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BIO 221 01 > CH_15 > Flashcards

CH_15 Flashcards

To learn and retain information from CH 15 from the course Cell Biology

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1
Q

What do extracellular messenger molecules do?

A

Transmit messages between cells

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2
Q

What is autocrine signaling?

A

The cell has receptors on its surface that respond to the messenger

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3
Q

What is paracrine signaling?

A

Messenger molecules travel short distances through extracellular space, function on the neighboring cells

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4
Q

What is endocrine signaling?

A

Hormones are the messenger molecules, they reach their target cells through the bloodstream

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5
Q

What are the signaling pathways initiated by extracellular messenger molecules?

A

Ligand and Receptor

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6
Q

What is Ligand?

A

The extracellular signaling molecule, specifically binding to receptors

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7
Q

What is a Receptor?

A

On the cell membrane or in the cytoplasm, different cells have a different set of receptors

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8
Q

What are the two major routes for signaling?

A

Via the second messenger, effector, an enzyme responsible to generate second messenger molecules

Cascade protein cascading signaling, receptor serving as a protein recruiting station

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9
Q

What is a signal transduction pathway?

A

The overall process in which information carried by extracellular messenger molecules is translated into changes that occur inside a cell

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10
Q

What is the signal transduction pathway consisted of?

A

A series of proteins

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11
Q

What does each protein in the signal transduction pathway contain?

A

They contain multiple domains: catalytic, regulatory, protein-protein interaction, etc.

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12
Q

What does each protein do to the previous protein in the signal transduction pathway?

A

It alters the conformation of the next protein

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13
Q

What is protein conformation usually altered by?

A

It is altered phosphorylation

Kinases add phosphate groups, phosphatases remove them

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14
Q

What do target proteins do?

A

They receive a message to alter cell activity

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15
Q

What does protein phosphorylation do?

A

They can change protein behavior in different ways

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16
Q

What are the sites of phosphorylation?

A

Serine, threonine, and tyrosine

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17
Q

What are the functions of phosphorylation?

A

It can activate or inactivate an enzyme

It can increase or decrease protein-protein interactions

It can change the subcellular location of the protein

It can trigger protein degradation

Phosophorylation patterns differ between cell types

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18
Q

What are some examples of extracellular messengers and their receptors?

A

Amino acids and their derivatives( acetylcholine, epinephrine, dopamine), gases( NO and CO), steroids (regulate sexual differentiation, pregnancy, carbohydrate metabolism) eicosanoids (lipids), various peptides, and proteins

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19
Q

What do almost all extracellular messengers bind to?

A

They bind to specific receptors to send a signal

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20
Q

What are some receptor types?

A

G-protein coupled receptors (GPCRs), Receptor protein-tyrosine kinases (RTKs), Ligand-gated channels, Steroid hormone receptors, and specific receptors such as B-and T-cell receptors

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21
Q

What do G protein-coupled receptors (GPCRs) do?

A

They constitute the single largest superfamily of proteins encoded by animal genomes

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22
Q

What type of domains to GPCRs have?

A

They have seven alpha-helical transmembrane domains

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23
Q

What are the ligand binding domains?

A

Three loops outside the cell
(e.g. natrual ligands: hormones (both plant and animal), neurotransmitters, opium derivatives, chemoattractants (odorants, tastants, and photons)

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24
Q

What are protein interaction domains?

A

Three loops inside the cell, they interact with the G proteins inside

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25
Q

1- What happens to the receptor after the ligand binds to it?

A

It alters the conformation of the receptor and increases its affinity for the G protein to bind to

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26
Q

2- What replaces the GDP after the Ga subunit releases it?

A

GTP

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27
Q

3- What happens after the Ga subunit after it dissociates from the Gby complex?

A

It binds to an effector (adenylyl cyclase), activating it

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28
Q

4- What does the activated adenylyl cyclase produce?

A

cAMP

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29
Q

What is desensitization?

A

The process that blocks active receptors from turning on additional G proteins

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30
Q

What does it mean to be resensitized?

A

If receptors are recycled and returned to the cell surface, the cells remain sensitive to the ligand

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31
Q

What is the function of the second messengers?

A

Can diffusing inside the cytoplasm

To amplify the response to a single extracellular ligand

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32
Q

What are some common second messengers?

A 
caMP
Ca2+
Nitric oxide
cGMP
Phosphoinosides 
Inositol triphosphates 
Diacylglycerol
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33
Q

What do the colors represent in regards to cAMP concentration?

A

Blue: low cAMP concentration
Yellow: intermediate concentration
Red: high concentration

34
Q

Why would there be a localized formation of cAMP?

A

It is in response to the addition of an extracellular messenger molecule

35
Q

What can help regulate blood glucose levels?

A

GPCRs and their second messengers

36
Q

What do glucagon and epinephrine do?

A

Stimulate glycogen and breakdown and inhibit its synthesis

37
Q

What does insulin do?

A

Stimulate glycogen synthesis and inhibit its breakdown

38
Q

What does cAMP do?

A

Evokes a reaction cascade that leads to glucose mobilization

39
Q

How does protein-tyrosine kinase function?

A

It functions by phosphorylating tyrosine residues on target proteins

40
Q

What two type of protein-tyrosine kinases are there?

A

Receptor and Non-receptor (cytoplasmic)

41
Q

What are the characteristics of (RTKs)

A

Cell surface receptors of the protein-tyrosine kinase family

1 transmembrane domain

1 ligand binding domain

42
Q

How are RTKs activated?

A

Dimerization of receptors results from ligand binding

43
Q

What are the mechanisms for dimerization?

A

Ligand-mediated dimerization and receptor-mediated dimerization

44
Q

What are the functions of autophosphorylation sites on RTKs?

A

Regulation of receptor’s activity

Providing binding sites for cytoplasmic signaling molecules

45
Q

What does phosphotyrosine-dependent protein-protein interaction do?

A

It binds effector proteins that have SH2 domains and PTB domains

46
Q

What kind of different proteins can RTKs interact with?

A

They can interact with different signaling proteins, such as: adaptor proteins, docking proteins, transcription factors, signaling enzymes

47
Q

What are the functions of adaptor proteins?

A

They function as linkers (e.g. Grb2)

48
Q

What are the functions of docking proteins

A

They supply receptors with additional tyrosine phosphorylation sites (e.g. IRS)

49
Q

What are some examples and the functions of signaling enzymes?

A

(e.g. protein kinases, protein phosphatase, lipid kinase, phospholipase, GTPase) they lead to changes in cell

50
Q

What happens with the termination of signal transduction by RTKs?

A

Usually terminated by the internalization of RTKs

51
Q

What happens after the internalization of RTKs?

A

Degraded in the lysosomes

Return to the plasma membrane

Engage in continued intracellular signaling

52
Q

How does insulin regulate blood glucose levels?

A

It increases the cell glucose uptake

53
Q

What is the insulin receptor?

A

A protein-tyrosine kinase

54
Q

What are the characteristics of the insulin receptor?

A

Composed of an alpha and beta chain
Are present as stable dimers
Inactive without insulin binding

55
Q

What does the autophosphorylated receptor only associate with?

A

A small family of docking proteins

56
Q

What are some characteristics of insulin receptor substrates (IRSs)?

A

Possess PTB-domain

IRSs bind proteins with SH2 domains to activate downstream signal molecules
- PI 3-kinase (PI3K)

57
Q

What do active PI3K do?

A

They produce phosphorylated lipids that trigger activation of downstream proteins (Akt, PDK1)

58
Q

What are the terminal effects of PI3K?

A

Activation include decreased protein synthesis, glucose uptake, and glycogen synthesis

59
Q

What percentage of people have Type 1 diabetes?

A

5-10%

60
Q

How does Type 1 diabetes affect insulin

A

Inability to produce insulin

61
Q

What percentage of people have Type 2 diabetes?

A

90-95%

62
Q

How does Type 2 diabetes affect insulin?

A

Insulin resistance of target cells

63
Q

What does it mean when a signaling pathway converges?

A

Signals form unrelated receptors can activate a common effector

64
Q

What does it mean when a signaling pathway diveregs?

A

Identical signals can activate a variety of effectors

65
Q

What does it mean when a signaling pathway participates in crosstalk?

A

Signals can be passed back and forth between pathways

66
Q

What is apoptosis?

A

An ordered normal process leading to the cell death in animals

67
Q

What are the characterisitcs of apoptosis?

A

Overall shrinkage in volume of the cell and its nucleus

Loss of adhesion to neighboring cells

Formation of blebs at the cell surface

Dissection of chromatin into small fragments

Rapid engulfment by phagocytosis

68
Q

What is necrosis?

A

A process of cell death which generally follows some type of physical trauma or biochemical insult

Also considered as a regulated and programmed cell death, but much less orderly

69
Q

What are the characteristics of necrosis?

A

Swelling of both cell and its internal membranous organelles

Membrane breakdown

Leakage of cell contents into the medium

Resulting induction of inflammation

70
Q

Who is apoptosis active in?

A

The adult where about 10^10- 10^11 cells die every day (e.g. elimination of cells with irreparable genomic damage, elimination of cells no longer needed)

71
Q

What is reduced or elevated apoptosis linked to?

A

Caner, Parkinsons, Alzheimers, Huntington’s, diabetes type 1

72
Q

What type of stimuli initiates apoptosis?

A

External stimuli

73
Q

What is a common stimulus for apoptosis (extrinsic pathway)?

A

Tumor necrosis factor (TNF)

74
Q

What is the first step of apoptosis (extrinsic pathway)?

A

TNF bounds to TNF receptors to recruit (procaspases) to the intracellular domain of the receptor

75
Q

What is the second step of apoptosis (extrinsic pathway)?

A

Procaspases convert other procaspases to caspases

76
Q

What is the third and final step of apoptosis (extrinsic pathway)?

A

Caspases activate executioner caspases, leading to apoptosis

77
Q

What is another type of stimuli that initiates apoptosis?

A

Internal

78
Q

What is the first step of apoptosis (intrinsic pathway)?

A

Proapoptotic proteins stimulate mitochondria to leak proteins, mostly cytochrome c

79
Q

What is the second step of apoptosis (intrinsic pathway)?

A

Once in the cytosol, cytochrome c forms part of a multi-protein complex called the apoptosome, that also includes several molecules of procaspase-9

80
Q

What is the third final step of apoptosis (intrinsic pathway)?

A

The release of apoptotic mitochondrial proteins irreversibly commits the cell to apoptosis.

BIO 221 01 (11 decks)

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