Gas Exchange Flashcards
Do large organisms have a high or low SA:V and why
Low, have a large volume for their surface area=most cells do not have a surface in contact with their environment
How to calculate SA:V
Divide SA by V, volume is 1
What is metabolic demand
How much oxygen and nutrients an organism needs to take in daily to respire enough to maintain the metabolic rate
Characteristics of gas exchange in unicellular organisms and why
-large SA:V= can rely on diffusion of gases through cells on surface(all cells have surface exposed to outside)
-short diffusion distance as little distance to get from outside to centre of organism so diffusion fast
Disadvantages of diffusion through cells on surface in unicellular
-lose heat energy and water quickly as diffusion is so rapid meaning organisms cannot survive extreme heat/cold
Characteristics of gas exchange in multicellular organisms
-small SA:V so cannot absorb enough substances to supply large volume through small outer surface
-diffusion distance is large, too slow to efficiently supply all cells
Advantages of gas exchange in multicellular
Lose less energy as heat so can survive more easily in cold environments
How do multicellular organisms get oxygen and nutrients to inner cells
Exchange systems eg circulatory and respiratory systems
Adaptations a small organism could have for surviving in cold environment
-thick fur
-streamlined compact body shape
-blubber
Adaptations a large organism could have to survive hot environment
-large ears(increase surface area)
-kidney adaptations mean produce less urine to compensate for water lost through evaporation
Three factors included in Fick’s law of diffusion and how they relate to rate of diffusion
-SA=directly proportional to ROD
-concentration gradient= ROD directly proportional to difference in concentration across gas exchange surface
-thickness of gas exchange surface= ROD inversely proportional
Fick’s law equation
Rate of diffusion proportional to SA x concen gradient / thickness of membrane
Role of alveoli
Provide a large surface area within the lungs for the exchange of gases between the air and the blood
Adaptations of alveoli
-large SA
-numerous capillaries around alveoli
-steep concentration gradient for oxygen between alveolar air and blood
-thin walls of alveoli and capillaries=short diffusion distance
