Flashcards in 3.3.1 Surface area to volume ratio Deck (22):
The name given to the environment surrounding a cell
Single celled organisms can match their metabolic demands by
Exchange of materials in living organisms occurs at ..
exchange surfaces e.g. lungs, intestine
How much material that needs to be exchanged in an organism depends on
its size and its metabolic rate
Substances a cell exchanges with its environment include
oxygen, carbon dioxide, nutrients (glucose)
Exchange of materials in living organisms takes place via (4 types of transport)..
As an organism gets larger what happens to its surface area to volume ratio?
its gets smaller - less efficient exchange.
Special exchange surfaces therefore required i.e. lungs
How do larger organisms cope with their increasing size?
They have specialised exchange surfaces - which have large surface area:volume ratio!
they are flat and thin therefore no cell is too far away from the surface
What is ficks law?
diffusion rate is directly proportional to surface area x difference in concentration divided by length of the diffusion pahway
How are specialised exchange surfaces adapted?
1. Large surface area to volume ratio
2. Thin - short diffusion pathway
3. Selectively permeable
4. Extensive blood supply to maintain concentration gradient
single celled organisms SA: volume ratio is described as
large surface area to volume ratio
single celled organisms obtain their nutrients via..
Why are insects usually small
their tracheal system relies on diffusion, for this to be efficient the diffusion path needs to be short and this is only achieved if the insects are small
If a cube had a side length of 1cm, what would it's SA be?
If a cube had a side length of 1cm, what would it's volume be?
What is the SA:V ratio of a cube with a side of 1cm
How do you calculate the volume of a sphere?
4/3 x 3.14 x r3
(3.14 = pi, r = radius)
How do you calculate the surface area of a sphere?
4 x 3.14 x r2
(3.14 = pi, r = radius)
List 4 features of specialised exchange surfaces
1. Large SA - increases rate of exchange
2.Thin - short diffusion distance
3. Selectively permeable - allows selected materials to cross
4. Diffusion gradient maintained - eg by movement of medium - blood, air
Remember substances not only have to move into cells, they have to move into organelles too.
What would move into mitochondria and why?
Oxygen and glucose for (aerobic) respiration
explain the relationship between size and surface area to volume ratio in organisms
as size increases, SA:volume ratio decreases