Oxygen’s Journey: From Alveoli to Cells

Q1. Which component is the main site where oxygen moves from inhaled air into the blood?
- Alveoli
- Red blood cells
- Arteries
- Mitochondria
Answer: Alveoli. Mechanism: Oxygen diffuses across the alveolar-capillary surface into nearby capillaries.
Q2. Which component carries most of the oxygen through the bloodstream?
- Hemoglobin inside red blood cells
- Platelets inside arteries
- Plasma inside alveoli
- Mitochondria inside capillaries
Answer: Hemoglobin inside red blood cells. Mechanism: Hemoglobin binds oxygen in the lungs and transports it within red blood cells.
Q3. Which component pumps oxygenated blood away from the heart and through the systemic circulation?
- The heart
- The alveoli
- The mitochondria
- The tissue cells
Answer: The heart. Mechanism: The heart generates the pressure that moves oxygenated blood into the blood vessels.
Q4. Which sequence best describes the blood-vessel route that distributes oxygen toward body tissues?
- Arteries, arterioles, then capillaries
- Capillaries, arteries, then alveoli
- Veins, alveoli, then arterioles
- Arterioles, veins, then arteries
Answer: Arteries, arterioles, then capillaries. Mechanism: Arteries carry blood away from the heart, arterioles regulate its distribution, and capillaries bring it close to cells.
Q5. Which component releases oxygen so it can move from tissue blood into nearby cells?
- Tissue capillaries
- The heart valves
- The alveoli
- The pulmonary arteries
Answer: Tissue capillaries. Mechanism: Oxygen diffuses out of capillaries across their thin walls toward tissues where oxygen concentration is lower.
Q6. Which cell component uses delivered oxygen during aerobic respiration?
- Mitochondria
- Hemoglobin
- Arterioles
- Alveoli
Answer: Mitochondria. Mechanism: Mitochondria use oxygen in aerobic respiration, allowing cells to obtain usable energy.

Oxygen’s Journey: From Alveoli to Cells

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