We need oxygen to breathe because it is essential for cellular respiration, the process by which our cells produce energy. Oxygen is used to break down glucose, creating energy that powers our cells and, by extension, our bodies. Without oxygen, our cells cannot produce energy efficiently, leading to cell damage or death.
Why do we need Oxygen?
MCQs
1. Why is oxygen important for our muscles?
A) It makes them look bigger
B) It helps them contract
C) It changes their color
D) It keeps them cold
Answer: B) It helps them contract
Explanation: Oxygen is vital for muscle contraction. When our muscles have enough oxygen, they can work harder and longer before getting tired, which is why we need to breathe more heavily during exercise.
2. What happens if our brain doesn’t get enough oxygen?
A) It grows bigger
B) We become more intelligent
C) We can feel confused or dizzy
D) It changes color
Answer: C) We can feel confused or dizzy
Explanation: The brain relies on oxygen to work properly. If it doesn’t get enough oxygen, it can lead to confusion, dizziness, or even unconsciousness because the brain cells aren’t getting the energy they need to function.
3. Which part of the air is oxygen?
A) 78%
B) 21%
C) 100%
D) 55%
Answer: B) 21%
Explanation: Air is made up of several gases, and oxygen makes up about 21% of Earth’s atmosphere. The rest is mostly nitrogen, along with small amounts of other gases.
4. How do plants help us get oxygen?
A) By taking in carbon dioxide
B) By releasing oxygen
C) Both A and B
D) By providing shade
Answer: C) Both A and B
Explanation: Plants take in carbon dioxide and, through the process of photosynthesis, convert it into oxygen, which they release into the air, increasing the oxygen we have available to breathe.
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