Endocrine System Flashcards
Molecules secreted directly into bloodstream to target tissue. Messngers for communication within the body.
Hormones
Secrete Hormones
Glands
List classifications of hormones by chemical strucutre.
- Peptide/Protein Hormones
- Steroid Hormones
- AA Derivatives
What are peptifde hormones made of and where do they come from?
- Composed of AA
- Derived from larger precursor proteins cleaved during post-translational modifcation (after post-translational modification cleaves precursor proteins, these smaller molecules are transported from Rough ER to golgi-apparatus for further modification)
Defining characteristic of peptide hormones.
- Charged molecules
- Hydrophilic (this cannot pass through plasma membrane)
Since peptide hormones cannot pass through plasma membrane, how are they able to have an impact on a cell?
- Leave their home cell via exocytosis
- Find Target Cell
- Bind to specific extracelluar receptors on their target cell to induce a signal
- Receptors may activate multiple enzymes, which can trigger a number of secondary messengers
- Signal is transduced to interior of cell via secondary messengers
- Initiates signalling cascade where secondary messenger can activate/deactivate already existing proteins/enzyme within cytoplasm - alterig function of proteins within enzymes
Signaling cascade
series of chemical reactions within target cell initiated by the binding of a peptide hormone to extracellular receptor on target cell. During signaling cascade, AMPLIFICATION occurs where the where each step can increase the intensity of the signal.
List 3 examples of secondary messenger.
- cAMP
- IP3 (Inositol triphosphate)
- Calcium
Are peptide hormones rapid or short lived?
- Short lived (b/c these hormones act through a transient messenger and once the peptide hormone is no longer bound, signalling cascade stops because signal stopsS
- Quicker to turn on and off when compared to steroid hormones
Which can travel freely through bloodstream and which needs a carrier?
A) Peptide Hormone
B) Steroid Hormone
1) Peptide Hormone can travel freely.
2) Steroid hormone needs a carrier
Structure of steroid hormone.
- Derived from cholesterol
- Non-Polar/Hydrophobic
How do steroid hormones get to and act on target cell?
1) Carried through bloodstream to target cell
2) “Slides” through membrane of target cell
3) After sliding through membrane, binds to receptor of secondary messengers (Intracellular or intranuclear)
4) Promotes conformation change
5) Complex then goes to nucleus (if not already there) and initiates transcripton of a specific gene
Steroid Hormones: Short or long term affect?
Long Term (slow-onset but long lived )
Hormones dervied from one or two AA, usually with a few additional modifications.
AA derivative hormones (share features with peptide and steroid hormones - thus chemistry of this family is considerably less predictable)
Examples of AA derivatives
- Catecholamines: Epinephrine (nor-epinephrine)
- Thyroxine
- Triiodothyronine
