Apoptosis and Cell Death Questions and Answers

Answer: C

Both are true and the reason explains the reliability: the protein has no business in the cytosol, so its presence there can only mean the mitochondrial outer membrane has been permeabilised. That permeabilisation is the point of no return in the intrinsic pathway.

Answer: D

Immune cells use this route to instruct an infected or unwanted cell to die. The two pathways converge on the same executioner caspases despite their different starts. Convergence lets one execution machinery serve two quite different triggers.

Answer: A

Some members promote release of cytochrome c and others prevent it, so the balance between them decides the cell's fate. The family is named after the gene first found overexpressed in a lymphoma. The balance is tipped rather than switched by any single member.

Answer: B

Bcl-2 itself is anti-apoptotic, so overexpressing it keeps cells alive that should have died. That is exactly why its overexpression contributes to certain lymphomas. Blocking death is as dangerous to a tissue as excessive division.

Answer: C

Both are true and the reason gives the route: a cell carrying damage would normally be removed, and blocking that removal lets damaged cells accumulate and acquire further mutations. Evading apoptosis is counted among the hallmarks of cancer.

Answer: D

Correct answer: the separation of the fingers

The hand forms first as a paddle, and the digits are freed by the death of the cells in the webs between them. It is the standard illustration that apoptosis is a sculpting process rather than a response to damage - and when it fails the fingers remain joined, which is the developmental basis of syndactyly.

Answer: A

Sculpting digits, removing a tadpole's tail and eliminating surplus neurons all depend on it, so it is as constructive a process as growth. Regarding it purely as damage misses most of what it does. Development depends on removal quite as much as on growth.

Answer: B

A day contains 86,400 seconds, and 60 billion divided by that is close to 700,000. Cell production must match this loss almost exactly for tissue size to stay constant. Turnover on this scale goes entirely unnoticed in a healthy body.

Answer: C

The nucleus condenses and fragments and the cell breaks into membrane-bound bodies. Swelling and rupture are the appearance of necrosis instead, so the two can be told apart under a microscope without any further test.

Answer: D

The lipid is normally confined to the inner leaflet, so its appearance outside is an eat-me signal. This is a use of membrane asymmetry as a deliberate signal. The flippases that maintain the asymmetry are switched off as the cell dies.