Gaseous Exchange is one of 10 topics in the Grade 11 Life Sciences CAPS syllabus, covered across 3 lessons on Study Vault. Below are real practice questions from this topic with full worked answers.
Sample practice questions
Easy
1. What is the site of actual gas exchange between air and blood in the human lungs?
Alveoli
Bronchi
The trachea
The diaphragm
Answer: Alveoli — Alveoli are the tiny, thin-walled air sacs at the end of the smallest bronchioles where gas exchange between air and blood actually takes place.
Easy
2. What structure holds the trachea permanently open, preventing it from collapsing?
C-shaped rings of cartilage
Cilia only
The diaphragm
Alveoli
Answer: C-shaped rings of cartilage — C-shaped rings of cartilage in the trachea wall hold it permanently open, preventing it from collapsing as air moves through during breathing.
Medium
3. Why does each alveolus being surrounded by a dense network of blood capillaries, with both walls only one cell thick, make gas exchange efficient?
It keeps the diffusion distance between air and blood extremely short, allowing gases to move quickly by diffusion
It increases the distance oxygen must travel, slowing gas exchange deliberately
It prevents any gas exchange from occurring at all
It allows blood to bypass the lungs entirely
Answer: It keeps the diffusion distance between air and blood extremely short, allowing gases to move quickly by diffusion — The extremely thin alveolar and capillary walls (each just one cell thick) minimise the diffusion distance between air in the alveoli and blood in the capillaries, allowing rapid, efficient gas exchange.
