17.1 Signaling Molecules and Their Receptors

Question 1

cell signaling can result from either:

Answer 1

1. direct cell-cell signaling
2. action of secreted signaling molecules

Question 2

cell signaling results from direct contact between neighboring cells

Answer 2

direct cell-cell signaling

Question 3

the types of secreted signaling molecules (according to increasing size)

Answer 3

1. steroid hormones and the nuclear receptor family
2. signaling by other small molecules
3. peptide hormones and growth factors

Question 4

Secreted signaling molecules act on cells by binding to either:

Answer 4

1. cell surface receptors
2. intracellular receptors

Question 5

binding to the receptor initiates downstream chain reactions inside the cell

Answer 5

cell surface receptors

Question 6

receptors whose signal molecules must be hydrophobic in order to pass through the PM

Answer 6

intracellular receptors

Question 7

the 3 main modes of cell-cell signaling are:

Answer 7

1. endocrine signaling
2. paracrine signaling
3. autocrine signaling

Question 8

signaling molecules are secreted by specialized endocrine cells and carried through blood circulation to act on target cells at distant body sites

Answer 8

endocrine signaling

Question 9

the signaling molecules in endocrine signaling are predominantly ()

Answer 9

hormones

Question 10

example of endocrine signaling

Answer 10

estrogen is produced by the ovaries and stimulates development and maintenance of the female reproductive system and secondary sex characteristics

Question 11

cell-cell signaling in which a molecule released by one cell acts on neighboring target cells

Answer 11

paracrine signaling

Question 12

example of paracrine signaling

Answer 12

neurotransmitters carry signals between nerve cells at a synapse

Question 13

cell-cell signaling in which signaling molecules acts on the cell that released it instead of neighboring cells

Answer 13

autocrine signaling

Question 14

example of autocrine signaling

Answer 14

response of cells of the vertebrate immune system to foreign antigens; T lymphocytes synthesize a growth factor that drives their own proliferation

Question 15

() respond to small hydrophobic molecules that diffuse across the PM → receptors are intracellular proteins located in the cytosol or nucleus

Answer 15

steroid hormones

Question 16

all steroid hormones are synthesized from ()

Answer 16

cholesterol

Question 17

examples of steroid hormones

Answer 17

1. sex steroids: testosterone, progesterone, estrogen
2. corticosteroids
3. thyroid hormone
4. vitamin D3
5. retinoic acid and other retinoids

Question 18

once inside the cell, the steroids bind to protein receptors that are part of the ()

Answer 18

nuclear receptor superfamily

Question 19

members of the nuclear receptor superfamily are () that contain related domains for ligand binding, DNA binding, and transcriptional activation

Answer 19

transcription factors

Question 20

() of nuclear receptor family members regulates their function as activators or repressors of target genes → steroid hormones and related molecules directly regulate gene expression

Answer 20

ligand binding

Question 21

give an example of a nuclear receptor super family member that is inactive in the absence of hormones

Answer 21

glucocorticoid receptor remains bound to Hsp90 chaperones in absence of glucocorticoids

Question 22

in other cases, nuclear receptor superfamily member binds DNA in either the presence or absence of hormones → hormone binding alters activity of the receptor as a ()

Answer 22

transcriptional regulatory molecule

Question 23

example of nuclear receptor whose activity as a transcriptional regulatory molecule is altered by binding of certain ligands

Answer 23

thyroid hormone:
- acts as a repressor in presence of corepressor histone deacetylase (HDAC)
- acts as an activator in presence of coactivator histone acetyltransferase

Question 24

in presence of () thyroid hormone acts as repressor of genes

Answer 24

histone deacetylase (HDAC)

Question 25

in presence of (), thyroid hormone acts as gene activator

Answer 25

histone acetyltransferase

Question 26

examples of small signaling molecules

Answer 26

1. nitric oxide (NO - gas
2. acetylcholine - neurotransmitter
3. gamma-aminobutyric acid (GABA) - neurotransmitter
4. indole-3-acetic acid - plant hormone (auxin)

Question 27

function of nitric oxide as a signaling molecule

Answer 27

alters the activity of the intracellular target enzyme guanylyl cyclase → stimulates cyclic GMP synthesis inside the cell

Question 28

nitric oxide is a () in the nervous system, as well as immune and circulatory system

Answer 28

paracrine signaling molecule

Question 29

a molecule that relays a signal from a receptor to a target signal

Answer 29

second messenger

Question 30

overview of blood vessel dilation with NO

Answer 30

1. neurotransmitters (e.g. acetylcholine) are released from nerve cell termini in the blood vessel wall
2. neurotransmitters act on endothelial cells to stimulate NO synthesis
3. NO diffuses to neighboring smooth muscle cells where it activates guanylyl cyclase
4. activation of guanylyl cyclase leads to cyclic GMP synthesis → induces cell relaxation and blood vessel dilation

Question 31

signaling molecules that carry signals between neurons or from neurons to other types of target cells (e.g. muscle cells)

Answer 31

neurotransmitters

Question 32

release of neurotransmitters is signaled by the () at the terminus of a neuron

Answer 32

arrival of an action potential

Question 33

many neurotransmitter receptors are ()

Answer 33

ligand-gated ion channels (e.g. acetylcholine receptor)

Question 34

other neurotransmitter receptors are ()

Answer 34

G protein-coupled receptors

Question 35

group of small molecules that regulate plant growth and development;

Answer 35

plant hormones

Question 36

how do plant hormones coordinate the responses of tissues (in different parts of the plant) to environmental signals

Answer 36

concentrations of plant hormones depend on environmental factors

Question 37

first plant hormone identified (by Darwin); involved in plant cell elongation through weakening of cell wall

Answer 37

auxins

Question 38

other examples of plant hormones

Answer 38

1. gibberellins
2. ethylene
3. cytokinins
4. abscisic acid

Question 39

plant hormone involved in stem elongation

Answer 39

gibberellins

Question 39

plant hormone involved in fruit ripening

Answer 39

ethylene

Question 40

plant hormone involved in cell division

Answer 40

cytokinins

Question 41

plant hormone involved in onset of dormancy

Answer 41

abscisic acid

Question 42

peptides have the widest variety of signaling molecules in animals; they include:

Answer 42

1. peptide hormones
2. neuropeptides
3. polypeptide growth factors

Question 43

example of peptide hormones

Answer 43

1. insulin
2. pituitary gland hormones (e.g. growth hormone, follicle-stimulating hormone, prolactin, etc.)

Question 44

examples of neuropeptides

Answer 44

1. enkephalins
2. endorphins

Question 45

natural analgesics that decrease pain responses in the central nervous system; naturally occurring compounds that bind to the same receptors (on the surface of brain cells) as morphine does

Answer 45

neuropeptides

Question 46

() include a wide variety of signaling molecules that control animal cell growth and differentiation

Answer 46

polypeptide growth factors

Question 47

member of polypeptides that regulate the development and survival of neurons; first growth factor discovered; found by Rita Levi-Montalcini

Answer 47

nerve growth factor (NGF)

Question 48

served as the prototype of a large array of growth factors that play critical roles in controlling animal cell proliferation, both during embryonic development and in adult organisms

Answer 48

epidermal growth factor (EGF)

Question 49

epidermal growth factor (EGF) stimulates ()

Answer 49

cell proliferation

Question 50

involved in wound healing; stimulates proliferation and movement of fibroblasts in the vicinity of the clot → contributing to regrowth of damaged tissue

Answer 50

platelet-derived growth factor (PDGF)

Question 51

regulate the development and differentiation of blood cells and control the activities of lymphocytes during the immune response

Answer 51

cytokines

Question 52

examples of cytokines

Answer 52

1. erythropoietin
2. interleukin-2