SA:Vol and Gas exchange Flashcards
What is tissue fluid?
The environment around cells of multicellular organisms. The majority of cells are too far from exchange surfaces for diffusion alone to supply their tissue fluid with the various materials needed to keep its composition relatively constant
Do organisms with a high metabolic rate require a large or small SA:Vol? Why?
Larger SA:Vol because they will exchange more materials
What happens to the SA:Vol as an organism gets bigger?
Decreases
Larger organisms have a ……. surface area to volume ratio. Smaller organisms have a ……. surface area to volume ratio
Larger organisms have a smaller surface area to volume ratio. Smaller organisms have a larger surface area to volume ratio
Why can single celled organisms allow molecules to move through the cell surface membrane by diffusion and active transport alone?
Because they have a large enough SA:Vol that is adequate
Why do multicellular organisms need specialised gas exchange surfaces?
Have a small SA:Vol which is not adequate to obtain sufficient molecules eg oxygen. The diffusion distance is too great and outer cells will use up the then and nutrients before they reach the inner one. Needs to be overcome by having specials gas exchange surfaces eg lungs/gills
Why do more active animals require more respiration?
Because they require more oxygen and glucose to supply energy for movement and maintain their body temperature
How are respiratory gases (give examples) interchanged?
Simple diffusion
Eg carbon dioxide and oxygen
How are nutrients (give examples) interchanged?
• glucose and amino acids = by facilitated diffusion or active transport (when against conc gradient)
• fatty acids/vitamins/ minerals = simple diffusion
How are excretory products (name examples) interchanged?
Simple diffusion
eg Urea and carbon dioxide
What effect does a large surface area have on gas exchange?
Increases diffusion rate
What effect does thin walls have on gas exchange?
Short diffusion distance
What effect does a selectively permeable membrane have on gas exchange?
Oxygen and carbon dioxide can diffuse freely through phospholipid bilayer
What effect does good ventilation/ movement of surrounding medium (water) have on gas exchange?
Maintain steep concentration/ diffusion gradient
What effect does a good transport system (blood supply)have on gas exchange?
Maintain steep concentration/diffusion distance
What is the equation explaining how diffusion is affected?
