Question

which protein serves as a chemical messenger?
○ hemoglobin
○ actin
○ myosin
● insulin

Explanation:

• Hemoglobin: Transports oxygen in blood, not a chemical messenger.
• Actin: Involved in cell structure/movement, not a messenger.
• Myosin: Involved in muscle contraction, not a messenger.
• Insulin: A protein hormone (chemical messenger) that regulates blood glucose.

Answer:

D. insulin (assuming the options are labeled A to D with D as insulin; if original labels differ, adjust, but here the correct option is insulin, so the answer is the option with insulin, e.g., if the last option is D, then D. insulin)