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BIOL 271 / BIOL271 Final Exam (Latest 2026/2027
Update) Microbiology | Verified Questions & Answers
| Grade A | 100% Correct – Portage Learning
2 types of bulk flow
1) ventilation: moving medium over respiratory surface
2) circulation: transport gasses in the circulatory system
What is the equation for bulk flow (law of bulk flow)
Q = ∆P/R
Poiseuille's Law concerns what factors
change in pressure, radius, viscosity of fluid, length of tube
changing what factor would result in the greatest change in flow
changing radius
according to poiseuille's equation, changing what factors would result in better flow
decreasing length of tube, decreasing viscosity of fluid, increasing radius,
What does Poiseuille's Law state?
more detailed version of bulk flow and the factors that effect flow
what is diffusion coefficient - and which equation is it involved in
(D) - each molecule has its own chemical properties where some move more readily than others
- it is concerned in fick's equation - when calculating diffusion rate
How does surface area affect the rate of diffusion?
larger surface area = more diffusion can cross = which will increase flow
when discussion flow in terms of gasses, which factor is considered instead of this other one
pressure instead of concentration
what will improve diffusion rate?
increasing surface area, high diffusion coefficient of the molecule, and increasing energy
gradients, decreasing diffusion distance
,what gas is highest in concentration
nitrogen followed by oxygen then argon then carbon dioxide
what is the pressure exerted by a gas related to?
number of moles the gas has and the volume of the chamber
What does Henry's Law state?
Gas molecules in air must first dissolve in liquid to diffuse into cell
why is it that even if number of molecules of oxygen is lower inside than outside a container -
they could still be at equilibrium in VS out
Because partial pressures are equal in and out despite concentration not being the same
what compartment is most soluble for oxygen and how do you know
cell membrane because if you measure partial pressure in VS out - would be at equilibrium
where there is no net movement
what does grahm's law state?
diffusion rate is proportional to solubility of gas but inversely proportional to root of molecular
weight
combining all 3 laws (ficks, henrys, grahm's) what factors are required for increasing diffusion
rate
increase SA, increase D, increase solubility, decrease MW, decrease diffusion distance (X)
compare solubility of oxygen VS carbon dioxide in air and in water
oxygen and carbon dioxide are equal in solubility in air but oxygen is way less soluble in water
than carbon dioxide
what happens to the volume when you pull syringe in water
volume does not change and will only change if you open valve (which will decrease pressure by
increasing volume)
what happens to SA to volume ratio when animal grows
decrease in ratio of SA to volume, volume will increase will SA will decrease - less SA for
diffusion and increases diffusion distance
why is it that large animals can't rely on diffusion
because small surface area + large diffusion distance
, 2 reasons why metabolic rate must decrease as animal gets bigger
1) animal would over heat because not enough surface area to dissipate heat from metabolic rate
2) demand of nutrients is too high to highly metabolic tissues
what are the 3 respiratory strategies
1) move external medium through the body
2) diffusion of gasses across body surface which is accompanied by circulatory transport
3) diffusion of gasses across specialized respiratory surfaces then accompanied by circulatory
system (gills and lungs as specialized respiratory surfaces)
what are the requirements for strategy 2) of the 3 respiratory strategies
to have moist and thin skin because gasses need to dissolve through skin then moved around by
bulk flow
what are the 3 types of ventilation
1) non-directional: medium moves across respiratory surfaces in an unpredictable pattern
2)tidal: medium enters the same way it exits
3) unidirectional: medium enters one point and exits another
what effects the efficiency of gas exchange
movement of medium at respiratory surface and movement of blood through respiratory surface
(because medium and blood interacts)
in nondirectional ventilation: compare thin respiratory surface VS thick respiratory surface
thick respiratory surface means that when the first layer of O2 is picked up by medium, there is
now a boundary layer where there is no O2. Now the diffusion distance is greater which reduces
rate of diffusion = decreased O2 picked up by blood compared to thin respiratory surface
what could cause a thick respiratory surface
by disease that cause a thick mucus layer - decrease diffusion
what happens to the O2 concentration in tidal ventilation
as PO2 gets picked up by blood from the medium, PO2 decreases from the medium because it is
limited to per breath
what are the 3 types of flow of blood in unidirectional ventilation and which why is most
efficient
1) concurrent
2)countercurrent
3)crosscurrent
most efficient way is countercurrent
water VS air: in terms of ventilation
water is more dense and viscous than air so it is harder to ventilate water and high energy
BIOL 271 / BIOL271 Final Exam (Latest 2026/2027
Update) Microbiology | Verified Questions & Answers
| Grade A | 100% Correct – Portage Learning
2 types of bulk flow
1) ventilation: moving medium over respiratory surface
2) circulation: transport gasses in the circulatory system
What is the equation for bulk flow (law of bulk flow)
Q = ∆P/R
Poiseuille's Law concerns what factors
change in pressure, radius, viscosity of fluid, length of tube
changing what factor would result in the greatest change in flow
changing radius
according to poiseuille's equation, changing what factors would result in better flow
decreasing length of tube, decreasing viscosity of fluid, increasing radius,
What does Poiseuille's Law state?
more detailed version of bulk flow and the factors that effect flow
what is diffusion coefficient - and which equation is it involved in
(D) - each molecule has its own chemical properties where some move more readily than others
- it is concerned in fick's equation - when calculating diffusion rate
How does surface area affect the rate of diffusion?
larger surface area = more diffusion can cross = which will increase flow
when discussion flow in terms of gasses, which factor is considered instead of this other one
pressure instead of concentration
what will improve diffusion rate?
increasing surface area, high diffusion coefficient of the molecule, and increasing energy
gradients, decreasing diffusion distance
,what gas is highest in concentration
nitrogen followed by oxygen then argon then carbon dioxide
what is the pressure exerted by a gas related to?
number of moles the gas has and the volume of the chamber
What does Henry's Law state?
Gas molecules in air must first dissolve in liquid to diffuse into cell
why is it that even if number of molecules of oxygen is lower inside than outside a container -
they could still be at equilibrium in VS out
Because partial pressures are equal in and out despite concentration not being the same
what compartment is most soluble for oxygen and how do you know
cell membrane because if you measure partial pressure in VS out - would be at equilibrium
where there is no net movement
what does grahm's law state?
diffusion rate is proportional to solubility of gas but inversely proportional to root of molecular
weight
combining all 3 laws (ficks, henrys, grahm's) what factors are required for increasing diffusion
rate
increase SA, increase D, increase solubility, decrease MW, decrease diffusion distance (X)
compare solubility of oxygen VS carbon dioxide in air and in water
oxygen and carbon dioxide are equal in solubility in air but oxygen is way less soluble in water
than carbon dioxide
what happens to the volume when you pull syringe in water
volume does not change and will only change if you open valve (which will decrease pressure by
increasing volume)
what happens to SA to volume ratio when animal grows
decrease in ratio of SA to volume, volume will increase will SA will decrease - less SA for
diffusion and increases diffusion distance
why is it that large animals can't rely on diffusion
because small surface area + large diffusion distance
, 2 reasons why metabolic rate must decrease as animal gets bigger
1) animal would over heat because not enough surface area to dissipate heat from metabolic rate
2) demand of nutrients is too high to highly metabolic tissues
what are the 3 respiratory strategies
1) move external medium through the body
2) diffusion of gasses across body surface which is accompanied by circulatory transport
3) diffusion of gasses across specialized respiratory surfaces then accompanied by circulatory
system (gills and lungs as specialized respiratory surfaces)
what are the requirements for strategy 2) of the 3 respiratory strategies
to have moist and thin skin because gasses need to dissolve through skin then moved around by
bulk flow
what are the 3 types of ventilation
1) non-directional: medium moves across respiratory surfaces in an unpredictable pattern
2)tidal: medium enters the same way it exits
3) unidirectional: medium enters one point and exits another
what effects the efficiency of gas exchange
movement of medium at respiratory surface and movement of blood through respiratory surface
(because medium and blood interacts)
in nondirectional ventilation: compare thin respiratory surface VS thick respiratory surface
thick respiratory surface means that when the first layer of O2 is picked up by medium, there is
now a boundary layer where there is no O2. Now the diffusion distance is greater which reduces
rate of diffusion = decreased O2 picked up by blood compared to thin respiratory surface
what could cause a thick respiratory surface
by disease that cause a thick mucus layer - decrease diffusion
what happens to the O2 concentration in tidal ventilation
as PO2 gets picked up by blood from the medium, PO2 decreases from the medium because it is
limited to per breath
what are the 3 types of flow of blood in unidirectional ventilation and which why is most
efficient
1) concurrent
2)countercurrent
3)crosscurrent
most efficient way is countercurrent
water VS air: in terms of ventilation
water is more dense and viscous than air so it is harder to ventilate water and high energy
