Apoptosis Mechanisms

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary characteristic of necrosis compared to apoptosis?

Necrosis causes inflammation and affects surrounding areas. (correct)

Necrosis involves a programmed death process.

Necrosis is always beneficial for cellular maintenance.

Necrosis occurs only when cells are instructed to die.

Which protein plays a crucial role in activating the intrinsic pathway of apoptosis?

Fas ligand

BH3-only proteins (correct)

BAX

BCL2

What initiates the extrinsic pathway of apoptosis?

Leakage of cytochrome C from mitochondria

DNA damage within the cell

Internal cellular stress signals

Binding of death ligands to death receptors (correct)

The activation of which proteins leads to the release of cytochrome C in the intrinsic pathway?

Pro-apoptotic proteins Signup and view all the answers

What is the effect of anti-apoptotic proteins like BCL2 in the intrinsic pathway?

They inhibit the leakage of pro-apoptotic proteins from the mitochondria. Signup and view all the answers

Which of the following is NOT a trigger for the intrinsic pathway of apoptosis?

Binding of Fas ligand Signup and view all the answers

What role do initiator caspases play in the apoptosis process?

They activate other downstream executioner caspases. Signup and view all the answers

Which of the following correctly describes the role of CD8 T-cells in apoptosis?

They bind to death ligands and trigger caspase activation. Signup and view all the answers

What initiates the formation of the Death Inducing Signalling Complex (DISC) in the extrinsic pathway of apoptosis?

Binding of FADD to pro-caspase 8 Signup and view all the answers

Which pathway is directly influenced by the activation of executioner caspases 3, 6, and 7?

Intrinsic apoptotic pathway Signup and view all the answers

How does granzyme B contribute to the activation of the intrinsic apoptotic pathway?

By cleaving Bid and activating caspase 3 Signup and view all the answers

What is the role of cytotoxic T cells in the apoptosis process?

To recognize and bind to abnormal antigens Signup and view all the answers

Which feature is NOT associated with the processes carried out by activated executioner caspases during apoptosis?

Formation of protrusions in cell membranes Signup and view all the answers

In the intrinsic pathway, what triggers the release of cytochrome C from the mitochondria?

Activation of BH3-only proteins Signup and view all the answers

What is the primary change in cells that undergo hypertrophy due to stress?

Increase in cell size Signup and view all the answers

Which process is inhibited during apoptosis to prevent uncontrolled cell growth?

Caspase activation Signup and view all the answers

What is the role of Cytochrome C in the intrinsic pathway of apoptosis?

It binds to APAF-1 to form the apoptosome. Signup and view all the answers

Which of the following correctly describes the role of caspase 9?

It activates executioner caspases after being processed from pro-caspase 9. Signup and view all the answers

What initiates apoptosis in the extrinsic pathway?

Attachment of FAS ligands to FAS receptors on target cells. Signup and view all the answers

What role does FADD play in the apoptosis process?

It acts as a bridge between FAS ligands and initiator caspases. Signup and view all the answers

Which of the following is NOT a method by which executioner caspases induce apoptosis?

Activation of growth factor receptors. Signup and view all the answers

What is the function of CD 8 T-cells in the apoptosis process?

They bind to FAS receptors on damaged cells to trigger apoptosis. Signup and view all the answers

During apoptosis, which of the following events occurs last in the intrinsic pathway?

Activation of executioner caspases. Signup and view all the answers

Which statement about death ligands and their receptors is accurate?

Death ligands initiate the aggregation of their respective receptors. Signup and view all the answers

Which mechanism of cell death is characterized by inflammation and uncontrolled cell destruction?

Necrosis Signup and view all the answers

Which pathway is primarily regulated by internal stress signals like DNA damage?

Intrinsic pathway Signup and view all the answers

What is the role of BH3-only proteins in the intrinsic pathway of apoptosis?

Activate pro-apoptotic proteins and inhibit anti-apoptotic proteins Signup and view all the answers

What is the primary consequence of the activation of pro-apoptotic proteins in the intrinsic pathway?

Formation of channels in the mitochondrial membrane Signup and view all the answers

Which of the following is a key characteristic distinguishing apoptosis from necrosis?

Apoptosis is a programmed cell death process. Signup and view all the answers

In the extrinsic pathway of apoptosis, what initiates the signaling cascade leading to cell death?

Binding of death ligands to their receptors Signup and view all the answers

Which of the following proteins is inhibited by BH3-only proteins during the intrinsic pathway?

BCL2 Signup and view all the answers

What triggers the release of cytochrome C into the cytoplasm during apoptosis?

Formation of mitochondrial channels by pro-apoptotic proteins Signup and view all the answers

Which type of cell death is best described as a controlled process crucial for normal development?

Apoptosis Signup and view all the answers

What is the main role of executioner caspases in apoptosis?

Execute the final steps of cell death Signup and view all the answers

What is the best description of cellular adaptation?

A change in structure or function to survive stress. Signup and view all the answers

Which type of cellular response involves an increase in cell size?

Hypertrophy Signup and view all the answers

What happens during reversible injury to a cell?

The cell can recover if the stressor is removed. Signup and view all the answers

What is a likely outcome of prolonged or intense cellular stress?

Irreversible injury and potentially cell death. Signup and view all the answers

What is metaplasia in cellular response to stress?

A change from one cell type to another. Signup and view all the answers

Which of the following factors does NOT significantly influence a cell's response to stress?

Color of the tissue Signup and view all the answers

In the context of cellular stress responses, what does atrophy indicate?

Decrease in cell size and function. Signup and view all the answers

What is a characteristic of irreversible injury in cells?

Cell death occurs due to severe damage. Signup and view all the answers

How does adaptation help cells cope with low oxygen levels?

By producing more red blood cells. Signup and view all the answers

What is a common adaptive response to high toxic exposure?

Metaplasia Signup and view all the answers

What occurs after caspase-8 is activated in the apoptosis process?

It activates executioner caspases 3, 6, and 7. Signup and view all the answers

How do cytotoxic T cells trigger apoptosis in target cells?

By releasing perforin that creates pores in the target cell membrane. Signup and view all the answers

What is the role of granzyme B in the apoptosis process?

To activate pro-apoptotic proteins and executioner caspases. Signup and view all the answers

What eventually results from the activation of executioner caspases in apoptosis?

Cleavage of structural proteins and DNA fragmentation. Signup and view all the answers

What type of cellular adaptive response involves an increase in cell size?

Hypertrophy. Signup and view all the answers

What is the role of BH3-only proteins in the apoptosis pathway?

To promote the release of cytochrome C from the mitochondria. Signup and view all the answers

Which feature is characteristic of apoptosis as a mechanism of cell death?

Formation of apoptotic bodies. Signup and view all the answers

What is a consequence of pro-caspase cleavage during the apoptosis process?

Activation of caspase enzymes for cell breakdown. Signup and view all the answers

Which statement accurately describes the intrinsic apoptosis pathway?

It is initiated by the release of cytochrome C from mitochondria. Signup and view all the answers

What is the primary function of the Death Inducing Signalling Complex (DISC) in apoptosis?

To bind initiator caspases and activate them for apoptosis. Signup and view all the answers

What is the first step that occurs when cytochrome C leaks into the cytoplasm?

Binding with APAF-1 to form the apoptosome Signup and view all the answers

Which molecule is activated by the binding of caspase 9 with executioner caspases?

Caspases 3 and 6 Signup and view all the answers

What role do executioner caspases play in the apoptosis process?

They cause DNA fragmentation and cleave structural proteins. Signup and view all the answers

Which of the following statements about the binding of FAS ligands and receptors is correct?

Binding of FAS ligands to FAS receptors initiates apoptosis in damaged cells. Signup and view all the answers

What is the primary function of FADD in the apoptosis pathway?

To bridge FAS ligands and initiator caspases. Signup and view all the answers

Which type of apoptosis pathway is described as originating from outside the cell?

Extrinsic pathway Signup and view all the answers

During the extrinsic pathway, what is the effect of death ligands binding to their receptors?

They cause aggregation of death receptors. Signup and view all the answers

Which of the following does NOT occur as a method of apoptosis by executioner caspases?

Release of cytochrome C into the cytoplasm Signup and view all the answers

Which role do cytotoxic CD 8 T-cells serve in apoptosis?

They induce apoptosis in damaged cells via FAS ligands. Signup and view all the answers

What outcome results from the aggregation of death receptors in the extrinsic apoptosis pathway?

Recruitment of initiator caspases Signup and view all the answers

Study Notes

Apoptosis

Apoptosis is a process of programmed cell death that is essential for normal development, tissue homeostasis, and the elimination of damaged or unwanted cells.
It is a highly regulated process that eliminates cells in a controlled manner, minimizing damage to surrounding cells.
Key features include:
- Cell shrinkage
- Nuclear fragmentation
- Formation of apoptotic bodies
- No inflammatory response

Mechanisms of Apoptosis

Intrinsic pathway (mitochondrial pathway): This pathway is activated by internal stress signals, such as DNA damage, oxidative stress, or protein misfolding.
- BH3-only proteins are activated by the stress signal.
- They activate pro-apoptotic proteins (BAX and BAK), leading to the formation of channels in the mitochondrial membrane.
- These channels release proteins (cytochrome C, SMAC/DIABLO) into the cytoplasm.
- Cytochrome C binds to the adaptor protein APAF-1, forming a complex called the apoptosome.
- The apoptosome activates caspase-9, an initiator caspase.
- Caspase-9 activates executioner caspases like caspase-3 and -6.
- Executioner caspases cause the breakdown of cellular components, ultimately leading to apoptosis.
Extrinsic pathway: This pathway is activated by external signals, such as death ligands (Fas ligand, TNF) binding to their respective death receptors (Fas receptor, TNF receptor). - Binding of death ligands triggers the formation of a complex called the death-inducing signaling complex (DISC) which activates caspase-8 (or caspase-10). - Caspase-8 can directly activate executioner caspases or activate BH3-only proteins, triggering the intrinsic pathway.
Granzyme/Perforin pathway: This pathway is used by cytotoxic T lymphocytes (CTL) and natural killer (NK) cells to eliminate infected or cancerous cells.
- CTL and NK cells release perforin, a pore-forming protein, and granzymes, serine proteases, into the target cell.
- Perforin creates pores in the target cell membrane, allowing granzymes to enter the cell.
- Granzyme B, a key granzyme, activates the intrinsic pathway by cleaving caspase-3 or Bid, a pro-apoptotic BH3-only protein.

Adaptations to Stress

Adaption is a cellular response to stress that enables cells to maintain function or avoid injury.
Hypertrophy is an increase in cell size, often seen in cells that are unable to divide in response to increased workload.
Atrophy is a decrease in cell size due to reduced workload or nutrient deficiency.
Metaplasia occurs when one cell type is replaced by another, often in response to chronic injury. This can be reversible.
Dysplasia refers to abnormal cell growth and is often considered precancerous.

Cell Death

Cell death can occur via two major pathways:
- Necrosis: It's uncontrolled cell death caused by severe damage to the cell. It results in inflammation.
- Apoptosis: It's a programmed and controlled cell death that helps maintain tissue homeostasis and eliminates damaged cells without causing inflammation.

Cellular Responses to Stress

Cells respond to stress based on stressor type, intensity, and duration.
Adaptation is the cell's response to mild or chronic stress for survival.
Reversible Injury occurs when intense but short-lived stress causes recoverable damage.
Irreversible Injury and Cell Death is caused by prolonged or intense stress leading to cell death.

Irreversible Injury and Cell Death

Necrosis is uncontrolled cell death resulting from severe damage and inflammation.
Apoptosis is programmed cell death, a controlled process vital for development and maintenance.

Apoptosis Pathways

Intrinsic Pathway (Mitochondrial Pathway): Triggered by internal signals like DNA damage.
- BH3-ONLY Proteins activate pro-apoptotic proteins (BAX, BAK) and inhibit anti-apoptotic proteins (BCL2, BCLXL).
- Cytochrome C is released from mitochondria, activating the apoptotic cascade.
Extrinsic Pathway: Triggered by external death ligands binding to death receptors on the cell surface.
- Death Ligands (Fas ligand, TNF) bind to receptors (Fas, TNF receptor) and activate initiator caspases.
Granzyme/Perforin Pathway: Cytotoxic T cells release perforin to create pores in target cells, allowing granzymes to enter and activate apoptosis.

Adaptive Responses to Stress

Hypertrophy: Increase in cell size, common in cells that don't divide, like muscle cells responding to increased workload.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the intricate process of apoptosis, which is vital for cell regulation and development. This quiz covers both the intrinsic and extrinsic pathways involved in programmed cell death, featuring key concepts like mitochondrial involvement and apoptotic bodies.