Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) are second messengers that act as regulators of cellular functions in both prokaryotes and eukaryotes. Biological processes mediated by these molecules include gene regulation, metabolism, memory and immune function.
Second messengers are intracellular molecules that are released in response to the first messengers. The second messengers trigger the signalling cascades in the cell. Other examples of the second messengers include calcium, inositol trisphosphate and diacylglycerol.
The cyclic nucleotides consist of a sugar, nitrogen base and a phosphate group like other nucleotides. The base is attached at the 1’ carbon of the sugar, and phosphate at the 5’ carbon of the sugar. The bond that makes the structure cyclic is the attachment of the phosphate group at the 3’ carbon of the sugar.
What is cAMP?
cAMP is a cyclic nucleotide that is a derivative of adenosine triphosphate (ATP). It is a second messenger that was discovered by Earl W. Sutherland. He was later awarded the Nobel Prize for his discovery.
cAMP is synthesised by ATP with the help of the enzyme adenylate cyclase. The cAMP molecule functions intracellularly to pass on the effects of hormones such as glucagon and adrenaline to the cell. It also activates protein kinases and is involved in the regulation of ion channels.
In bacterial cells, cAMP molecules increase the expression of several genes. For example, the lac operon of the bacteria is modulated by cAMP. In low glucose concentrations, cAMP binds to the activator protein, which in turn makes the placement of RNA polymerase on the operon easier and hence easy transcription.
What is cGMP?
cGMP is a cyclic nucleotide that is synthesised by guanosine triphosphate (GTP) with the help of the guanylate cyclase enzyme.
The functions of cGMP include phototransduction (the phenomenon of conversion of light energy to electrical energy in the retina so that the visual information can be sent to the brain), ion channel modulation, glycogenesis and apoptosis regulation.
cAMP vs cGMP
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Cyclic Adenosine Monophosphate |
Cyclic Guanosine Monophosphate |
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It is the derivative of ATP. |
It is the derivative of GTP. |
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It is synthesised by the enzyme adenylate cyclase. |
It is synthesised by the enzyme guanylate cyclase. |
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It has a shorter life. |
It is synthesised slowly, giving it a longer life. |
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Explore BYJU’S Biology to learn more interesting topics.
Also see:
- What Is cAMP Receptor Protein?
- What Is The Second Messenger In Hormones?
- Why Is Lactose Called Inducer in Lac Operon?
Frequently Asked Questions
What are the similarities between cAMP and cGMP molecules?
Following are the points of similarities between cAMP and cGMP molecules:
- Both are hydrophilic molecules.
- Both are known to activate protein kinases.
- Both are degraded to their NMP (Nucleotide Monophosphate) forms by the hydrolysis of their phosphodiester bond.
- Both are monophosphates.
How is cGMP activated?
Nitric oxide (NO) activates cGMP, which in turn dilates the blood vessels.
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