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Cell Biology > Cellular Communication > Flashcards

Cellular Communication Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the two types of perception in cellular communication?

A

1) Perception of the environment
2) Perception of signals from other cells

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2
Q

Describe Perception of the environment

A

cells receive signals from the environment which cause a response appropriate to the environment

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3
Q

Examples of signals from the environment?

A
  • single celled organisms – eg. Light, nutrients
  • multicellular organisms – via specific sense organs
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4
Q

Describe Perception of signals from other cells

A

cells perceive signals from other cells – intercellular communication

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5
Q

Examples of signals from other cells?

A
  • single celled organisms – reproduction
  • multicellular organisms - development/homeostasis/cellular interaction
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6
Q

To accomplish mating yeast cells secrete …

A

…‘mating factors’

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7
Q

Yeast come in two…

A

… ‘sexes’, ‘a’ and ‘α’.

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8
Q

the two types of yeast cell (a and alpha) cause …

A

…protrusions which grow towards each other (a shmoo) and fuse.

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9
Q

Define a shmoo

A

protrusions which grow towards each other

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10
Q

How are the mating factors perceived and how do they make the yeast cells form the shmoo?

A

The a type secrete a protein called ‘a factor’ which attracts α cells.

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11
Q

Cells depend on …

A

…signals to survive

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12
Q

In complex organisms cells receive…

A

…multiple signals and in many cases these are required for continuing cell survival.

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13
Q

Signals ensure cells respond by:

A

1) Surviving
2) Growing/dividing
3) Differentiating
4) Dying (lack of signals)
5) Movement

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14
Q

In multicellular organisms signals act over a…

A

…range of distances.

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15
Q

Paracrine in this case may also include …

A

…‘autocrine’ where the cell signals to itself.

  • e.g. T lymphocytes
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16
Q

If the cell does not recognise the other cell…

A

… it will kill it.

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17
Q

Where organisms are particularly complex they may …

A

…employ endocrine signals from special organs

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18
Q

Endocrine signals are…

A

…perceived by target cells

  • e.g. insulin, adrenaline
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19
Q

Signals are perceived in two ways:

A

1) Signalling molecule binds at the cell surface
2) Signalling molecule binds an internal receptor

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20
Q

Signalling molecule binds at the cell surface and the signal is then …

A

…transmitted into the cell where the cell responds to the signal

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21
Q

Signalling molecule binds an internal receptor and transported to the …

A

… nucleus where it has its effect directly on gene expression

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22
Q

Nuclear receptors are found in …

A

…both the cytoplasm and the nucleus

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23
Q

Where receptors are in the cytoplasm …

A

…binding of ligand exposes Nuclear Localisation Sequence.

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24
Q

Exposure of Nuclear Localisation Sequence causes the receptor/ligand complex to …

A

…migrate to the nucleus where it acts directly on gene regulation.

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25
Q

Where receptors are in the nucleus, ligands …

A

…diffuse across the nuclear membrane and enter the nucleus where they bind and change the receptor to an active state.

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26
Q

Example of ligands?

A

Steroid hormones

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27
Q

Some signals are …

A

…non-proteins such as steroid hormones.

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28
Q

non protein signals such as steroid hormones circulate in the…

A

…blood in association with carrier proteins, dissociate and cross the plasma membrane directly.

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29
Q

Non-proteinaceous signals are common in …

A

…plants, such as phytohormones (auxin, gibberellin, abscisic acid, cytokinin, ethylene).

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30
Q

Auxin is taken up by…

A

…transporter proteins in the membrane and effect gene expression.

  • Can have multiple effects in the plant.
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31
Q

Binding of steroid hormones to their receptor causes …

A

…a conformational change in the receptor protein.

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32
Q

define conformational change

A

a change in the shape of a molecule

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33
Q

binding of steroid hormone to its receptor opens up part of…

A

…the protein nuclear localisation sequence, NLS causing it to be transported to the nucleus.

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34
Q

The activated steroid hormone receptor then binds to …

A

…regulatory elements in the promoters of genes and activates or represses transcription.

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35
Q

The hormone can turn gene expression …

A

…on or off

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36
Q

Whether it gets turned on or off depends on…

A

… the hormone

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36
Q

On interaction between receptor and ligand there is a change in conformation of the receptor so that ions are …

A

…drawn into the cell through ion channels.

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36
Q

a change in conformation occurs in the receptor – G-protein coupled receptors interact with …

A

…membrane associated proteins.

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37
Q

Classically these are receptor kinases; on ligand/receptor interaction the …

A

…catalytic domain becomes activated

38
Q

What happens when catalytic domain becomes activated?

A

signals to downstream proteins.

39
Q

Classically signals are perceived at the …

A

…cell surface by receptor proteins.

40
Q

Once signals are perceived at the cell surface by receptor proteins, the signal is then…

A

…transduced through the cell where it has an effect either on metabolic enzymes, cytoskeletal proteins or gene regulatory proteins

41
Q

Signal transduction utilises …

A

…many different intermediate proteins.

42
Q

Effector proteins are called effector proteins because …

A

…they are what cause the effect inside of the cell.

43
Q

THE SIGNALS MAY BE …

A

…proteins

44
Q

Many kinds of proteins that are secreted …

A

…outside of a cell and are perceived by ‘target cells’

45
Q

Proteins as signals often called …

A

…ligands

46
Q

ligands interact with…

A

…receptor molecules mostly on the cell surface.

47
Q

insulin is secreted from β-cells in…

A

…the pancreas

48
Q

insulin is secreted in response to…

A

…increased glucose

49
Q

insulin travels in the…

A

…bloodstream

50
Q

Insulin acts on…

A

…target cells

51
Q

Insulin acts on target cells causing an increase in…

A

…glycogen synthesis

52
Q

Insulin regulates…

A

…glucose because by creating glycogen, glucose is taken out of the bloodstream.

53
Q

Remember the plasma membrane is a…

A

…phospholipid bilayer.

54
Q

Proteins cross the membrane usually as an …

A

…alpha helix

55
Q

The amino acids forming the transmembrane domain are …

A

…mostly hydrophobic

56
Q

Amino acids/proteins fold into an alpha helix so that…

A

…H-bonds between peptide bonds form.

57
Q

One of the most common forms of signal/receptor interactions in animals is via …

A

…G-protein coupled receptors (GPCRs)

58
Q

G-protein coupled receptors (GPCRs) form a …

A

… large family of proteins

59
Q

G-protein coupled receptors (GPCRs) are involved in…

A

…the perception of many different signals (e.g. polypeptide hormones, light, pheromones)

60
Q

Whats a GPCR?

A

G-protein coupled receptors

61
Q

GPCRs have in common …

A

…7 transmembrane helices and hence sit in the plasma membrane

62
Q

Part of the G-protein faces the …

A

…outside of the cell and is available for ligands (e.g. adrenaline) to interact.

63
Q

Part of the protein faces the inside of the cell and can…

A

…interact with proteins in the cytoplasm or other membrane associated proteins.

64
Q

G-proteins are described as…

A

…heterotrimeric

65
Q

What does heterotrimeric mean?

A

they contain α, β and γ subunits

66
Q

α and γ subunits are anchored in the membrane via…

A

..lipids

67
Q

ligand binding to GPCR causes …

A

…conformational change in GPCR

  • causes conformational change in G-protein
68
Q

GDP is exchanged for…

A

..GTP

69
Q

exchanged GDP for GTP, this activates β/γ complex and α-subunit and regulates …

A

…target proteins

70
Q

Both activated subunits of G-proteins can activate other proteins, these in turn can…

A

…relay the system on.

71
Q

proteins interact with each other and change conformation – when they change their conformation…

A

… they can change their state from inactive to active and vice versa.

72
Q

proteins interact with each other and change…

A

…conformation

73
Q

Sometimes the interaction is just via …

A

…proteins binding

74
Q

at other times it is the addition of molecules…

A

…cAMP, Ca2+ and most importantly phosphate groups (second messengers).

75
Q

The process of GPCR signalling causes a…

A

…change in gene expression in the cell

76
Q

What are secondary messengers?

A

molecules that are released on the perception of a signal which then bind to proteins activating them in specific ways

77
Q

Examples of secondary messengers?

A

Apart from cAMP these include Ca2+ , cGMP, nitric oxide (NO) and various lipid molecules (e.g. inositol triphosphate – IP3)

78
Q

Calcium (Ca2+ ) is one of the best characterized as its involved in …

A

…activation of many kinase enzymes (these phosphorylate other proteins so changing their activation state).

79
Q

Norepinephrine acts as both a…

A

…stress hormone and neurotransmitter.

80
Q

Norepinephrine is released from…

A

…the ends of sympathetic nerve fibres.

81
Q

Norepinephrine acts to…

A

…increase the force of skeletal muscle contraction (rate and force of contraction of the heart).

82
Q

Many of the signal transduction processes that effect changes in gene regulation depend upon …

A

…the activation or deactivation of proteins by the addition or removal of phosphate groups

83
Q

addition of a phosphate to a protein will alter its …

A

…charge

84
Q

Remember that addition of a phosphate to a protein will alter its charge and will therefore…

A

…affect its conformation.

85
Q

Many of the proteins involved in signal transduction are:

A
  • kinases – add phosphate groups
  • phosphatases – remove phosphate groups
86
Q

Mitogen-activated protein kinase (MAPK) is specific to the …

A

…amino acids serine and threonine.

87
Q

What is MAPK?

A

Mitogen-activated protein kinase

88
Q

Depending on their input, kinases can act as…

A

…central regulators modulating responses to different signals.

89
Q

regulation of gene expression is controlled by …

A

…binding of activator or repressor proteins to regulatory elements in the promoters of genes.

90
Q

What are activators?

A

These proteins bind to genes at sites known as enhancers. Activators help determine which genes will be switched on and they speed the rate of transcription.

91
Q

What are repressors?

A

These proteins bind to selected sets of genes at sites known as silencers. They interfere with the functioning of activators and thus slow transcription.

92
Q

What are coactivators?

A

These adapter molecules integrate signals from activators and perhaps repressors and relay the results to basal factors.

93
Q

What are basal transcription factors?

A

In response to injunctions from activators, these factors position RNA polymerase at the start of the protein-coding region of a gene and send the enzyme its way.

94
Q

Yeast mating depends on …

A

…perception by GPCRs and transduction of the signal via second messengers and a MAP kinase cascade – altered gene expression and movement.

Cell Biology (19 decks)

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