Surface Area To Volume Ratio Flashcards
What are organisms doing in relation to the environment
They are constantly exchanging materials with their environment
What can microscopic/single celled organisms do
They can exchange all the substances it needs directly through the cell membrane
Why can these single celled organisms do this
Low rate of respiration as they are not very active organisms
The surface area of the cell membrane is relatively large compared to the volume of the cell (large SA:VOL ratio)
How is SA:VOL ratio calculated
SA/VOL
What is the formula for the surface area and volume of a sphere
4 pi r squared - surface area
4/3 pi r cubed - volume
What do single celled organisms have
A relatively large surface area to volume ratio, sot hey can transfer all the chemicals that they need across the cell membrane.
What do larger multicellular organisms have
A much smaller SA:VOL ratio
What have multicellular organisms evolved
They have evolved two specialised systems to compensate for
What are the two specialised systems that they have evolved
A specialised gas exchange surface with a very large surface area
A specialised transport system to carry molecules around their body
What is the first feature that all specialised exchange surfaces have in common + examples
Increased surface area - provides the area needed to exchange and it overcomes the limitations of the SA:VOL ratio of larger organisms
For example root hair cells in plant and the villi in the small intestine of animals
What is the second and third feature that all specialised exchange surfaces have in common
Thin layers - this means that the distances that substances have to diffuse are short making the process fast and efficient
Good blood supply - which means that substances are constantly delivered to and removed from the exchange surface maintaining the steep concentration gradient for diffusion
What is the fourth feature that all specialised exchange surfaces have in common
Ventilation to maintain diffusion gradient - where a ventilation system helps to maintain concentration gradients and makes the process more efficient.
