APOPTOSIS
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It is a process of normal or programmed “cell death.”
The word “APOPTOSIS” comes from the Greek meaning “falling petals from a flower” or “falling leaves
from a tree in autumn.”
 Apoptosis or Programmed cells death (PCD) is mode of cell death that occurs under normal
physiological condition and the cell is an active participant in its own demise.
 It is important for the development of multicultural organism (embryonic development) and
homeostasis of their tissues (adult)
 In human body, cells were producing every second by MITOSIS which is similar number dyeing cells by
APOPTOSIS.
 Apoptosis also exerts a role opposite to mitosis in the maintenance of cell populations”
 In human body, cells were producing every second by MITOSIS which is similar number dyeing cells by
APOPTOSIS. (BALANCE)
APOPTOSIS HAS TWO TYPES
 PHYSIOLOGICAL (programmed cell)
 Which means unwanted or useless cell are eliminated during development and other normal biological
process.
EXAMPLE:
o Embryogenesis
o Death of cells that have completed their functions.
 Lack of apoptosis in humans can lead to webbed fingers called “SYNDACTYLY”.
 PATHOLOGICAL (Unprogrammed cell)
 Which occur when cells are exposed to a serios physical or chemical insult.(heat, radiation).
EXAMPLES:
o DNA damage
o Accumulation of misfolded proteins
o Cell death in certain infection
 VIRAL INFECTION (HIV) “human infected diseases”
SIGNALING PATHWAY APOPTOSIS
(A) INTRIMSIC PATHWAY
 The intrinsic pathway of apoptosis pathway begins when an injury occurs INSIDE the cell and the
resulting stress activates the apoptotic pathway
 DNA Damage
 Misfold proteins
 Malfunction of telomeres
(B) EXTRIMSIC PATHWAY
 The extrinsic pathway of apoptosis begins OUTSIDE a cell, when conditions in the extracellular
environment determine that a cell must die
 Radiation (X-rays)
 Viral infection (HIV)
 Nutrient loss
MECHANISMS
Death signal/STIMULI (EXTRINSIC OR ONTRINSIC)
Regulator of apoptosis (BCL2 proteins)
INITATION (Death decision)
EXECUTION (Executioner enzymes “Caspase”)
DEGRADATION (Apoptic body)
ENGULFMENT (Phagocyte, scavenger cells)