Cell death Flashcards
What are the two main types of cell death?
Necrosis and apoptosis
How does necrosis differ from apoptosis?
Necrosis is an uncontrolled, inflammatory form of cell death, whereas apoptosis is a programmed, controlled process.
What are the two main pathways that lead to apoptosis?
The extrinsic (receptor-mediated) and intrinsic (intracellular stress) pathways.
What protein family regulates apoptosis by maintaining a balance between pro- and anti-apoptotic factors?
The BCL2 family.
Why is the balance between pro- and anti-apoptotic factors important?
It determines whether a cell undergoes apoptosis or survives, impacting processes like tumor suppression and immune function.
Name the two main apoptosis pathways.
Extrinsic (receptor-mediated) and intrinsic (intracellular stress).
What is the primary difference between necrosis and apoptosis?
Necrosis is an uncontrolled, inflammatory form of cell death that occurs due to acute injury, while apoptosis is a highly regulated and energy-dependent process designed to eliminate unwanted or damaged cells without causing inflammation.
Why is the balance between pro- and anti-apoptotic factors important?
The balance determines whether a cell survives or undergoes apoptosis. An imbalance can lead to diseases such as cancer (too little apoptosis) or neurodegenerative disorders (too much apoptosis).
Name the two main apoptosis pathways and describe how they differ.
Extrinsic pathway: Activated by death receptors (e.g., Fas/CD95, TNF receptors) that bind extracellular ligands, triggering caspase cascades.
Intrinsic pathway: Triggered by intracellular stress (e.g., DNA damage, oxidative stress) and involves mitochondrial release of cytochrome c.
What key protein is involved in DNA damage-induced apoptosis?
The p53 protein, known as the ‘guardian of the genome,’ detects DNA damage and can induce apoptosis if the damage is irreparable.
What role do oxygen free radicals play in cell injury?
Oxygen free radicals (reactive oxygen species, ROS) cause oxidative stress, leading to lipid peroxidation, DNA damage, and mitochondrial dysfunction, which can trigger apoptosis or necrosis.
Is lethal injury always irreversible?
Yes, lethal injury results in permanent cell death through either necrosis or apoptosis, depending on the severity and control of the process.
Is apoptosis always a form of programmed cell death?
Yes, but not all programmed cell death is apoptosis. Other forms include pyroptosis, ferroptosis, and necroptosis.
Give an example of apoptosis in embryonic development.
Apoptosis is crucial in shaping organs, such as removing webbing between fingers and forming lumens in developing tubes.
How does apoptosis contribute to immune defense?
It eliminates infected or malfunctioning cells, such as virus-infected cells targeted by cytotoxic T lymphocytes and Natural Killer (NK) cells.
What happens to DNA during apoptosis?
DNA is cleaved into small, ladder-like fragments by endonucleases, making it distinct from the random degradation seen in necrosis.
How are apoptotic cells recognized and removed by macrophages?
They expose phosphatidylserine on their surface, acting as an ‘eat-me’ signal for macrophages and non-professional phagocytes.
Name an example of an extrinsic apoptosis receptor.
Fas (CD95), which is part of the tumor necrosis factor (TNF) receptor family.
What type of immune cells use extrinsic apoptosis to destroy target cells?
Cytotoxic T lymphocytes (CTLs) and Natural Killer (NK) cells.
What are the key features of extrinsic apoptosis?
It involves receptor activation, recruitment of adaptor proteins, and activation of caspases, leading to controlled cell death.
What molecules do T cells use to induce apoptosis?
Perforin and granzymes, which enter target cells to trigger apoptosis.
Name a situation where T cell-mediated apoptosis occurs.
During viral infections, where T cells kill infected cells to prevent viral replication.
What organelle is key in intrinsic apoptosis?
The mitochondria, which release cytochrome c to activate the caspase cascade.
