Gas Exchange Flashcards
What is Fick’s Law?
Rate of diffusion ∝ (surface area × difference in concentration) / thickness of exchange surface.
How do single-celled organisms exchange gases?
Diffusion across their body surface due to a large surface area to volume ratio (SA:V).
Why is a large SA:V ratio important for gas exchange?
It increases the rate of diffusion, allowing efficient exchange of gases.
How do insects minimise water loss during gas exchange?
They have a waterproof exoskeleton, close spiracles when inactive, and use hairs around spiracles to trap water.
What are spiracles in insects?
Small openings on the surface of the body that allow gas exchange.
How do gases move through the insect tracheal system?
Diffusion, mass transport (via muscle contraction), and volume changes in the tracheal system.
What is the role of tracheoles in insects?
Tracheoles provide a large surface area for gas exchange, delivering oxygen directly to tissues.
How do fish perform gas exchange?
Through gills, using a counter-current system to maximise oxygen uptake.
What is counter-current flow in fish?
Blood and water flow in opposite directions, maintaining a diffusion gradient across the entire gill.
Why is counter-current exchange more efficient than parallel flow?
It maintains a concentration gradient across the entire length of the gill, maximising oxygen absorption.
How do gill filaments and lamellae aid gas exchange in fish?
Gill filaments increase surface area, while lamellae (on the filaments) provide a thin diffusion pathway and maintain a diffusion gradient.
How do plants control gas exchange?
Through stomata, which open and close depending on water availability and light intensity.
What are stomata?
Pores on the leaf surface that allow gas exchange.
What role do guard cells play in gas exchange?
Guard cells control the opening and closing of stomata.
How do guard cells open and close stomata?
Guard cells absorb water by osmosis, becoming turgid and opening the stomata. When they lose water, they become flaccid and close the stomata.
What adaptations do xerophytes have to reduce water loss?
Thick waxy cuticle, rolled leaves, sunken stomata, and hairs to trap moisture.
Why do xerophytes have sunken stomata?
To trap moist air and reduce the water potential gradient, minimising water loss.
What is the primary gas exchange surface in humans?
The alveoli in the lungs.
How are alveoli adapted for efficient gas exchange?
Large surface area, thin walls (one cell thick), and a rich capillary network to maintain a diffusion gradient.
What is ventilation?
The process of moving air in and out of the lungs to maintain a concentration gradient.
How does inhalation occur?
Diaphragm contracts and flattens, external intercostal muscles contract, thoracic volume increases, and pressure decreases, causing air to move in.
How does exhalation occur?
Diaphragm relaxes, external intercostal muscles relax, thoracic volume decreases, pressure increases, and air moves out.
What is pulmonary ventilation?
The total volume of air moved into the lungs in one minute.
How is pulmonary ventilation calculated?
Pulmonary ventilation = tidal volume × breathing rate.
What is tidal volume?
The volume of air inhaled and exhaled per breath during rest.
What is the function of the bronchi and bronchioles?
Bronchi carry air to and from the lungs, while bronchioles control airflow and lead to the alveoli.
How do alveolar walls maintain efficient gas exchange?
They are made of a single layer of epithelial cells to reduce diffusion distance.
What is the role of surfactant in the alveoli?
It reduces surface tension, preventing alveoli from collapsing.
How does smoking affect gas exchange?
It damages alveoli, reducing surface area and causing conditions like emphysema.
What is emphysema?
A condition where alveolar walls break down, reducing surface area and making gas exchange less efficient.
How does fibrosis affect gas exchange?
It thickens alveolar walls, increasing diffusion distance and reducing the rate of diffusion.
What is asthma, and how does it affect gas exchange?
Asthma causes inflammation and narrowing of airways, reducing airflow and oxygen uptake.
How is oxygen transported in the blood?
Oxygen binds to haemoglobin in red blood cells, forming oxyhaemoglobin.
What is the Bohr effect?
Increased CO₂ reduces haemoglobin’s affinity for oxygen, releasing oxygen more readily to tissues.
