Topic 7 - Cell Death Flashcards
What is programmed cell death?
A type of cell death where particular cells die in a reproducible, controlled manner as a result of the action of proteins encoded by the cells themselves. Because of its predictable nature, this form of death was believed to occur as the result of a death ‘programme’, and so was named programmed cell death. Well-known examples are the loss of the cells between digits (e.g. during the development of fingers), and in the tail of the tadpole, when it metamorphoses into a frog. In adult tissues, cell death usually balances cell division, ensuring that tissues and organs retain the same size and structure as old cells are replaced.
What is apoptosis?
A type of programmed cell death that removes cells without causing inflammation. Characterised by cell shrinkage, membrane blebbing, chromatin condensation, DNA fragmentation and activation of caspase enzymes.
What is necrosis?
Typical response of cells to injury in the form of harmful reagents, infections or wounds. The damaged cell swells because the cell membrane fails to control the passage of ions and water, and finally lyses (bursts), releasing its contents, which in vertebrates can stimulate a potentially damaging inflammatory response.
What is cell membrane blebbing?
In relation to cell membranes - the formation of membrane protrusions, involving detachment of the cell membrane from cytoskeletal components. A feature of apoptotic cell death and, in some cases, necrotic cell death.
What are DAMPs?
Damage-associated molecular pattern molecules. Inflammatory molecules that are lost from leaky necrotic cells.
What is an apoptosome?
A multi-protein complex formed by the association of cytochrome c, dATP and Apaf-1. The binding of procaspase 9 to the apoptosome leads to dimerisation and activation of procaspase 9 monomers, thereby triggering the caspase activation cascade.
What is AMP-activated protein kinase (AMPK)?
A protein kinase that plays a central role in cellular energy homeostasis. AMPK is activated when the cytosolic concentration of adenosine monophosphate (AMP) increases.
What is mitophagy?
A form of autophagy where dysfunctional or unwanted mitochondria are digested.
What are reactive oxygen species (ROS)?
Collective term for both oxygen-based radicals (such as nitric oxide) and reactive non-radical oxidants (such as hydrogen peroxide (H2O2) and lipid peroxide). ROS are generated as by-products of oxidative metabolism and other cellular reactions. They are potentially damaging to cells, because they cause oxidative damage to macromolecules and membranes.
What is mPT (mitochondrial permeability transition)?
mPT or mitochondrial permeability transition marks a sudden increase in the flux of ions and solutes across the inner mitochondrial membrane. This leads to mitochondrial swelling and rupture, which precipitates necrotic cell death.
During an adaptive immune response, there is a massive proliferation of the specific types of lymphocytes (white blood cells) needed to overcome an infection. What do you think would happen to the cells once the infection is over?
Once the infectious agents have been destroyed, the lymphocytes are no longer needed. Some of them differentiate into memory cells, but the majority are removed by apoptosis.
During nervous system development, sufficient neurons must be generated to innervate their target tissue. The formation of appropriate neuronal connections is ensured by the production of excess neurons during early development. What do you think would happen to those neurons that do not form connections during development?
The neurons that do not form connections with other neurons or target tissues die via apoptosis and are removed. This ensures that only connected neurons are retained.
The neurons that form connections receive signals that promote cell survival, whereas those cells that do not form connections undergo apoptosis by default.
What are caspases?
Cysteine-dependent aspartate-directed proteases. A family of proteases that all contain cysteine at their catalytic sites, and cleave their protein substrates on the carboxyl side of aspartate residues. Caspases are present in cells as inactive precursors (zymogens) known as procaspases. Initiator caspases activate effector caspases, which in turn hydrolyse specific proteins thereby committing a cell to die.
Define pro-apoptotic
The term used to describe events, or regulatory proteins, that promote apoptosis.
What are initiator caspases?
Caspases that, when activated, trigger apoptosis. They activate effector caspases, which hydrolyse cellular proteins
