Formation of Cyclic AMP cAMP

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Formation of Cyclic AMP (cAMP)
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Breakdown of cAMP
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Pathways relay signals from receptors to cellular
responses.
Protein kinase enzyme that phosphorylates a
protein.
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How are pathways turned off?

• Phosphatases inactivate the enzymes.

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Stimulation of Glycogen Hydrolysis
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Fate of Glucose-1-phosphate
Gluose-1-phosphate
hydrolyzed
Glucose P
glycolysis
Bloodstream for transport to other cells
ATP
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Why are signal transduction pathways so complex?

• To amplify the signal
• A single hormone such as epinepherine can produce
  different responses in different cells.

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Signal Amplification

• 1 molecule of epinepherine can cause the release
  of millions of glucose molecules

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Signal Amplification
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Specificity of Response

• Epinepherine - fight or flight
• Liver - Breakdown of glycogen
• Heart - Makes the heart beat faster

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4 Responses
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Some hormones and growth factors trigger the
synthesis of new proteins.

• Growth factor molecule that stimulates cell
  division.

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Nuclear Response
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What happens if the growth factor receptor is
permanently turned on?
Cancer
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Examples of Selectivity

• Enzymes
• Transporters
• Receptor-mediated endocytosis
• Receptors for hormones, neurotransmitters and
  growth factors