4C. Apoptosis

Apoptosis

A controlled process of programmed cell death, removing damaged or unnecessary cells without causing inflammation. Essential for maintaining tissue health.

Intrinsic Pathway (Mitochondrial Pathway)

An apoptosis pathway triggered by internal cellular damage (e.g., DNA damage, oxidative stress). Cytochrome c is released from mitochondria, activating caspase enzymes.

Extrinsic Pathway (Death Receptor Pathway)

An apoptosis pathway triggered by external signals. A ligand binds to death receptors on the plasma membrane, activating caspases to initiate cell death.

Caspase Enzyme

A family of proteases (enzymes) that cleave intracellular components, systematically breaking down the cell during apoptosis.

Cytochrome c

A protein in the inner mitochondrial membrane involved in electron transport. In apoptosis, it is released into the cytosol, triggering caspase activation.

Blebbing

The plasma membrane bulges outward, forming protrusions as the cytoskeleton breaks down. These protrusions later form apoptotic bodies.

Apoptotic Bodies

Small, membrane-bound vesicles containing fragmented cellular material that break off from an apoptotic cell and are later engulfed by phagocytes.

Phagocyte

A type of immune cell that engulfs and digests apoptotic bodies, pathogens, and cellular debris.

Phagocytosis

A process where a phagocyte engulfs solid material (e.g., apoptotic bodies, bacteria) and digests it using lysosomes.

Ligand

A signalling molecule that binds to a receptor on a target cell, triggering a response (e.g., apoptosis via death receptor activation).

Pro-apoptotic Protein

A protein that promotes apoptosis, often by triggering cytochrome c release from mitochondria. Example: Bax, Bak.

Anti-apoptotic Protein

A protein that prevents apoptosis by blocking cytochrome c release and caspase activation. Example: Bcl-2, Bcl-xL.

Kinase

An enzyme that transfers phosphate groups to proteins, regulating many cellular processes, including apoptosis.

Necrosis

A pathological form of cell death caused by injury, toxins, or infection, often leading to inflammation and tissue damage.

Tumour

A mass of abnormal cells that arise due to uncontrolled cell division.

Benign Tumour

A non-cancerous tumour that does not invade surrounding tissues or spread to other parts of the body.

Malignant Tumour

A cancerous tumour that can invade nearby tissues and spread (metastasise) to other body parts.

Cancer

A disease caused by uncontrolled cell division and the ability of abnormal cells to invade other tissues.

Metastasis

The spread of cancer cells from the primary tumour site to distant parts of the body via the bloodstream or lymphatic system.

Engulf

The process where a cell surrounds and takes in particles, such as apoptotic bodies, through phagocytosis.