72 Questions
What is the main characteristic of apoptotic cells?
Their plasma membrane breaks
Which of the following is NOT a cause of physiological apoptosis?
Pathological conditions
In which type of cell death does the cell activate intrinsic enzymes to degrade its own nuclear DNA and proteins?
Apoptosis
What happens to the plasma membrane of apoptotic cells?
It remains intact but changes structurally
Which term best describes the programmed nature of apoptosis?
Programmed cell death
During which physiological process would you expect to observe apoptotic cell death?
Brain development
What is the primary function of apoptosis in the immune system?
To eliminate potentially harmful self-reactive lymphocytes
What is a common cause of apoptosis in cells?
DNA damage
What is the outcome of apoptosis in an infected cell?
Cellular death
What is a common morphological change observed during apoptosis?
Chromatin condensation
What happens to apoptotic cells or bodies?
They are phagocytosed by macrophages
What is the primary mechanism by which apoptosis occurs in cells?
Through the absence of survival signals
What is the role of caspases in apoptosis?
Break down DNA
Which proteins become imbalanced in the mitochondrial pathway of apoptosis?
Proteins of the BCL2 family
What happens to cytoplasmic proteins in the mechanism of apoptosis?
They shrink
How do the two pathways of apoptosis differ?
In induction and regulation
Which proteins leak from mitochondria in the mitochondrial pathway of apoptosis?
Cytochrome C
What is the main function of the Death receptor (Extrinsic) Pathway in apoptosis?
Activate signaling pathways
What is the primary role of the "death-including signalling complex" in the death receptor pathway?
Activating caspases
Which of the following is a specific example of apoptosis induced by the immune system?
Cytotoxic T lymphocyte stimulated apoptosis
In apoptosis, what happens to the size of the cell compared to necrosis?
Reduced (shrinkage)
Which factor distinguishes the plasma membrane of a cell undergoing apoptosis from that in necrosis?
Intact membrane; altered lipid orientation
What is a common characteristic of cellular contents in necrosis compared to apoptosis?
Enzymatic digestion; may leak out of cell
Which process is more likely to be physiologic rather than pathologic?
Apoptosis in eliminating unwanted cells
Apoptosis is a form of cell death that involves an uncontrolled activation of enzymes.
False
Necrosis and apoptosis have similar features in terms of the cellular response to cell death signals.
False
During apoptosis, cells break up into fragments known as necrotic bodies.
False
Apoptotic cells are not appealing targets for phagocytosis due to their altered plasma membrane structure.
False
Physiological apoptosis occurs during hormone-dependent involution in adult endometrial cells.
True
Apoptosis does not play a role in programmed destruction of cells during embryogenesis.
False
Apoptosis can be initiated through only one signaling pathway.
False
In the mitochondrial pathway of apoptosis, an imbalance in BCL2 proteins leads to caspase activation.
True
Phagocytic recognition in apoptosis is mediated by the expression of annexin V on the cell membrane.
False
Protein cleavage during apoptosis is achieved through the action of protease 'caspases'.
True
Apoptotic bodies formed during DNA breakdown are engulfed by the apoptotic cell itself.
False
The main function of the execution phase in apoptosis is to initiate cell division.
False
Apoptosis can occur due to accumulation of misfolded proteins in endoplasmic reticulum stress.
True
Pathologic atrophy can be observed in parenchymal organs following duct obstruction in the liver.
False
Apoptosis is a common cause of cell death in tumors during active growth.
True
Apoptotic cells are usually phagocytosed by neutrophils during an immune response.
False
Apoptosis is more likely to occur in cells deprived of necessary survival signals like growth factors.
True
In HIV infection, apoptosis can lead to cell death during viral replication.
True
Apoptosis and necrosis can be distinguished by the size of the cell and the status of the nucleus.
True
Necrosis is exclusively a physiological process, while apoptosis is primarily pathologic.
False
The primary role of the 'death-including signalling complex' in the death receptor pathway is to directly activate executioner caspases.
True
In apoptosis, cellular contents may undergo enzymatic digestion, leading to leakage out of the cell.
False
Apoptosis is frequently associated with adjacent inflammation, unlike necrosis.
False
DNA damage-mediated apoptosis is a specific example of apoptosis primarily seen in inflammatory cells.
False
Apoptosis is a pathway of cell death that is induced by an unregulated suicide program.
False
During apoptosis, cells break up into fragments known as apoptotic bodies.
True
Necrosis and apoptosis have identical features in terms of cellular response to cell death signals.
False
Apoptotic cells are not appealing targets for phagocytosis due to their altered plasma membrane structure.
False
Apoptosis primarily occurs in cells when they are damaged beyond repair, especially affecting the cells' RNA.
False
In programmed destruction of cells during embryogenesis, apoptosis does not play a role.
False
Apoptotic bodies are engulfed by the apoptotic cell itself.
False
Protein cleavage during apoptosis is achieved through the action of protease 'caspases'.
True
Necrosis is always pathologic, while apoptosis can be both physiologic and pathologic.
True
Physiological apoptosis occurs during hormone-dependent involution in adult endometrial cells.
False
Apoptosis does not play a role in the programmed destruction of cells during embryogenesis.
False
The main function of the execution phase in apoptosis is to initiate cell division.
False
Apoptosis can be initiated through two main pathways: Death receptor (Extrinsic) Pathway and Mitochondrial (Intrinsic) Pathway.
True
Protein hydrolysis in apoptosis is carried out by protease 'caspases' to break up nuclear scaffold and cytoskeleton.
True
Phagocytic recognition in apoptosis is achieved by expressing phosphatidylserine and annexin V on the cell membrane.
False
Apoptosis is more likely to occur in cells deprived of necessary survival signals like growth factors.
True
During the mitochondrial pathway of apoptosis, proteins of the BCL2 family become imbalanced leading to caspases activation.
True
Activation of caspases is the final step in the execution phase of apoptosis.
False
Apoptosis can be caused by DNA damage resulting from exposure to cytotoxic anticancer drugs.
True
Apoptotic bodies formed during apoptosis are typically phagocytosed by neutrophils.
False
Phagocytosis of apoptotic cells is mainly carried out by lymphocytes.
False
Apoptosis plays a role in the pathologic atrophy of organs like the pancreas.
True
ER stress is a common cause of apoptosis in the central nervous system.
True
Apoptosis can occur in tumorous cells during both regression and growth phases.
True
Study Notes
Apoptosis
- Apoptosis is a pathway of cell death that is induced by a tightly regulated suicide program in which cells destined to die activate intrinsic enzymes that degrade the cells’ own nuclear DNA and nuclear and cytoplasmic proteins.
Characteristics of Apoptosis
- Cell shrinkage (increased density of cytoplasm with tightly packed organelles)
- Chromatin condensation
- Formation of cytoplasmic blebs and apoptotic bodies
- Phagocytosis of apoptotic cells or cell bodies, usually by macrophages
Physiological Situations that can Cause Apoptosis
- Programmed destruction of cells during embryogenesis, implantation, organogenesis, developmental involution, and metamorphosis
- Hormone-dependent involution in the adult endometrial cells that break down during the menstrual cycle
- Cell loss in proliferating cell populations intestinal crypt epithelium (homeostasis)
- Elimination of potentially harmful self-reactive lymphocytes to prevent reactions against one’s own tissues
- Death of neutrophils in an acute inflammatory response and lymphocytes at the end of an immune response cells undergo apoptosis — deprived of necessary survival signals (growth factor)
Pathological Conditions that can Cause Apoptosis
- DNA damage: Radiation, cytotoxic anticancer drugs, and hypoxia can damage DNA either directly or via production of free radicals
- Accumulation of misfold proteins: ER stress – basis of several degenerative diseases of the CNS and other organs
- Cell death in certain infections: particularly viral infections (HIV infection, Viral Hepatitis)
- Pathologic atrophy in parenchymal organs after duct obstruction: pancreas, parotid gland, and kidney
- Cell death in the tumors (during regression or active growth)
Mechanism of Apoptosis
- Two main pathways: Death receptor (Extrinsic) Pathway and Mitochondrial (Intrinsic) Pathway
- Proteolytic cascade involving executioner caspases
- Endonuclease activation
- Breakdown of cytoskeleton
- Nuclear fragmentation and cytoplasmic bleb
- Apoptotic bodies
- Phagocytosis
Comparison of Necrosis and Apoptosis
- Necrosis: Cell size enlarged (swelling), Nucleus: Pyknosis → karyorrhexis → karyolysis, Plasma membrane: Disrupted
- Apoptosis: Cell size reduced (shrinkage), Nucleus: Fragmentation into nucleosome size fragments, Plasma membrane: Intact; altered structure, especially orientation of lipids
Learn about apoptosis, a pathway of cell death induced by a tightly regulated suicide program. This quiz covers the definition of apoptosis, causes of physiological and pathological apoptosis, mechanisms involved, and a comparison of necrosis and apoptosis.
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