Apoptosis is best described as
Answer: A
The cell dismantles itself according to a genetic programme and is removed without disturbing its neighbours. Death by injury follows an entirely different and far messier course. The two are distinguished by how the cell dies, not by whether it dies.
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Necrosis differs from apoptosis chiefly in that necrosis
Answer: B
Spilling the contents provokes inflammation in the surrounding tissue, whereas apoptotic fragments are engulfed quietly. The difference matters clinically as much as it does biologically. A heart attack kills tissue by necrosis, with inflammation following.
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State whether the following is true or false.
Apoptosis typically provokes inflammation in the surrounding tissue.
Answer: C
The cell packages itself into membrane-bound bodies that neighbours engulf before anything leaks out, so no inflammation results. Necrosis is the form of death that does provoke it. Neat packaging is what keeps the immune system uninterested.
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Assertion (A): Apoptosis does not provoke inflammation whereas necrosis does.
Reason (R): An apoptotic cell keeps its contents enclosed until they are engulfed by a neighbour.
Answer: D
Both are true and the reason gives the cause: it is the release of intracellular contents that alerts the immune system, and an orderly death avoids that release entirely. The distinction has real clinical consequences in injury and disease.
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Apoptosis requires energy from the dying cell, which means it
Answer: A
A cell that has run out of ATP dies by necrosis instead, since the orderly programme cannot be carried out. This is one reason severe ischaemia produces necrosis rather than apoptosis. The cell must be alive enough to kill itself in an orderly way.
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The enzymes that carry out apoptosis are the
Answer: B
They are proteases that cut after aspartate residues and exist as inactive precursors until required. Once activated they cleave hundreds of cellular targets in a controlled sequence. Their name records both the cysteine in the active site and the aspartate specificity.
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Caspases exist in healthy cells as
Answer: C
Keeping them ready but inert lets the cell commit to death within minutes without waiting for new protein to be made. Activation is usually by cleavage, which is itself carried out by other caspases. Initiator caspases activate executioner caspases in a short cascade.
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State whether the following is true or false.
Caspase activation is rapid because the enzymes are already present in the cell.
Answer: D
Storing them as inactive precursors means the decision to die can be executed almost at once. Waiting for transcription and translation would make the response far too slow. Commitment to death can then be made within minutes of the signal.
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The intrinsic pathway of apoptosis is triggered by
Answer: A
Damage that cannot be repaired causes mitochondria to release cytochrome c, which assembles the apoptosome and activates the caspases. The extrinsic pathway begins outside the cell instead. Which route is taken depends on where the death signal originates.
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Cytochrome c, released from mitochondria during apoptosis, normally functions in
Answer: B
Its role in death is quite separate from its everyday job in respiration, and the double use is a striking piece of economy. Its appearance in the cytosol is an unambiguous signal that something has gone wrong. The same protein therefore serves life and death in one cell.
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