The development of the term apoptosis
- Already since the mid-nineteenth century, many observations have indicated that cell death plays a considerable role during physiological processes of multicellular organisms, particularly during embryogenesis and metamorphosis .
- The term programmed cell death was introduced in 1964, proposing that cell death during development is not of accidental nature but follows a sequence of controlled steps leading to locally and temporally defined self-destruction
- Eventually, the term apoptosis had been coined in order to describe the morphological processes leading to controlled cellular self-destruction and was first introduced by Kerr, Wyllie and Currie in 1972.
- Apoptosis is of Greek origin, having the meaning “falling off or dropping off”, in analogy to leaves falling off trees or petals dropping off flowers.
- This analogy emphasizes that the death of living matter is an integral and necessary part of the life cycle of organisms.
- The apoptotic mode of cell death is an active and defined process which plays an important role in the development of multicellular organisms and in the regulation and maintenance of the cell populations in tissues upon physiological and pathological conditions.
- It should be stressed that apoptosis is a well-defined and possibly the most frequent form of programmed cell death, but that other, non-apoptotic types of cell death also might be of biological significance .
The significance of apoptosis
- The development and maintenance of multicellular biological systems depends on a sophisticated interplay between the cells forming the organism, it sometimes even seems to involve an altruistic behaviour of individual cells in favour of the organism as a whole.
- During development many cells are produced in excess which eventually undergo programmed cell death and thereby contribute to sculpturing many organs and tissues.
- Taken together, apoptotic processes are of widespread biological significance, being involved in e.g. development, differentiation, proliferation/homoeostasis, regulation and function of the immune system and in the removal of defect and therefore harmful cells.
- Thus, dysfunction or deregulation of the apoptotic program is implicated in a variety of pathological conditions.
- Defects in apoptosis can result in cancer, autoimmune diseases and spreading of viral infections, while neurodegenerative disorders and AIDS diseases are caused or enhanced by excessive apoptosis.
- Due to its importance in such various biological processes, programmed cell death is a widespread phenomenon, occurring in all kinds of metazoans such as in mammals, insects, nematodes.
- Moreover, programmed cell death also might play a role in plant biology, and apoptosis-like cell death mechanisms even have been observed and used as a model system in yeast.
- Fascinating insights into the origin and evolution of programmed cell death might possibly be given by the fact, that programmed cell death is also an integral part of the life cycle of other unicellular eukaryotes and that even prokaryotes.
Morphological features of apoptosis
- Apoptotic cells can be recognized by stereotypical morphological changes: the cell shrinks, shows deformation and looses contact to its neighboring cells.
- Its chromatin condenses and migrate at the nuclear membrane and finally the cell is fragmented into compact membrane-enclosed structures, called ‘apoptotic bodies’ which contain cytosol, the condensed chromatin, and organelles.
- The apoptotic bodies are engulfed by macrophages and thus are removed from the tissue without causing an inflammatory response.
- Those morphological changes are a consequence of characteristic molecular and biochemical events occurring in an apoptotic cell, most notably the activation of proteolytic enzymes which eventually mediate the cleavage of DNA into oligo-nucleosomal fragments as well as the cleavage of a multitude of specific protein substrates which usually determine the integrity and shape of the cytoplasm or organelles .
🧬 Section 1: Origin and Definition of Apoptosis
- Who coined the term “apoptosis”?
A) Darwin
B) Kerr, Wyllie, and Currie
C) Watson and Crick
D) Schleiden and Schwann
Answer: B) Kerr, Wyllie, and Currie - In which year was the term “apoptosis” introduced?
A) 1964
B) 1972
C) 1982
D) 1950
Answer: B) 1972 - The word “apoptosis” is derived from which language?
A) Latin
B) Sanskrit
C) Greek
D) Hebrew
Answer: C) Greek - What is the literal meaning of “apoptosis”?
A) Death by accident
B) Growing together
C) Falling off or dropping off
D) Splitting into two
Answer: C) Falling off or dropping off - Which process was apoptosis compared to, according to its Greek meaning?
A) Falling snow
B) Petals dropping from flowers
C) Ice melting
D) Wind blowing
Answer: B) Petals dropping from flowers - Which of the following is the most frequent form of programmed cell death?
A) Necrosis
B) Autophagy
C) Apoptosis
D) Pyroptosis
Answer: C) Apoptosis - What does the term “programmed cell death” suggest?
A) Cell death is accidental
B) Cell death follows a defined sequence
C) Cells die due to infections only
D) Cells never die naturally
Answer: B) Cell death follows a defined sequence - In which year was the term “programmed cell death” first introduced?
A) 1954
B) 1964
C) 1972
D) 1980
Answer: B) 1964 - Which processes first indicated the presence of cell death in development?
A) DNA replication
B) Embryogenesis and metamorphosis
C) Cell fusion
D) Photosynthesis
Answer: B) Embryogenesis and metamorphosis - Apoptosis is a type of:
A) Passive process
B) Random process
C) Active and defined process
D) Inflammatory process
Answer: C) Active and defined process
🌱 Section 2: Biological Significance of Apoptosis
- Apoptosis contributes to which of the following?
A) Organ shaping during development
B) Muscle hypertrophy
C) Cell wall formation
D) Protein synthesis
Answer: A) Organ shaping during development - Apoptosis is involved in all of the following EXCEPT:
A) Immune system function
B) Homeostasis
C) Random cell lysis
D) Differentiation
Answer: C) Random cell lysis - Which disease is associated with defective apoptosis?
A) Cancer
B) Fever
C) Hypertension
D) Obesity
Answer: A) Cancer - Which condition is caused or enhanced by excessive apoptosis?
A) Diabetes
B) Neurodegenerative disorders
C) Obesity
D) Asthma
Answer: B) Neurodegenerative disorders - Apoptosis is often described as a form of:
A) Aggressive cell behavior
B) Altruistic cell behavior
C) Passive cell degeneration
D) Viral response
Answer: B) Altruistic cell behavior - What is the consequence of impaired apoptotic mechanisms?
A) Faster healing
B) Uncontrolled cell proliferation
C) Enhanced memory
D) Increased photosynthesis
Answer: B) Uncontrolled cell proliferation - Which disease is NOT directly associated with apoptosis malfunction?
A) Autoimmune diseases
B) Cancer
C) Viral infections
D) Flu
Answer: D) Flu - Which organisms show evidence of apoptosis-like cell death?
A) Only mammals
B) Only plants
C) Only bacteria
D) All metazoans and even some unicellular organisms
Answer: D) All metazoans and even some unicellular organisms - In yeast, apoptosis-like mechanisms are used as:
A) Viruses
B) Model systems
C) Growth regulators
D) Inflammation triggers
Answer: B) Model systems - Which of the following is NOT a function of apoptosis?
A) Removal of harmful cells
B) Organ development
C) Inflammatory response
D) Cell population regulation
Answer: C) Inflammatory response
🔬 Section 3: Morphological Features of Apoptosis
- What is the first morphological change seen in an apoptotic cell?
A) Cell swelling
B) Cell shrinking
C) Cell explosion
D) Membrane rupture
Answer: B) Cell shrinking - What happens to the chromatin during apoptosis?
A) It melts
B) It condenses and migrates to the nuclear membrane
C) It is excreted
D) It duplicates
Answer: B) It condenses and migrates to the nuclear membrane - Apoptotic bodies are:
A) Swollen cells
B) Virus particles
C) Membrane-bound fragments containing cytosol and organelles
D) Nucleus-free fragments
Answer: C) Membrane-bound fragments containing cytosol and organelles - Apoptotic bodies are removed by:
A) Neurons
B) RBCs
C) Macrophages
D) Bacteria
Answer: C) Macrophages - Apoptosis does NOT cause:
A) DNA fragmentation
B) Inflammatory response
C) Activation of proteases
D) Formation of apoptotic bodies
Answer: B) Inflammatory response - Which enzymes play a key role in apoptosis?
A) DNA ligases
B) Proteolytic enzymes (proteases)
C) Kinases only
D) RNA polymerases
Answer: B) Proteolytic enzymes (proteases) - Which process is a hallmark of apoptosis at the molecular level?
A) DNA methylation
B) DNA fragmentation into oligonucleosomal units
C) Telomerase activation
D) RNA splicing
Answer: B) DNA fragmentation into oligonucleosomal units - During apoptosis, the cell:
A) Loses contact with neighboring cells
B) Rapidly divides
C) Forms multinucleated structures
D) Undergoes lysis
Answer: A) Loses contact with neighboring cells - Which structure is NOT found in apoptotic bodies?
A) Cytosol
B) Condensed chromatin
C) Organelles
D) Ribosomes
Answer: D) Ribosomes - What protects surrounding tissues from damage during apoptosis?
A) Inflammation
B) Apoptotic lysis
C) Membrane-enclosed apoptotic bodies
D) Cell fusion
Answer: C) Membrane-enclosed apoptotic bodies
🧪 Section 4: Miscellaneous and Evolutionary Aspects
- Which system shows involvement of apoptosis in regulating cell numbers?
A) Nervous system
B) Respiratory system
C) Immune system
D) Digestive system
Answer: C) Immune system - Apoptosis is considered crucial for:
A) Growth of bacteria
B) Metabolism in protozoa
C) Life cycle regulation in multicellular organisms
D) Photosynthesis in plants
Answer: C) Life cycle regulation in multicellular organisms - Excess production of cells followed by apoptosis during development is called:
A) Cell aging
B) Sculpturing of tissues
C) Mutation
D) Necrosis
Answer: B) Sculpturing of tissues - The apoptotic program helps prevent:
A) Cell division
B) Excess oxygen
C) Proliferation of defective cells
D) Cell respiration
Answer: C) Proliferation of defective cells - Which unicellular organisms also show programmed cell death?
A) Amoeba only
B) Yeast and prokaryotes
C) Viruses
D) Algae only
Answer: B) Yeast and prokaryotes - Apoptosis in plants is:
A) Impossible
B) Non-existent
C) Possibly present
D) Fully absent
Answer: C) Possibly present - Which disease is not linked to defective apoptosis?
A) AIDS
B) Alzheimer’s
C) Tuberculosis
D) Cancer
Answer: C) Tuberculosis - Apoptotic response to infection helps to:
A) Spread the infection
B) Inhibit immune cells
C) Limit viral spread
D) Increase cell growth
Answer: C) Limit viral spread - Apoptosis is observed in which metazoans?
A) Mammals
B) Insects
C) Nematodes
D) All of the above
Answer: D) All of the above - Which form of cell death causes inflammation?
A) Apoptosis
B) Programmed cell death
C) Necrosis
D) Autophagy
Answer: C) Necrosis
🔁 Section 5: Applied and Functional Understanding
- Programmed cell death is a:
A) Rare phenomenon
B) Widespread phenomenon
C) Human-specific process
D) Accidental process
Answer: B) Widespread phenomenon - Which system is regulated by apoptosis?
A) Muscular
B) Excretory
C) Immune
D) Circulatory
Answer: C) Immune - Which of these is a key hallmark of apoptosis?
A) Random cell swelling
B) Loss of organelles
C) Nuclear chromatin condensation
D) Cell lysis
Answer: C) Nuclear chromatin condensation - Which feature distinguishes apoptosis from necrosis?
A) Random process
B) Energy independence
C) Absence of inflammation
D) Cell fusion
Answer: C) Absence of inflammation - Which is an evolutionary implication of apoptosis?
A) Supports mutation spread
B) Prevents evolution
C) May be traced in unicellular organisms
D) Unique to vertebrates
Answer: C) May be traced in unicellular organisms - Which is NOT a feature of apoptosis?
A) DNA fragmentation
B) Protease activation
C) Cytosol condensation
D) Osmotic burst
Answer: D) Osmotic burst - What removes apoptotic bodies from tissues?
A) Neutrophils
B) Macrophages
C) Erythrocytes
D) Lymphocytes
Answer: B) Macrophages - Apoptotic cells lose contact with:
A) DNA
B) Other organs
C) Neighboring cells
D) Ribosomes
Answer: C) Neighboring cells - Apoptosis is involved in the maintenance of:
A) Metabolism
B) Homeostasis
C) pH balance
D) Blood pressure
Answer: B) Homeostasis - What prevents apoptosis from causing inflammation?
A) Cytolysis
B) Controlled degradation and phagocytosis
C) Cell explosion
D) ROS release
Answer: B) Controlled degradation and phagocytosis