3.1.1- Exchane Surfaces Flashcards
Define what the surface area to volume ratio is.
The surface area is divided by its volume and expressed as a ratio. It is an important concept.
In order to survive, all organisms need a constant supply of _______ and ________.
Oxygen
Nutrients
Why do all organisms need to remove waste products?
To prevent them building up and becoming toxic.
Explain why some small and single felled organisms do not need an exchange system.
The cytoplasm is very close to the environment they live in- therefore diffusion can simply take place across the single cell later to supply enough oxygen to keep the cells alive and active.
Explain how diffusion pathway length affects the rate of diffusion.
The longer the pathway, the slower the rate of diffusion
Explain two reasons why large, multicellular organisms have an exchange system.
They have many layers of cells that create a long diffusion pathway that massively slows dissuasion and the surface area to volume ratio is too low to supply enough oxygen to the body.
Give two examples of waste products in the human body that are needed to get rid of.
Urea
Co2
In the surface area to volume ratio, which one should always be presented as ‘1’?
Volume.
If an organism has a large surface area to volume ratio, it means…
Their surface area is large enough to supply their cells with enough oxygen, therefore there is no need for an exchange surface.
Explain why larger organisms have a smaller surface area to volume ratio.
As surface area increases, so does volume- but volume increases faster.
Explain how the level of activity of an organism affects its need for an exchange system.
The cells of a more active organism needs a larger supply of oxygen and nutrients to its cells for an energy supply for this organism. This activity used energy from food and requires oxygen to release the energy in aerobic respiration. The more active, more chance of needing exchange system to supply more oxygen.
What are the four features of a good exchange surface for an organism?
- a good fast blood supply to maintain conc gradient
- large surface area
- thin barrier for small diffusion path
- moisture
Explain why a large surface area is a good feature of an exchange surface.
It provides more space for molecules to pass through- can be achieved by golfing the walls and membranes and walls- e.g; root hairs in plants.
explain why a good blood supply is a feature of a good exchange surface for gases in organisms.
It keeps the concentration gradient stable and high. It removes molecules from the demand side (removes oxygen when flows away) to maintain gradient between alveoli and blood and keeps a stable gradient so diffusion an occur properly.
explain why a thin barrier is a feature of a good gas exchange surface.
It reduces the diffusion distance in the pathway- keeping the rate of diffusion higher. E.g; alveoli in the lungs (one cell thick).
