Hormone Receptors Flashcards
What are the main ways that hormones can change their target cells?
Activation of enzymes and modulation of gene expression
Activation of enzymes causes transitions between active and inactive states, while modulation of gene expression stimulates or shuts off transcription of genes.
What are the two main classes of hormone receptors?
Cell surface receptors and intracellular receptors
Cell surface receptors are found on the plasma membrane, while intracellular receptors are located in the cytoplasm or nucleus.
What types of hormones signal through cell surface receptors?
Proteins and peptides, catecholamines, and eicosanoids
These hormones generate second messengers that alter the activity of molecules within the cell.
What types of hormones signal through intracellular receptors?
Steroid and thyroid hormones
These hormones alter the transcriptional activity of responsive genes.
What is the principle mechanism of action for cell surface receptors?
Generation of second messengers
This process alters the activity of other molecules, typically enzymes, within the cell.
What is a ligand-binding domain (LBD)?
A region of the receptor that interacts with and binds the hormone
It is essential for the receptor’s activation upon hormone binding.
What is the role of second messengers in hormone signaling?
They mediate cell activity by relaying a signal from an extracellular molecule
Second messengers amplify the response within the cell.
What is the function of protein kinases in signaling pathways?
They modify other proteins by chemically adding phosphate groups to them
This process is known as phosphorylation, which can activate or inactivate target proteins.
What happens during cyclic AMP signaling?
Hormone binds to receptor, G-protein is activated, and ATP is converted to cAMP
cAMP acts as a second messenger that activates protein kinases.
What is signal amplification in signaling pathways?
The increase in the number of activated participants at each step of the pathway
For example, one epinephrine-activated GPCR can lead to the activation of millions of molecules.
Describe the PIP-Calcium signaling pathway.
Hormone binds to receptor, activating G-protein, which activates phospholipase C
Phospholipase C splits PIP2 into DAG and IP3, both acting as second messengers.
What distinguishes intracellular receptors from cell surface receptors?
Intracellular receptors are located inside the cell and are typically activated by lipophilic hormones
They function as ligand-dependent transcription factors.
What are the two main groups of intracellular receptors?
Nuclear receptors and other organelle receptors
Nuclear receptors are primarily involved in gene transcription regulation.
What is the function of nuclear receptors?
They act as ligand-dependent transcription factors to regulate gene expression
Without hormone binding, they are usually complexed with chaperone proteins.
What structural domains are present in nuclear receptors?
N-terminal domain, DNA binding domain, and C-terminal or ligand-binding domain
Each domain plays a specific role in receptor activation and function.
What occurs when a hormone binds to a nuclear receptor?
Conformational changes enable the receptor to bind DNA and regulate transcription
Receptor-hormone complexes bind to hormone response elements in the DNA.
True or False: Multiple hormones can utilize the same second messenger system.
True
Additionally, a single hormone can utilize more than one signaling system.
