Hormones and Signaling Pathways

Flashcards on hormones, their mechanisms, and signaling pathways.

What are hormones?

Organic signaling molecules that act on a target cell to produce specific effects.

What is autocrine signaling?

When a hormone acts on the same cell that secreted it.

What is paracrine signaling?

When a hormone affects neighboring cells.

What is endocrine signaling?

When a hormone travels through the bloodstream to act on distant cells.

What is exocrine signaling?

Uses ducts and glands to affect cells on other animals.

Name a peptide hormone example.

Insulin, vasopressin/ADH.

Why can't peptide hormones enter cells directly?

They are water-soluble and must bind to surface receptors.

Give an example of paracrine action of peptide hormones.

Local tissue response in the pancreas.

Give an example of endocrine action of peptide hormones.

Insulin traveling through the blood to affect the liver/muscle.

What are amino acid derivative hormones derived from?

Single amino acids.

What amino acid is epinephrine derived from?

Tyrosine.

What amino acid is serotonin derived from?

Tryptophan.

Are amino acid derivative hormones usually smaller or larger than peptide hormones?

Smaller.

What type of receptor do amino acid derivative hormones generally use?

Surface receptors.

What are steroid hormones derived from?

Cholesterol.

Give examples of steroid hormones.

Testosterone, cortisol.

How do steroids affect cells?

Pass directly through the cell membrane and bind intracellular receptors leading to gene activation.

What are fatty acid derivative hormones derived from?

Fatty acids like arachidonic acid.

Give an example of a fatty acid derivative hormone.

Prostaglandins.

What type of signaling do fatty acid derivative hormones use?

Paracrine and autocrine, not endocrine.

What is a target cell?

A cell that has the receptor for a specific hormone.

What happens after a signal molecule (ligand) binds to a membrane receptor?

The receptor changes shape and activates intracellular signaling.

List some general effects of hormones.

Alter plasma membrane permeability, stimulates protein synthesis, activates or deactivates enzymes, induces secretory activity, stimulates mitosis.

What are short-term effects of hormones?

Enzyme activation, ion channel opening, cell movement.

What are long-term effects of hormones?

Gene expression via transcription changes.

How does insulin regulate glucose uptake into cells?

By regulating glucose transporters.

What happens when blood glucose levels rise?

Insulin is released to help lower it.

Why does insulin bind to a receptor on the outside of the cell?

Because it is water soluble and cannot enter the cell.

What are GLUT4 vesicles?

Vesicles that store glucose transporters inside the cell.

What happens to GLUT4 vesicles when insulin is released?

They move to the membrane and fuse with it, inserting GLUT4 into the membrane.

How does GLUT4 affect glucose uptake?

It allows glucose to enter the cell, reducing blood glucose levels.

What happens to GLUT4 when glucose levels are low?

GLUT4 transporters are removed from the membrane and go back into vesicles.

Give two examples of lipid-soluble hormones

Steroid hormones and thyroxine.

How do lipid-soluble hormones affect cells?

They pass through the plasma membrane, bind to intracellular receptors, and directly activate genes.

How do water-soluble hormones affect cells?

Bind to membrane receptors, activate G proteins, which activate intracellular second messengers.

What does GPCR stand for?

G protein-coupled receptor.

What is the function of the effector protein?

To make the 2nd messenger which spreads the signal inside the cell; typically cAMP or calcium ions

What are the two pathways when using cAMP as a second messenger?

The activating and inhibitory pathways

What hormones use the activating pathway that uses cAMP as a second messenger?

Dopamine, Serotonin and Calcitonin

What determines if the cAMP pathway activates or inhibits?

The type of G protein (Gs or Gi) determines if the pathway activates or inhibits the response

What does Gs stimulate?

Gs stimulates adenylate cyclase; converts ATP to cAMP

What step is it when Adenylate cyclase converts ATP to cAMP; cyclic AMP

Step 3

What results are caused when camp activates kinase A

Activates enzymes, Stims ceullular secretions, Open ion channels, etc )

What happens in the inhibitory pathway?

Water soluble hormone b binds to cell surface/plasma membrane receptor b, Activates Gi, inhibits adenylate cyclase, reduces cAMP levels, reduces/block the cell response

What is the pathway when using Calcium

Activating pathway

What kind of hormones trigger the Calcium activating pathway?

Triggered by water soluble hormones that bind to GPCRs and activate the Gq protein

What is PLC?

Phospholipase C; a membrane bound enzyme

What is the function of PLC

It tragets PIP2; a phospholipid component of the cell membrane

What does PLC split PIP2 into?

DAG; diacylglycerol and IP3; inositol triphosphate

What does DAG do?

Stays in the membrane and activates protein kinase C (PKC)

What does IP3 do?

Moves into cytoplasm

What does IP3 trigger?

Release of Ca

List the steroid hormones

Testosterone, Estrogen, Progesterone and Cortisol

What are the 3 domains of a hormone?

Hormone Binding Domain, Hinge domain and DNA binding Domain

What determines how strongly a target cell responds to a hormone?

Specificity, Blood levels of hormone, Number of receptors on/in target cell and Affinity/strength of receptor bidning the hormone

What happens during up regulation?

Hormones binds -> increased receptor density -> inc sensitivity -> increased response

What happens during down regulation?

Hormones binds too often -> decreased receptors -> reduced response

What does repeated drug administration cause?

Decreased effect over time.

List two examples of water-soluble hormones.

Insulin and Epinephrine

How does activated G protein subunit affect the effetor protein?

Binds the effector, triggering a change, and then GTP is hydrolyzed to GDP ending the signal

What mechanism of signaling do lipid-soluble hormones use?

Direct gene activation

What is the function of the hinge domain?

Allows nuclear entry