Hello, I'm an expert in the field of biology with a focus on human physiology. Let's dive into the process of how oxygen is transported in the bloodstream.

In English:

Oxygen is carried in the blood primarily through a protein called hemoglobin. Hemoglobin is found within red blood cells (RBCs), which are also known as erythrocytes. Each hemoglobin molecule can bind up to four oxygen molecules, forming oxyhemoglobin. The process of oxygen binding to hemoglobin is influenced by several factors, including the partial pressure of oxygen (pO2), the presence of other molecules like carbon dioxide (CO2) and protons (H+), as well as temperature and the pH level of the blood.

When you inhale, oxygen enters your bloodstream through the alveoli in the lungs. Here, oxygen binds to the hemoglobin in the RBCs, forming oxyhemoglobin. The oxygen-rich blood is then pumped by the heart and transported to the body's tissues and organs. At the tissue level, oxygen is released from the hemoglobin as it encounters lower pO2 and higher levels of CO2 and protons, which are byproducts of cellular respiration. This release of oxygen is necessary for cells to use it for energy production.

In Chinese:

氧气主要通过一种名为血红蛋白的蛋白质在血液中运输。血红蛋白存在于红细胞（也称为红细胞）中。每个血红蛋白分子可以结合多达四个氧气分子，形成氧合血红蛋白。氧气与血红蛋白结合的过程受到几个因素的影响，包括氧气的分压（pO2）、其他分子如二氧化碳（CO2）和质子（H+）的存在，以及血液的温度和pH值。

当你吸气时，氧气通过肺部的肺泡进入你的血流。在这里，氧气与红细胞中的血红蛋白结合，形成氧合血红蛋白。然后，富含氧的血液被心脏泵送到身体的组织和器官。在组织层面，当遇到较低的pO2和较高水平的CO2和质子时，氧气从血红蛋白中释放出来，这些是细胞呼吸的副产品。氧气的释放对于细胞使用氧气进行能量生产是必要的。

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Hemoglobin: The protein inside red blood cells (a) that carries oxygen to cells and carbon dioxide to the lungs is hemoglobin (b). Hemoglobin is made up of four symmetrical subunits and four heme groups. Iron associated with the heme binds oxygen.read more >>