Cell Signalling Pathways Questions and Answers

Answer: C

Correct answer: False

The two are different diseases. Type 1 is autoimmune destruction of the pancreatic beta cells, so insulin genuinely is not produced and must be replaced. Type 2 is primarily resistance: insulin is produced, often in increased amounts at first, but the target cells respond poorly, and secretion may fail later as the beta cells are exhausted. The distinction determines the treatment entirely.

Answer: D

Millimolar is a thousandth of a mole and nanomolar a billionth, so the ratio is a million. Amplification within the cell is what allows such tiny quantities to have an effect. Without amplification such concentrations would be useless as signals.

Answer: A

Correct answer: which receptors and relay proteins it possesses

The signal carries no instruction of its own - the response is determined by the machinery of the receiving cell. That is why acetylcholine slows the heart, contracts skeletal muscle and stimulates salivary secretion: three cell types, three sets of receptors and relay proteins, three responses to the same molecule.

Answer: B

Both are true and the reason accounts for the difference: meaning resides in the receiving apparatus rather than in the signal, so one molecule can carry opposite instructions to two tissues. The meaning is assigned by the receiver, not carried by the messenger.

Answer: C

The first two are correct and follow from solubility. The third is wrong, since binding depends on complementary shape, and raising the concentration of the wrong molecule does not create a fit. Specificity is structural rather than a matter of concentration.

Answer: D

Correct answer: hold successive components close together

A scaffold binds several members of a cascade at once, holding them in proximity so the signal passes efficiently from one to the next. It also prevents cross-talk, since components tied to one scaffold do not stray into a parallel pathway using the same kinases - which is how a cell runs several pathways through shared components without confusing them.

Answer: A

Shared components let pathways modulate one another, which allows a cell to integrate several inputs into one decision. It also makes the consequences of a drug harder to predict than a single pathway would suggest. Side effects often trace back to crosstalk of this kind.

Answer: B

Survival, growth and differentiation typically require a particular combination of inputs, and the pathways converge on shared targets. A cell receiving conflicting signals may arrest or die rather than choose. Integration happens at shared downstream targets rather than at the receptor.

Answer: C

The default state for such cells is death, which is prevented only while the signals continue. This arrangement helps ensure cells survive only where they are wanted. Cells that stray from their proper tissue are removed by default.

Answer: D

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason explains the phenomenon. Animal cells require continuous survival signals from their neighbours and their matrix, and in their absence the default programme of apoptosis proceeds. It is a control mechanism rather than a frailty: a cell that has strayed from its proper tissue dies, which is one of the barriers a metastasising cancer cell must overcome.