Module 3- Exchange and transport Flashcards
Give an example of an organism that requires diffusion to provide all of its oxygen?
The microscopic organism Amoeba.
Why is diffusion alone enough to supply the needs of single-celled organisms?
The metabolic activity of a single-celled organism is usually low, so the oxygen demands and carbon dioxide production of the cell are relatively low.
The surface area to volume(SA:V) ration of the organism is large.
Why do muscle cells have a build-up of carbon dioxide?
The oxygen demands of muscle cells when used to contract and move the organism through the water mean that they are used a lot and therefore produce a lot of carbon dioxide.
What is the challenge for diffusion in an organism?
Diffusion distance. The larger the organism the greater the diffusion distance between the area of the organism that require delivery and removal of gases. Gases cannot be exchanged fast enough or in large amounts for the organism to survive.
What does the SA:V ratio affect in an organism?
An organisms ability to exchange materials with the environment.
What is the formula to calculate the surface area of a sphere?
4πr^2
What is the equation to calculate the volume of a sphere?
4/3 πr^3
What should you take the value of π to be?
3.14
What happens to the SA:V ratio when the organism gets bigger?
The bigger the organism, the smaller the surface area to volume ratio becomes, and the distances need to travel from the outside to reach the cells at the centre of the body get longer. This makes it harder to absorb enough oxygen through the available surface area to meet the needs of the body.
What are the 4 features of an effective exchange surface?
Increased surface area
Thin layers
Good blood supply
Ventilation to maintain diffusion gradient.
Why is increased surface area an effective feature of an exchange surface?
It provides the area needed for exchange and overcomes the limitations of the SA:V ratio of larger organisms. Examples include root hair cells in plants and the villi in the small intestine of mammals.
Why are thin layers an effective feature of an exchange surface?
These mean the distances that substances have to diffuse are short, making the process fast and efficient. Examples include the alveoli in the lungs and the villi of the small intestine.
Why is a good blood supply an effective feature of an exchange surface?
The steeper the concentration gradient, the faster diffusion takes place. Having a good blood supply ensures substances are constantly delivered to and removed from the exchange surface. This maintains a steep concentration gradient for diffusion. For example the alveoli of the lungs, the gills of a fish, and the villi of the small intestine.
