1. 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.

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

3. 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

4. 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).

5. 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?

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

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

8. 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

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

10. 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.

11. 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!)

12. 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