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Biology > Chapter 9: Cell Communication > Flashcards

Chapter 9: Cell Communication Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

intercellular signalling

A

communication between cells

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2
Q

intracellular signalling

A

communication within a cell

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3
Q

signalling cell

A

cell that delivers signals to other cells

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4
Q

ligand

A

molecule that binds to another specific molecule

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5
Q

receptor

A

protein that can receive ligands from signalling cells

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6
Q

target cell

A

cell that has a receptor to receive ligands from signalling cells

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7
Q

What are the four categories of chemical signalling in multicellular organisms?

A

Paracrine signalling, endocrine signalling, autocrine signalling and direct signalling across gap junctions

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8
Q

paracrine signal

A

signalling between nearby cells

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9
Q

How do paracrine signals reach the target cell?

A

They diffuse through the extracellular matrix towards the target cell

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10
Q

What happens to a paracrine signal after it has reached its target cell?

A

It is degraded by enzymes or removed by neighbouring cells

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11
Q

Why do paracrine signals last a short time?

A

Removing the paracrine signal quickly reestablishes the concentration gradient so signals can travel freely again

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12
Q

synaptic signal

A

chemical signal that travels between nerve cells

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13
Q

neurotransmitter

A

ligand released by nerve cells

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14
Q

chemical synapse

A

small space between nerve cells

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15
Q

How are signals propagated through nerve cells?

A

They are propagated by electrical impulses

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16
Q

How are signals transferred from nerve cell to nerve cell?

A

Neurotransmitters are released from the signalling nerve cell to the target nerve cell

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17
Q

What happens to neurotransmitters after they have been received by the target cell?

A

They are destroyed by enzymes or are reabsorbed for further use

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18
Q

What type of chemical signalling is synaptic signalling?

A

Paracrine signalling

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19
Q

endocrine signal

A

signalling between cells that are very far away

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20
Q

endocrine cell

A

cells that secrete and send hormones in endocrine signalling

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21
Q

hormone

A

signalling molecules that are the ligands in endocrine signalling

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22
Q

How do hormones travel from the signalling cell to the target cell?

A

They travel through the bloodstream

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23
Q

How is endocrine and paracrine signalling different?

A
  1. Endocrine signalling is slower and longer lasting

2. Endocrine signalling ligands are found in lower concentrations

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24
Q

autocrine signal

A

when the signalling cell binds to the ligand that it produces

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25
Q

What cells are affected in autrocrine signalling?

A

The signalling cell and sometimes the neighbouring cells are affected

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26
Q

When does autocrine signalling usually occur?

A

During early development of an organism to ensure cells develop correctly

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27
Q

intracellular mediator

A

small molecule that transfers signals inside a cell

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28
Q

How can intracellular mediators diffuse to other cells?

A

Through gap junctions and plasmodesmata

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29
Q

internal receptor

A

receptors that are found in the cytoplasm of a cell

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30
Q

In what process are internal receptors often involved in?

A

They are used to regulate mRNA synthesis

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31
Q

How do internal receptors control DNA transcription?

A

When a ligand binds to an internal receptor, a DNA binding site is exposed on the receptor, which binds to DNA in the nucleus to promote transcription

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32
Q

cell-surface receptor

A

cell surface integral proteins that bind to external ligands

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33
Q

How much of the plasma membrane does a cell-surface receptor span?

A

They are all transmembrane receptors

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34
Q

What are the three components of a cell-surface receptor?

A

An extracellular, transmembrane and intracellular domain

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35
Q

What are the three types of cell-surface receptors?

A

Ion channel-linked receptors, G-protein-linked receptors and enzyme-linked receptors

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36
Q

ion channel-linked receptor

A

channel proteins that have a binding site for ligands to allow ions through

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37
Q

G-protein-linked receptor

A

receptor that activates G-proteins to transmit signals to membrane components

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38
Q

How many transmembrane domains does a G-protein-linked receptor have?

A

Seven

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39
Q

G-protein-coupled receptor

A

G-protein-linked receptor that has a G-protein bound to it

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40
Q

heterotrimeric G-protein

A

G-protein made up of an alpha, beta and gamma subunit

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41
Q

How are G-proteins activated?

A

An inactive G-protein binds to the receptor, and when a signalling molecule binds to the receptor, GDP in the alpha subunit is released and replaced with GTP, then the activated G-protein is split into an alpha and beta-gamma fragment to be used

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42
Q

How does an active G-protein become inactive?

A

The GTP in the alpha subunit is hydrolysed to GDP, and the alpha and beta-gamma fragments come back together to form an inactive G-protein

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43
Q

What are the main symptoms of cholera?

A

Dehydration and diarrhoea

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44
Q

What bacterium is responsible for cholera?

A

Vibrio cholerae

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45
Q

Which part of the body does Vibrio cholerae invade?

A

The small intestines

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46
Q

How does Vibrio cholerae invade the small intestines?

A

It produces a toxin called choleragen which modifies a G-protein to be constantly active and leads to water loss from the body

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47
Q

enzyme-linked receptor

A

receptors that have intracellular domains that interact directly with an enzyme or is an enzyme itself

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48
Q

What is the transmembrane domain of an enzyme-linked receptor like?

A

It is a single alpha-helical region spanning the membrane

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49
Q

How does an enzyme linked receptor work?

A

When a ligand binds to the extracellular domain, a signal is transferred through the membrane to activate the enzyme

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50
Q

receptor tyrosine kinase

A

enzyme-linked receptor that phosphorylates tyrosine residues to transmit a signal

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51
Q

How does a receptor tyrosine kinase work?

A

Ligands bind to two nearby receptor tyrosine kinases which are dimerised and the tyrosine residues are phosphorylated for a cellular response

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52
Q

What type of molecules are the main small hydrophobic ligands?

A

Steroid hormones

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53
Q

What is the main female sex hormone?

A

Estradiol

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54
Q

estrogen

A

group of steroid hormones in the female body

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55
Q

What is the main male sex hormone?

A

Testosterone

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56
Q

What is the precursor to all steroid hormones?

A

Cholesterol

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57
Q

What are the two main types of ligands?

A

Small hydrophobic ligands and water-soluble ligands

58
Q

water-soluble ligand

A

ligand that is polar and cannot enter the cell unaided

59
Q

nitric oxide

A

gas that acts as a ligand

60
Q

Why is nitric oxide a good ligand?

A

It can diffuse across the plasma membrane

61
Q

signal transduction

A

continued propagation of a signal through the cytoplasm

62
Q

In which type of receptors does signal transduction occur in?

A

Cell-surface receptors

63
Q

Why does signal transduction happen in surface-cell receptors but not internal receptors?

A

Internal receptors can move and interact with the cytoplasm and nucleus, but since surface-cell receptors are integrated with the membrane, they must use signal transductioin

64
Q

dimerisation

A

when two molecules bind to each other

65
Q

signalling pathway

A

the chain of events that follows after the activation of a receptor’s intracellular domain

66
Q

downstream event

A

event that occurs after a certain point

67
Q

upstream event

A

event that occurs before a certain point

68
Q

signal integration

A

when signals from two or more different receptors merge to trigger the same response

69
Q

What are the two main methods used in intracellular signalling?

A

Phosphoryation and using second messengers

70
Q

amino acid residue

A

R group of an amino acid

71
Q

What is usually phosphorylated in intracellular signalling?

A

Nucleotides or amino acid residues of proteins

72
Q

Which amino acid residues are usually phosphorylated in intracellular signalling?

A

Serine, threonine and tyrosine residues

73
Q

Where does a phosphate group bind to during phosphorylation in intracellular signalling?

A

It replaces the hydroxyl group of the amino acid

74
Q

What does the phosphorylation of serine and threonine residues do in intracellular signalling?

A

It often activates an enzyme

75
Q

What does the phosphorylation of tyrosine do in intracellular signalling?

A

It either affects an enzyme or it creates a binding site that interacts with the downstream events of a signalling pathway

76
Q

second messenger

A

small molecule that propagates a signal after a ligand has bound to a receptor

77
Q

Which ion is used as a common second messenger?

A

Ca2+

78
Q

Where do calcium ions come from in intracellular communication?

A

They are stored in cytoplasmic vesicles or are accessed from outside the cell

79
Q

Why is calcium used as a second messenger?

A

Membrane pumps constantly remove calcium ions, so the concentration gradient created allows for easy movement of the ions

80
Q

How are calcium ions used as a second messenger?

A

Ligand-gated calcium ion channels allow ions outside the cell and inside vesicles to enter the cytoplasm, triggering a cellular response

81
Q

cyclic AMP

A

molecule synthesised from ATP and acts as a second messenger

82
Q

What is the main role of cyclic AMP?

A

To bind to an enzyme called cAMP-dependent kinase

83
Q

A-kinase

A

cAMP-dependent kinase

84
Q

How is cAMP made from ATP?

A

Adenylyl cyclase cleaves a pyrophosphate from ATP to create cAMP

85
Q

pyrophosphate

A

Two phosphate groups joined together to create P2O7

86
Q

Which enzyme synthesises cAMP from ATP?

A

Adenylyl cyclase

87
Q

What is the main role of A-kinase?

A

It regulates many metabolic pathways by phosphorylating serine and threonine residues

88
Q

inositol phospholipid

A

type of phospholipid that is found in small quantities in the plasma membrane

89
Q

inositol

A

carbohydrate that is a glucose isomer

90
Q

What is the structure of an inositol phospholipid?

A

It is a phospholipid with a inositol as its phosphate head group

91
Q

What is the main inositol phospholipid involved in cellular signalling?

A

Phosphatidylinositol

92
Q

What is created when PI is phosphorylated?

A

Either PI-phosphate or PI-bisphosphate

93
Q

PIP

A

phosphatidylinositol-phosphate

94
Q

PIP2

A

phosphatidylinositol-bisphosphate

95
Q

Which two second messengers can PIP2 be cleaved into?

A

Diacylglycerol and inositol triphosphate

96
Q

Which enzyme cleaves PIP2 into DAG and IP3?

A

Phospholipase C

97
Q

DAG

A

diacylglycerol

98
Q

IP3

A

inositol triphosphate

99
Q

What does DAG do as a second messenger?

A

DAG stays in the membrane after being cleaved and activates protein kinase C

100
Q

PKC

A

protein kinase C

101
Q

What does IP3 do as a second messenger?

A

It diffuses into the cell after being cleaved and binds to ligand-gated calcium channels in the ER to release Ca2+

102
Q

EGF

A

epidermal growth factor

103
Q

EGFR

A

epidermal growth factor receptor

104
Q

What is the role of EGF?

A

To regulate protein synthesis

105
Q

How is EGFR activated?

A

When EGF binds to EGFR, tyrosine residues are phosphorylated and a signalling pathway is triggered

106
Q

inhibitor

A

molecule that binds to a protein to reduce or prevent function

107
Q

How does PKC activate DNA transcription?

A

It phosphorylates serine and threonine residues in Iκ-B, which allows NF-κB to initiate RNA transcription

108
Q

Iκ-B

A

inhibitor protein that prevents RNA transcription

109
Q

NF-κB

A

regulatory protein required in RNA transcription

110
Q

What is another name for cAMP-dependent kinase?

A

Protein kinase A

111
Q

PKA

A

protein kinase A

112
Q

What receptor does adrenaline activate?

A

Beta-adrenergic receptors

113
Q

What happens when beta-adrenergic receptors are activated?

A

They release cAMP

114
Q

What happens when adrenaline increases cAMP levels?

A

It activates PKA which in turn activates two enzymes?

115
Q

Which two enzymes does PKA activate during an adrenaline rush?

A

GPK and GS

116
Q

GPK

A

glycogen phosphorylase kinase

117
Q

GS

A

glycogen synthase

118
Q

What happens when GPK is activated?

A

It activates glycogen phosphorylase

119
Q

GP

A

glycogen phosphorylase

120
Q

What happens when GP is activated?

A

Glycogen is catabolised into glucose

121
Q

What happens when GS is activated?

A

The cell is unable to form glycogen from glucose

122
Q

growth factor

A

ligands that promote cell growth

123
Q

MAPK/ERK pathway

A

chain of proteins in a cell that communicates a signal from a cell-surface receptor to nuclear DNA

124
Q

apoptosis

A

programmed cell death

125
Q

How can apoptosis be triggered?

A

When abnormalities are detected in the cell or from external signalling

126
Q

How is apoptosis necessary for embryonic development of vertebrates?

A

Web-like tissue between fingers and toes must be eliminated through apoptosis

127
Q

How is apoptosis necessary in T-cell development?

A

Immature T-cells that bind to self proteins undergo apoptosis to prevent further harm

128
Q

T-cell

A

immune cell that binds to foreign molecules for self destruction

129
Q

phosphatase

A

enzymes that remove phosphate groups attached by kinases

130
Q

phosphodiesterase

A

enzyme that degrades cAMP into AMP

131
Q

How is cAMP degraded into AMP?

A

Phosphodiesterase degrades cAMP into AMP

132
Q

mating factor

A

signalling molecule secreted by yeast to indicate that they are ready to mate

133
Q

How do budding yeast cells mate?

A

Two haploid yeast cells combine to form a diploid cell and then start to bud offspring

134
Q

What happens when mating factor binds to a cell-surface receptor in yeast?

A

Yeast stops its normal growth cycle and a signalling pathway is triggered

135
Q

Why was yeast mating studied extensively?

A

Their signalling pathways had protein kinases, GTP-binding proteins and other similarities

136
Q

quorum sensing

A

method of cellular communication in bacteria to determine bacteria density

137
Q

autoinducer

A

signalling molecule that bacteria secrete to communicate with other bacteria of its kind

138
Q

What do autoinducers do?

A

They can turn certain genes on and off

139
Q

What happens when there is a high concentration of bacteria?

A

Concentration of autoinducers increases, which triggers many genes, including autoinducers, creating a positive feedback loop

140
Q

biofilm

A

large and complex colonies of bacteria

141
Q

How do biofilms attack a host?

A

Bacteria in the biofilm exchange signals to coordinate the release of toxins to attack the host

Biology (9 decks)

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