ch 6 cell signaling

Question 1

three general methods of communication between cells

Answer 1

1. gap junctions
2. cell-to-cell binding
3. extracellular chemical messengers

Question 2

function of gap junctions

Answer 2

through connexons, ions and small molecules can diffuse from the cytosol of one cell to the cytosol of another cell

Question 3

where are gap junctions found

Answer 3

in a variety of tissues, including nervous tissue between some neurons, cardiac muscle, and some types of smooth muscle

Question 4

cell-to-cell binding

Answer 4

a surface molecule on one cell binds to a surface molecule on another cell

Question 5

importance of cell-to-cell binding

Answer 5

important during development and for leukocytes to recognize and respond to potentially dangerous foreign cells

Question 6

process of extracellular chemical messengers

Answer 6

begins when a cell secrets a chemical messenger into the ECF, the chemical messenger then diffuses through the ECF and may randomly come in contact with many different types of cells. however, the extracellular messenger has an effect only on specific target cells

Question 7

target cells

Answer 7

a cell that can respond to the extracellular messenger

Question 8

steps on how an extracellular messenger causes an effect on its target cell

Answer 8

1. binding of the extracellular messenger to a receptor
2. signal transduction
   - process by which the signal molecule is converted into a response by the target cell
3. cellular response

Question 9

extracellular chemical messenger

Answer 9

a molecule that is released by a cell, enters the ECF, and then binds to a receptor on or in its target cell to cause a response

Question 10

three major types of extracellular chemical messengers

Answer 10

1. hormones
2. neurotransmitters
3. local mediators

Question 11

hormones

Answer 11

extracellular chemical messengers that are carried by the blood to distant target cells

Question 12

endocrine signaling

Answer 12

cell signaling that is mediated through hormones

Question 13

neurotransmitters

Answer 13

extracellular chemical messengers that are released from a neuron into a synapse in order to reach a nearby target cell

Question 14

synaptic signaling

Answer 14

cell signaling that is mediated through neurotransmitters

Question 15

local mediators

Answer 15

extracellular chemical messengers that act on nearby target cells without entering the bloodstream

Question 16

paracrines

Answer 16

local mediators that act on neighboring cells

Question 17

autocrines

Answer 17

local mediators that act on the same cell that secreted them

Question 18

local signaling

Answer 18

cell signaling that occurs through local mediators

Question 19

cytokines

Answer 19

a type of local mediator that regulates many cell functions, including cell growth and differentiation

Question 20

nitric oxide

Answer 20

a type of local mediator that is released by endothelial cell lining blood vessels, which causes relaxation of nearby smooth muscle fibers in blood vessels, which in turn causes vasodilation

Question 21

eicosanoids

Answer 21

molecules released by many cells of the body in response to chemical or mechanical stimuli. act as local mediators on nearby target cells

Question 22

three major types of eicosanoids

Answer 22

prostaglandins
leukotrienes
thromboxanes

Question 23

growth factors

Answer 23

substances that play important roles in tissue development, growth, and repair
are mitogenic substances - they cause growth by stimulating cell division

Question 24

examples of water-soluble extracellular messengers

Answer 24

peptide or protein hormones (such as oxytocin)
amine hormones (such as norepinephrine)
nearly all of the neurotransmitters
larger number of local mediators, including eicosanoids and growth factors

Question 25

examples of lipid-soluble extracellular messengers

Answer 25

steroid hormones (such as testosterone and estrogens) thyroid hormones nitric oxide

Question 26

three functions of transport proteins

Answer 26

1. they make lipid soluble hormones temporarily water soluble, increasing their solubility in blood 2. they retard passage of small hormone molecules through the filtering mechanism in the kidneys, slowing the rate of hormone loss in the urine 3. they provide a ready reserve of hormones, already present in the bloodstream

Question 27

properties of messenger-receptor binding

Answer 27

specificity affinity saturation competition

Question 28

agonist

Answer 28

a substance that binds to and activates a receptor, in the process mimicking the effect of the endogenous messenger

Question 29

antagonist

Answer 29

a substance that binds to and blocks a receptor, thereby preventing the endogenous messenger from exerting its effect

Question 30

plasma membrane receptor

Answer 30

receptor located in the plasma membrane because water-soluble extracellular messengers are unable to pass through the hydrophobic interior of the plasma membrane

Question 31

intracellular receptor

Answer 31

receptors present inside the target cell, either in the cytosol or in the nucleus

Question 32

down-regulation

Answer 32

an effect that occurs if an extracellular messenger is present in excess, the number of target-cell receptors may decrease - ultimately makes the target cell less sensitive to the messenger

Question 33

up-regulation

Answer 33

an effect when a messenger is deficient, the number of target-cell receptors may increase - ultimately makes the target cell more sensitive to the messenger

Question 34

signal transudction

Answer 34

the process by which a molecule (the messenger) is transduced (converted) into a cellular response

Question 35

signal transduction pathway/signaling pathway

Answer 35

the specific sequence of events that occur between the binding of the extracellular messenger to the receptor and the cellular response

Question 36

effector protein

Answer 36

causes the cellular response

Question 37

relay proteins

Answer 37

convey the signal between the receptor and the effector protein

Question 38

first messenger

Answer 38

the extracellular messenger binds to its receptor, then an intracellular messenger is generated in the cytosol of plasma membrane of the target cell to help mediate the transduction process

Question 39

second messenger

Answer 39

the intracellular messenger usually generated by special types of receptors that have enzymatic activity or by certain enzymes that are relay proteins. once formed, typically binds to and activates the next relay protein of the signaling pathway

Question 40

protein kinase

Answer 40

an enzyme that phosphorylates a target protein