Q: Receptors are described as being 'constantly synthesized and broken down.' Which equation best represents the dynamic equilibrium of receptor concentration ($[R]$) in a cell?

$[R] = \frac{\text{rate of synthesis} - \text{rate of breakdown}}{\text{cell volume}}$

Question 1

Which of the following best describes the process of down-regulation in hormone receptor dynamics?

Accepted Answer

A decrease in the number of receptors in response to excessive hormone levels.

Question 2

A patient is diagnosed with hyperthyroidism, resulting in elevated thyroid hormone levels. According to receptor regulation principles, what is the most likely cellular response?

Accepted Answer

Down-regulation of thyroid hormone receptors.

Question 3

Which statement correctly explains up-regulation of hormone receptors?

Accepted Answer

It occurs when hormone production is significantly decreased.

Question 4

Receptors are described as being 'constantly synthesized and broken down.' Which equation best represents the dynamic equilibrium of receptor concentration ($[R]$) in a cell?

Accepted Answer

$[R] = \frac{	ext{rate of synthesis} - 	ext{rate of breakdown}}{	ext{cell volume}}$

Question 5

A cell exposed to chronically low levels of a hormone will most likely respond by:

Accepted Answer

Increasing the number of hormone receptors (up-regulation).

Question 6

Which of the following is a plausible consequence of down-regulation in the context of drug tolerance?

Accepted Answer

Cells become less responsive to the drug due to fewer available receptors.

Question 7

If a hormone binds only to receptors with specific glycoprotein structures, what would be the effect of a mutation that alters the glycoprotein composition of these receptors?

Accepted Answer

The hormone would fail to bind to the mutated receptors.

Question 8

A researcher observes that the number of hormone receptors on a cell membrane decreases after prolonged exposure to high hormone concentrations. Which mechanism is most likely responsible?

Accepted Answer

Down-regulation

Question 9

Which of the following best illustrates the concept of specificity in hormone-receptor interactions?

Accepted Answer

A hormone binds only to receptors with a matching glycoprotein structure.

Question 10

In a scenario where the body suddenly stops producing a particular hormone, what is the most likely cellular adaptation regarding receptor numbers?

Accepted Answer

Up-regulation of receptors.

Question 11

Which of the following equations best models the relationship between hormone concentration ($[H]$) and receptor number ($[R]$) during down-regulation?

Accepted Answer

$[R] \propto \frac{1}{[H]}$

Question 12

A patient with Addison's disease has abnormally low cortisol levels. What receptor adaptation would you expect in their cells?

Accepted Answer

Up-regulation of cortisol receptors.

Question 13

Which of the following is NOT a plausible reason for the breakdown of hormone receptors?

Accepted Answer

To increase the cell's sensitivity to a hormone.

Question 14

A cell's response to a hormone depends on the number of available receptors. If the rate of receptor synthesis is $S$ and the rate of breakdown is $B$, which equation gives the net change in receptor number per unit time?

Accepted Answer

$\Delta R = S - B$

Question 15

Which of the following scenarios would most likely trigger up-regulation of hormone receptors?

Accepted Answer

Chronic administration of a hormone antagonist.

Question 16

If a hormone receptor is described as 'specific,' what does this imply about its interaction with hormones?

Accepted Answer

It binds only to hormones with a complementary structure.

Question 17

A cell exposed to a hormone antagonist for an extended period is likely to:

Accepted Answer

Increase the number of hormone receptors (up-regulation).

Question 18

Which of the following best explains why receptor numbers are regulated in response to hormone levels?

Accepted Answer

To maintain homeostasis and prevent over- or under-reaction to hormonal signals.

Question 19

A cell with a mutation that prevents receptor breakdown would most likely:

Accepted Answer

Become hypersensitive to its hormone due to excess receptors.

Question 20

Which of the following is the most accurate definition of 'down-regulation'?

Accepted Answer

A decrease in receptor number in response to increased hormone levels.

Hormone Receptors: Regulation and Function

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