At high speed and enormous:

https://www.sciencemagazinedigital.org/sciencemagazine/library/item/15_november_2024/42...

"Healthy humans produce ∼2.4 million mature red blood cells (RBCs) every second. This process, called erythropoiesis, begins with the differentiation of multipotent hematopoietic stem cells (HSCs) to lineage-committed erythroid precursors, followed by drastic morphological and functional changes, including the formation of a specialized plasma membrane, loss of most organelles, contraction of the proteome, and massive production of hemoglobin, which constitutes >95% of RBC cytosolic protein.

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"Metabolic requirements vary during development, and our understanding of how metabolic activity influences cell specialization is incomplete. Here, we describe a switch from glutamine catabolism to synthesis required for erythroid cell maturation. Glutamine synthetase (GS), one of the oldest functioning genes in evolution, is activated during erythroid maturation to detoxify ammonium generated from heme biosynthesis, which is up-regulated to support hemoglobin production. Loss of GS in mouse erythroid precursors caused ammonium accumulation and oxidative stress, impairing erythroid maturation and recovery from anemia. In β-thalassemia, GS activity is inhibited by protein oxidation, leading to glutamate and ammonium accumulation, whereas enhancing GS activity alleviates the metabolic and pathological defects. Our findings identify an evolutionarily conserved metabolic adaptation that could potentially be leveraged to treat common red blood cell disorders."

Comment: this is an enormous production of a vital protein which carries both oxygen in and carbon dioxide out. Hemoglobin is highly complex protein that supports the concept of design.