IB C2.1 Cellular Signaling

What is a tyrosine-kinase receptor?

• A type of receptor that activates its intrinsic kinase activity upon ligand binding, leading to phosphorylation of tyrosine residues on target proteins.

• A receptor that binds to ligands and initiates a cascade of secondary messenger signaling.

• A type of ion channel that opens in response to ligand binding, allowing ions to flow across the membrane.

• A receptor that exclusively binds to steroid hormones and regulates gene expression.

What is the role of feedback mechanisms in cellular signaling?

• To enhance the signaling pathways for faster responses.

• To regulate signaling pathways to maintain homeostasis and prevent overactivation or underactivation of responses.

• To completely inhibit all cellular responses.

• To initiate signaling pathways without any regulation.

What is the role of ligands in cellular signaling?

• Ligands bind to receptor proteins, causing them to relay messages to intracellular proteins, leading to a cellular response.

• Ligands act as enzymes that break down cellular waste products.

• Ligands are structural components of the cell membrane that provide stability.

• Ligands are hormones that regulate metabolic processes.

What is a secondary messenger?

• A molecule that transmits signals from a receptor to target molecules inside the cell, amplifying the signal.

• A type of hormone that regulates metabolism.

• A protein that helps in the formation of cell membranes.

• A neurotransmitter that transmits signals between neurons.

What is a ligand?

• A type of enzyme that catalyzes reactions.

• A signaling molecule that binds to a receptor to initiate a cellular response.

• A structural protein that provides support to cells.

• A carbohydrate that stores energy in cells.

How do ligands interact with cell-surface receptors?

• Ligands bind to cell-surface receptors, triggering conformational changes that activate intracellular signaling pathways.

• Ligands are repelled by cell-surface receptors, preventing any interaction.

• Ligands dissolve in the cell membrane, bypassing the need for receptors.

• Ligands bind to intracellular proteins, which then affect cell-surface receptors.

How do hormones act as ligands in cellular signaling?

• Hormones are enzymes that catalyze reactions in cells.

• Hormones are signaling molecules that can act as ligands, binding to specific receptors to initiate physiological responses.

• Hormones are waste products that are excreted by cells.

• Hormones are structural proteins that provide support to cells.

What is the importance of signal amplification in cellular signaling?

• It allows a small number of signaling molecules to produce a large cellular response, enhancing the effectiveness of the signal.

• It prevents the overreaction of cells to external stimuli.

• It ensures that all cells respond equally to a signal.

• It reduces the time taken for a signal to reach its target.

What are the consequences of receptor desensitization?

• Increased cell responsiveness to a ligand

• Receptor desensitization has no effect on cell responsiveness

• Receptor desensitization reduces the cell's responsiveness to a ligand after prolonged exposure, preventing overstimulation.

• Enhanced stimulation of the receptor by the ligand

What is the function of protein kinases in signaling pathways?

• Protein kinases phosphorylate target proteins, which can activate or deactivate their function, thus propagating the signal.

• Protein kinases break down proteins to release energy for cellular processes.

• Protein kinases transport molecules across the cell membrane.

• Protein kinases synthesize new proteins from amino acids.