Hormone Receptors and Cell Signaling

40 Questions

What is the primary mechanism by which lipophilic hormones interact with their receptors?

By diffusing through the plasma membrane and binding to receptors in the cytosol or nucleus

Which type of hormone is synthesized as a precursor molecule and then processed and secreted upon a physiologic cue?

Insulin

What is the role of the ligand-receptor complex in hormone signaling?

It generates a secondary messenger

Where do polypeptide/protein hormones and catecholamines bind to their receptors?

On the plasma membrane

How do hormones that bind to surface receptors communicate with intracellular metabolic processes?

Through the release of a secondary messenger

What is the characteristic of hormones derived from cholesterol?

They are synthesized in final form and secreted immediately

What is the primary mechanism by which water-soluble hormones interact with their receptors?

By binding to receptors on the plasma membrane, generating a secondary messenger

What is the effect of the interaction between lipophilic hormones and their receptors?

It directly affects the transcription rate of specific genes

What is the immediate result of angiotensin-converting enzyme action on angiotensin I?

Formation of angiotensin II

What is the function of C-peptide in the context of insulin?

It is a marker for endogenous insulin

Where are catecholamines stored before release into the circulation?

In the chromaffin cells of the adrenal medulla

What is the characteristic of steroid hormones and 1,25(OH)2-D3?

They are synthesized in their final active form

What is the effect of angiotensin II on renin release?

It inhibits renin release

What is the site of pro-insulin processing to form mature insulin?

Golgi apparatus

What is the function of renin in the renin-angiotensin-aldosterone system?

It catalyzes the formation of angiotensinogen precursor

What is the characteristic of polypeptide hormones, such as insulin?

They are synthesized as precursors that undergo processing

What is the primary characteristic of hormone concentrations in the extracellular fluid?

Low concentrations in the femto- to nanomolar range

Which of the following is a classification method for hormones?

Solubility properties

What is the characteristic of hormone action in terms of affected cell types?

A given hormone can affect several different cell types

Which type of hormone is synthesized from cholesterol?

Steroid hormones

What is the primary mechanism of hormone action in terms of distance?

Hormones can act on both adjacent and distant cells

What is the characteristic of hormone receptors in terms of location?

Receptors can be located on the surface or within the cytoplasm

What is the characteristic of hormone action in terms of signal mediation?

Hormones can use multiple types of signals to mediate action

What is the characteristic of hormone synthesis in terms of protein and peptide hormones?

Protein and peptide hormones are synthesized from amino acids

What is the function of Na+-K+-ATPase-dependent thyroidal I− transporter in the synthesis of T3 and T4 hormones?

To regulate the ratio of iodide in thyroid to iodide in serum

Which of the following statements about T3 synthesis is true?

Even though T3 synthesis occurs in the thyroid gland, major amounts are produced in peripheral tissues

What is the primary component of thyroglobulin?

Monoiodotyrosine (MIT) and diiodotyrosine (DIT) residues

What is the role of thyroglobulin in the synthesis of T3 and T4 hormones?

To iodinate and then glycosylate to form T4 and T3

What is the characteristic of peptide hormones such as insulin and parathyroid hormone?

They are synthesized as a precursor molecule and then processed and secreted

What is the name of the protein precursor from which several hormones are derived?

Pro-opiomelanocortin (POMC)

What is the process by which T4 is converted to T3 in peripheral tissues?

Deiodination

What is the ratio of iodide in thyroid to iodide in serum regulated by?

TSH

Which of the following hormones is a lipophilic hormone?

Thyroxine (T4)

What is a characteristic of Group II (Class II) hormones?

They are water-soluble

Which of the following hormones is a peptide hormone?

Growth hormone (GH)

What is the effect of binding to a protein on the half-life of a lipophilic hormone?

It increases the half-life

Which of the following hormones is a steroid hormone?

Estrogen

What is the biological form of a lipophilic hormone?

Free hormone

Which group of hormones includes those that are water-soluble and have a peptide structure?

Group II (Class II)

Why do lipophilic hormones need to associate with plasma transport or carrier proteins in the circulation?

Because they are lipophilic

Study Notes

Hormone Classification and Mechanisms

Hormones are classified into two groups based on their solubility and receptor location:
- Group I (Class I): Lipophilic hormones that bind to intracellular receptors, have a shorter half-life, and are transported by plasma transport proteins.
- Group II (Class II): Water-soluble hormones with a peptide structure, bind to surface receptors, and have a shorter half-life.
Hormones are synthesized and modified in various ways, such as:
- Hormones derived from cholesterol are synthesized in their final form and secreted immediately.
- Catecholamines are synthesized in their final form and stored in producing cells.
- Hormones like insulin are synthesized as precursor molecules, processed, and secreted upon a physiologic cue.

Hormone Structure and Properties

Hormones are synthesized from various sources, including:
- Cholesterol (e.g., glucocorticoids, mineralocorticoids, androgens)
- Amino acids (e.g., tyrosine derivatives, tryptophan derivatives)
- Protein/peptides of various sizes (e.g., insulin, parathyroid hormone, thyrotropin-releasing hormone)
Hormones have specific structures and properties, such as:
- Lipophilic steroid hormones (e.g., estrogen, progesterone, thyroid hormone) interact with intracellular receptors, directly affecting gene transcription.
- Water-soluble hormones (e.g., catecholamines, insulin) bind to surface receptors, generating a secondary messenger or signal.

Hormone Mechanisms and Action

Hormones bind to specific receptors, triggering a response:
- Lipophilic hormones bind to intracellular receptors, influencing gene transcription.
- Water-soluble hormones bind to surface receptors, generating a secondary messenger or signal.
- The ligand-receptor complex acts as an intracellular messenger, affecting various cellular functions.
Hormones can have multiple effects on different cell types, and multiple hormones can affect a single cell type.

Specific Hormones and Systems

Insulin:
- Synthesized as a preprohormone in pancreatic beta cells.
- Processed into pro-insulin, then mature insulin and C-peptide.
- Released in response to elevated blood glucose levels, regulating metabolic effects.
Renin-Angiotensin-Aldosterone System:
- Activated when blood pressure decreases.
- Angiotensinogen is converted into angiotensin I, then angiotensin II, which stimulates aldosterone production, leading to Na+ retention, volume expansion, and increased blood pressure.
Thyroid Hormones:
- Synthesized from tyrosine in the thyroid gland.
- Iodinated to form T4 and T3, with 70% of iodide in thyroglobulin existing in inactive precursors and 30% in metabolically active forms.
- T3 is produced in peripheral tissues through deiodinase activity.

This quiz covers the process of hormone binding to receptors on the plasma membrane and how they communicate with intracellular receptors. Learn about the role of carrier proteins and how hormones interact with lipophilic plasma membranes.

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