Apoptosis and Cell Regulation Quiz

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Questions and Answers

During which days of embryogenesis does apoptosis occur?

16.5 to 18.5 days

14.5 to 16.5 days

10.5 to 12.5 days

12.5 to 14.5 days (correct)

What happens to liver cell proliferation when part of the liver is removed in an adult rat?

Liver cells proliferate to compensate for the loss (correct)

Liver cells stop dividing completely

Liver cells undergo apoptosis immediately

Liver cells continue to divide at the same rate

What role does apoptosis play in the development of the nervous system?

It increases neuron proliferation

It only occurs during injury recovery

It eliminates excess neurons to form proper connections (correct)

It has no significant role in nervous system development

Which condition is associated with excess apoptosis?

Neurodegenerative diseases Signup and view all the answers

What typically regulates the balance between cell division and cell death in adult tissues?

Both cell division and apoptosis rates Signup and view all the answers

What initiates the extrinsic pathway of apoptosis?

Clustering of death receptors by ligand binding. Signup and view all the answers

Which protein is specifically expressed by activated T cells and is crucial for the extrinsic apoptotic pathway?

Fas ligand (FasL) Signup and view all the answers

Which adaptor protein binds to the cytoplasmic tail of the Fas receptor?

FADD Signup and view all the answers

What role does caspase 8 play in the apoptotic cascade?

It triggers downstream effector caspases like caspase 3. Signup and view all the answers

What is the role of the death domain (DD) in Fas receptor signaling?

To facilitate the interaction with adaptor proteins. Signup and view all the answers

Which family of proteins is cleaved by caspase-8 to regulate mitochondrial integrity during apoptosis?

Bcl-2 family proteins Signup and view all the answers

During apoptosis, which cellular substrates are cleaved by effector caspases?

Actin and lamin Signup and view all the answers

How does Fas ligand (FasL) lead to the death of target cells?

By binding to Fas and activating the extrinsic apoptotic pathway. Signup and view all the answers

Which of the following accurately describes the role of BH3-only proteins in apoptosis?

They are essential initiators of apoptosis that antagonize pro-survival relatives. Signup and view all the answers

What is the function of death receptors in the extrinsic pathway of apoptosis?

They bind ligands to trigger homotrimerization for apoptosis signaling. Signup and view all the answers

Which cytokine is NOT a ligand for death receptors in the extrinsic apoptotic pathway?

Bcl-2 Signup and view all the answers

What happens to procaspases after the formation of the death-inducing signaling complex (DISC)?

They are activated to caspase 8 and 10. Signup and view all the answers

Which process is considered mitochondria-independent in apoptosis?

Extrinsic pathway via death receptors. Signup and view all the answers

What is the role of effector caspases during apoptosis?

They target and cleave key cellular proteins. Signup and view all the answers

How does the cleavage of lamins contribute to apoptosis?

It leads to the disassembly of the nuclear lamina. Signup and view all the answers

What is the effect of activated caspases on cell morphology during apoptosis?

They cause surface blebbing and changes in cell shape. Signup and view all the answers

Which component is primarily responsible for chromosome fragmentation during apoptosis?

Caspase Activated DNase (CAD) Signup and view all the answers

What family of proteins regulates apoptosis by affecting mitochondria?

Bcl-2 family Signup and view all the answers

Which of the following statements about procaspases is correct?

Procaspases must be activated to cleave other proteins in the apoptosis process. Signup and view all the answers

What is the outcome when FAK is cleaved by effector caspases during apoptosis?

Detachment of the apoptotic cell from neighboring cells Signup and view all the answers

What happens to the proteolytic cascade once it is initiated by caspases?

It becomes destructive and self-amplifying. Signup and view all the answers

What is the role of Bax and Bak in the intrinsic pathway of apoptosis?

They induce the release of cytochrome c from mitochondria. Signup and view all the answers

Which caspase is activated first in the apoptosome?

Caspase-9 Signup and view all the answers

What happens when cytochrome c is released into the cytosol?

It promotes the formation of the apoptosome. Signup and view all the answers

Which proteins regulate the intrinsic pathway of apoptosis?

Bcl-2 and pro-apoptotic BH3-only proteins Signup and view all the answers

What is the final outcome of the caspase cascade initiated by the apoptosome?

Apoptosis and cell digestion Signup and view all the answers

What triggers the intrinsic pathway of apoptosis?

Cellular stress and mitochondrial damage Signup and view all the answers

What activates the effector caspases in the intrinsic apoptosis pathway?

Caspase-9 cleaving them Signup and view all the answers

How do growth factors relate to apoptosis regulation?

They promote the synthesis of anti-apoptotic Bcl-2 proteins. Signup and view all the answers

What is the primary role of the interaction between pro-apoptotic Bax and anti-apoptotic Bcl-xL?

To prevent Bax from accumulating in the outer mitochondrial membrane. Signup and view all the answers

How do BH3-only proteins contribute to apoptosis?

They facilitate oligomerization of Bax and Bak in the mitochondrial membrane. Signup and view all the answers

What effect does Akt kinase phosphorylation have on Bad?

It releases Bcl-2, restoring its anti-apoptotic potential. Signup and view all the answers

Which BH3-only proteins can activate apoptosis on their own?

BIM and PUMA Signup and view all the answers

What happens to the mitochondrial membrane when anti-apoptotic molecules are lost?

It becomes permeable, leading to protein leakage. Signup and view all the answers

Which statement best describes the binding specificity of NOXA?

It only binds A1 and MCL1. Signup and view all the answers

What are IAPs primarily involved in regarding apoptosis?

Inhibiting caspases. Signup and view all the answers

Which Bcl-2 family proteins have all four BH domains?

Bcl-2 and Bcl-xL. Signup and view all the answers

Study Notes

Apoptosis

Apoptosis is a programmed cell death process, crucial for multicellular organisms.
It involves a highly organized, tightly regulated sequence of events removing unwanted or damaged cells.
Multicellular organisms regulate cell numbers both through controlling cell division and by controlling the rate of cell death.
Apoptosis helps regulate animal cell numbers, not merely by controlling cell division but also through a process often termed programmed cell death.
Apoptosis is a carefully orchestrated intracellular process of self-destruction, with distinct morphological changes.

Types of Cell Death

Necrosis: Accidental cell death.
- Results from injury or stress.
- Usually associated with inflammation as the cell's contents are released.
Apoptosis: Programmed cell death
- A tightly regulated process that ensures proper removal of unwanted or damaged cells.
- Characterized by fragmentation into apoptotic bodies that are subsequently engulfed by phagocytes.
- No inflammatory response is associated with apoptosis.
Autophagy: Autophagic cell death.
- Involves the formation of cytoplasmic vesicles called autophagosomes that engulf the cell's cytoplasm and organelles.
- Vesicle contents are then degraded by lysosomal enzymes.

Apoptosis vs. Necrosis

Cellular swelling: Occurs in necrosis but not in apoptosis.
Membrane Integrity: Membranes remain intact in apoptosis, but break down in necrosis.
ATP: ATP levels are depleted in necrosis but maintained in apoptosis for a short time.
Inflammatory response: Necrosis triggers an inflammatory response. Apoptosis does not.
DNA fragmentation: DNA fragmentation is random in necrosis, but has a ladder pattern in apoptosis.

Steps in Apoptosis

Initiation: The decision to initiate apoptosis.
Execution: The actual death of the cell.
Phagocytosis: Removal of the cell debris; engulfed cell's remains are digested by phagocytic cells.

Regulation of Apoptosis

Physiological conditions: Necessary for growth, development, and homeostasis; involved in embryonic development and in adult tissues.
Pathological conditions: Crucial in various diseases including degenerative disorders, cancer, tumors and autoimmune disorders.

Caspases

Caspases are cysteine proteases involved in apoptosis.
They exist in inactive precursors (procaspases) and become active through proteolytic cleavage.
Active caspases trigger a cascade that causes morphological changes in the dying cells. (executioners).
Caspase activation is tightly regulated for cellular homeostasis.

Bcl-2 Family

Bcl-2 family proteins: Important regulators involved in apoptosis.
Some are pro-apoptotic (e.g., Bax, Bak)
Some are anti-apoptotic (e.g., Bcl-2, Bcl-xL)
The balance between pro- and anti-apoptotic factors determine whether a cell survives or undergoes apoptosis.

Intrinsic Pathway (Mitochondrial Pathway)

Initiated by internal cellular stresses like DNA damage, and leads to activation of pro-apoptotic factors such as Bax and Bak leading to permeability of mitochondrial membranes (MOMP).
Cytochrome c release into cytosol triggers a cascade involving Apaf-1 which leads to activation of caspase-9, and eventually executioner caspases that cause DNA fragmentation and cell death.

Extrinsic Pathway (Death receptor pathway)

Initiated by external signals like FasL (or TNF-α) binding to death receptors like Fas (or TNF-R).
The binding activates the death-inducing signaling complex (DISC).
The DISC activates initiator caspases (caspase-8).
The activated caspases then trigger a signaling cascade leading to apoptosis.

Convergence of Intrinsic and Extrinsic Pathways

Both pathways converge to activate effector caspases (caspase-3, -6, -7), initiating the final stages of apoptosis.

Regulation of Caspases

Proteolytic cascade (cascade of events involving the cleavage of various proteins to activate downstream caspases) is not only destructive, self-amplifying but also irreversible.
Regulation is essential, as it defines the final decision about whether a cell will die or survive.

Physiological Conditions

Key role in embryonic development; involved in cell number regulation in adult tissues.
Metamorphosis in frogs is an example of programmed cell death.
Normal bodily functions like immune system responses require apoptosis to maintain balance within the cell.

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Description

Test your knowledge on apoptosis during embryogenesis, its role in liver cell proliferation, and its significance in the nervous system. Understand the mechanisms of apoptosis, including the extrinsic pathway and key proteins involved. This quiz will enhance your comprehension of cellular processes and their implications.