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BIO 304 . WEEK 5 . FRIDAY . LAB WORKBOOK
Hormone Mechanisms
Two pathways: steroid hormones acting on intracellular receptors; peptide hormones acting through membrane receptors and second messengers.
Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.
1A. What you will draw
Hormones are signaling molecules. The chemistry of the hormone determines its mechanism: steroids (lipid-soluble) cross the membrane and act on receptors inside the cell; peptides (water-soluble) act on receptors at the cell surface. Draw both pathways.
Box A. Steroid hormone mechanism
Directions
- Draw a target cell with its plasma membrane, cytoplasm, and nucleus visible.
- Outside the cell, draw a steroid hormone (small ring structure, label e.g., cortisol or estrogen).
- Show the hormone crossing the plasma membrane (it's lipid-soluble, so it passes directly through).
- Inside the cytoplasm, show the hormone binding an intracellular receptor protein. Label receptor.
- Show the hormone-receptor complex moving into the nucleus.
- Inside the nucleus, show the complex binding DNA at a specific gene. Label DNA, gene.
- Show transcription starting, then mRNA leaving the nucleus, then a new protein being made on ribosomes in the cytoplasm.
- Note: response takes hours (gene transcription is slow), but effects last long.
Draw here. Sketch by hand.
Box B. Peptide hormone mechanism
Directions
- Draw a target cell with its plasma membrane and cytoplasm.
- Outside the cell, draw a peptide hormone (chain structure, label e.g., insulin or glucagon).
- Show the hormone binding to a receptor on the OUTSIDE of the plasma membrane (it cannot cross). Label the membrane receptor.
- Show the receptor activating a G-protein on the inside of the membrane. Label G-protein.
- Show the G-protein activating an enzyme (e.g., adenylyl cyclase), which converts ATP to cAMP. Label the second messenger cAMP.
- Show cAMP activating protein kinase A, which phosphorylates target proteins inside the cell, changing their activity.
- Note: response is rapid (seconds to minutes), and amplification means one hormone produces many cellular changes.
Draw here. Sketch by hand.
1C. Structures to label (14)
After you finish each drawing, label every structure below directly on your sketch.
- Steroid hormone
- Plasma membrane (lipid-soluble crosses)
- Cytoplasmic receptor
- Hormone-receptor complex
- Nucleus
- DNA
- Gene transcription
- mRNA
- Peptide hormone
- Membrane receptor
- G-protein
- Adenylyl cyclase
- cAMP (second messenger)
- Protein kinase A
Part 2 of 2
Physiology Lab
2A. Steroid vs peptide comparison
Fill in the table. Then answer the two follow-up questions.
| Property | Steroid hormones | Peptide hormones |
|---|
| Solubility (lipid / water) | | |
|---|
| Receptor location | | |
|---|
| Speed of onset (minutes / hours) | | |
|---|
| Duration of effect | | |
|---|
| Mechanism of action | | |
|---|
| Example hormone | | |
|---|
Peptide hormones use second messengers (cAMP, IP3, Ca-squared-plus, etc.) to amplify their signal. Explain why amplification is important for water-soluble hormones acting at low concentrations.
Steroid hormones often produce long-lasting effects (hours to days). Explain mechanistically why steroid effects outlast peptide effects, and why steroid pulses are slower than peptide pulses.
2B. Synthesis questions
Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.
1. Cortisol (a steroid) and epinephrine (a peptide-like catecholamine) both raise blood glucose during stress. Compare their speeds of action and durations, and explain why the body uses both.
2. A patient takes oral prednisone (a synthetic steroid) for several weeks, then suddenly stops. They become very ill (Addisonian crisis). Explain mechanistically why abrupt steroid withdrawal is dangerous, in terms of feedback to the hypothalamus and pituitary.
3. Insulin is a peptide and CANNOT be taken orally. Explain mechanistically why oral insulin doesn't work, while a steroid hormone like prednisone CAN be taken orally.
3. What to submit
Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.