Concept 11.2: Reception: A signaling molecule binds to a receptor protein, causing it to change shape

Question 1

the signals emitted by an a mating type yeast cell are “heard” only by its prospective mates,

Answer 1

α cells.

Question 2

In the case of the epinephrine circulating throughout the bloodstream of the impala in Figure 11.1, the hormone encounters many types of cells, but only certain target cells detect and react to the

Answer 2

epinephrine molecule.

Question 3

the term for a molecule that specifically binds to another (often larger) molecule

Answer 3

ligand,

Question 4

Ligand binding generally causes a receptor protein to undergo a change in

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shape.

Question 5

For many receptors, this shape change directly activates the receptor, enabling it to interact with other

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cellular molecules.

Question 6

For other kinds of receptors, the immediate effect of ligand binding is to cause the aggregation of

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two or more receptor proteins, which leads to further molecular events inside the cell

Question 7

Most signal receptors are plasma membrane proteins, but others are located inside the

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cell.

Question 8

The largest family of human cell-surface receptors is the

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G protein-coupled receptors (GPCRs).

Question 9

example is the co-receptor hijacked by

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HIV to enter immune cells

Question 10

Most water-soluble signaling molecules bind to specific sites on transmembrane receptor proteins that transmit information from the

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extracellular environment to the inside of the cell.

Question 11

We can see how cell-surface transmembrane receptors work by looking at three major types:

Answer 11

G protein-coupled receptors (GPCRs), receptor tyrosine kinases, and ion channel receptors.

Question 12

Given the many important functions of cell-surface receptors, it is not surprising that their malfunctions are associated with many human diseases,

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including cancer, heart disease, and asthma.

Question 13

Although cell-surface receptors represent 30% of all human proteins, determining their structures has proved challenging: They make up only 1% of the proteins whose structures have been determined by

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X-ray crystallography

Question 14

For one thing, cell-surface receptors tend to be flexible and inherently unstable, thus difficult to

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crystallize.

Question 15

In that case, the β-adrenergic receptor was stable enough to be crystallized only while it was among membrane molecules and in the presence of a molecule mimicking its

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ligand.

Question 16

Abnormal functioning of receptor tyrosine kinases (RTKs) is associated with many types of

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cancers.

Question 17

For example, breast cancer patients have a poor prognosis if their tumor cells harbor excessive levels of a receptor tyrosine kinase called

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HER2

Question 18

Using molecular biological techniques, researchers have developed a protein called ____________ that binds to HER2 on cells and inhibits cell division, thus thwarting further tumor development

Answer 18

Herceptin

Question 19

Intracellular receptor proteins are found in either the

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cytoplasm or nucleus of target cells.

Question 20

To reach such a receptor, a signaling molecule passes through the

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target cell’s plasma membrane.

Question 21

A number of important signaling molecules can do this because they are either

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hydrophobic enough or small enough to cross the hydrophobic interior of the membrane

Question 22

The hydrophobic signaling molecules include both

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steroid hormones and thyroid hormones of animals.

Question 23

Another chemical signaling molecule that possesses an intracellular receptor is

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nitric oxide (NO), a gas; this very small molecule readily passes between the membrane phospholipids.

Question 24

Once a hormone has entered a cell, its binding to an intracellular receptor changes the receptor into a

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hormone-receptor complex that is able to cause a response—in many cases, the turning on or off of particular genes.

Question 25

The behavior of aldosterone is a representative example of how .

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steroid hormones work

Question 26

This hormone is secreted by cells of the adrenal gland,

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a gland that lies above the kidney

Question 27

Aldosterone then travels through the blood and enters

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cells all over the body.

Question 28

In these cells, the hormone binds to and activates the

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receptor protein.

Question 29

With aldosterone attached, the active form of the receptor protein then enters the nucleus and turns on specific genes that control

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water and sodium flow in kidney cells, ultimately affecting blood volume

Question 30

recall that the genes in a cell’s DNA function by being transcribed and processed into

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messenger RNA (mRNA), which leaves the nucleus and is translated into a specific protein by ribosomes in the cytoplasm

Question 31

Special proteins called ____________________ control which genes are turned on—that is, which genes are transcribed into mRNA—in a particular cell at a particular time.

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transcription factors

Question 32

When the aldosterone receptor is activated, it acts as a transcription factor that turns on

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specific genes

Question 33

By acting as a transcription factor, the aldosterone receptor itself carries out the transduction part of the

Answer 33

signaling pathway