Biology Chapter 62: Hormones

Questions and Answers

Which statement accurately describes the characteristics of steroid hormones?

They primarily act by binding to receptors on cell membranes.

They are secreted solely by the pituitary gland.

They are derived from cholesterol or its derivatives. (correct)

They are synthesized from amino acids directly.

What is a key feature of hormone receptors?

Each receptor is specific to one single hormone. (correct)

Receptors are located exclusively in the nucleus of target cells.

Receptors are only present in the adrenal cortex.

Each receptor can bind to multiple different hormones.

How do hormones primarily exert their effects on target cells?

By directly entering the target cell cytoplasm.

By promoting cellular apoptosis immediately.

By altering the permeability of the cell membrane. (correct)

By forming a complex that alters receptor shape.

Which hormones are classified as protein hormones?

Large or small peptides secreted by specific glands. Signup and view all the answers

Where can hormone receptors be found in target cells?

In both the cytoplasm and nucleus of target cells. Signup and view all the answers

Which type of hormone has receptors primarily located in the nucleus of target cells?

Thyroid hormones Signup and view all the answers

What is the primary source of secretion for testosterone?

Testis Signup and view all the answers

What occurs during down regulation of hormone receptors?

Decrease in the number of receptors Signup and view all the answers

What is the main consequence of up regulation in hormone receptors?

Increased number of receptors Signup and view all the answers

Which hormone is produced by the anterior pituitary gland?

Luteinizing hormone Signup and view all the answers

What term describes the process through which hormone-receptor complexes enter target cells?

Endocytosis Signup and view all the answers

Which of the following hormones is classified as a steroid hormone?

Cortisol Signup and view all the answers

Where are the receptors for adrenal medullary hormones generally located?

Cell membrane Signup and view all the answers

What initiates the activation of protein kinase C (PKC) in the hormone signaling pathway?

Diacylglycerol (DAG) remaining in the cell membrane Signup and view all the answers

Which hormone is primarily responsible for the transcription activation within the nucleus after binding to its receptor?

Steroid hormones Signup and view all the answers

What is the role of inositol triphosphate (IP3) in the signaling mechanism?

It binds to calcium channels in the endoplasmic reticulum Signup and view all the answers

Which division of the pituitary gland is responsible for producing hormones rather than storing them?

Anterior Pituitary Signup and view all the answers

What is the effect of protein kinases following their activation in the hormone signaling pathway?

They phosphorylate target proteins to elicit physiological responses Signup and view all the answers

Which response is NOT produced by cyclic AMP?

Direct binding to DNA Signup and view all the answers

Which of the following hormones is released by the posterior pituitary?

Oxytocin Signup and view all the answers

What role does calmodulin play in hormone action?

It activates myosin kinase in smooth muscle Signup and view all the answers

In the context of steroid hormone action, what occurs after mRNA is produced?

It leaves the nucleus to facilitate protein synthesis Signup and view all the answers

Which statement regarding inositol triphosphate (IP3) is correct?

IP3 releases calcium ions from the endoplasmic reticulum Signup and view all the answers

What type of reaction does phospholipase C catalyze in the hormone signaling pathway?

Hydrolysis of PIP2 into DAG and IP3 Signup and view all the answers

Which of the following substances acts like cyclic AMP in signaling pathways?

Cyclic guanosine monophosphate (cGMP) Signup and view all the answers

What initiates the production of inositol triphosphate (IP3) and diacylglycerol?

Activation of phospholipase C by G protein Signup and view all the answers

How do thyroid hormones execute their function within target cells?

By acting on genes in the target cells Signup and view all the answers

What is the role of diacylglycerol in hormone signaling?

To activate protein kinase C through phosphorylation Signup and view all the answers

Which of the following best describes the relationship between adenyl cyclase and cAMP?

Adenyl cyclase converts ATP into cAMP Signup and view all the answers

What is the role of the hormone-receptor complex in hormonal action?

It facilitates the execution of hormonal action. Signup and view all the answers

Which of the following statements about second messengers is true?

They are essential for amplifying hormonal signals inside the cell. Signup and view all the answers

Which physiological action is primarily mediated by cyclic AMP?

Activation of intracellular enzymes. Signup and view all the answers

What triggers the dissociation of the α-GTP unit and β-γ dimer from the receptor?

The exchange of GDP for GTP on the α-subunit. Signup and view all the answers

Which G protein subunit primarily exerts biological effects upon activation?

α subunit Signup and view all the answers

What initiates the activation of adenyl cyclase in the second messenger cascade?

Activation of the α-GTP unit. Signup and view all the answers

What occurs when acetylcholine binds to its receptors at the neuromuscular junction?

It increases permeability of the postsynaptic membrane to sodium. Signup and view all the answers

What is a common second messenger involved in protein hormone signaling?

Cyclic AMP (cAMP) Signup and view all the answers

Which statement best describes the function of G proteins in hormonal signaling?

They are inactive in the membrane until hormones bind to their receptors. Signup and view all the answers

Study Notes

Chemistry of Hormones

Hormones are classified into steroid hormones, protein hormones, and tyrosine-derived hormones, based on their chemical nature.
Steroid hormones are synthesized from cholesterol and secreted by adrenal cortex, gonads, and placenta.
Protein hormones consist of large or small peptides produced by the pituitary gland, parathyroid glands, pancreas, and placenta.
Tyrosine-derived hormones include thyroid hormones (like thyroxine) and adrenal medullary hormones (such as adrenaline and noradrenaline).

Hormonal Action

Hormones interact with specific receptors on target cells to form a hormone-receptor complex, resulting in cellular changes.
Each cell has thousands of specific receptors, with each receptor designed for only one type of hormone.

Location of Hormone Receptors

Receptors for protein hormones and catecholamines are found in the cell membrane.
Steroid hormone receptors are located in the cytoplasm.
Thyroid hormone receptors reside in the cell nucleus.

Regulation of Hormone Receptors

Down regulation occurs when there is an excess of a hormone, leading to decreased receptor numbers.
Up regulation increases the number of receptors when there is a deficiency of the hormone.
Hormone-receptor complexes may be internalized in the cell, where they can be recycled or degraded.

Mechanism of Hormonal Action

Hormonal actions are mediated through processes like altering cell membrane permeability, activating intracellular enzymes, or acting directly on genes.
Hormones serve as first messengers; the second messengers, such as cyclic AMP (cAMP), facilitate the hormonal effects within target cells.

Action of Cyclic AMP

cAMP acts as a second messenger that mediates the effects of protein hormones and catecholamines by activating protein kinase A.
Key responses initiated by cAMP include muscle contraction and relaxation, altering cell membrane permeability, substance synthesis, and secretion.

Other Second Messengers

Calcium ions and calmodulin can also act as second messengers, facilitating various cellular responses, especially in muscle contraction.
Inositol triphosphate (IP3) and diacylglycerol (DAG) are formed from phosphatidylinositol bisphosphate (PIP2) and contribute to signaling cascades.
Cyclic guanosine monophosphate (cGMP) resembles cAMP and acts through protein kinase A.

Mode of Action of Steroid Hormones

Steroid hormones pass through cell membranes to bind with receptors in the nucleus, activating gene transcription.
This interaction leads to mRNA production, directing protein synthesis and eliciting physiological responses.

Pituitary Gland

The pituitary gland, located in the sphenoid bone, has anterior (adenohypophysis) and posterior (neurohypophysis) divisions.
Anterior Pituitary hormones include growth hormone, prolactin, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, and luteinizing hormone.
The Posterior Pituitary stores and releases antidiuretic hormone (ADH) and oxytocin, produced by the hypothalamus.

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Description

Explore the fascinating world of hormones in Chapter 62. This quiz covers the chemistry of different hormone types, their actions, and the mechanisms by which they influence cellular functions. Test your understanding of steroid hormones, protein hormones, and more!