Signal Transduction — Flashcards & Quiz

Q1: What is signal transduction and how does it regulate gene expression?

Signal transduction is the process by which cells receive and respond to external signals. Steps: 1) A signalling molecule (ligand) binds to a cell-surface receptor. 2) The receptor undergoes a conformational change. 3) An intracellular signalling cascade is activated (often involving kinases that phosphorylate proteins). 4) The signal reaches the nucleus and activates or represses specific transcription factors. 5) Target genes are transcribed or silenced, changing the cell's behaviour.

Q2: What are the key components of a signal transduction pathway?

Components: 1) Signalling molecule (ligand) — e.g., hormone, growth factor, neurotransmitter. 2) Receptor — cell-surface (transmembrane) or intracellular. 3) Intracellular signalling molecules — kinases, second messengers (cAMP, Ca²⁺), G-proteins. 4) Target molecules — transcription factors, enzymes, cytoskeletal proteins. 5) Cellular response — gene expression change, cell division, apoptosis, differentiation. Signal amplification occurs through cascades where each step activates multiple downstream molecules.

Q1: Signal transduction pathways allow cells to respond to external signals by changing gene expression.

Answer: TRUE

External signals (hormones, growth factors) bind to receptors, triggering intracellular signalling cascades that ultimately activate or repress transcription factors, altering gene expression patterns.

Q2: Signal amplification in transduction pathways means each step can activate multiple downstream molecules.

Answer: TRUE

At each step of a signalling cascade, one activated molecule can activate many downstream molecules (e.g., one kinase phosphorylates many substrates). This amplifies the signal so a few receptor activations produce a large cellular response.