B3.1 Gas Exchange Flashcards
(34 cards)
Define gas exchange.
Gas exchange is a vital function in all living organisms as it facilitates the interchange of materials required for metabolic reactions
Oxygen is required for aerobic respiration, whereby cells produce large amounts of chemical energy (ATP)
Carbon dioxide is a waste product of this process and excess levels must be removed from the organism
* In photosynthesising organisms, carbon dioxide is a required substrate for the synthesis of organic molecules via carbon fixation
Why gas exchange becomes more challenging with size?
As organisms increase in size, their volume increases much faster than their surface area.
This means that for larger organisms, there is less surface area available for gas exchange in relation to the volume that requires oxygen.
Compare gas exchange in smaller and larger organisms.
Smaller organisms
* For small organisms, such as bacteria and simple animals, the surface area-to-volume ratio is relatively high, making gas exchange through the surface of the organism efficient.
* Gases can diffuse across the surface and reach all cells quickly and easily.
Small organisms = High SA:V ratio, gas exchange is efficient.
Larger organisms
* As organisms increase in size, their volume (which requires oxygen) grows faster than their surface area (which facilitates gas exchange).
* For large organisms, the diffusion of gases becomes inefficient because the gases would have to travel longer distances to reach cells deep within the body.
Large organisms = Low SA:V ratio, less surface area for gas exchange compared to their volume.
Outline the adaptations of larger organisms for effective gas exchange.
Large surface area: Examples: alveoli in lungs, gill filaments in fish.
Thin barriers: Minimizes diffusion distance.
Moist surfaces: Gases dissolve in water for diffusion.
Permeable surfaces: Allow gases to pass freely.
Name 4 key properties of gas exchange surfaces.
Permeability
Thin tissue layers
Moisture
Large surface area
Outline the function of the key properties of gas-exchange surfaces.
Permeable to allow the movement of gases like oxygen and carbon dioxide.
Large surface area to volume ratio maximises the area available for gas diffusion
Thin tissue layers to minimize the diffusion distance
Moist surfaces to dissolve the gases and facilitate their diffusion
State the reason why concentration gradients must be maintained at exchange surfaces.
Gas exchange relies on diffusion, where gases move from high to low concentration.
For this to work, there must be a constant concentration gradient - oxygen needs to be high in the lungs and blood low, while carbon dioxide is high in the blood and low in the lungs.
State the three main processes for maintaining concentration gradients.
Dense capillary networks increase surface area.
Continuous blood flow keeps gases moving, preventing equilibrium.
Ventilation keeps external gradients intact by constantly refreshing oxygen and removing carbon dioxide.
Explain the role of capilaries in maitaining concentration gradients.
These networks ensure that oxygen can quickly be transported away from the exchange surface, and carbon dioxide can be transported to the surface for removal.
By continuously removing oxygen from the exchange surface and delivering carbon dioxide to be expelled, the blood helps maintain the concentration gradient.
Explain the role of continous blood flow in maitaining concentration gradients.
The continuous flow of blood through the blood vessels ensures that the gas-exchange surface is always exposed to a fresh supply of blood, which helps maintain the concentration gradient.
Continuous blood flow ensures that oxygenated blood is constantly removed from the exchange surface, keeping the partial pressure of oxygen low in the blood.
Explain the role of ventilation in maitaining concentration gradients.
Ventilation brings in fresh oxygen to replace the oxygen that has diffused into the blood and expels carbon dioxide to maintain a high concentration of CO₂ at the gas-exchange surface.
This continuous exchange ensures the maintenance of the concentration gradients necessary for efficient diffusion.
Explain the role of countercurrent exchange in maitaining concentration gradients in fish.
Fish utilize a countercurrent exchange mechanism, where water flows in the opposite direction to the blood flow in the gills.
This maintains a concentration gradient for oxygen across the entire length of the gill, maximizing oxygen absorption.
Outline the structures of mammalian lungs that are adapted to maximizing gas exchange.
High Surface Area: The large number of alveoli provides an enormous surface area for diffusion.
Short Diffusion Distance: The thin walls of alveoli and capillaries minimize the distance gases must travel.
Moist Surface with Surfactant: Moisture facilitates gas dissolution, while surfactant prevents alveolar collapse.
Dense Capillary Network: Close contact between alveoli and capillaries ensures efficient gas exchange.
Branched Airways: The bronchioles distribute air evenly and increase the total surface area for gas exchange.
What is gas exchange?
Gas exchange is the process by which oxygen and carbon dioxide are exchanged between living organisms and their environment.
What are three factors that determine the rate of diffusion in gas exchange?
The three factors that determine the rate of diffusion in gas exchange are:
* size of the respiratory surface
* concentration gradient
* diffusion distance
How does ventilation contribute to gas exchange?
Ventilation brings oxygen close to the gas exchange surface and removes carbon dioxide, helping to maintain concentration gradients.
How are the alveoli adapted for gas exchange?
The alveoli have thin walls to minimise diffusion distance, a good blood supply to maintain a steep concentration gradient and surfactant to increase the rate of diffusion.
How do bronchioles help regulate airflow into the lungs?
Bronchioles are lined with smooth muscle that can dilate when more air is needed and constrict when an allergen is present, regulating airflow.
What structure is found at the end of bronchioles?
Groups of alveoli are found at the end of bronchioles.
How do alveoli contribute to efficient gas exchange?
Alveoli provide a large surface area for gas exchange and are surrounded by an extensive network of capillaries.
What is the function of surfactant in the alveoli?
Surfactant lowers the surface tension in the alveoli, preventing them from collapsing and sticking together during expiration.
What maintains the concentration gradient between alveoli and blood?
Deoxygenated blood enters the capillary beds from a branch of the pulmonary artery while oxygenated blood leaves via a branch of the pulmonary vein, maintaining the concentration gradient.
What is ventilation and why is it important?
Ventilation is the process of breathing in and out, which is essential for effective gas exchange in the lungs by replacing older air with fresh air and maintaining concentration gradients.
Define inspiration in the context of ventilation.
Inspiration is the process of breathing in, which causes the volume of the chest to increase and air pressure to decrease until it is lower than atmospheric pressure.
