Warm-Up (12/08) On the piece of white paper from the back, answer the following question. Name Date Period Create a model showing a generic cell signaling pathway before and after a ligand binds to a receptor. Show how binding to a ligand regulates gene expression.

The Endocrine System Glands release hormones (protein ligands) which travel through the body through the bloodstream. Signal-sending cell P Signal-receiving cell

Blood glucose stays low The Endocrine System Glands release hormones (protein ligands) which travel through the body through the bloodstream. Example: Insulin signaling Signal-receiving cell P insulin 2nd messenger Genes encoding proteins which release glucose Blood glucose stays low

Cell Communication Cells can communicate… Long distance: by, for example, hormones released in the blood. Short-range: by, for example, neurotransmitters across a synapse (Thursday). Directly: by, for example, immune cells recognizing antigens on pathogens (Wednesday).

Critical Thinking Question #1 Discuss this question with your partner and write or represent it. I will call on three people to share their partners’ answers. Explain why ligands can be secreted by signal-sending cells or attached to the surface of signal-sending cells. Which case would be used to send a long-distance signal?

Whole-Body Functions Hormones regulate whole-body functions. Liver Hormones regulate whole-body functions. Glycogen breaks down to release glucose. Adrenaline

Whole-Body Functions Signal transmission determines cell function. amount of ligand Gene expressed What if this was activated in the head?

Whole-Body Functions Signal transmission determines cell function. Fly with this much ligand in the head. Fly with this much ligand in the head. amount of ligand Gene expressed

Unicellular Functions Unicellular bacteria communicate with each other through quorum sensing. Bacterium Ligand

Critical Thinking Question #2 Discuss this question with your partner and write or represent it. I will call on three people to share their partners’ answers. Patients suffering from Type I diabetes are required to take regular insulin injections to maintain low blood sugar levels. Insulin is a hormone ligand that has been proven to reduce the release of glucose from liver cells. Justify the claim that insulin causes liver cells to stop secreting glucose.

Drugs work by blocking receptors. Example: blood-pressure drugs, birth-control drugs ligand Signal-receiving cell (not activated!) 2nd messenger P (not activated!) drug receptor Target gene (not activated!) (not activated!)

Closure On the piece of white paper from the back, answer the following question: Name Date Period Explain how a drug could affect signal reception between cells and, consequently, the entire signal transduction pathway. Scale 1 – 10