Retta - L17

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Questions and Answers

What are the two major mechanisms that regulate apoptosis?

Intrinsic and extrinsic pathways (correct)

Cell growth and cell division

Necrosis and autophagy

Mitogenic and inhibitory pathways

Which family of proteins plays a crucial role in mediating apoptosis?

Proteasome family

Bcl2 family (correct)

MAP kinase family

Cyclin family

How does cell proliferation relate to cell division?

They are independent processes regulated by different factors. (correct)

Cell proliferation is the direct outcome of cell division.

Cell division depends solely on the intrinsic pathways.

Cell proliferation requires growth factors but not mitogens.

What role do growth factors play in cellular processes?

They promote cell growth by increasing protein synthesis and decreasing degradation. Signup and view all the answers

What is the function of the protein kinase mentioned in the content?

To phosphorylate proteins and stimulate synthesis Signup and view all the answers

What are extracellular growth factors known to influence?

Both cell growth and division, depending on the cell type Signup and view all the answers

Which compound is mentioned as having a therapeutic potential for treating certain diseases?

Rapamycin Signup and view all the answers

What is a significant characteristic of apoptosis in animal cells?

It is a physiological process with meaningful regulation. Signup and view all the answers

What is the role of p53 when DNA damage occurs in cells?

p53 is phosphorylated, stabilizing it to trigger cell cycle arrest or apoptosis. Signup and view all the answers

Which of the following factors must be present for cellular proliferation to occur?

Both growth factors and nutrients must be present. Signup and view all the answers

How does the accumulation of p21 relate to DNA damage response?

p21 inhibits cyclin-dependent kinases, blocking the cell cycle. Signup and view all the answers

What is the relationship between Bax and bcl2 in apoptosis regulation?

Bax induces apoptosis while bcl2 inhibits it. Signup and view all the answers

What occurs to abnormal cells when DNA damage is severe and irreparable?

They are induced to undergo apoptosis. Signup and view all the answers

What defines the physiological process of apoptosis?

A tightly regulated mechanism mediated by caspases. Signup and view all the answers

How does the ATM/ATR kinase system respond to DNA damage?

It senses DNA damage and activates downstream kinases. Signup and view all the answers

What does a mutation in Ras typically lead to in the context of cell proliferation?

Constant activation that promotes excessive Myc synthesis. Signup and view all the answers

What is the consequence of an imbalance between cell proliferation and apoptosis?

Development of tissue atrophy when apoptosis is prevalent. Signup and view all the answers

What is the role of initiator caspases in the apoptosis process?

They activate other caspases that play a direct role in apoptosis. Signup and view all the answers

What process is responsible for recycling functional macromolecules and eliminating harmful proteins in cells?

Autophagy Signup and view all the answers

Which statement best describes the relationship between protein structure and function in the context of procaspases?

Structural conformation changes can activate procaspases. Signup and view all the answers

What mechanism triggers apoptosis through cell surface death receptors?

Extrinsic stimuli sensed by death receptors. Signup and view all the answers

Which type of autophagy specifically targets altered proteins for degradation?

Chaperone-mediated autophagy Signup and view all the answers

What is one morphological feature that distinguishes apoptotic cells from necrotic cells?

Apoptotic cells exhibit rounded shape and intact plasma membranes. Signup and view all the answers

What is the main purpose of mitophagy?

To degrade abnormal mitochondria Signup and view all the answers

What is the key characteristic of microautophagy?

Engulfs cargo directly into the lysosome Signup and view all the answers

What is a primary function of IAP (inhibitor of apoptosis) proteins concerning apoptosis?

IAPs inhibit apoptotic inducers to promote cell survival. Signup and view all the answers

Which feature is indicative of apoptotic cells during biochemical analysis?

Fragmentation of chromosomal DNA. Signup and view all the answers

Who was awarded the Nobel Prize in 2016 for discovering the mechanism of autophagy?

Yoshinori Ohsumi Signup and view all the answers

How does phosphorylation primarily affect the conformation of proteins?

It adds phosphate groups changing the protein shape. Signup and view all the answers

What is the impact of cytochrome c relocation during apoptosis?

It promotes the activation of downstream effector caspases. Signup and view all the answers

Which apoptosis receptor is related to the monitoring of external death signals?

FAS. Signup and view all the answers

What signifies the intrinsic pathway of apoptosis with respect to mitochondria?

Loss of mitochondrial membrane potential. Signup and view all the answers

What feature distinguishes apoptosis from necrosis during cell death?

Chromatin condensation Signup and view all the answers

What role do phagocytic cells play in apoptosis?

They remove apoptotic bodies. Signup and view all the answers

Which statement accurately describes the process of autophagy?

It recycles cellular components for reuse. Signup and view all the answers

What is a primary function of necroptosis?

To act as a backup cell death mechanism when apoptosis is inhibited. Signup and view all the answers

How do necrotic cells primarily affect surrounding tissues?

By causing inflammatory responses and tissue damage. Signup and view all the answers

What initiates the formation of an autophagosome?

The development of a phagophore around damaged organelles. Signup and view all the answers

What happens during the necrotic cell death process?

Cell membranes break down and release contents. Signup and view all the answers

In which scenario is apoptosis favored over necrosis?

When cells are moderately damaged with sufficient ATP. Signup and view all the answers

Which cellular change is NOT characteristic of necrosis?

Cellular membrane integrity maintenance Signup and view all the answers

What is the primary outcome of the autophagy process?

Degradation of damaged organelles and proteins. Signup and view all the answers

Study Notes

Apoptosis Overview

Apoptosis is a physiological process that regulates animal cell numbers through controlled cell death.
Two main pathways of apoptosis: intrinsic and extrinsic, which are influenced by extracellular factors.

Mechanisms of Cell Growth and Division

Cell proliferation equals cell division, influenced by extracellular growth factors that also promote cell growth.
Different organisms may separate triggers for cell growth and division; some require both growth factors and nutrients.
Protein kinases, such as mTOR, stimulate protein synthesis while inhibiting degradation.

Balance Between Cell Proliferation and Cell Death

Coordination of cell proliferation and apoptosis is crucial for regulating tissue growth.
Bax promotes apoptosis, while Bcl-2 supports cell survival; an equilibrium between these factors is essential for normal physiological processes.

DNA Damage and Apoptosis

DNA damage can trigger apoptosis if repair mechanisms fail; this serves as protection against pathological conditions like cancer.
Activation of the ATM/ATR kinase system phosphorylates p53, which promotes cell cycle arrest or induces apoptosis.

Caspases and Apoptosis

Apoptosis is mediated by caspases, proteolytic enzymes that cleave specific proteins to induce cell death.
Initiator caspases (e.g., caspases 8 and 9) activate effector caspases (e.g., caspases 3 and 7) to trigger the apoptotic cascade.

Extrinsic and Intrinsic Pathways

The extrinsic pathway is initiated by cell surface death receptors (e.g., TNF-alpha, Fas, TRAIL).
The intrinsic pathway involves mitochondrial signaling, with caspases activated regardless of the pathway.

Morphological Features of Apoptosis

Characteristic features of apoptotic cells include chromatin condensation, nuclear fragmentation, and formation of apoptotic bodies.
Apoptotic bodies are essentially vacuoles containing cytoplasm and intact organelles, which are eventually cleared by phagocytes.

Distinctions Between Apoptosis and Necrosis

Apoptosis is a controlled process that avoids inflammation, while necrosis is accidental cell death that can damage surrounding tissues; necrotic cells release inflammatory signals.
Key differences: apoptosis features chromatin condensation and organized cell death, while necrosis involves cell rupture and inflammation.

Alternate Cell Death Mechanisms

Necroptosis is a form of programmed necrosis, often triggered in response to viral infections when caspase pathways are inhibited.
Autophagy refers to the process of self-eating, wherein damaged organelles are degraded to prevent toxicity; it is more of a survival mechanism than a cell death process.

Role of Autophagy

Autophagy involves formation of phagophores that encapsulate damaged organelles, fusing with lysosomes to degrade materials into reusable components.
Proper autophagy is essential for cellular health; dysfunction can lead to various diseases.### Autophagy Overview
Autophagy is a catabolic process essential for maintaining intracellular energy balance.
It eliminates harmful proteins and damaged organelles, such as dysfunctional mitochondria.
Functional macromolecules are recycled into cells, contributing to amino acid availability for cellular functions.

Types of Autophagy

Macroautophagy: Classical form of autophagy that engulfs large cellular components.
Chaperone-Mediated Autophagy (CMA): Targets altered proteins for degradation by delivering them to lysosomes.
Microautophagy: Involves direct engulfment of cellular cargo by lysosomes for degradation.

Mitophagy

Mitophagy is a specialized autophagic process focused on degrading abnormal mitochondria.
Degradation of dysfunctional mitochondria plays a crucial role in various pathophysiological conditions.

Nobel Prize in Autophagy

Yoshinori Ohsumi received the Nobel Prize in 2016 for elucidating the mechanisms of autophagy, significantly advancing understanding of cellular degradation processes.

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Description

This quiz focuses on the critical topic of apoptosis, exploring both the intrinsic and extrinsic pathways involved in cell death. We will discuss the regulatory mechanisms and physiological roles of apoptosis in maintaining proper cell numbers in animal organisms. Prepare to test your understanding of these vital cellular processes.