Q: Which of the following equations best represents the relationship between hormone concentration ($$L$$), receptor number ($$R$$), and the likelihood of a cellular response?

$$L + R \rightarrow LR \rightarrow \text{Response}$$

Question 1

Which of the following best explains why water-soluble hormones cannot directly activate genes inside a target cell?

Accepted Answer

They cannot cross the plasma membrane due to their hydrophilic nature and must act via membrane receptors and second messengers.

Question 2

A patient is given a synthetic steroid hormone. Which of the following is the most likely sequence of events for this hormone's action?

Accepted Answer

It binds to an intracellular receptor, forms a hormone-receptor complex, and directly activates gene transcription.

Question 3

Which of the following hormones would most likely require a transport protein in the blood?

Accepted Answer

Cortisol

Question 4

A mutation causes a target cell to lack G-proteins. Which hormone signaling pathway would be most directly affected?

Accepted Answer

Epinephrine activation of the cAMP second messenger system

Question 5

Which of the following best describes the role of phospholipase C (PLC) in hormone signaling?

Accepted Answer

PLC splits PIP$$_2$$ into DAG and IP$$_3$$, which act as second messengers.

Question 6

A researcher blocks the release of Ca$$^{2+}$$ from the endoplasmic reticulum in a target cell. Which hormone signaling pathway would be most directly impaired?

Accepted Answer

PIP$$_2-$$Calcium signaling mechanism

Question 7

Which of the following is TRUE regarding the action of insulin?

Accepted Answer

Insulin binds to a receptor that is a tyrosine kinase enzyme, triggering phosphorylation cascades.

Question 8

Which of the following best explains why steroid hormones can have long-lasting effects on target cells?

Accepted Answer

They directly activate genes, leading to new protein synthesis.

Question 9

A patient with low blood calcium levels is found to have increased secretion of parathyroid hormone (PTH). This is an example of which type of endocrine gland stimulus?

Accepted Answer

Humoral stimulus

Question 10

Which of the following scenarios best illustrates the concept of 'down-regulation' of hormone receptors?

Accepted Answer

A target cell decreases the number of receptors in response to high hormone levels.

Question 11

Which of the following equations best represents the relationship between hormone concentration ($$L$$), receptor number ($$R$$), and the likelihood of a cellular response?

Accepted Answer

$$L + R ightarrow LR ightarrow 	ext{Response}$$

Question 12

Which of the following is a correct statement about the specificity of hormone action?

Accepted Answer

A target cell must have a specific receptor for a hormone to respond.

Question 13

During a severe stress response, the nervous system inhibits insulin release from the pancreas. What is the physiological benefit of this action?

Accepted Answer

It allows blood glucose levels to rise, providing more energy for the fight-or-flight response.

Question 14

Which of the following best describes the amplification effect in second messenger systems?

Accepted Answer

A single hormone molecule can trigger the formation of many second messenger molecules, leading to a large cellular response.

Question 15

Which of the following is NOT a second messenger in hormone signaling?

Accepted Answer

Cortisol

Question 16

A cell exposed to persistently high levels of a hormone begins to lose its receptors for that hormone. This process is called:

Accepted Answer

Down-regulation

Question 17

Which of the following best explains why thyroid hormone, although derived from amino acids, acts like a steroid hormone?

Accepted Answer

It is lipid-soluble, requires a transport protein, and binds to intracellular receptors.

Question 18

Which of the following is a direct result of IP$$_3$$ production in the PIP$$_2-$$Calcium signaling pathway?

Accepted Answer

Release of Ca$$^{2+}$$ from intracellular stores

Question 19

Which of the following best describes the action of a hormone that binds to a receptor tyrosine kinase?

Accepted Answer

It directly phosphorylates intracellular proteins, leading to a cellular response.

Question 20

Which of the following is an example of a neural stimulus for hormone release?

Accepted Answer

Sympathetic stimulation of the adrenal medulla to release epinephrine

Hormone Structure, Transport, and Mechanisms of Action

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