Cell Death in Medical Science

Questions and Answers

What is the primary purpose of apoptosis in the context of DNA damage?

To enhance cell growth and division

To remove cells that may lead to cancer (correct)

To repair damaged DNA directly

To promote mutation through cellular replication

Which of the following is a consequence of thymine dimers on DNA?

They enhance replication accuracy

They stabilize DNA structure

They disrupt DNA structure (correct)

They promote cell division

During apoptosis, which of the following morphological changes does NOT occur?

Chromatin condenses and fragments

Cell surface bulges into blebs

Nuclear envelope disassembles

Cell size increases significantly (correct)

What role do caspases play in apoptosis?

They are involved in the signaling cascade for apoptosis Signup and view all the answers

What initiates the activation of initiator caspases?

Dimerization triggered by apoptotic signals Signup and view all the answers

Which of the following best describes 'apoptotic bodies' during apoptosis?

They are fragments of cells engulfed and destroyed by macrophages Signup and view all the answers

What is the function of executor caspases in the apoptosis process?

They activate changes in cell biology through cleavage Signup and view all the answers

What typically leads to the formation of 'sunburn cells' in skin keratinocytes?

Excessive UVB radiation exposure Signup and view all the answers

What can contribute to the development of cancers?

An increase in cell division or a decrease in apoptosis Signup and view all the answers

What is often found at the center of solid tumors due to insufficient blood supply?

Necrotic core Signup and view all the answers

What role does p53 play in the intrinsic pathway of apoptosis?

It detects DNA damage and facilitates Bax and Bak aggregation. Signup and view all the answers

Which of the following is NOT a focus in the study of apoptosis?

Tumor metastasis Signup and view all the answers

What is the function of cytochrome c in the intrinsic pathway of apoptosis?

To form the apoptosome complex with Apaf1. Signup and view all the answers

What is the overall consequence of mitochondrial outer membrane permeabilization (MOMP)?

Release of pro-apoptotic factors into the cytosol. Signup and view all the answers

Which statement accurately describes the role of mutations in cancer development?

Mutations trigger cancer and further mutations develop the tumor. Signup and view all the answers

How does apoptosis differ from necrosis?

Apoptosis is a controlled process while necrosis results from damage. Signup and view all the answers

What initiates the caspase cascade in the intrinsic pathway of apoptosis?

Formation of the apoptosome complex. Signup and view all the answers

Which proteins aggregate in the mitochondrial membrane to facilitate apoptosis?

Bax and Bak. Signup and view all the answers

What is a significant aspect of how cancer can develop based on cell division and apoptosis?

Decreased apoptosis can lead to excessive cell accumulation. Signup and view all the answers

What is the primary trigger for the intrinsic apoptosis pathway?

DNA damage detected by the cell. Signup and view all the answers

What is the role of CAD in DNA fragmentation during apoptosis?

Functions as a specific endonuclease to cleave DNA. Signup and view all the answers

What initiates the extrinsic pathway of apoptosis?

Binding of Fas ligand to the Fas receptor. Signup and view all the answers

Which statement correctly describes iCAD's function in apoptosis?

iCAD is degraded by executioner caspases to allow CAD activation. Signup and view all the answers

The binding of Fas ligand to its receptor leads to the formation of which complex?

Death-inducing signalling complex (DISC). Signup and view all the answers

What is the primary function of executioner caspases in the apoptosis process?

To degrade iCAD, allowing CAD activation. Signup and view all the answers

Which family do death receptors belong to in the context of apoptosis?

Tumor necrosis factor (TNF) family. Signup and view all the answers

How does DNA fragmentation occur during the apoptotic process?

Via the cleaving of nucleosomes by CAD activation. Signup and view all the answers

Which of the following best describes the process of apoptosis activation by cytotoxic T-cells?

Binding of Fas ligand to Fas receptors on target cells. Signup and view all the answers

What characterizes apoptosis in contrast to necrosis?

It is a type of regulated cell death. Signup and view all the answers

Which statement accurately describes necrosis?

Necrosis is associated with cell damage due to lack of ATP. Signup and view all the answers

What is a key clinical importance of apoptosis?

It is critical for removing damaged or unnecessary cells. Signup and view all the answers

Which of the following is NOT a trigger for apoptosis?

Lack of oxygen (ischemia). Signup and view all the answers

During which process does apoptosis play a significant role?

In the establishment of the adaptive immune system. Signup and view all the answers

What occurs during necrosis that differs from apoptosis?

An inflammatory response is triggered. Signup and view all the answers

Which of the following describes the nature of apoptosis?

Cell death that is programmed and controlled. Signup and view all the answers

What is a primary difference between intrinsic and extrinsic pathways in apoptosis?

Intrinsic pathways are related to internal cellular damage. Signup and view all the answers

Study Notes

Teaching Objectives

Understand the timing and significance of cell death.
Differentiate between necrosis and apoptosis.
Define apoptosis and necrosis intracellular pathways.
Recognize the clinical implications of apoptosis.

Apoptosis vs Necrosis

Apoptosis:
- Regulated cell death, occurs in a controlled manner.
- Cells quickly removed without releasing contents.
- Triggers include extrinsic factors (e.g., Fas ligand) and intrinsic factors (e.g., DNA damage).
- Does not invoke an inflammatory response.
Necrosis:
- Accidental cell death due to lack of ATP (e.g., hypoxia or ischemia).
- Results from physical damage to cells.
- Contents released, leading to inflammation.

Role of Apoptosis

Essential in tissue remodeling and development.
Critical during:
- Metamorphosis in amphibians.
- Limb development in embryos.
- Establishment of the adaptive immune system.

Removal of Damaged Cells

Apoptosis eliminates cells with excessive DNA damage such as thymine dimers (caused by UVB exposure).
Thymine dimers can disrupt DNA replication, leading to potential mutations and cancer development.
Keratinocytes in skin form "sunburn cells" and undergo apoptosis from excessive UV exposure.

Morphological Changes in Apoptosis

Cells shrink and lose cytoskeletal structure.
Disassembly of the nuclear envelope and fragmentation of chromatin.
Formation of membrane-bound "apoptotic bodies."
Rapid clearance of apoptotic bodies by macrophages with minimal observable dead cells.

Caspases and Their Role

Caspases, a family of proteases, mediate the apoptosis process.
Synthesized as inactive precursors; activated by cleavage.
Initiator caspases: Triggered by external signals, dimerize, and get activated.
Executor caspases: Activated by initiators to carry out cellular changes associated with apoptosis.

DNA Fragmentation Mechanism

Executioner caspases cleave iCAD, allowing CAD (specific endonuclease) to fragment DNA.
Results in ladder-like patterns of DNA fragments due to cleavage between nucleosomes.

Extrinsic Apoptosis Pathway

Triggered by external signals via death receptors on cell membranes.
Activation of Fas receptor by Fas ligand leads to the formation of the death-inducing signaling complex (DISC), initiating the caspase cascade.
Part of the TNF receptor family.

Intrinsic Apoptosis Pathway

Activated in response to intracellular DNA damage via the p53 pathway.
p53 facilitates the aggregation of Bax and Bak proteins in the mitochondrial membrane.
Mitochondrial outer membrane permeabilization leads to cytochrome c release, forming the apoptosome with Apaf1, recruiting initiator caspases and triggering apoptosis.

Apoptosis and Cancer

Cancers result from uncontrolled cell proliferation owing to mutations.
An increase in cell division or a decrease in apoptosis contributes to tumor development.
Tumors often have necrotic cores due to insufficient blood supply.

Summary Points

Recognize significant differences between necrosis and apoptosis.
Understand the functional roles of apoptosis in biological processes.
Comprehend both extrinsic and intrinsic pathways of apoptosis.
Appreciate the crucial role of survival factors in cell fate.

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Description

This quiz focuses on the fundamental concepts of cell death, including the differences between necrosis and apoptosis. It will explore intracellular pathways involved in both processes and their clinical significance. Prepare to assess your understanding of cell biology related to medical science.