Unit 4: Cell Communication and Signaling Flashcards

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1
Q

ligand

A

chemical signals that start off signal transduction; interact with target cells; may be hydrophilic or hydrophobic

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2
Q

autocrine signaling

A

cell SECRETES a ligand; ligand binds to a receptor on the cell that secreted the ligand, triggering a response within the cell; REMEMBER: auto = self - cell signaling itself to generate a response; ex. cancer cell

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3
Q

juxtacrine signaling

A

depends on DIRECT CONTACT between the cell sending the ligand and the cell receiving and responding to the ligand via a surface receptor; ex. plasmodesmata in plants (ligands move through channels connecting the plants) and antigen-presenting cells in the immune system (signal helper T cells through direct cell-to-cell contact)

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4
Q

paracrine signaling

A

cell secretes a ligand that travels a SHORT DISTANCE, eliciting an effect on cells in the nearby area; these ligands are referred to as LOCAL REGULATORS as they only affect cells in the immediate vicinity of the cell sending the signals; ex. neurotransmitters that travel across a synapse

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5
Q

endocrine signaling

A

some ligands travel a LONG DISTANCE between the sending and receiving cells; these are called HORMONES; ex. insulin is produced and released by the pancreas then travels through the circulatory system to trigger responses in cells throughout the body

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6
Q

signal transduction

A

determines how a cell responds internally to a signal in its environment; important processes like gene expression, cell growth & division, and hormone release depend on this

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7
Q

target cells

A

respond to the presence of a ligand after interacting with one

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8
Q

hydrophilic ligands

A

cannot cross the phospholipid bilayer of the cell membrane and enter the cell; interact with cell membrane receptors to trigger a series of chemical reactions inside the cell

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9
Q

hydrophobic ligands

A

enter the cell by sliding between the phospholipids of the cell membrane; bind to intracellular receptors in the cell’s cytosol; after binding, the ligand can then cross the nuclear membrane and bind to the DNA in the nucleus to change the expression of genes

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10
Q

signal transduction’s three major steps

A

reception, transduction, response

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11
Q

reception

A

ligand binds to specific receptor in/on target cell; receptors contain ligand-specific binding domains (if a cell doesn’t have the receptor for a specific ligand, the cell will not respond to that ligand); upon ligand’s binding to the receptor, the receptor undergoes a conformational shape change that triggers the next step in the cell’s processes

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12
Q

G-protein coupled receptors

A

one of three major types of cell-surface transmembrane receptors; work with cytoplasmic G proteins; ligand binding activates the receptor, which activates a specific G protein, which activates another protein, propagating the signal

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13
Q

receptor tyrosine kinases

A

one of three major types of cell-surface transmembrane receptors; react to the binding of signaling molecules by forming dimers, then adding phosphate groups to the tyrosines on the cytoplasmic part of the other monomer making up the dimer; relay proteins in the cell can then be activated by binding to different phosphorylated tyrosines, allowing this receptor to trigger several pathways at once

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14
Q

ligand-gated ion channels

A

one of three major types of cell-surface transmembrane receptors; open or close in response to binding by specific signaling molecules, regulating the flow of specific ions across the membrane

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15
Q

intracellular receptors

A

cytoplasmic or nuclear proteins; signaling molecules that are hydrophobic or small enough o cross the plasma membrane bind to these receptors inside the cell

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16
Q

transduction

A

series of chemical reactions (triggered by the binding of the ligand to its receptor) that helps the cell choose the appropriate response; most complicated part of signal transduction; possible components include signaling cascades, kinases, phosphatases, and enzymes

17
Q

signaling cascades

A

a series of chemical reactions in which one molecule activates multiple molecules, amplifying the cell’s response to a signal (process known as signal amplification)

18
Q

phosphorylation cascade

A

when a series of protein kinases each add a phosphate group to the next one in line, activating it

19
Q

kinases

A

can transfer phosphate groups to other molecules, which activate those molecules (opposite of phosphatases)

20
Q

phosphatases

A

can remove phosphate groups from other molecules, which inactivates those molecules (opposite of kinases)

21
Q

enzymes (in cell communication)

A

produce secondary messengers; ex. adenylyl cyclase, which produces the secondary messenger cyclic AMP (cAMP) from ATP

22
Q

secondary messengers

A

diffuse throughout the cytosol to help signals broadcast quickly

23
Q

response

A

final step of signal transduction and ultimate result generated by the ligand; examples of cellular responses: activation of genes by steroid hormones, opening of ligand-gated ion channels, and the initiation of cell processes (like apoptosis); terminated by reversal of ligand bonding

24
Q

signal transduction pathways

A

series of chemical reactions that mediate the sensing and processing of stimuli

25
Q

long-distance signaling

A

includes hormones that are hydrophobic and can cross the membrane; once inside the cell, the hormone attaches to a protein, which brings it to the nucleus, where transcription can be stimulated

26
Q

disruptions to signal transduction pathways

A

(1) since receptors are specific to certain ligands, a mutation in a gene meant to code a receptor protein could result in changing the receptor’s shape to stop it from binding to its specific ligand; without a functional receptor for the ligand, the cell with the mutated receptor protein would not be able to respond to the ligand; (2) disruption can occur when molecules in the environment interfere with a ligand’s ability to bind to its receptor; (3) mutations in the gene for adenylyl cyclase can interfere with a cell’s ability to produce the secondary messenger cAMP, disrupting all steps in the signal transduction process that depend on that secondary messenger; (4) a disruption to any step in the signal transduction process will affect not only that step but will also affect any subsequent steps the process that are dependent on the products of the previous steps

27
Q

feedback mechanisms

A

help living organisms respond to changes in the environment while maintaining the internal environment of the cell; cell communication and signaling are crucial in feedback mechanisms

28
Q

negative feedback

A

returns a system to its original condition and helps maintain homeostasis; ex. (1) if the body temp is too high, cell signaling processes will trigger sweat release (2) control of blood glucose levels by insulin and glucagon: if blood sugar levels get too high, the pancreas releases insulin, which causes body cells to absorb glucose from the blood; the opposite happens with glucagon if the levels are too low

29
Q

positive feedback

A

magnifies cell processes; ex. oxytocin stimulates contractions of the uterine muscles in contractions during childbirth, and this contraction triggers the production of even more oxytocin, which in turn increases contractions of the uterine muscles (increases on both sides in a repeating cycle)

30
Q

scaffolding proteins

A

increase signaling efficiency