Cellular Communication and Signal Transduction

What are receptors in the context of cellular communication?

• Molecules that transmit signals between cells

• Proteins that receive information from outside the cell

• Channels that allow substances to pass through the cell membrane

• Enzymes that catalyze reactions inside the cell

What characteristic describes the active site of a receptor?

• It can bind to any molecule

• It is highly specific to one molecule or a small collection of molecules

• It changes its shape randomly

• It only binds to other receptors

Which of the following best describes a ligand?

• A protein that spans the plasma membrane

• A molecule that binds to a receptor's active site

• A cellular component that triggers a response

• An enzyme that breaks down other molecules

What is the immediate effect when a ligand binds to a receptor's active site?

• The cell immediately divides

• The receptor undergoes a conformational change

• The ligand is broken down by the receptor

• The cell membrane becomes permeable to all substances

What is the primary role of second messengers like cAMP in signal transduction?

• To directly activate genes in the nucleus

• To transport ligands across the cell membrane

• To amplify the message carried by the initial ligand

• To break down the receptor after activation

What is a phosphorylation cascade?

• A process where molecules are transported across the cell membrane

• A chain reaction where molecules exchange phosphate groups

• The breakdown of complex molecules into simpler ones

• The synthesis of new proteins from amino acids

For a signaling molecule to activate an intracellular receptor, what characteristic must it possess?

• It must be a large protein

• It must be highly polar

• It must be able to pass through the plasma membrane on its own

• It must be attached to a G-protein

What can occur if a cell's signaling pathway for regulating cell division malfunctions?

• Increased metabolic rate

• Enhanced gene activation

• Tumor growth

• Faster absorption of substances