AS Booklet 5- Organisms and Exchange Flashcards
What type of substances does a cell exchange with the environment?
Out: CO2, heat, waste products.
In: O2, nutrients (glucose).
What is SA:V? Why is it important in diffusion?
Surface Area : Volume relates to short or long diffusion pathways. The smaller the organism, the larger surface area to volume ratio. Larger SA:V means longer diffusion pathway so organism must adapt exchange structures to reduce diffusion pathway to maintain adequate diffusion rates.
Where does gaseous exchange take place in a mammal?
Describe the structure
In the lungs.
Trachea: supported by incomplete rings of cartilage to prevent collapsing during pressure changes during ventilation.
Divides into two bronchi, divide into bronchioles iwith alveoli at the end.
O2 not just O on its own so not the most efficient (fish has most efficient system).
What is Fick’s Law?
Distance (diffusion pathway)
It is directionally proportional to rate of diffusion.
How are Alveoli adapted for gas exchange?
- Shape and large umber so large SA.
- Fluid lining so gases can dissolve and diffuse across.
- Two cell layers between blood and air so short diffusion pathway. Single layer of flattened epithelial cells (alveolar wall). Single layer of endothelial cells (capillary wall).
- Network of capillaries around alveoli so large SA for diffusion in and out of blood.
- Circulatory system maintains high diffusion gradient by transporting deoxygentaed blood into lungs and then oxygenated away immediately.
- Ventilation mechanism maintains high diffusion gradient by providing air with high O2 conc. and taking low O2 conc. air away.
How does gas exchange occur in humans?
- O2 in alveolar air space dissolves in fluid lining of epithelium.
- O2 diffuses across flattened epithelial cells of alveolus an endothelial cells. Short diffusion pathway and distance.
- O2 combines with haemoglobin in red blood cells to form oxyhaemoglobin, oxygenated blood transported away from lungs.
- CO2 diffuses in opposite direction into alveolar space.
- Blood flow ensures deoxygenated blood reaches alveoli and oxygenated blood removed to maintain a high diffusion pathway.
- Ventilation mechanism constantly replenishes air in alveolar space so high O2 and low CO2 conc., maintains a high diffusion gradient.
What is the ventilation mechanism in mammals?
Inspiration: Active process.
- External intercostal muscles contract (int. relax), pulls ribs up and out. Diaphragm contracts causing diaphragm to flatten.
- Increases volume of thorax.
- Pressure inside lungs decrease below atmospheric pressure so air enters lungs along pressure gradient.
Expiration: Passive process.
- Internal intercostal muscles contract (ext. relax), pulls ribcage down and in. Diaphragm relaxes.
- Decreases volume of thorax.
- Pressure inside lungs increases above atmospheric pressure and air forced out of lungs.
- Elastic recoil of lung tissue helps force air out.
What risk factors within lifestyle can affect health?
Poor diet, lack of exercise, smoking, drinking excessive alcohol, occupation. Air pollution.
Where does gaseous exchange take place in insects?
Describe the structure
Tracheal system.
Spiracles-tracheae-tracheoles-cells
How does gaseous exchange take place in insects?
- Spiracles on insect’s surface, have valves so they can close to reduce water loss.
- Spiracles lead to tracheae, held open by spiral bands of cuticles. Trachea branch to tracheoles.
- O2 diffuses from air, through spiracles along trachea and tracheoles into cells.
- Tracheoles are thin, provides short diffusion pathway. High in number so large SA.
- O2 diffuses into cells through cell membrane of tracheole. CO2 leaves insect’s cells and travels to atmosphere by reverse pathway.
Where does gaseous exchange happen in fish?
Describe the structure
In the gills.
Lamellae with filaments.
How are the lamellae adapted to gas exchange?
Large surface area as large number of hill filaments which contain MANY lamellae.
Short diffusion pathway because blood and water are separated by epithelial layer of hill lamellae + endothelial layer of blood capillaries.
How does gas exchange occur in fish?
- Water with high concentration of O2 flows over gills.
- Blood flows in opposite direction, high diffusion gradient is maintained as circulatory system pumps deoxygenated blood towards gills and oxygenated away.
- Ventilation mechanism provides continual glow of H2O over gills, brings O2 removes CO2 so high diffusion gradient maintained.
- Countercurrent system means deoxygenated blood meets with water at higher O2 conc. so high diffusion gradient is maintained along whole length of lamellae and equilibrium is not reached.
How and where does gaseous exchange occur in plants?
Each cuticle allows little gas exchange so stomata, mesophyll cells and air spaces are main components.
- Stomata (pores in epidermis) are surrounded by two guard cells.
- Gases diffuse in and out via stomata.
- Leaves are thin so short diffusion pathway.
- Gases dissolve in moist cell walls of mesophyll cells.
- Gases diffuse across cell wall and membrane of mesophyll cells.
- Respiration and Photosynthesis maintain diffusion gradients by using/producing O2 and CO2.
What is the rule of SA:V?
As the size of an organism increases, the SA:V decreases.
