BIOL. 1406: CH11 Cell Communication Flashcards

1
Q

Quorum Sensing

A

a process that allows bacteria to sense local population density through concentration of signaling molecules

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2
Q

Example of Quorum Sensing

A

fromation of biofilm

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3
Q

Biofilm

A

aggregation of bacterial cells adhered to a surface

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4
Q

Local and Long-Distance Signaling

A

cells in a multicellular organism communicate via signaling molecules

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5
Q

Local Signaling

A

paracrine signaling;
animal cells communicating by direct contact;

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5
Q

Growth Factors

A

local regulators in animals that stimulate nearby target cells to grow and divide

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6
Q

Synaptic Signaling

A

process that occurs in animal nervous system when a neurotransmitter is release in response to an electric signal

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7
Q

Hormones

A

molecules released by plants and molecules in long-distance signaling

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8
Q

Hormonal (Endocrine) Signaling

A

hormones travel to target cells via the circulatory system;
the ability of cell to respond to a signal depends on whether or not the cell has a receptor specific to that signal

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9
Q

Three Steps of Cell Signaling

A

1) signal reception
2) signal transduction
3) cellular response

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10
Q

Signal Reception

A

the target cell detects a signaling molecule that binds to a receptor protein on the cell surface

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11
Q

Signal Transduction

A

binding of the signaling molecule altering the receptor and initiating a signal transduction pathway;
it often occurs in a series of steps

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12
Q

Cellular Reception

A

transduced signal triggering a specific response in the target cell

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13
Q

Signal Reception

A

the binding between a signal molecule (ligand) and receptor is highly specific;
a shape change of the receptor is usually the first step in the transduction of the signal;
most signal receptors are plasma membrane proteins, but other are located inside the cell

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14
Q

3 Main Membranes of Plasma Membrane Receptors

A

1) G protein-coupled receptor
2) receptor tyrosine kinase
3) ion channel receptor

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15
Q

Receptors in the Plasma Membrane

A

most water-soluble signal molecules bind to specific sites on receptor proteins that transmit information from the extracellular environment to the inside of cell;
G protein-coupled receptors are the largest group of plasma membrane receptors

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16
Q

G protein-coupled receptor

A

is a cell-surface transmembrane receptor that works with the help of a G-protein;
G proteins bind the energy rich GTP;
G proteins are very similar in structure;
GPCRs are widespread and diverse in their functions

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17
Q

Receptor Tyrosine Kinase (RTK)

A

a membrane receptor that catalyzes the transfer of phosphate groups from ATP to another protein;
this receptor can trigger multiple signal transduction pathways at once;
abnormal functioning of this receptor is associated with many types of cancers

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18
Q

Ligand-Gated Ion Channel

A

receptor that acts as a gate that opens and closes when the receptor shape changes;
when a signal molecule binds as a ligand to the receptor, the gate allows specific ions to pass through

19
Q

Intracellular Receptor Protein

A

receptor that is found in cytoplasm or nucleus inside target cell;
small or hydrophobic molecules can cross the membrane t activate this type of receptor;
examples of hydrophobic messengers: steroid and thyroid hormones of animals;
an activated hormone-receptor may act as a transcription factor, turning on or off specific genes

20
Q

Signal Transduction

A

cell signaling is usually a multistep process;
multistep processing can greatly amplify a signal;
multistep pathways provide more opportunity for coordination and regulation of cellular response

21
Q

Signal Transduction Pathway

A

the binding of a ligand molecule to a receptor triggers the first step in a chain of molecular interactions;
the activated protein activates another, which in turn activates the next one until the the one producing the cellular response is activated;
at each step, the signal is is transduced into a different form (usually in the form of protein shape change)

22
Q

Phosphorylation and Dephosphorylation

A

Commonly used to regulate protein activity;
system that works as a molecular switch, turning activities on or off, up or down, as required

23
Q

Protein Kinase

A

transfer phosphates from ATP to a protein in a process of phosphorylation

24
Phosphorylation Cascade
many relay molecules in signal pathways, which are protein kinases
25
Protein Phosphatases
proteins that rapidly remove a phosphate group in a process of dephosphorylation
26
Second Messengers
small, non-proteins, water soluble molecules or ions that spread throughout the cell by diffusion; participate in pathways initiated by GPCRs and RTKs; cAMPs and calcium ions serve as ones
27
Adenylyl Cyclase
an enzyme in the plasma membrane that converts ATP to cAMP in response to an extracellular signal; regulation of cell metabolism is provided by G protein systems that inhibit its activity
28
Cyclic AMP (cAMP)
a molecule produced from ATP; it is one of the most widely used second messengers; many small molecules trigger its formation; components of its pathways are GPCR, GP, and protein kinases; it activates protein kinase A that phosphorylates a protein
29
Cholera Bacterium
vibrio cholerae; it produces a toxin that modifies G protein, so it is stuck in its active form; the protein continually makes cAMP, causing the intestinal walls to secrete salt; water follows by diffusion; if untreated a person can die from loss of salt and water
30
Calcium Ions and Inositol Triphosphate (IP3)
Ca+ ions are used widely as second messengers (even more than cAMPs); its concentration is much lower in cytosol; diffusion results in great change of concentration; a signal relayed by signal transduction pathway may trigger the release of Ca+ into the cytosol; pathways leading to the release of Ca+ ions involve inositol triphosphate (IP3) and diacyglycerol (DAG) as additional second messengers; IP3 and DAG are produced by cleavage of certain kind of phospholipid in the plasma membrane
31
Cellular Response
cell signaling leads to regulation of transcription or cytoplasmic activities
32
Output Response
a cell's response to an extracellular signal
33
Nuclear and Cytoplasmic Responses
a cell transduction leads to regulation of one or more cellular activities; signal molecules, relay molecules, second messengers participate in a variety of pathways that lead to the following responses
34
Nuclear Responses
many signaling pathways regulate the synthesis of enzymes or other proteins by turning genes on or off inside the nucleus; the final activated molecule in a signaling pathway acts as a transcription factor
35
Regulation of the Response
a response to a signal may not be simply on or off; there are four aspects of its regulation: 1) amplification of the response 2) specificity of the response 3) overall efficiency of response (enhanced by scaffolding proteins) 4) termination of the signal
36
Signal Amplification
enzyme cascades amplify the cell's response to a signal; at each step, the products are much greater than in the preceding one
37
Specificity of Cell Signaling and Coordination of the Response
different kinds of cells have different kinds of proteins; these different proteins allow cells to detect and respond to different signals; the same signal can have different effects in cells with different proteins and pathways; pathway branching and cross-talk help cell further coordinate incoming signals
38
Signaling Efficiency
Scaffolding Proteins and Signaling Complexes
39
Scaffolding Proteins
large relay proteins to which other proteins are attached; increase signal transduction efficiency by grouping together different proteins involved in the same pathway; in some cases, may also help activate some relay proteins
40
Termination of the Signal
inactivation mechanisms are essential part of cell signaling; if the concentration of extracellular signaling falls fewer receptors are activated; unbound receptors revert to an inactive state
41
Apoptosis
cells that are infected, damaged, or at the end of the functional lives often undergo "programmed cell death"; components of cells are chopped up and packaged into vesicles that are digested by scavenger cells; it prevents enzymes from backing out of dying cells and damaging neighboring cells
42
Apoptosis in Soil Worm Caenorhabditis Elegans
is triggered by signals that activate a cascade of suicide proteins in cells destined to die; a protein Ced-9 in the outer mitochondrial membrane serves as a master regulator of this process; when death signal is activated Ced-9 (apoptosis-inhibiting protein) is inactivated; a pathway activates proteases and nucleases that cut up proteins and DNA of cell; main proteases are caspases (the chief caspase is Ced-9)
43
Apoptotic Pathways and the Signals that Trigger Them
in humans and other mammals, several different pathways, involving about 15 caspases, can carry out apoptosis; apoptosis may be triggered by external or internal signals; internal signals result from excessive protein misfolding or irreparable DNA damage; apoptosis is essential in animal evolution and is essential in development and maintenance; ex: formation of hands and feet; apoptosis may be involved in some diseases (Parkinson's, Alzheimer's, etc)
44
Relay Molecules
Simply pass signal onto the next member in the chain