Understanding Plasma Transport in Blood

Plasma is the liquid component of blood, making up about 55% of its total volume. It is a complex mixture of water, proteins, electrolytes, nutrients, hormones, and waste products. Its primary function is to transport various substances throughout the body.

Step 1: Analyze the Options

Let's evaluate what each substance is and how it is typically carried in the blood:

• Carbon monoxide (CO): This is a toxic gas that binds irreversibly to hemoglobin in red blood cells, not dissolved in plasma.
• Nitrogenous wastes (e.g., urea, ammonia): These are water-soluble waste products from protein metabolism. They are dissolved directly in the plasma for transport to the kidneys.
• Oxygen (O$O_2$): This gas is primarily transported bound to hemoglobin inside red blood cells. A very small amount is dissolved in plasma, but this is not its main transport method.
• Red blood cells (RBCs): These are the solid, cellular components of blood. They are suspended in plasma but are not themselves transported by it. Plasma is the medium they are carried in.

Step 2: Identify the Correct Transport Mechanism

The question asks what plasma transports. This means we are looking for a substance that is dissolved or carried within the plasma fluid itself.

• Nitrogenous wastes like urea (${\mathrm{CO}}_{\left(N{H}_2\right)}$) are small, soluble molecules that are freely dissolved in plasma water for transport to excretory organs.

Final Answer

Plasma transports nitrogenous wastes.

Related Topics & Formulae

Composition of Blood Plasma:

• Water (~92%)
• Plasma Proteins (~7%) - Albumin, Globulins, Fibrinogen
• Other Solutes (~1%) - Electrolytes (Na${+}^{}$, K${+}^{}$, Ca${+}^2$, Cl${-}^{}$), Nutrients (Glucose, Amino Acids, Fatty Acids), Gases (O$O_2$, CO$O_2$), Hormones, and Nitrogenous Wastes (Urea, Uric Acid, Creatinine).

Key Theory: The transport function of plasma is crucial for homeostasis. It delivers nutrients and oxygen to cells, carries hormones to target organs, and transports waste products to sites of elimination (e.g., kidneys, lungs). The solubility of a substance in water determines if it is carried dissolved in plasma or requires a carrier protein or cell.