Exchange Surfaces Flashcards
Explain diffusion
Diffusion is the net random movement of particles from an area of higher concentration to an area of lower concentration down a concentration until an equilibrium is reached.
Why may diffusion alone be usually enough to satisfy the needs of single celled organisms.
This is due to single celled organisms low metabolic activity / short diffusion pathway / SA:V ratio is high
Explain how increased surface area supports gas exchange and provide examples
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 vili in the small intestine of mammals.
Explain how thin layers supports gas exchange and provide examples
These mean that 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.
Explain how good blood supply supports gas exchange and provide examples
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 to the lungs, the gills for fish and the vili of the small intestine.
Explain how does ventilation work to maintain the diffusion gradient to supports gas exchange and provide examples
For gases, a ventilation system also helps maintain concentration gradients and makes the process more efficient.
For example the alveoli and the gills for a fish where ventilation means a flow of water carrying dissolved gases.
Why do microscopic organisms exchange all substances it needs directly through the cell membrane
Has a relatively low rate of respiration (not very active organisms)
The surface area of the cell membrane of the amoeba is relatively large ,compared to the volume of the cell.
How to calculate surface area to volume ration
Surface area to volume ratio=
Surface area
———————
Volume
What is the trend with SA:V as organism get larger
As organisms get larger the surface area to volume ratio decreases
What systems do multicellular organisms have to combat the small SA:V
Specialised gas exchange surface with a large SA
Specialised transport systems in order to carry molecules around the body
Explain what is a spirometer
It is a device used to measure lung volume. A person using a spirometer breathes in and out of the airtight chamber, thus causing it to move up and down, leaving a trace on a graph which can then be interpreted.
Define vital capacity
Vital capacity - the maximum volume of air that can be inhaled or exhaled in a single breath. Varies depending on gender, age, size as well as height
Define tidal volume
Tidal volume - the volume of air we breathe in and out at each breath at rest
Define breathing rate
Breathing rate - the number of breaths per minute, can be calculated from the spirometer trace by counting the number of peaks or troughs in a minute
Define residual volume
The volume of air which is always present in the lungs is known as the residual volume.