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.

Alveoli are tiny air sacs with very thin walls, large surface area and rich blood supply, which allow oxygen and carbon dioxide to diffuse rapidly between air and blood.

Gills have thin filaments and many lamellae that provide a large surface area and use countercurrent flow to absorb dissolved oxygen from water into the blood.

Insects have a tracheal system: air enters via spiracles and moves through branching tracheae and tracheoles directly to cells, allowing gas exchange by diffusion without using the blood to transport oxygen.

When the diaphragm contracts it flattens and the chest cavity expands, lowering internal pressure and drawing air into the lungs.

Haemoglobin in red blood cells binds oxygen in the lungs and releases it in tissues where it is needed for respiration.

Diffusion is driven by partial pressure gradients: oxygen has higher partial pressure in alveolar air than in blood, so it diffuses into the blood.

Alveoli are numerous and small, providing a very large total surface area for diffusion which increases the rate of gas exchange.

Birds have air sacs that produce a continuous, one-way flow of air through the lungs, maintaining a higher and more constant oxygen gradient across the respiratory surface.

Tidal volume is the amount of air moved in or out of the lungs during a normal, resting breath.

Carbon dioxide produced by cellular respiration is carried to the lungs and exhaled; its removal prevents acidification of the blood and helps maintain pH balance.

The Bohr effect describes how an increase in carbon dioxide (or lower pH) reduces haemoglobin's affinity for oxygen, promoting oxygen release to active tissues.

Haemoglobin is the iron-containing protein in red blood cells responsible for transporting oxygen; chlorophyll is in plants and hemocyanin occurs in some invertebrates.

Cilia sweep mucus and trapped microbes out of the airways; smoking destroys cilia function, allowing mucus and pathogens to build up and cause infections.

The epiglottis is a flap of tissue that closes the glottis during swallowing, directing food into the oesophagus and preventing it from entering the trachea.

About 98% of oxygen is carried bound to haemoglobin; only a small fraction is dissolved directly in the plasma.

CO2 enters red blood cells, is converted to bicarbonate by carbonic anhydrase, and most bicarbonate diffuses into plasma for transport to the lungs.

Emphysema destroys alveolar walls and reduces total respiratory surface area, which decreases the rate of oxygen and carbon dioxide exchange.

Pleural fluid lubricates the pleural surfaces so the lungs can expand and contract smoothly within the chest during breathing.

Vital capacity is the greatest volume of air a person can expel after taking the deepest possible breath and is used to assess lung function.

Many amphibians have thin, moist skin rich in blood vessels that allows oxygen and carbon dioxide to diffuse directly between the environment and the blood.

Tracheoles end close to individual cells, and gases move by diffusion across the thin tracheolar walls into cells, so the insect's circulatory fluid is not required to carry oxygen.

Countercurrent flow means water and blood flow in opposite directions across the gill lamellae, keeping the oxygen gradient along the entire surface and maximising oxygen uptake.

Rapid breathing expels CO2 faster than it is produced, reducing carbonic acid in blood and causing a temporary rise in pH (respiratory alkalosis), which can cause dizziness.

Alveolar walls are made of a single thin layer of squamous epithelial cells to minimize diffusion distance and speed up gas exchange.

Chemoreceptors in the medulla and carotid bodies respond primarily to increased CO2 (and lower pH) by stimulating faster and deeper breathing to remove excess CO2.