How does the phosphorylation of IRS 1 contribute to insulin signaling, and what is its significance?

• A. Phosphorylation of IRS 1 inhibits downstream signaling pathways, reducing cell growth.
• B. Phosphorylation of IRS 1 has no significant role in insulin signaling.
• C. Phosphorylation of IRS 1 activates downstream signaling pathways, crucial for cell growth and metabolism.
• D. Phosphorylation of IRS 1 leads to its degradation, terminating the signal.

Answer: (C)