Edexcel iGCSE Biology-3.10 role of plasma in  transport- Study Notes- New Syllabus

Plasma and Its Role in Transport

📝 Introduction

Plasma = the liquid part of blood, a pale-yellow fluid.
Makes up about 55% of blood volume.
Mainly water (90%) but also contains dissolved substances.
Acts as the transport medium for many important substances around the body.

🚚 Substances Transported by Plasma

• Carbon Dioxide (CO₂)
  Produced as a waste gas during respiration.
  Dissolves in plasma (mostly as hydrogen carbonate ions).
  Carried from body tissues → lungs for exhalation.
• Digested Food
  After digestion in the small intestine, nutrients (e.g., glucose, amino acids, fatty acids, glycerol) are absorbed into blood.
  Plasma transports them to cells for respiration, growth, and repair.
• Urea
  Waste product from deamination of amino acids in the liver.
  Plasma carries urea → kidneys for excretion in urine.
• Hormones
  Chemical messengers secreted by endocrine glands.
  Transported in plasma to target organs (e.g., insulin → liver/muscle, adrenaline → heart/muscles).
• Heat Energy
  Plasma is mostly water, which has a high heat capacity.
  Distributes heat around the body → helps regulate body temperature.

📊 Summary Table

⚡ Quick Recap
Plasma = liquid transport medium.
Carries:
– CO₂ → lungs.
– Nutrients → cells.
– Urea → kidneys.
– Hormones → target organs.
– Heat → all parts of body.