Cell Signaling 1

Answer 1

-The ability of cells to receive and act on signals from outside their plasma membrane is fundamental to life

Question 2

-SIGNALING PATHWAY ? (5)
-Conversion of information into a chemical change –> ?

Answer 2

-SIGNALING PATHWAY

1) Signal = information
2) signal detection = specific receptor
3) Plasme membrane
4) transduction & information conversion
5) cellular response, involving a chemical process

-Conversion of information into a chemical change –>
SIGNAL TRANSDUCTION

Question 3

Chain of ? molecular ?

Multiple sites for ? and for ? drug action

The elements of chemical-signaling pathways are often ? conserved, the same molecules or same basic types of molecules are used in a wide variety of ? stimulus-response pathways

Answer 3

Chain of sequential molecular interactions

Multiple sites for regulation and for therapeutic drug action

The elements of chemical-signaling pathways are often highly conserved, the same molecules or same basic types of molecules are used in a wide variety of different stimulus-response pathways

Question 4

-The ? of a response depends on the turnover of signaling molecules (allosteric change or gene expression)

-Negative feedback loop?
-Positive feedback loop?

Answer 4

-The speed of a response depends on the turnover of signaling molecules (allosteric change or gene expression)

-Negative feedback loop – output inhibits its own production

-Positive feedback loop – output stimulates its own production

Question 5

-Signal transductions are ? ? and ? ?

(a) Specificity ?
(b) Sensitivity ?
-affinity?
-cooperativity
-amplification by enzyme cascades
(c) Desensitization (adaptation) ?
(d) Integration ?

Answer 5

-Signal transductions are highly specific and extremely sensitive!

(a) Specificity:
* Achieved by precise molecular complementarity between signal and receptor molecules,
* In multicellular organisms: specific receptors are present in specific cell types

(b) Sensitivity:
-Affinity
 Described by dissociation constant Kd
 Receptor detects picomolar concentrations
of signal molecule
-Cooperativity
 Small changes in ligand concentration cause large changes in receptor activation
-Amplification by enzyme cascades
 Enzyme once activated catalyzes activation of many molecules of a second enzyme, each of which activates many molecules of third enzyme, and so on
 Can produce amplifications of several orders of magnitude

(c) Desensitization (adaptation)
* Cells can adjust their sensitivity to a signal
* Continuous presence of a signal can cause desensitization of the receptor system, decreasing the cell response to that level of stimulus

(d) Integration
* Ability of a system to receive multiple signals and produce unified and appropriate response
* Each cell type is programmed to respond to specific combinations of extracellular signals
* Each cell type displays a set of receptors that enables it to respond to a corresponding set of signal molecules produced by other cells

Question 6

Signals to which cells respond ? (14)

Answer 6

• Antigens
• Cell surface glycoproteins/oligosaccharides
• Developmental signals
• Extracellular matrix components
• Growth factors
• Hormones: Hydrophilic & Lipophilic
• Mechanical touch (mechanotransduction)
• Light (phototransduction)
• Osmolarity
• Neurotransmitters
• Nutrients
• Odorants
• Tastants
• Pheromones

Question 7

LIGANDS

• Means to ?
  -Their only function is to ? the ? of the receptor

Answer 7

LIGANDS

• Means to bind
  -Their only function is to change the properties of the receptor