Respiratory System - Sample Question and Answer

Why do we breathe faster when we exercise?

When we exercise, our body needs more energy. We breathe faster to take in more oxygen at a faster rate so that our body cells can carry out cellular respiration faster to release more energy.
When we exercise, our body cells also produce more carbon dioxide. We breathe faster to exhale this greater amount of carbon dioxide faster.

Circulatory System - Sample Question (2)

Here is another sample question on the human circulatory system:

The diagram below shows the circulation of blood in the human body.

(a) Name the organs that X and Y represent. (1 m)

X: Lungs
Y: Heart

Comment: The heart will have to pump blood to and from all parts of the body, including the lungs.

(b) Which part, P, Q, R or S, represents blood vessels that have the highest level of oxygen? Give a reason for your answer. (1 m)

Q. Blood vessel Q transports blood from the lungs where oxygen from the inhaled air passes through the walls of the air sacs into the blood. 

Circulatory System - Sample Question (1)

During Science examinations, pupils are often required to use comparison skills when answering open-ended questions. Below is a sample question on the circulatory system.

The diagram below shows how blood flows in certain parts of the body.

(a) The blood at D contains a greater amount of a substance than at C. What is this substance? Give a reason for your answer.

Answering Technique:

Comparison is needed as there is a comparative word "greater" in the question stem. 

Focus only on carbon dioxide in your explanation.

Carbon dioxide. The blood at D flows from the legs where the body cells give out carbon dioxide when they carry out cellular respiration. The blood at C flows from the heart which flows from the lungs where carbon dioxide has been expelled from the body 

(b) Why is the amount of oxygen in the blood lower at A than at B?

Answering Technique:

Comparison is needed as there is a comparative word "lower" in the question stem. 

Focus only on oxygen in your explanation.

The blood at A flows from the head and the legs where the body cells take in oxygen when they carry out cellular respiration. The blood at B flows from the heart which flows from the lungs where oxygen from the inhaled air passes through the walls of the air sacs into the blood.