Endocrinology

Which statement best describes a hormone receptor?

A protein that binds a hormone in a specific manner.

A receptor with high affinity for a hormone has which property?

It binds the hormone strongly even at a low concentration.

A receptor that is active when no hormone is bound shows what type of activity?

Constitutive activity

Cell-surface receptor signaling does NOT usually require the hormone to do which action?

 

Cross the plasma membrane before signaling begins

Which bioregulator does NOT act principally through a nuclear receptor?

Epinephrine

Which hormone binds to a receptor tyrosine kinase?

Insulin

Norepinephrine and epinephrine normally bind to which receptor class?

 

Alpha- and beta-adrenergic GPCRs

A bioregulator has a catechol ring attached to an amine-containing side chain. What type of molecule is it?

A catecholamine

Which amino acid is the direct starting material for catecholamine synthesis?

Tyrosine

Which enzyme catalyzes the rate-limiting step in catecholamine synthesis?

Tyrosine hydroxylase9

What is the main effect of hypothalamic dopamine on prolactin release?

It inhibits prolactin release from the pituitary

Which enzymes are most directly involved in catecholamine degradation?

 

Monoamine oxidase and catechol-O-methyltransferase

Which amino acid is the primary precursor for serotonin and melatonin?

Tryptophan

Which enzyme provides the rate-limiting control of melatonin synthesis?

 

N-acetyltransferase

Synthesis of a peptide hormone begins with which process?

Transcription of the hormone-coding gene into mRNA

What is the main function of the signal peptide on a secreted preprohormone?

 

It directs the translating molecule to the rough endoplasmic reticulum.

Which event converts proinsulin into mature insulin?

 

Removal of the connecting C-peptide

Where do most amine and peptide hormones bind their receptors?

On the cell surface

In beta-adrenergic signaling, which pairing is correct?

 

Epinephrine is the first messenger, and cAMP is the second messenger.

Which sequence correctly describes beta-adrenergic signaling?

 

Epinephrine, beta receptor, Gs, adenylyl cyclase, cAMP, protein kinase A

Phospholipase C converts PIP2 into which two second messengers?

IP3 and DAG

Which intracellular protein binds cytosolic calcium and regulates many target proteins?

Calmodulin

Cross talk between hormone signaling pathways can produce which result?

Cooperative reinforcement or antagonistic inhibition

Which process can reduce the number of occupied receptors on the cell surface?

 

Endocytosis followed by lysosomal degradation

Which structure forms the basic steroid nucleus?

 

Three six-membered rings and one five-membered ring with a 17-carbon core

In the steroid convention presented, what does beta orientation indicate?

The group projects in front of the plane, toward the viewer.

Which steroid class and carbon-number pairing is correct?

Estrogens are C18 steroids

What is the parent compound for all vertebrate steroid hormones?

Cholesterol

P450 side-chain cleavage converts cholesterol into which steroid?

Pregnenolone

A steroid produces a response within seconds through a membrane receptor. Which mechanism best explains the response?

The membrane receptor activates a G protein or kinase signaling pathway.

A high-affinity receptor can bind its hormone effectively at a relatively low hormone concentration.

True

Some nuclear receptors can be activated by intracellular signaling pathways even without direct ligand binding.

True

Hypothalamic dopamine stimulates prolactin release from the pituitary.

False

Tryptophan is a precursor for serotonin and melatonin synthesis

True

The signal peptide of a secreted preprohormone directs the translating molecule to the rough endoplasmic reticulum.

True

In beta-adrenergic signaling, cAMP is the extracellular first messenger that binds the receptor.

False

Cytosolic calcium can bind calmodulin and regulate cellular proteins.

True

All vertebrate steroid hormones are synthesized from cholesterol.

True

The final conversion of vitamin D to active 1,25-dihydroxycholecalciferol occurs in the liver.

False

Phase II conjugation usually decreases steroid water solubility and prevents excretion.

False