Chapter 5.1 Flashcards
What is a gland
A gland is an organ that secretes hormones
What is a hormone
A hormone is a signalling molecule that is secreted into the bloodstream to target a distant tissue
What are the three types (in terms of chemical derivative) of hormones?
- Peptide Hormones
- Steroid Hormones
- Amino Acid Derivatives
What kinds of molecules can easily pass the cell membrane?
Extremely small molecules and non-polar molecules.
What are the characteristics of peptide hormones?
- Peptide hormones are made up of amino acids.
- Peptide hormones can range in size from very small to very large.
- Peptide hormones are polar/charged hormones.
- Peptide hormones are hydrophilic.
Can peptide hormones easily cross the cell membrane?
Peptide hormones can be large and are always polar, so we would not expect them to be able to cross the cell membrane easily.
How do peptide hormones exert their effects on target cells?
Because peptide hormones cannot pass the cell membrane, they must interact with receptors on the outside of the membrane that carry the signal into the cell.
What is a first messenger?
In a situation where a molecule must bind to a receptor on the surface of a cell, the first messenger is the molecule that binds to the extracellular receptor.
What is a second messenger?
In a situation where a molecule must bind to a receptor on the surface of a cell, the second messenger is the molecule that is activated inside the cell by the first messenger.
What is a signalling cascade?
A signalling cascade is the connection between hormones at the surface interacting with receptors and the effects brought about by the second messengers they activate.
What is amplification in the context of signalling cascades?
Amplification is the possiblity that a hormone can activate a receptor multiple times before it is degraded, leading to an increase in the intensity of the signal as it cascades. For example, 1 hormone molecule may be released, but it can bind to the receptor 10 times before it degrades. This means that, in the cell, there are 10 activated secondary messengers even though there was only one hormone molecule. Amplification can happen at any of the many steps of a signalling cascade.
What are some common second messengers?
- Cyclic Adenosine Monophosphate (cAMP)
- Inositol Triphosphate (IP3)
- Calcium
What is a G protein-coupled receptor?
A G protein-coupled receptor is the archetypal structure by which signal cascading occurs. It is a large protein that crosses the memrbane 7 times. When the appropriate molecule binds to the G protein-coupled receptor, enzymes that influence the levels of second messengers (almost always cAMP) are activated or deactivated.
Peptide hormones bind to _____ to target cells
extracellular receptors
Steroid hormones ______ through the membrane of target cells
pass
Peptide hormones exert their effects through [secondary messenger systems or direct binding to DNA?] of target cells.
secondary messenger systems
Steroid hormones exert their effects through [secondary messenger systems or direct binding to DNA?] of target cells.
direct binding to DNA
Describe the timing of peptide hormone signals
Because of amplification in the secondary messenger system, the effects of peptide hormones are usually rapid, but short lived. That is to say that it is quicker to turn a peptide hormone’s effects on or off, but their effects won’t last without constant stimulation.
Are peptide hormones water soluable?
Yes
What kinds of moleucles can travel through the bloodstream with no assistance?
Water soluble molecules
What kinds of moleucles need special carriers in order to travel through the bloodstream?
Water insoluble molecules
What molecule are steroid molecules derived from?
Cholesterol
Can steroid hormones easily cross the cell membrane?
Steroid hormones are relatively small and nonpolar, so we would expect them to be able to cross the cell membrane.
How do steroid hormones exert their effects on target cells?
Steroid hormones can pass through the membrane and then bind to receptors that are in the cytosol or the nucleus itself. The hormone-receptor complex often dimerizes with another complex (but doesn’t have to) then acts as a transcription factor.
Describe the timing of steroid hormone signals
Steroid hormones directly affect DNA, which takes longer to do, but leads to longer lasting changes in the cell. Therefore, steroid hormones effects activate slowly, but stick around for a while.
Are steroid hormones water soluable?
No
What are amino acid derivative hormones?
Amino acid derivative hormones are hormones that are made from a few modifications of one or two amino acids.
Are the characteristics of amino acid hormones more similar to steroid hormones or peptide hormones?
It depends! Amino acid hormones can have very different properties. Some act like steroid hormones, and some act like peptide hormones.
What are 4 of the most common amino acid derivative hormones and state whether they are peptide-like or steroid-like in their timing and mechanism
- Epinephrine - Peptide like
- Norepinephrine - Peptide like
- Thyroxine - Steroid like
- Triiodothyronine - Steroid like
What are the two classifications of hormone based on what type of tissue they effect?
- Direct
- Tropic
