Principles of Biochemistry, Volume 3 - A. Lehninger 1985

Selected Aspects of Human Biochemistry
Digestion, Nutrient Transport, and Intermediary Metabolism
Blood carries large volumes of oxygen

A normal adult male at complete rest consumes about 375 liters of pure oxygen per day, which is equivalent to The amount of oxygen contained in 1,900 liters of air. During sedentary work, the oxygen demand increases at least twofold. In a trained athlete during running or swimming competitions, The rate of oxygen consumption sometimes exceeds the resting level by 10 times. Table 24-5 shows the relative amounts of oxygen consumed by the Morphology/4.html">MAIN Organs OF the adult human body at rest and during heavy muscular exertion.

Class="center">Table 24-5. Oxygen consumption (in relative values) by major human body organs (adult male)

Rest

Light physical work

Heavy physical work

Skeletal Muscles

0.30

2.05

6.95

Abdominal organs

0.25

0.24

0.24

Heart

0.11

0.23

0.40

Kidneys

0.07

0.06

0.07

Brain

0.20

0.20

0.20

Skin

0.02

0.06

0.08

Other

0.05

0.06

0.06

Total

1.00

2.90

8.00

As we have already seen (Section 8.12 et seq.), the bulk of oxygen is transported by erythrocyte Hemoglobin. These Cells constitute a vital "tissue" of The Human Body, as their total volume is 3 liters (in an adult male) and their total weight is almost equal to that of the Liver. Erythrocytes are highly specialized, degenerate cells lacking a Nucleus, Cell/35.html">Mitochondria, and other intracellular Organelles. They do not consume oxygen in their own METABOLISM. A relatively small amount of the ATP they require is produced via the glycolytic conversion of glucose, supplied by the Blood, into lactate. The primary function of erythrocytes is The transport of O2 from the Lungs to the Tissues and Participation in the transport of CO2 from the tissues to the lungs. Hemoglobin accounts for 35% of the erythrocyte mass, making up 90% of the total protein content within The Cell.



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