A Level Biology C9 Recap

Which structure in the respiration system acts as a gas exchange surface?

• Trachea

• Bronchus

• Pleural membrane

• Alveolus

Which gases are diffusing in and out of the lungs and blood in the respiratory system? (choose all that apply)

• Nitrogen

• Oxygen

• Carbon dioxide

• Argon

Answer explanation

Nitrogen makes up the bulk of the air we breathe in, but our body does not utilise it. Hence, it is fully exhaled. Oxygen and carbon dioxide on the other hand take part in gas exchange, diffusing between our lungs and blood. This changes their composition in inhaled and exhaled air.

Alveoli are very small, but collectively have a very large surface area. What significance does this have for gas exchange?

• Gas exchange can occur without energy consumption

• Gas exchange can occur at a very high rate

• Gas exchange can continue indefinitely

• Gas exchange moves against the concentration gradient

The lungs are enclosed in pleural membranes which contain pleural fluid. What are the functions of these structures? (choose all that apply)

• To provide mechanical protection to the lungs

• Allows friction-free movement as the lungs expand and relax

• Filters bacteria and other pathogens

• Maintains body temperature in the lungs

Which component of the trachea keeps the airway open and maintains low air resistance during respiration?

• Bone

• Cartilage

• Smooth muscles

• Collagen fibers

Which structure in the respiratory system contains irregularly shaped cartilage as shown in the image?

• Trachea

• Bronchi

• Bronchioles

• Alveoli

Answer explanation

Only the trachea and bronchi contain cartilage. In the trachea, C-shaped cartilage maintains its shape, while irregularly-shaped cartilage provide structural integrity to the bronchi.

Why is it important for inhaled air to be moistened before reaching the lungs?

• Improves gas exchange

• Oxygen must bind with water for gas exchange

• Prevents the inner structures of the lungs from desiccating

• Brings air to body temperature

Which component in lungs produces mucin?

• Goblet cells

• Smooth muscles

• Cilia

• Cartilage

What molecule in mucin makes it sticky, thus enabling it to effectively trap inhaled particles?

• Antibodies

• Sugars

• Glycoproteins

• Enzymes

Other than trapping inhaled particles, what other function does cilia on epithelial cells perform?

• Water absorption

• Pushes mucus up the trachea for elimination

• Acts as a gas exchange surface

• Produces mucus