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Biology 1406 > Chapter 11 (Notes) > Flashcards

Chapter 11 (Notes) Flashcards

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1
Q

Cell-to-cell communication is essential for both

A

multicellular and unicellular organisms

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2
Q

Biologists have discovered some universal mechanisms of

A

cellular regulation

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3
Q

Cells most often communicate with each other via

A

chemical signals.

For example, the fight-or-flight response is triggered by a signaling molecule called epinephrine

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4
Q

External signals are converted to

A

responses within the cell

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5
Q

Microbes provide a glimpse of the role of

A

cell signaling in the evolution of life

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6
Q

A signal transduction pathway is a

A

series of steps by which a signal on a cell’s surface is converted into a specific cellular response

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7
Q

Signal transduction pathways convert signals on a cell’s surface into

A

cellular responses

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8
Q

Pathway similarities suggest that

A

ancestral signaling molecules evolved in prokaryotes and were modified later in eukaryotes

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9
Q

Cells in a multicellular organisms communicate by

A

chemical messengers

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10
Q

Animal and plant cells have cell junctions that

A

directly connect the cytoplasm of adjacent cells

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11
Q

In local signaling, animal cells may communicate by

A

direct contact, or cell-cell recognition

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12
Q

In many other cases, animal cells communicate using

A

local regulators, messenger molecules that travel only short distances

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13
Q

paracrine signaling-

local regulator

A

grown factors from one cell stimulate numerous neighboring cells

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14
Q

synaptic signaling-

local regulator

A

neurotransmitters

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15
Q

In long-distance signaling, plants and animals use

A

chemicals called hormones

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16
Q

Endocrine signaling-

long-distance signaling. hormones

A

hormones are released into the circulatory system to reach distance regions of the body

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17
Q

The ability of a cell to respond to a signal depends on whether or not it has a

A

receptor specific to that signal

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18
Q

Earl W. Sutherland discovered how the hormone

A

epinephrine acts on cells

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19
Q

Sutherland suggested that cells receiving signals went through three processess:

A

Reception
Transduction
Response

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20
Q

Reception: a signaling molecules binds to a

A

receptor protein, causing it to change shape

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21
Q

The binding between a signal molecule (ligand) and receptor is

A

highly specific

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22
Q

Ligand-

A

a molecule that specifically binds to a larger molecule

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23
Q

A shape change in a receptor is often the

A

initial transduction of the signal

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24
Q

Most signal receptors are

A

plasma membrane proteins

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25
Q

Most water-soluble signal molecules bind to

A

specific sites on receptor proteins that span the plasma membrane

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26
Q

There are three main types of membrane receptors

A
  1. G protein-coupled receptors
  2. Receptor tyrosine kinases
  3. Ion channel receptors

Also have intracellular receptors

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27
Q

G protein-coupled receptors (GPCRs) are

A

the largest family of cell-surface receptors

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28
Q

A G protein-coupled receptor (GPCR) is a

A

plasma membrane receptor that works with the help of a G protein

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29
Q

The G protein acts as an

A

on/off switch: If GDP is bound to the G protein, the G protein is inactive

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30
Q

Receptor tyrosine kinases (RTKs) are

A

membrane receptors that attach phosphates to tyrosines

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31
Q

A kinase is an

A

enzyme that catalyzes the transfer of phosphate groups

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32
Q

A receptor tyrosine kinase can trigger

A

multiple signal transduction pathways at once

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33
Q

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

A

many types of cancers

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34
Q

A ligand-gated ion channel receptor acts as a

A

gate when the receptor changes shape

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35
Q

When a signal molecule binds as a ligand to the receptor, the

A

gate allows specific ions, such as NA+ or CA^2+, through a channel in the receptor

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36
Q

Important in the nervous system

A

-neurotransmitter release

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37
Q

Intracellular receptor proteins are found in the

A

cytosol or nucleus of target cells

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38
Q

Small or hydrophobic chemical messengers can

A

readily cross the membrane and activate receptors

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39
Q

Examples of hydrophobic messengers are

A

the steroid and thyroid hormones of animals

40
Q

An activated hormone-receptor complex can act as a

A

transcription factor, turning on specific genes

41
Q

Transduction:

A

cascades of molecular interactions relay signals from receptors to target molecules in the cell

42
Q

Signal transduction usually involves

A

multiple steps

43
Q

Multistep pathways can amplify

A

a signal: A few molecules can produce a large cellular response

44
Q

Multistep pathways provide more opportunities for

A

coordination and regulation of cellular response

45
Q

(Signal transduction pathways)

The molecules that relay a signal from receptor to

A

response are mostly proteins

46
Q

(Signal transduction pathways)

Like falling dominoes, the receptor activates another protein, which

A

activates another, and so on, until the protein producing the response is activated

47
Q

(Signal transduction pathways)

At each step, the signal is transduced into a different form, usually a

A

shape change in a protein

-usually phosphorylation

48
Q

((Protein phosphorylation and dephosphorylation))

In many pathways, the signal is transmitted by

A

a cascade of protein phosphorylations

49
Q

((Protein phosphorylation and dephosphorylation))

Protein kinases transfer phosphates from

A

ATP to protein, a process called phosphorylation

50
Q

Protein phosphatases remove the phosphates from

A

proteins, a process called dephosphorylation

51
Q

((Protein phosphorylation and dephosphorylation))

This phosphorylation and dephosphorylation system acts as a

A

molecular switch, turning activities on and off or up or down, as required

52
Q

Small molecules and ions as

A

second messengers

53
Q

The extracellular signal molecule (ligand) that binds to the receptor is a

A

pathway’s “first messenger”

54
Q

Second messengers are

A

small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion

55
Q

Second messengers participate in pathways initiated by

A

GPCRs and RTKs

56
Q

Cyclic AMP and calcium ions are

A

common second messengers

57
Q

Cyclic AMP (cAMP) is one of the

A

most widely used second messengers

58
Q

Adenylyl cyclase, an enzyme in the plasma membrane, converts

A

ATP to cAMP in response to an extracellular signal

59
Q

Many signal molecules trigger formation of

A

cAMP

60
Q

Other components of cAMP pathways are

A

G proteins, G protein-coupled receptors, and protein kinases

61
Q

cAMP usually activates

A

protein kinase A, which phosphorylates various other proteins

62
Q

Further regulation of cell metabolism is provided by G-protein systems that inhibit

A

adenylyl cyclase

63
Q

Calcium ions (Ca^2+) act as a

A

second messenger in many pathways

64
Q

Calcium is an important second messenger because

A

cells can regulate its concentration

65
Q

A signal relayed by a signal transduction pathway may trigger an increase in

A

calcium in the cytosol

66
Q

Pathways leading to the release of calcium involved

A

inositol triphosphate (IP3) and diaclyglycerol (DAG) as additional second messengers

67
Q

Response:

A

Cell signaling leads to regulation of transcription or cytoplasmic activities

68
Q

The cell’s responses to an extracellular signal is sometimes called the

A

“output response”

69
Q

Ultimately, a signal transduction pathway leads to a

A

regulation of one or more cellular activities

70
Q

The response may occur in the

A

cytoplasm or in the nucleus

71
Q

Many signaling pathways regulate the synthesis of

A

enzymes or other proteins, usually by turning genes on or off in the nucleus

72
Q

The final activated molecule in the signaling pathway may function as

A

a transcription factor

73
Q

Other pathways regulate the activity of

A

enzymes rather than their synthesis

74
Q

There are four aspects of fine-tuning to consider

A
  1. Amplification of the signal (and thus the response)
  2. Specificity of the response
  3. Overall efficiency of response, enhanced by scaffolding proteins
  4. Termination of the signal
75
Q

Enzyme cascades amplify the

A

cell’s response

76
Q

(((signal amplification)))

At each step, the number of activated products is much greater than in the

A

preceding step

77
Q

Amplification stems from the fact that these proteins persist in the active form long enough to

A

process numerous molecules of substrate before they become inactive again

78
Q

Few numbers of signal can affect

A

hundreds of millions of end molecules

79
Q

Different kinds of cells have

A

different collections of proteins

80
Q

These different proteins allow cells to

A

detect and respond to different signals.

  • A liver cell in the presence of epinephrine breaks down glycogen
  • A heart cell in the presence of epinephrine contracts
81
Q

Even the same signal can have different effects in cells with

A

different proteins and pathways

82
Q

Pathway branching and “cross-talk” further help

A

coordinate incoming signals

83
Q

Scaffolding proteins are

A

large relay proteins to which other relay proteins are attached

84
Q

Scaffolding proteins can

A

increase the signal transduction efficiency by grouping together different proteins involved in the same pathway

85
Q

In some cases, scaffolding proteins may also help

A

activate some of the relay proteins

86
Q

Inactivation mechanisms are an

A

essential aspect of cell signaling

87
Q

If ligand concentration falls,

A

fewer receptors will be bound

88
Q

Unbound receptors revert to an

A

inactive state

  • signal molecules are reversible (on/off)
  • allows the cell to be ready for any new signals
89
Q

Apoptosis integrates

A

multiple cell-signaling pathways

90
Q

Apoptosis is

A

programmed or controlled cell suicide

91
Q

Components of the cell are

A

chopped up and packaged into vesicles that are digested by scavenger cells

92
Q

The cell shrinks and becomes

A

lobed (blebbing)

93
Q

Apoptosis prevents enzymes from

A

leaking out of a dying cell and damaging neighboring cells

94
Q

Caspases are the main

A

proteases (enzymes that cut up proteins) that carry out apoptosis

95
Q

Apoptosis can be triggered by

A
  • an extracellular death-signaling ligand
  • DNA damage in the nucleus
  • protein misfolding in the endoplasmic reticulum
96
Q

Apoptosis evolved early in animal evolution and is essential for

A

the development and maintenance of all animals

97
Q

Apoptosis may be involved in some

A

diseases (for example, parkinson’s and alzheimer’s); interference with apoptosis may contribute to some cancers

Biology 1406 (53 decks)

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