Which molecules bind to receptors that have intracellular tyrosine kinase domains?

• A. Growth factors such as epidermal growth factor (EGF)
• B. Steroid hormones like cortisol
• C. Cyclic AMP (cAMP)
• D. Neurotransmitters such as acetylcholine

Answer: (A)

Verified step by step guidance

1. Understand the concept of intracellular tyrosine kinase domains: These are regions within certain receptors that have enzymatic activity capable of phosphorylating tyrosine residues on proteins. This phosphorylation is a key step in signal transduction pathways.
2. Identify the types of molecules that typically bind to receptors with intracellular tyrosine kinase domains: These receptors are often associated with growth factors, which are signaling molecules that regulate cell growth, proliferation, and differentiation.
3. Analyze the role of growth factors such as epidermal growth factor (EGF): EGF binds to its receptor, which has an intracellular tyrosine kinase domain, triggering a cascade of phosphorylation events that lead to cellular responses.
4. Clarify why steroid hormones like cortisol do not bind to tyrosine kinase receptors: Steroid hormones typically bind to intracellular receptors that act as transcription factors, not receptors with tyrosine kinase domains.
5. Explain why cyclic AMP (cAMP) and neurotransmitters like acetylcholine are not involved: cAMP is a secondary messenger in signal transduction, and acetylcholine binds to other types of receptors, such as ionotropic or metabotropic receptors, rather than tyrosine kinase receptors.