1. Cell death
Apoptosis and necrosis
Name : Amani Riyadh Ahmad Alsharidah.
University number : 435203244
Course: 532 zoo
2. Content
Apoptosis .
Mechanism of apoptosis .
Necrosis.
Necrosis and serum enzyme.
Biological significance .
some necrosis disease .
3. Introduction
The body is very good at maintaining a constant number of
cells.
So there has to exist mechanisms for ensuring other cells in
the body are removed, when appropriate.
Two forms
Apoptosis - suicide - programmed cell death
Necrosis - killing - decay and destruction
4. Apoptosis
is a mode of cell death that occurs under normal physiological
conditions and the cell is an active participant in its own
demise (“cellular suicide”).
It is most often found during normal cell turnover and tissue
homeostasis, embryogenesis, induction and maintenance of
immune tolerance, development of the nervous system and
endocrine-dependent tissue atrophy.
5. Apoptosis
Cell deprived of survival factors activate an intracellular suicide program and die by a process of
programmed cell death called apoptosis .
Cell undergoing apoptosis :
1. Shrink in size but don’t lyse .
2. Their plasma membrane remains intact but portion of the membrane eventually bud off or bleb .
3. Loss their asymmetry and ability to attach to neighboring cell in a tissue .
4. The membrane phospholipid phosphatidylesrine which is normally present on the inner
membrane leaflet oriented toward the cytosol, invert and become exposed on the cell's surface .
5. An active ATP requiring process .
6. Mitochondria of apoptotic cell release cytochrome c but remain within the membrane blebs
7. Chromatin of apoptotic cells segments and condenses .
6. Apoptosis
Apoptotic cell are engulfed by phagocytic cells, macrophages , and
dendritic cells , which bind to the phosphatidylserine on the
membrane surface.
A macrophage internalize and then degrades an apoptotic cell ,
reducing the risk of inflammation from the cell death .
Phagocytic cell also release cytokines and transforming growth
factor that inhibit inflammation .
Therefore , there is no extensive damage done to neighboring cell
in a tissue when a nearby resident cell undergoes apoptosis .
Apoptosis is completed within a few hours .
8. Mechanism of apoptosis
The mechanisms of apoptosis are highly complex and sophisticated, involving an
energy dependent cascade of molecular events
To date, research indicates that there are two main apoptotic pathways :
1. the extrinsic or death receptor pathway
2. the intrinsic or mitochondrial pathway.
there is now evidence that the two pathways are linked and that molecules in one
pathway can influence the other .
10. Necrosis
Necrosis occurs when cells are exposed to extreme variance
from physiological conditions (e.g., hypothermia, hypoxia)
which may result in damage to the plasma membrane.
Under physiological conditions direct damage to the plasma
membrane is evoked by agents like complement and lytic
viruses.
11. Necrosis
Is a passive , pathological process induced by acute injury or disease.
A group of cell in a localized region of a tissue generally undergo
necrosis at the same time after experiencing an insult .
Cell that die by necrosis :
1. Increase the volume and lyse ( burst ).
2. Releasing their intracellular content.
3. Mitochondria and other intracellular components are released.
4. Often inducing a potentially damaging inflammatory response
5. The necrotic process is completed with in several day .
13. Necrosis and serum enzyme
Because intracellular content , including enzyme are released from
necrotic cells .
Measurement of enzyme in serum samples prepared from patients
blood is often done to aid in diagnosis and help to determine a
prognosis .
For example, most cell contain lactate dehydrogenase ,an enzyme that
all cell use to generate ATP from glucose.
When cell from any tissue die by necrosis LDH will appear in the blood .
In fact, LDH is often used as a general marker of necrotic cell death .
14. Biologic significance
Necrosis is atraumatic process resulting in widespread cell death , tissue
damage , inflammation.
Apoptosis has the advantage of eliminating individual cell whose survival
would be harmful to the organism or whose elimination is critical for normal
development or function .
Function of apoptosis :
Elimination of damage cells example when cell damaged beyond repair
infected with virus , or experiencing starvation or the effect of ionizing
radiation or toxin
Development of embryo example apoptotic death of cell between developing
digits must occur for formation of individual fingers and toes .
Homeostasis in normal ,healthy adult the number of cell is kept relatively
constant owing to balance between cell division and cell death .
18. References
Cell and molecular biology book by nalini chandar ,susan viselli ,2010.
Google picture
http://www.fvza.org.
Apoptosis, Cell Death, and Cell Proliferation Manual pdf .
Apoptosis: A Review of Programmed Cell Death , Susan Elmore ,NIEHS,
Laboratory of Experimental Pathology, Research Triangle Park, North Carolina
27709, USA.
