Grade 10 biology – Gaseous Exchange and Respiration Quiz

The primary role of the respiratory system is gas exchange: supplying oxygen to the blood for cellular respiration and removing carbon dioxide, a metabolic waste.

Alveoli are tiny air sacs with very thin walls and large surface area, specialised for rapid diffusion of oxygen and carbon dioxide between air and blood.

Countercurrent flow keeps a gradient along the gill lamellae so blood encounters water with progressively higher oxygen, maximising diffusion into blood.

Insects use tracheae and tracheoles that carry air directly to cells, so oxygen does not rely on the circulatory system for delivery.

Many amphibians (e.g., frogs) exchange gases through moist skin as well as lungs; the skin must stay moist to allow diffusion of gases.

When the diaphragm contracts it flattens and moves downward, increasing chest cavity volume and causing air to flow into the lungs.

Pleural fluid lubricates the pleural surfaces so the lungs can expand and recoil smoothly during breathing.

Haemoglobin binds oxygen in red blood cells and transports the majority of oxygen from lungs to tissues; only a small amount is dissolved in plasma.

Increased muscle activity raises CO2 and H+ levels; central and peripheral chemoreceptors detect these changes and increase breathing to remove CO2 and supply more oxygen.

Gases diffuse from areas of higher partial pressure to lower partial pressure; oxygen moves from alveolar air (higher pO2) into blood (lower pO2).

Alveoli provide a huge surface area and thin (one-cell-thick) walls to shorten diffusion distance and speed up gas exchange.

Countercurrent flow keeps blood encountering water with higher oxygen, maintaining diffusion gradient across the whole surface and maximising uptake.

Gill filaments have many thin lamellae which provide a large surface area and short diffusion distance for oxygen to enter blood.

Surfactant reduces surface tension of the thin fluid lining alveoli, preventing collapse (atelectasis) and making breathing easier.

External intercostal muscles contract to lift and expand the ribcage, increasing thoracic volume during inspiration.

Vital capacity is the total usable lung volume (max inspiration followed by max expiration) and is commonly measured in respiratory tests.

CO2 reacts with water to form carbonic acid, which dissociates to bicarbonate; most CO2 is transported this way in plasma after conversion in red blood cells.

Carbon monoxide has a high affinity for haemoglobin and forms carboxyhaemoglobin, blocking oxygen binding and reducing oxygen delivery to tissues.

Higher temperature, more CO2 and increased acidity reduce haemoglobin's affinity for oxygen, promoting O2 release to active tissues (Bohr effect).

Smoke damages the cilia in airways, so mucus cannot be cleared effectively, increasing infection risk and reducing airflow and gas exchange.

Water holds less dissolved oxygen and diffusion is slower, so aquatic animals have specialised gills and ventilatory adaptations to extract enough oxygen.

Gases move by diffusion from regions of higher partial pressure to lower partial pressure across thin, moist respiratory surfaces.

Alveolar epithelium is extremely thin and covered by a small amount of fluid with surfactant to permit gas diffusion while preventing collapse.

Many amphibians use buccal pumping: they push air into their lungs using movements of the mouth floor (positive pressure), unlike the negative pressure breathing of mammals.

Chemoreceptors in the carotid bodies and brainstem sense changes in CO2, O2 and pH and send signals to adjust rate and depth of breathing to maintain homeostasis.