Introduction
The human body is composed of various elements, with oxygen being the most abundant by mass. Understanding the percentage of oxygen in the body is crucial for studies in biology and medicine.

Percentage of Oxygen in the Human Body
- The average percentage of oxygen in the human body is approximately **65%**.
- This figure reflects the proportion of oxygen by mass, highlighting its importance in biological processes.

Sources of Oxygen in the Body
- Oxygen primarily exists in the body as part of water (H₂O), which constitutes about **60%** of body weight.
- Oxygen is also a key component of organic molecules, including carbohydrates, proteins, and fats.

Functions of Oxygen
- Oxygen plays a vital role in **cellular respiration**, the process by which cells generate energy.
- It is essential for the metabolism of nutrients, allowing the body to produce ATP (adenosine triphosphate), the energy currency of cells.

Conclusion
- Understanding the role of oxygen emphasizes its significance in maintaining life and metabolic functions.
- The 65% figure highlights how integral this element is to human physiology, underlining its importance in health and disease management.
In summary, oxygen's presence in our body is not only substantial but also critical for sustaining life, making its understanding essential in various scientific fields.