What is the compositional difference between lymph and plasma?

• A. Lymph contains a much lower concentration of suspended proteins
• B. Lymph contains more suspended proteins than plasma
• C. Lymph has higher cholesterol
• D. Lymph is more acidic

Answer: (A)

The key idea is that lymph is essentially the filtrate of plasma that has left capillaries to become interstitial fluid and then enter lymphatic vessels. Proteins are large and mostly stay inside blood vessels, so the plasma is rich in suspended proteins, while the fluid that forms lymph has far fewer of those proteins. That makes lymph a low-protein fluid compared with plasma. The other statements don’t fit: lymph isn’t known for higher protein content, it isn’t defined by higher cholesterol, and its pH isn’t consistently more acidic than plasma.