Cell Signalling Pathways Questions and Answers

Q: State whether the following is true or false.Type 1 and type 2 diabetes both result from a failure to produce insulin.

Correct answer: FalseThe 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.

Q: Scaffold proteins in signalling pathways serve to

Correct answer: hold successive components close togetherA 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.

31.

State whether the following is true or false.
Type 1 and type 2 diabetes both result from a failure to produce insulin.

A.False only at small scales
B.True
C.False
D.True only at large scales

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.

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32.

A hormone is effective at a blood concentration of 10 nanomolar. How many times more dilute is that than a 10 millimolar metabolite?

A.one thousand times
B.one hundred times
C.ten thousand times
D.one million times

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.

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33.

A cell's response to a given signal depends on

A.which receptors and relay proteins it possesses
B.the concentration of the arriving signal alone
C.the distance that the signal has already travelled
D.the physical size of the signalling molecule itself

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.

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34.

Assertion (A): Acetylcholine causes skeletal muscle to contract but slows the heart.
Reason (R): The two tissues express different receptors for the same molecule.

A.A is false but R is true
B.Both A and R are true, and R is the correct explanation of A
C.Both A and R are true, but R is not the correct explanation of A
D.A is true but R is false

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.

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35.

Consider the following statements about signal reception.
1. A steroid hormone binds an intracellular receptor.
2. A peptide hormone binds a receptor at the cell surface.
3. Any hormone can bind any receptor if the concentration is high enough.

A.1 only
B.All of them
C.1 and 2 only
D.3 only

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.

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36.

Scaffold proteins in signalling pathways serve to

A.destroy the signal molecule once it has acted
B.carry the signal across the plasma membrane
C.supply all the ATP that the cascade requires
D.hold successive components close together

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.

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37.

Crosstalk between signalling pathways means that

A.one pathway can influence the output of another
B.two separate signals must always arrive together
C.receptors exchange places within the plasma membrane
D.a pathway repeats itself over and over continuously

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.

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38.

State whether the following is true or false.
A cell integrates several signals at once rather than responding to each independently.

A.False only at small scales
B.True
C.False
D.True only at large scales

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.

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39.

Apoptosis triggered by the absence of survival signals shows that many cells

A.are entirely immune to any external signalling
B.can survive indefinitely without any input at all
C.depend on continual signalling to stay alive
D.die only when they are actively instructed to do so

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.

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40.

Assertion (A): Many animal cells die if removed from their tissue and deprived of signals.
Reason (R): Their survival depends on continual signalling from neighbouring cells.

A.Both A and R are true, but R is not the correct explanation of A
B.A is true but R is false
C.A is false but R is true
D.Both A and R are true, and R is the correct explanation of A

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.

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