p53 gene
a lack of cell sensitiviyt to trail
apoptotic cells are characterised by and what occurs after apoptosis and what can a failure in apoptosis lead to
cell shrinkage, blebbing, condensation of chromatin and fragmentation of DNA nad nucleus
phagocytosis occurs after apoptosis
failure in apoptosis can lead to cancer
differnece btween mitosis and apoptosis and After the initiation of apoptosis, caspases begin digesting what
mitosis is how cells are produced, whereas apoptosis is how cells are destroyed
after the intation of apoptosis, capscase begins digesting protein
What happens when DNA is damaged by radiation
apoptosis
signal transduction
the process of transferring a signal throughout an organism
function of capscase 3
breaks down cytokseleton
process death receptor pathway
Caspase enzymes are activated
Organelles begin to breakdown
The cell and nucleus shrinks
Blebbing of the plasma membrane occurs forming apoptotic bodies
Apoptotic bodies are engulfed by phagocytes (immune cell).
2 main functions of apoptosis
to sculpt the body
destory cells that are damaged
After caspase enzymes are activated, what happens
cell shrinks/collaspes
DNA condenses and fragments
Blebbing
apopotic bodies break away and phagocytosis occurs
