Necrosis vs. Apoptosis: Cell Death

Summary

The video explains two main forms of cell death: necrosis and apoptosis. Necrosis results from injury, causing cells to lose function, swell, and eventually rupture, which triggers inflammation. Apoptosis, on the other hand, is a regulated process of programmed cell death, with intrinsic and extrinsic pathways. It involves the activation of caspases, leading to controlled cell breakdown into apoptotic bodies, which are then cleared by immune cells. Unlike necrosis, apoptosis does not cause inflammation, and it occurs during normal physiological processes or as a response to damage.

Takeaways

• 🔬 There are two primary forms of cell death: necrosis and apoptosis.
• 💥 Necrosis is caused by cell injury and disrupts cellular function, often resulting in inflammation.
• 🫀 A common example of necrosis is cardiac cell death during a heart attack due to reduced blood flow and oxygen.
• 💧 Necrosis leads to cell swelling, lysosomal membrane damage, and leakage of enzymes that break down cell organelles.
• 🧬 In necrosis, the cell nucleus shrinks and dissolves, while cell contents leak out, attracting immune cells.
• 🗝️ Apoptosis, or programmed cell death, is a regulated process that involves two main pathways: intrinsic and extrinsic.
• ⚖️ The intrinsic pathway of apoptosis involves proteins from the Bcl family, and results in the release of cytochrome c from mitochondria.
• 🧩 The extrinsic pathway involves cell surface receptors like FAS and leads to the activation of caspases, which break down the cell.
• 🔄 During apoptosis, the cell shrinks, forms apoptotic bodies, and is phagocytosed by macrophages without causing inflammation.
• 👶 Apoptosis can be physiological, such as in embryogenesis, or a response to damage, like DNA damage, where it prevents harm to surrounding cells.

Q & A

What are the two main types of cell death mentioned in the script?

The two main types of cell death mentioned are necrosis and apoptosis.

What is the primary cause of necrosis?

Necrosis is usually caused by cell injury, such as decreased blood flow and oxygen during a heart attack.

How does necrosis affect cellular function?

Necrosis disrupts cellular function by impairing energy production, disabling the cell’s ability to control its fluid and ion balance, and leading to swelling and degradation of organelles.

What role do lysosomes play in necrosis?

In necrosis, lysosomes swell, leading to membrane damage and leakage of lysosomal enzymes, which degrade other cell organelles and the cell’s DNA.

What is karyolysis, and how does it relate to necrosis?

Karyolysis is the dissolution of the cell’s nucleus during necrosis, which occurs after the DNA is degraded and the nucleus shrinks.

What triggers apoptosis, and how is it different from necrosis?

Apoptosis is triggered by specific signals and pathways, either intrinsic or extrinsic, and is a regulated form of cell death. Unlike necrosis, apoptosis does not cause inflammation and the cell’s membrane remains intact.

What are the intrinsic and extrinsic pathways of apoptosis?

The intrinsic pathway is regulated by Bcl family proteins and involves the release of cytochrome c from mitochondria, while the extrinsic pathway is initiated by receptors on the cell surface like the FAS receptor.

What role does cytochrome c play in the intrinsic pathway of apoptosis?

Cytochrome c is released from the mitochondria during the intrinsic pathway of apoptosis, where it activates caspases that mediate cell death.

How is the FAS receptor involved in the extrinsic pathway of apoptosis?

The FAS receptor, also known as the death receptor, can be activated by cytotoxic T cells or messenger molecules like tumor necrosis factor. Once activated, it triggers a cascade leading to caspase activation and cell death.

Why does apoptosis not cause inflammation like necrosis?

Apoptosis does not cause inflammation because the cell membrane remains intact, preventing the leakage of cell contents. Additionally, apoptotic bodies are phagocytosed by macrophages and degraded in a controlled manner.