Specialised Exchange Surfaces
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55 Terms
Why do multicellular organisms need specialised exchange surfaces
To allow efficient diffusion of oxygen and carbon dioxide due to large size and high metabolic demand
Why can single celled organisms exchange substances directly
They have a large surface area to volume ratio and short diffusion distance
Why is diffusion insufficient in multicellular organisms
They have low surface area to volume ratio and long diffusion distances
What is surface area to volume ratio
Surface area divided by volume
What happens to surface area to volume ratio as size increases
It decreases
Why does a lower surface area to volume ratio reduce diffusion efficiency
Less surface area per unit volume for exchange
Why do active organisms need more oxygen
They have higher metabolic rate and need more respiration
What is an exchange surface
Specialised structure for exchange of substances between organism and environment
What is the function of exchange surfaces
To increase rate of diffusion of substances
What is a key feature of an efficient exchange surface
Large surface area
Why does a large surface area increase diffusion rate
More area for particles to cross
What is the role of thin exchange surfaces
Reduce diffusion distance
Why do thin surfaces increase diffusion rate
Shorter distance for molecules to travel
What is meant by steep concentration gradient
Large difference in concentration between two sides
Why is a steep concentration gradient important
It increases rate of diffusion
How is a concentration gradient maintained
By blood flow and ventilation
What is the role of blood supply in exchange surfaces
Removes and supplies substances to maintain gradient
What is the role of ventilation in exchange surfaces
Refreshes gases to maintain concentration gradient
What does selective permeability mean
Only certain substances can pass through membrane
What surrounds exchange surfaces
Selective plasma membrane
Why are exchange surfaces thin
To reduce diffusion distance
Why are exchange surfaces highly folded
To increase surface area
What is the main adaptation of alveoli
Large surface area thin walls and good blood supply
What is the main adaptation of root hair cells
Large surface area for absorption
What is the function of alveoli
Gas exchange in lungs
What gases are exchanged in alveoli
Oxygen and carbon dioxide
What is the function of specialised exchange surfaces in animals
To supply oxygen and remove carbon dioxide
Why do larger animals need ventilation systems
To maintain concentration gradients
What is the link between metabolic rate and gas exchange
Higher metabolic rate increases oxygen demand
What is diffusion
Movement of particles from high to low concentration
What limits diffusion in large organisms
Distance and low surface area to volume ratio
What is the role of capillaries in exchange surfaces
Carry substances to maintain gradients
What is required for efficient gas exchange
Large surface area thin barrier good blood supply ventilation
What is the function of epithelial cells in exchange surfaces
Form thin barrier for diffusion
Why is a thin diffusion barrier important
It reduces time taken for diffusion
What is meant by steep gradient maintenance
Keeping concentration difference high by continuous transport
Why do organisms need oxygen
For aerobic respiration
What is removed by gas exchange systems
Carbon dioxide
What happens if gas exchange is inefficient
Cells cannot respire efficiently
What is an example of a specialised exchange surface
Alveoli in lungs
What is another example of exchange surface
Fish gills
What is another example of exchange surface
Insect tracheal system
What is the key problem exchange surfaces solve
Slow diffusion in large organisms
What is the relationship between size and diffusion
As size increases diffusion becomes less efficient
What is ventilation
Movement of air or water over exchange surface
What is the function of blood flow in exchange surfaces
Transport gases and maintain gradient
Why is oxygen needed in cells
For ATP production in respiration
What is ATP used for
Energy for cellular processes
What is a key requirement for all exchange surfaces
Maximise rate of diffusion
What does increasing surface area do to diffusion rate
Increases diffusion rate
What does decreasing diffusion distance do
Increases diffusion rate
What does maintaining gradient do
Increases diffusion rate
What is the basic equation for surface area to volume ratio
Surface area divided by volume
Why do single celled organisms not need specialised systems
They rely on diffusion across surface
What is the main adaptation principle of exchange surfaces
Increase efficiency of diffusion