OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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What is the percentage composition of plasma in human blood?

The correct answer is: 55%

Plasma makes up approximately 55% of human blood, which is a vital component of the circulatory system. It acts as the liquid medium in which blood cells (red blood cells, white blood cells, and platelets) are suspended. Plasma contains water, electrolytes, nutrients, hormones, waste products, and proteins, which play critical roles in maintaining blood pressure, volume, and overall homeostasis. The high percentage of plasma in blood is essential because it facilitates the transport of various substances throughout the body, allowing for effective communication between different cells and organs, and supports numerous physiological functions.