Question

Which of the following is NOT a common second messenger in cell signaling?

A. Ca²⁺
B. Cyclic adenosine monophosphate / cAMP
C. Diacylglycerol
D. Tyrosine
E. Inositol trisphosphate / IP3

Answer 1

The molecule 'Tyrosine' is not a common second messenger in cell signaling; it is an amino acid involved in phosphorylation reactions. Common second messengers in cells include cAMP, Ca2+, DAG, and IP3.

Step-by-step explanation:

The concept you're asking about is related to second messengers in cell signaling, specifically which molecule mentioned is not a common second messenger. The options provided are Ca2+, cyclic adenosine monophosphate (cAMP), diacylglycerol (DAG), Tyrosine, and inositol trisphosphate (IP3). Among these, Tyrosine is not a common second messenger. Instead, it's an amino acid that can be phosphorylated by tyrosine kinases during cell signaling events.

The common second messengers for cell signaling include cAMP, which is synthesized from ATP by adenylyl cyclase and activates proteins by phosphorylation via cAMP-dependent protein kinase (PKA). Similarly, Ca2+ acts as a second messenger when released into the cytoplasm, affecting various enzymatic and cellular activities. Diacylglycerol (DAG) activates protein kinase C (PKC), and inositol trisphosphate (IP3) triggers the release of Ca2+ from intracellular storage areas.

Answer 2

Tyrosine is NOT a common second messenger in cell signaling; the common second messengers are cAMP, Ca²⁺, DAG, and IP3. Tyrosine is an amino acid that serves as a phosphorylation site, not a signaling molecule.

Step-by-step explanation:

The correct answer to the question "Which of the following is NOT a common second messenger in cell signaling?" is D. Tyrosine. Common second messengers in cell signaling include cyclic adenosine monophosphate (cAMP), Ca²⁺, diacylglycerol (DAG), and inositol trisphosphate (IP3).

These molecules help to propagate the signal initiated by the binding of a signaling molecule to a receptor, ultimately altering the behavior of cellular proteins. Tyrosine is not a second messenger but is an amino acid that can be phosphorylated by tyrosine kinases in response to cell signaling.

For example, cAMP is synthesized from ATP by the enzyme adenylyl cyclase and primarily functions to activate cAMP-dependent protein kinase (A-kinase), which then phosphorylates serine and threonine residues on target proteins. Similarly, Ca²⁺ can be released by IP3, leading to a cascade of intracellular events. In contrast, tyrosine itself serves as a phosphorylation site in proteins rather than a diffusible signaling molecule.