biology : class11 JAK-STAT Signaling : Receptors, Second Messengers, Gene Regulation : Hormone Action MCQ Questions and Answers
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JAK-STAT Signaling
MCQ questions and answers.
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MCQ Questions
1. What is the main role of the JAK-STAT pathway in cells?
A.
To transmit signals from the cell surface to the nucleus
B.
To digest proteins in lysosomes
C.
To produce ATP in mitochondria
D.
To transport oxygen in the blood
Correct Answer:
To transmit signals from the cell surface to the nucleus
Explanation:
The JAK-STAT pathway carries signals from receptors at the cell membrane to the nucleus, where gene expression can be regulated.
2. What does JAK stand for in JAK-STAT signaling?
A.
Janus kinase
B.
Junction-associated kinase
C.
Juvenile activation kinase
D.
Junctional amino kinase
Correct Answer:
Janus kinase
Explanation:
JAK stands for Janus kinase, an enzyme associated with the intracellular part of many cytokine receptors.
3. What does STAT stand for in the JAK-STAT pathway?
A.
Signal Transducer and Activator of Transcription
B.
Signal Transport and Translation
C.
Steroid Transfer and Activation
D.
Surface Transcription and Attachment
Correct Answer:
Signal Transducer and Activator of Transcription
Explanation:
STAT proteins act as signal transducers and activators of transcription after they are activated by JAKs.
4. What usually activates JAK proteins in the JAK-STAT pathway?
A.
Binding of a signaling molecule to its receptor
B.
Breakdown of glucose in the cytoplasm
C.
Direct entry of DNA into the cell
D.
Movement of ribosomes into the nucleus
Correct Answer:
Binding of a signaling molecule to its receptor
Explanation:
When a ligand binds to its cell-surface receptor, receptor-associated JAKs become activated and begin the signaling cascade.
5. After activation, what do JAKs commonly phosphorylate in the JAK-STAT pathway?
A.
STAT proteins
B.
Ribosomal RNA
C.
Cellulose molecules
D.
Mitochondrial lipids
Correct Answer:
STAT proteins
Explanation:
Activated JAKs add phosphate groups to STAT proteins, allowing the STATs to become active.
6. What happens to phosphorylated STAT proteins in a typical JAK-STAT response?
A.
They form dimers and move into the nucleus
B.
They are released outside the cell
C.
They are converted into glucose
D.
They dissolve the cell membrane
Correct Answer:
They form dimers and move into the nucleus
Explanation:
Phosphorylated STAT proteins pair to form dimers, which then enter the nucleus to regulate gene transcription.
7. What is the function of STAT dimers inside the nucleus?
A.
They regulate transcription of specific genes
B.
They replicate the entire cell membrane
C.
They break down hormones in the blood
D.
They produce ribosomes in mitochondria
Correct Answer:
They regulate transcription of specific genes
Explanation:
Inside the nucleus, STAT dimers bind to regulatory DNA sequences and influence the transcription of target genes.
8. Which type of receptor is commonly associated with JAK-STAT signaling?
A.
Cytokine receptor
B.
Nuclear steroid receptor
C.
Ion channel in the mitochondrial membrane
D.
Digestive enzyme receptor
Correct Answer:
Cytokine receptor
Explanation:
Many cytokine receptors use JAK-STAT signaling to transmit extracellular signals into the cell.
9. Where are JAK proteins generally located before a signal activates the pathway?
A.
Attached to the intracellular part of the receptor
B.
Inside the DNA double helix
C.
Inside the extracellular fluid
D.
Attached to hemoglobin
Correct Answer:
Attached to the intracellular part of the receptor
Explanation:
JAK proteins are usually associated with the cytoplasmic portion of the receptor and are activated when the receptor binds its ligand.
10. Why is the JAK-STAT pathway considered a direct signaling pathway?
A.
Activated STAT proteins can directly influence gene transcription in the nucleus
B.
The ligand directly becomes a DNA molecule
C.
The receptor permanently enters the bloodstream
D.
The pathway does not involve any proteins
Correct Answer:
Activated STAT proteins can directly influence gene transcription in the nucleus
Explanation:
The pathway is relatively direct because activated STAT proteins move to the nucleus and regulate target genes without requiring many intermediate second messengers.
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