Cell Signalling Pathways Questions and Answers

Q: One of the signalling molecules used for bacterial cell-cell communication are :

The bacterial signalling molecule is N-acyl homoserine lactone.Gram-negative bacteria such as Vibrio fischeri and Pseudomonas aeruginosa use acyl homoserine lactones (AHLs) for quorum sensing. A LuxI-type synthase makes the AHL, which diffuses across membranes; when the population is dense enough, the AHL reaches a threshold, binds a LuxR-type regulator, and switches on genes for bioluminescence, virulence or biofilm formation.The other names are distortions of the real one. A laccase is a copper-containing oxidase, not a signal, so both 'laccase' options are wrong; and the acyl chain, not an acetyl group, is the variable part that gives each species its own signal, which rules out 'N-acetyl homoserine lactone'.

Q: Which of the following molecules plays a pivotal role in presenting the paracrine factors to their target cells ?

The molecule is heparan sulphate (printed 'Heparin sulphate').Heparan sulphate proteoglycans on cell surfaces and in the extracellular matrix bind paracrine factors such as FGFs, Wnts and Hedgehog proteins. They concentrate these factors, control how far they spread, and present them to their receptors; FGF signalling, for example, needs heparan sulphate to form an active receptor complex.Fibronectin, laminin and collagen are extracellular matrix proteins concerned with cell adhesion, migration and structural support. They do not have the central role in presenting paracrine factors.

Q: Autocrine signalling occurs when a cell

Correct answer: responds to a signal it released itselfAutocrine signalling is a cell talking to itself: it secretes a molecule for which it carries the receptor. It is used to reinforce a decision a cell has already made - which is why it is common in development, where a group of neighbouring cells all releasing and receiving the same signal commits the whole group to one fate, and why it is a frequent feature of cancer cells driving their own proliferation.

11.

One of the signalling molecules used for bacterial cell-cell communication are :

A.N-acetyl hydroxy laccase
B.N-acyl homoserine laccase
C.N-acetyl homoserine lactone
D.N-acyl homoserine lactone

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: D

The bacterial signalling molecule is N-acyl homoserine lactone.

Gram-negative bacteria such as Vibrio fischeri and Pseudomonas aeruginosa use acyl homoserine lactones (AHLs) for quorum sensing. A LuxI-type synthase makes the AHL, which diffuses across membranes; when the population is dense enough, the AHL reaches a threshold, binds a LuxR-type regulator, and switches on genes for bioluminescence, virulence or biofilm formation.

The other names are distortions of the real one. A laccase is a copper-containing oxidase, not a signal, so both 'laccase' options are wrong; and the acyl chain, not an acetyl group, is the variable part that gives each species its own signal, which rules out 'N-acetyl homoserine lactone'.

Discuss in Forum

12.

Which of the following molecules plays a pivotal role in presenting the paracrine factors to their target cells ?

A.Fibronectin
B.Heparin sulphate
C.Laminin
D.Collagen

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: B

The molecule is heparan sulphate (printed 'Heparin sulphate').

Heparan sulphate proteoglycans on cell surfaces and in the extracellular matrix bind paracrine factors such as FGFs, Wnts and Hedgehog proteins. They concentrate these factors, control how far they spread, and present them to their receptors; FGF signalling, for example, needs heparan sulphate to form an active receptor complex.

Fibronectin, laminin and collagen are extracellular matrix proteins concerned with cell adhesion, migration and structural support. They do not have the central role in presenting paracrine factors.

Discuss in Forum

13.

Signalling in which a cell releases a molecule that acts on nearby cells is described as

A.paracrine
B.endocrine
C.autocrine
D.synaptic

Answer: A

The signal diffuses only a short distance and is usually degraded or taken up quickly, which keeps its effect local. Endocrine signals travel in the bloodstream to distant targets. The distinction is one of range rather than of chemistry.

Discuss in Forum

14.

Endocrine signalling is distinguished by the signal being

A.passed through a gap junction into a neighbour
B.carried in the bloodstream to distant targets
C.released directly onto an immediately adjacent cell
D.acting only on the very cell that released it

Answer: B

Hormones reach the whole body but affect only cells carrying the right receptor. This is why one circulating molecule can produce quite different effects in different tissues. Adrenaline dilates some blood vessels and constricts others for this reason.

Discuss in Forum

15.

Autocrine signalling occurs when a cell

A.releases a hormone into the bloodstream
B.transfers ions through a gap junction
C.responds to a signal it released itself
D.signals to a cell touching it directly

Answer: C

Correct answer: responds to a signal it released itself

Autocrine signalling is a cell talking to itself: it secretes a molecule for which it carries the receptor. It is used to reinforce a decision a cell has already made - which is why it is common in development, where a group of neighbouring cells all releasing and receiving the same signal commits the whole group to one fate, and why it is a frequent feature of cancer cells driving their own proliferation.

Discuss in Forum

16.

Assertion (A): A cancer cell may produce the very growth factor it responds to.
Reason (R): Autocrine signalling frees a cell from depending on signals made by other 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

Both are true and the reason gives the advantage to the tumour: self-sufficiency in growth signalling is one of the recognised hallmarks of cancer, and autocrine loops are one route to it. Independence from external growth signals is what the loop buys.

Discuss in Forum

17.

State whether the following is true or false.
A hormone circulating in the blood affects every cell it reaches.

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

Answer: A

Only cells bearing the appropriate receptor can respond, so the same molecule passes most tissues without effect. Specificity resides in the receptor rather than in the distribution of the signal. A cell without the receptor is simply blind to the message.

Discuss in Forum

18.

A steroid hormone typically binds its receptor

A.on the inner mitochondrial membrane
B.inside the cell, in cytoplasm or nucleus
C.on the outer face of the plasma membrane
D.within a lysosome after endocytosis

Answer: B

Being lipid-soluble it crosses the membrane unaided, and the receptor complex then acts directly on the DNA as a transcription factor. Water-soluble signals must instead be received at the surface. The route a signal takes follows directly from its solubility.

Discuss in Forum

19.

Assertion (A): Steroid hormones act more slowly than adrenaline but their effects last longer.
Reason (R): They work by changing gene transcription rather than by modifying existing proteins.

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

Answer: C

Both are true and the reason accounts for both halves: making new protein takes time, whereas phosphorylating an enzyme already present is nearly immediate, and the newly made protein persists after the signal has gone.

Discuss in Forum

20.

A signal molecule that cannot cross the plasma membrane must

A.be broken down before it can act
B.enter through a nuclear pore complex
C.be converted into a steroid first
D.bind a receptor on the cell surface

Answer: D

The receptor spans the membrane and relays the message inward without the signal itself entering. This is why the external molecule is called the first messenger and the internal relay the second. The message is thus handed across the membrane rather than carried through it.

Discuss in Forum

Loading…

Topics

Other Subjects

Tags: Cell Signalling Pathways Questions and Answers || Cell Signalling Pathways MCQ Questions and Answers || Cell Signalling Pathways GK Questions and Answers || Cell Signalling Pathways GK MCQ Questions || Cell Signalling Pathways Multiple Choice Questions and Answers || Cell Signalling Pathways GK || GK on Cell Signalling Pathways || Cell Biology Questions and Answers || Cell Biology MCQ Questions and Answers || Cell Biology GK Questions and Answers || GK on Cell Biology

Cell Signalling Pathways Questions and Answers

Topics

Other Subjects

About Us

Stay informed about all important Dates & Notifications