Biological Membranes - A. N. Ohurtsov 2012

Electrogenesis of Biomembranes
Intracellular Signaling
Multiple Messengers

Many Cells utilize several intracellular messengers simultaneously. For instance, Skeletal Muscle cells employ both Calcium Ions and cAMP as intracellular messengers.

Even before Cell contraction begins—initiated by a surge in cytosolic calcium concentration—preparations for the upcoming exertion are set in motion through the binding of adrenaline molecules to ß-adrenergic receptors. The release of adrenaline into the bloodstream by the Adrenal Glands is a physiological response signaling The Need for intense muscular activity, such as in a dangerous situation.

The adrenaline–adrenoreceptor complex activates the Gs protein and, consequently, adenylate cyclase. The resulting cAMP then activates cAMP-dependent protein kinase (protein kinase A).

Protein kinase A phosphorylates Glycogen phosphorylase kinase, which in turn activates glycogen phosphorylase. This triggers Glycogenolysis and the Synthesis of glucose-6-phosphate even before the concentration of Ca2+ in the Cytosol rises.

Consequently, by the time muscle contractions commence—triggered by Action Potential impulses arriving via neuromuscular synapses from motor Neurons—The Cell already possesses the metabolites required to perform physical work.

METABOLISM/35.html">Selection/41.html">Review Questions and Exercises

1. What substances are referred to as secondary messengers?

2. Which cellular components can be involved in signal Transduction cascades?

3. What are the Similarities and differences between The concepts of messenger and mediator?

4. Which metabolites are most commonly used as messengers?

5. What are the two main signal transduction pathways?

6. Name two hallmark properties of a secondary messenger.

7. Which Membrane Proteins recognize the appearance of specific Transmitters or other signaling molecules in the extracellular environment?

8. Describe The Mechanism of cytosolic Inositol trisphosphate synthesis in platelets in response to extracellular ADP molecules.

9. What activates the enzyme phospholipase C (PLCß), and what reaction does it catalyze?

10. Which protein acts as a GEF for the trimeric Gq protein in platelets?

11. Describe the mechanism behind the sharp increase in cytosolic calcium ion concentration in platelets in response to extracellular ADP.

12. What are the similarities and differences between the inositol trisphosphate-gated calcium channel and the ryanodine receptor?

13. What are the similarities and differences between ryanodine receptors in skeletal muscle and cardiomyocytes?

14. What is the Functional Significance of Intracellular Calcium Oscillations?

15. Which region of The Endoplasmic reticulum membrane is referred to as a "hot spot"?

16. Describe the MECHANISM OF ACTION potential generation in olfactory sensory neurons in response to extracellular odorant molecules.

17. Activation of which enzyme leads to an elevated cytosolic concentration of cyclic adenosine monophosphate?

18. Which enzyme decreases the cytosolic concentration of cyclic adenosine monophosphate molecules?



Last update: 13/08/2026

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