Apoptosis. Flashcards
Define caspase enzymes?
Enzymes that are involved in apoptosis.
What is apoptosis?
It is defined as programmed cell death.
Apoptosis is an important cellular function in what kind of organisms?
In multi-cellular organisms that must undergo growth and death.
What are the 2 different ways in which a cell can undergo cell death?
Necrosis.
Apoptosis.
When will a cell die by necrosis?
When the cell is exposed to a harmful environment.
When the tissue that contains the cell suffers an injury which damages the cell.
What are the 3 steps of necrosis?
The swelling of the nucleus and other cellular tissues.
This swelling eventually causes the cell to burst and the cellular contents will be expelled.
The release of the cellular contents activates antigens and this leads to an immune response and inflammation.
What are the 3 steps of apoptosis?
By condensation of the chromosomes and cell shrinkage.
The cellular organelles and cell membranes are preserved.
The cell is engulfed or phagocytosed by macrophages.
What is necrosis characterised by?
Inflammation.
What is apoptosis characterised by?
Caspase’s and DNA fragmentation.
What does apoptosis enable the body to do?
To get rid of unwanted or defective cells via a process which does not activate the inflammatory response.
What happens when the cell receives the signal telling it that apoptosis needs to take place?
It induces the shrinkage of chromatin within the nucleus and this causes the cytoplasm to shrink as well.
What is the membranous shrinkage that is characteristic of apoptosis known as?
As blebbing.
How long will blebbing continue for?
Until apoptotic bodies form.
What happens in apoptosis once the apoptotic bodies have formed?
Once the apoptotic bodies have formed macrophages will phagocytose them.
What is one of the major molecular markers of apoptosis?
Phosphatidylserine.
Where is phosphatidylserine found on a cell that is marked for apoptosis?
It is found on the surface of the outer membrane of the phospholipid bilayer.
What is the phosphatidylserine molecule also known as?
As the eat me signal as it acts as a signal for macrophages to ingest the cell.
Where is phosphatidylserine found on cells that are not marked for apoptosis?
On the inner membrane of the phospholipid bilayer.
How does phosphatidylserine move from the inner membrane to the outer membrane in a cell that is marked for apoptosis?
Caspase proteins 3 and 7 activate an enzyme called XRP-8 which will catalyse lipid scrambling.
This re-arrange’s the phospholipids and place’s phosphatidylserine on the outer membrane.
Does the process of apoptosis lead to an inflammatory response?
No
What is the first step of DNA degradation within cells marked for apoptosis?
Caspase proteins will activate a set of endonuclease enzymes called caspase activated DNAase.
What is the second step of DNA degradation within cells marked for apoptosis, after the caspase activated DNAAase has been activated?
They will cleave the chromosomes in the linker region that lies between the nucleosomes.
How can the cleavage of DNA by the caspase activated DNAAase enzymes be visualised?
By gel electrophoresis as fragments will separate into different bands on the gel.
How would DNA that had undergone necrosis appear after electrophoresis?
There would only be small remnants visible at the bottom the gel.
When will apoptosis be heavily used during development?
When forming the fingers and toes in the foetus.
Why is apoptosis heavily used during the formation of fingers and toes of the foetus?
Because the hands and feet of humans are webbed during the early embryonic stages.
How are the cells that make up the webbing within fingers and toes during foetal development removed?
By apoptosis.
Why is apoptosis important in frog development?
It is responsible for the removal of the tadpole tail.
What molecule stimulates the removal of a tadpole tail?
A particular thyroid hormone.
What 4 ways is apoptosis essential during adulthood?
It allows for cells that have DNA damage to be destroyed.
It destroys cells that have been infected by viruses and this helps to stop viral infections from spreading.
It helps to eliminate cancer cells.
It will eliminate any auto-immune components of the immune system.
How long does the c.elegans take to develop?
It takes exactly 3 days to develop an egg to a sexually mature organism.
How many cells are present in the adult c.elegans?
Exactly 959 somatic cells all of which have a lineage and function that has been determined.
What process allowed for determining the function of cells within a c.elegans?
Laser ablation.
How many cells will the 959 cells that form the C.elegans arise from?
From 1090 original cells.
How do the 1090 original cells of the c.elegans become the 959 cells that form the developed adult?
131 are killed by apoptosis.
What type of cells make up the 302 cells that are killed by apoptosis in the developing c.elegans?
Neurons.
Who was the scientist that discovered what controlled the fate of the 131 cells that are killed by apoptosis in a developing C.elegans?
Horvitz.
How did Horvitz discover what controlled the fate of the 131 cells that are killed by apoptosis in a developing C.elegans?
He screened for worms that contained undead cells.
What did Horvitz find in the undead cells of c.elegans?
He discovered that they contained 3 interesting genes called CED-3, CED-4 and CED-9.
What did Horvitz find happened to developing c.elegans that expressed mutations in the CED-3 and CED-4 genes?
They not undergo any apoptosis at all and all 1090 cells survived.
What did Horvitz find happened to developing c.elegans that expressed mutations in the CED-9 gene?
They did suffer from apoptosis and this apoptosis killed all 1090 cells.
What did Horzitz conclude from his study of developing C.elegans?
That the genes CED-3 and CED-4 were required for apoptosis.
That CED-9 was responsible for suppressing apoptosis.
