A Level Biology Practice Exam

Which statement best describes oxygenated blood?

1. Blood that contains high levels of carbon dioxide

2. Blood that has high levels of oxygen due to passing through gas exchange organs

3. Blood that carries nutrients to the body tissues

4. Blood that is produced in bone marrow

The correct answer is: Blood that has high levels of oxygen due to passing through gas exchange organs

Oxygenated blood is best described as blood that has high levels of oxygen due to passing through gas exchange organs. This process primarily occurs in the lungs for mammals, where blood picks up oxygen from inhaled air and releases carbon dioxide, which is a waste product of cellular respiration. The oxygen-rich blood is then transported from the lungs to the heart and pumped out to the rest of the body, delivering essential oxygen to tissues and organs. The other options do not accurately describe oxygenated blood. Blood with high levels of carbon dioxide would be deoxygenated, as carbon dioxide is typically transported away from the tissues back to the lungs for exhalation. The option about carrying nutrients is relevant to blood in general, but does not specifically pertain to the oxygenation status of the blood—it can carry nutrients in both oxygenated and deoxygenated forms. Lastly, the production of blood in bone marrow refers to the formation of blood cells, which does not have a direct relationship to the oxygenation status of the blood itself.