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AP Biology JCH > Chapter 11 Cell Communication > Flashcards

Chapter 11 Cell Communication Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

_________ is absolutely essential for multicellular organisms

A

Cell-to-cell communication

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2
Q

What indicates to biologists that cell-cell signaling has been conserved in evolution over time?

A

Biologists have discovered universal mechanisms of cellular regulation involving the same small set of cell-signaling mechanisms.

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3
Q

How do cells most often communicate?

A

Cells most often communicate by chemical signals, although signals may take other forms.

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4
Q

How does yeast use cell signaling?

A

• Saccharomyces cerevisiae, the yeast of bread, wine, and beer, identifies potential mates by chemical signaling.

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5
Q

What are the two yeast sexes?

A

There are two sexes, a and alpha

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6
Q

Describe the three steps in yeast mating.

A
  1. Exchange of mating factors- a and alpha each secrete a signaling molecule which binds to the receptor of the other mating type
  2. Mating-the two cells grow toward each other and undergo other cellular changes
  3. New alpha/a cell-The two cells fuse, or mate, to form an a/alpha cell containing the genes of both cells
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7
Q

What is a signal transduction pathway?

A

the process by which a signal on a cells surface is converted into a specific cellular response

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8
Q

Describe how cells communicate by direct contact.

A

-Cell junctions in animal and plant cells- signaling substances dissolved into the cytosol can pass through easily

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9
Q

What are the cell junctions in animal cells? Plant cells?

A
  • Gap junctions

- Plasmodesmata

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10
Q

Describe another way that animal cells can communicate by direct contact. What is this used for?

A
  • Membrane bound cell surface molecules (cell-cell recognition)
  • Embryonic development and the immune response
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11
Q

What do local regulators do?

A

signals that influence cells in the local vicinity

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12
Q

Name one type of local regulators.

A

Growth Factors- stimulate nearby target cells to grow and multiply

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13
Q

Name the two types of local signaling.

A

paracrine and synaptic

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14
Q

What is paracrine signaling?

A

when numerous cells simultaneously receive and respond to growth factors produced by a single cell in their vicinity

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15
Q

What is synaptic signaling?

A

a nerve cell produces a neurotransmitter that diffuses across a synapse to a single cell that is almost touching the sender

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16
Q

The transmission of a signal through the nervous system can also be considered and example of _________

A

long distance signaling

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17
Q

Name a feature of plant communication that is not well understood.

A

Local signaling is not well understood because of cell walls

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18
Q

What is used for long distance signaling?

A

hormones

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19
Q

How do hormones work in animals?

A

specialized endocrine cells release hormones into the circulatory system, by which they travel to other parts of the body

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20
Q

What are plant hormones called? And how do they travel?

A

Plant hormones called growth regulators may travel in vessels but more often travel through air diffusion

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21
Q

Describe two different plant and animal hormones.

A
  • Ethylene (C2H4) - promoted fruit ripening and regulated growth in plants- capable of passing through cell walls
  • Insulin- regulates blood sugar levels in mammals- protein with thousands of atoms
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22
Q

What are the three stages of signaling?

A

reception, transduction, and response

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23
Q

What did E. W. Sutherland’s work focus on?

A

how epinephrine stimulates the breakdown of glycogen in the liver and skeletal muscle

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24
Q

How does epinephrine work?

A
  • released from adrenal gland during physical or mental stress
  • mobilizes fuel reserves
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25
Q

What enzyme does epinephrine activate?

A
  • cytosolic enzyme- glycogen phosphorylase
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26
Q

What is a ligand?

A

a small molecule that binds with specificity to a larger molecule

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27
Q

What occurs when a ligand binds to a receptor?

A
  • causes the receptor protein to undergo a change in shape
  • activates receptor to interact with other molecules
  • may cause aggregation of receptor molecules, leading to further molecular events
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28
Q

What are most signal receptors like?

A

most signal receptors are plasma membrane proteins whose ligands are large water soluble molecules that are too larges to cross the plasma membrane

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29
Q

If receptor proteins are not on the membrane they may be__________

A

Intracellular

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30
Q

Where may signal receptors be dissolved inside a cell?

A

in the cytosol or nucleus

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31
Q

What must intracellular signals be to pass through the cellular membrane?

A

hydrophobic enough or small enough

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32
Q

Name a hydrophobic messenger and a small messenger.

A
  • hydrophobic messengers include the steroid and thyroid messengers of animals
  • nitric oxide is a gas whose small size allows it to pass between membrane phospholipids
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33
Q

Name an intracellular hormone. Describe how it works.

A

Testosterone

  • cytosol of target cells contains receptor molecules that bind testosterone activating the receptor
  • activated proteins enter the nucleus and turn on specific genes that control male sex characteristics
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34
Q

What do transcription factors do?

A

control which genes are turned on and may be transcribed into messenger RNA

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35
Q

What are the three types of membrane receptors?

A

G-protein linked receptor, receptor tyrosine kinases, and gated ion channels

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36
Q

What does a G-protein linked receptor consist of?

A

a receptor protein linked with a G-protein on the cytoplasmic side

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37
Q

What spans the membrane in a G-protein linked receptor?

A

7 alpha helices

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38
Q

What are three signaling molecules that G-protein linked receptors bind?

A

yeast mating factors, epinephrine, neurotransmitters

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39
Q

What does a G protein act like?

A

-an on/off switch

40
Q

Name the 4 steps in G-protein linked receptors

A
  • GDP is bound to the G-protein, and it is inactive
  • Signal binds to the outside of the receptor and G-protein binds GTP and becomes active
  • G-protein leaves receptor and diffuses along the plasma membrane to bind to an enzyme, altering its activity
  • activated enzyme triggers next step in a pathway
41
Q

What happens when he G-protein activates its pathway?

A

The g-protein acts as a GTPase enzyme to hydrolyze GTP to GDP, turning the G-protein off and returning to its original state

42
Q

What do G-protein systems function in?

A
  • embryonic development

- vision, and smell

43
Q

What diseases involve G-portien linked receptors?

A

Bacterial infections such a cholera and botulism

44
Q

When is the tyrosine kinase receptor system effective?

A

when the cell needs to trigger several signal transduction pathways and cellular responses at once

45
Q

What does the tyrosine kinase receptor system help the cell to do?

A

-regulate and coordinate many aspects or cell growth and reproduction

46
Q

What is a kinase?

A

an enzyme that catalyzes the transfer of phosphate groups

47
Q

What does the cytoplasmic side of a tyrosine kinase receptor function as and what does that mean?

A
  • functions as a tyrosine kinase- transferring atp from ATP to tyrosine on a substrate protein
48
Q

What are the parts of a tyrosine kinase receptor?

A
  • extracellular signal binding site
  • single alpha helix spanning membrane
  • intracellular tail with several tyrosine
49
Q

Describe the steps in a tyrosine kinase receptor.

A
  • signal molecule binds
  • two receptors dimerize
  • activates tyrosine tail
  • tyrosines add phosphate groups from ATP to the other tyrosine
  • phosphorylates a variety of specific relay proteins that bind to tyrosine molecules
  • activated relay proteins trigger many different transduction pathways and responses
50
Q

What is a ligand gated ion channel?

A

membrane receptor that can act as a gate when the receptor changes shape

51
Q

How does a ligand gated ion channel work?

A

When a signal molecule binds as a ligand to the receptor protein the gate opens to allow the flow of ions through a channel receptor

52
Q

What are ligand gated ion channels important to in the body?

A

nervous system

53
Q

How do ligand ion channels operate in the nervous system?

A

-Neurotransmitter molecules released at a synapse between two neurons bind as ligands to ion channels on the receiving cell

54
Q

What may gated ion channels respond to?

A

electrical signals instead of ligands

55
Q

Transduction is usually______

A

a multistep pathway, these pathways amplify a signal, and provide more opportunities for coordination and regulation

56
Q

Signal transduction pathways act like____

A

falling dominoes

57
Q

What do most of the relay molecules in transduction have in common?

A

mostly proteins

58
Q

What occurs at each step of transduction?

A
  • the signal is transduced into a different form by a conformational change brought about by phosphorylation
59
Q

Where does most phosphorylation occur?

A

serine or threonine amino acids of the substrate protein

60
Q

What is it called when protein kinases act on other protein kinases in a pathway?

A

phosphorylation cascade

61
Q

Why does phosphorylation lead to a conformational change?

A

because of the interaction between the newly activated phosphate group and charged or polar amino acids on the protein

62
Q

What does phosphorylation of a protein do?

A

converts it from an inactive form to an active form

63
Q

What does abnormal activity of protein kinases do?

A

can cause abnormal cell growth and may contribute to the development of cancer

64
Q

What turns off a signal transduction pathway?

A

protein phosphatases

65
Q

Name two functions of protein phosphatases.

A
  • removing phosphate groups from proteins

- make protein kinases available for reuse

66
Q

The activity of a protein regulated by phosphorylation depends on_______

A

the balance of active kinase molecules and active phosphatase molecules

67
Q

What are second messengers?

A

small, water soluble, non-protein molecules or ions

68
Q

How do second messengers travel through the cell?

A

they rapidly diffuse

69
Q

What pathways do second messengers participate in?

A

pathways initiated by both G-protein coupled receptors and tyrosine kinase receptors

70
Q

What are two of the most widely used second messengers?

A

cyclic AMP and calcium ions

71
Q

Describe a second messenger in epinephrine’s pathway.

A
  • Binding by epinephrine increases concentration of cAMP in cytosol
  • Receptor activates adenylyl cyclase which converts ATP to cAMP
  • cAMP is short lived as phosphodiesterase converts it to AMP
72
Q

What is the effect of caffeine on the body?

A
  • artificial way to keep the body alert

- blocks conversion of cAMP to AMP maintaining the system in a state of activation without epinephrine

73
Q

What may cAMP activate?

A

kinase A- which then phosphorylates various other proteins

74
Q

How can G-protein systems regulate cell metabolism?

A

Regulation of cell metabolism is provided by G-protein systems that inhibit adenylyl cyclase

75
Q

How does cholera cause disease?

A
  • disrupts G-protein signaling pathways
  • colonizes in the small intestine and produces a toxin that modifies a G-protei that regulates salt and water secretion
  • protein remains stuck in its active form and continuously stimulates adenylyl cyclase to make cAMP
  • intestinal cells secrete large amounts of water and salts into the intestines causing diarrhea
76
Q

Many signal molecules in animals induce responses through transduction pathways that release _______?

A

-Calcium ions

77
Q

What is the function of calcium in animal cells? Plant cells?

A

Animal cells- contraction of muscle cells, secretion of certain substances, cell division
Plant cells- pathway for greening in response to light

78
Q

Calcium ion concentration is _____ in the cytosol than outside the cell.

A

lower

79
Q

What mechanisms attempt to maintain correct calcium ion concentration?

A

Protein pumps transport Ca2+ outside the cell or into the ER.

80
Q

What does low calcium concentration in the cytosol mean?

A

small changes in the numbers of ions causes a large percentage change in calcium concentration

81
Q

What second messengers are involved in the release of calcium ions?

A

DAG diacylglycerol

IP3 inositol triphosphate

82
Q

How are DAG and IP3 created?

A

When phospholipase cleaves membrane phospholipid PIP2

83
Q

What does IP3 do?

A

activates a gated-calcium channel, releasing calcium ions from the ER

84
Q

List examples of responses.

A
  • turning on or off genes
  • synthesis of enzymes or other proteins
  • change in cell metabolism
85
Q

What are are the two benefits of signaling pathways with multiple steps?

A
  • amplify the response to a signal

- they contribute to the specificity of the response

86
Q

What happens when different cells receive the same signal? What are different examples of this?

A

they produce different responses

Epinephrine triggers liver cells to break down glycogen, and heart cells to contract

87
Q

What are scaffolding proteins?

A

relay proteins to which several other relay proteins attach

88
Q

What do scaffolding proteins do?

A

enhances the speed accuracy and efficiency of signal transfer

89
Q

What is just as important as activating mechanisms?

A

inactivation mechanisms, because for a cell to remain alert each molecular pathway must last a short time and must not be locked into one state

90
Q

Binding of signal molecules to receptors must be _______ .

A

Reversible

91
Q

What disease involves defecting or missing relay proteins?

A

Wiskott-Aldrich syndrome

92
Q

What is apoptosis?

A

programmed or controlled cell suicide

93
Q

What occurs during apoptosis?

A

a cell is hoped and packages into vesicles that are digested by scavenger cells

94
Q

When does apoptosis result?

A

when specific proteins that “accelerate” apoptosis override those that “put brakes on” apoptosis

95
Q

When does apoptosis most effectively shape and organism?

A

embryonic development

96
Q

What are caspases?

A

the main proteases that carry out apoptosis

97
Q

What can apoptosis be triggered by?

A
  • an extracellular death signaling ligand
  • DNA damage in the nucleus
  • Protein misfolding in the ER

AP Biology JCH (12 decks)

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