B2.2 The Challenges Of Size Flashcards
What is a surface area to volume ratio?
The surface area per unit of volume of an object
The larger the organism…
The smaller the surface area to volume ratio
What do lungs have to maximise the rate of diffusion of oxygen into the blood stream?
Many alveoli
State the adaptations of alveoli (why useful for diffusion) (3)
- very thin alveolus walls- short distance
- good blood supply, maintains concentration gradient
- spherical shape gives relatively large surface area
What is villi?
finger-like projections which cover the inside of your small intestine
What is the function of the villi?
- enhance the absorption surface area
How are villi adapted?
- filled with blood capillaries, the blood constantly moving in them means that a steep concentration gradient is maintained
- one cell thick for faster diffusion into the blood
Where is urea removed ands why is it?
Urea is so toxic that it must be transported to the kidney where it’s removed
How is urea made?
Your liver produces urea when it breaks down excess amino acids
Why is the function of the xylem tubes in plant transport system?
Carries water and mineral ions around a plant
What is the function of phloem tubes in plant transport system?
Transport sugars and amino acids
Explain why simple organisms, such as Amoeba, do not require a transport system. (2)
-The resources it needs to survive can just be transported through the cell membrane, and the waste materials too
-Their large surface area to volume ratio means it has a short diffusion pathway
why do multicellular organisms require adapted exchange surfaces? (2)
because their surface area to volume ratio is low
- so diffusion cannot occur fast enough to meet the organism’s demand
how have alveoli adapted to maximise diffusion? (4)
steep concentration gradient (ventilation through air)
thin alveoli walls (one cell thick - easy diffusion)
high surface area to volume ratio
capillaries close to the alveoli (less distance needed to travel)
how is the small intestine adapted to maximise diffusion rate?
finger like villi on walls
