Apoptosis Flashcards
what is apoptosis
the controlled death of cells in the body. it removes cells without spilling their contents into the internal environment.
what are the pathways of apoptosis
- mitochondrial pathway
- death receptor pathway
mitochondrial pathway or intrinsic pathway
- initiated by detecting internal damage to cells.
- when detected they release cytochrome C into the cytosol. These bind to proteins and form an apoptosome.
apoptosome
binds to proteins and activates caspase enzymes which will initiate apoptosis.
death receptor pathway or extrinsic pathway
detect death signaling molecules by death receptor proteins on the surface of the cell.
When they bind to the death receptor surface proteins, caspase enzymes are activated which will initiate apoptosis.
stages of apoptosis
- caspases are activated ( mitochondria detect internal DNA damage and release cytochrome c ).
- the contents of the cells is digested and organelles are broken down.
- the cell and nucleus shrinks as the intracellular materials are broken down.
- membrane blebbing and breakage occur as the cytoskeleton is digested. The membrane will wrap and detach itself from the cell is apoptotic bodies which contain broken down intracellular materials.
what happens if the cell cycle is insufficient or disrupted?
the damaged cells can replicate exponentially which can therefore lead to the development of cancer and tumors.
what happens when apoptosis decreases and why?
apoptosis may decrease due to inefficient cells being detected at the various checkpoints. As a result, cell growth can increase which will result in a tumor being formed.
types of tumors
benign tumors
malignant tumors
benign tumors
- slow growing
- generally enclosed in capsules that will prevent abnormal cells from separating and invading parts of the body.
malignant tumors
some cells of benign tumors can mutate and invade tissues. They can also enter the bloodstream. therefore it can grow and travel over time.
these tumors are the only tumors that are seen as cancerous. this is due to the fact that they migrate.
characteristics of tumors
- self sufficient
- antigrowth deactivation
- increased survival
- blood supply formation
- tissue invasion and metastasis.
characteristics self sufficiency
tumor cells replicate without the use of chemical signals. instead, they produce their own signal or activate cell growth and replication pathways.
characteristics antigrowth deactivation
they can disable mechanisms that prevent replication when they are not needed.
characteristics increased survival
due to the fact that apoptosis doesn’t occur in tumor cells, they can divide and enhance their survival
characteristics blood supply formation
they can form new blood vessels that maintains adequate nutrients and oxygen supplies.
characteristics tissue invasion and metastasis
once they become cancerous they invade layers of tissue through the blood vessels.
types of cell death
- necrosis
- apoptosis
necrosis
a form of cell death that is unregulated and uncontrolled through an external force like trauma or infection. the cell will swell and rupture its contents into the internal environment. This can cause inflammation in the tissue.
purpose of apoptosis
cells that are damaged are eliminated.
sculpts the body from tissue during the fetal stage
Initiation stage of apoptosis in the intrinsic pathway.
a type of death ligand that will be released by a natural killer cell which would find a cell that needs to die and releases FasL. FasL will bind to a receptor on the surface ( FasR) which will draw two other FasR’s. These will attract the molecules FADD ( two of them ). then they draw in two molecules called Procaspase 8. Procaspase 8 will then have its top cut of to create an enzyme called caspase 8 which attaches to procaspase 3, which has its head cut of and turns into caspase 3 which cuts the cytoskeleton. which results in the cell collapsing. this occurs in the mitochondrial pathway
execution
when the cytoskeleton is cut up during caspase 3, the cell will begin to shrink and starts blebbing whilst the chromatins and nucleus condense. The blebs break away from the cell body and chromatins and nucleus become fragmented.
phagocyte
a number of white cells used to engulf foreign matter
apoptotic vesicles
a bleb when it has broken away from the cell.
phagocytosis
the cell debris in the apoptotic vesicles is engulfed by phagocyte through exocytosis
cancer cells
cells that are unspecialised and grow rapidly and out of control which forms a tumor.
malignant
invades normal tissue.
