Which of the following is a protein found in blood plasma?

• A. Hemoglobin
• B. Albumin
• C. Myosin
• D. Keratin

Answer: (B)

Blood plasma contains several proteins with different roles, and the most abundant soluble protein in plasma is albumin. Albumin is produced by the liver and helps keep fluid inside blood vessels by maintaining colloid osmotic pressure, preventing excess fluid leakage into tissues. It also acts as a carrier for various substances, including fatty acids, hormones, bilirubin, and some drugs. Hemoglobin sits inside red blood cells and isn’t normally a plasma protein, so it isn’t listed as a plasma protein. Myosin is a motor protein in muscle, and keratin is a structural protein in hair and nails—they aren’t circulating plasma proteins. So albumin is the protein found in blood plasma.