What substance is predominantly found in red blood cells that allows for oxygen transport?

Hemoglobin is the substance predominantly found in red blood cells that facilitates the transport of oxygen throughout the body. This iron-containing protein has a unique ability to bind to oxygen molecules in the lungs, allowing for oxygen to be carried via the bloodstream to tissues and organs where it is needed for cellular respiration. The structure of hemoglobin consists of four subunits, each capable of binding to one molecule of oxygen, which significantly enhances its efficiency in oxygen transport. This characteristic is critical for maintaining adequate oxygen levels in the body, ensuring that all cells receive the necessary amount for energy production and other metabolic processes.

While myoglobin is related and also transports oxygen, it is primarily found in muscle tissues and functions differently than hemoglobin, specifically serving as a local oxygen reserve. Keratin and collagen, on the other hand, are structural proteins found in hair, skin, and connective tissues, and do not play a role in oxygen transport in the bloodstream.