Gas Exchange

Question 1

How many steps are there in gas transport? What types are they?

Answer 1

Four steps of transport - two connective and two diffusive

Long distance transport by convection, short range across barriers by diffusion

Question 2

Where do the steps of gas transport take place in humans?

Answer 2

Breathing in the lung

Diffusion across gas exchanger in lung from air to blood

Second convective step in blood circulation

Diffusion from capillary to mitochondria in the tissue

Question 3

How does the partial pressure of O2 change through the exchange process?

Answer 3

The partial pressure gradually decreases as the O2 moves from air to lungs and through the circulation

Question 4

What is the relationship between lung area and metabolism?

Answer 4

Respiratory surface area is proportional to metabolic rate

Question 5

What is the equilibrium reaction with CO2 and bicarbonate?

Answer 5

CO2 + H2O H+ + HCO3-

Question 6

What are the two ways acid-base balance is regulated?

Answer 6

Ventilatory regulation of PCO2

Ion exchange with HCO3- (or H+) in gills or kidneys

Question 7

What is the equation for the gas law?

Answer 7

PV=nRT

Question 8

What is the percentage of O2 and CO2 in dry air?

How do you calculate PO2 if water vapor is present?

Answer 8

21% of air is O2
CO2 is negligible

PO2 = 0.21 x (barometric pressure - water vapor pressure)

Question 9

In what direction do gasses diffuse?

Answer 9

Gasses diffuse down partial pressure gradients not concentration

Question 10

What is the equation for concentration of oxygen?

Answer 10

cO2 = PO2 x a (or B)

a = solubility
B = capacitance

Question 11

What is the general equation for convective transport in a gas exchange organ? What do the variables stand for?

Answer 11

M = V x (Ci - Co)

M = rate of O2 uptake or CO2 excretion
V = Ventilation (breathing rate)
Ci = concentration of inhaled gas

Question 12

How many lobes are in each side of the lungs?

Answer 12

Right lung has three lobes, left lung has two lobes

Question 13

What are tidal volume and vital capacity?

What is risidual volume?

Answer 13

Tidal volume is the normal inspiration and expiration

Vital capacity is the maximum inspiration and expiration

Volume that cannot be expired in order to keep the lungs from collapsing

Question 14

How to the ribs function in ventilation?

Answer 14

Intercostals rotate ribs
External rotate ribs up and out
Internal rotate ribs down and in

Question 15

How do birds ventilate differently from mammals?

How do frogs ventilate differently?

Answer 15

They have two air sacs - caudal and cranial. The air travels into caudal, across the bronchi and into the cranial. On exhalation the air moves from the cranial, out.

Frogs have no diaphragm, so they take a mouthful of air and push it into the lung

Question 16

How do trachea work in aquatic insects?

Answer 16

There are many different styles of breathing:

Some exchange gas with the outside air by breaking the surface

Some create a bubble of air to travel in

Some actually have gills

Question 17

What type of exchanger are fish gills? How many layers of folding are there and what are they?

Answer 17

They are countercurrent exchangers

3 layers of folding

• arches
• filaments
• lamellae

Question 18

How does the ventilation of fish gills work?

Answer 18

The buccal and opercular cavities are both filled at the same time when the mouth is open, but the operculum is closed.
The mouth closes, and the operculum opens to allow water from opercular cavity to leave and from buccal cavity to move across the gills

Question 19

What is the ventilated pool model? What is the pressure of oxygen like?

Answer 19

Each inhalation is mixed with a pool of gas remaining in the lung, with the PO2 in the lung remaining almost constant

Pexpired = Palveolar = Parterial

Question 20

How do water breathers compensate for the needed volume of water to get enough air?

Answer 20

They are able to extract 80% of oxygen from the water, compared to 33% in humans, so they don’t need to move as much water through. They also have a much lower metabolic rate

Question 21

What is ram ventilation? What animals do they take place in?

What are the one exception to flow-through rules?

Answer 21

High speed fish and sharks

When they swim quickly, they use that speed and locomotion muscles for ventilation

Lampreys use tidal ventilation

Question 22

What are the three features of hemoglobin binding? Briefly explain them

Answer 22

Reversible binding - tertiary structure causes pockets for O2

Sigmoid curve - Hemoglobin can only bind so much oxygen, when it carries four molecules it is saturated. The more O2 bound, the higher the affinity is to bind more

Affinity - High affinity means that O2 binds to Hb at low PO2 (P50). Loading is favoured by high affinity

Question 23

Explain Bohr shift and Haldane shift

Answer 23

Bohr shift is the effect of protons on O2 binding to Hb - favours dissociation of O2

Haldane shift is effect of O2 binding on protons - favours dissociation of protons to make Hb more acidic

Question 24

What are the three factors of pigment concentration?

Answer 24

Metabolic rate - high metabolic rate means high concentration

Type of circulation - open (lower concentration) or closed

Diving - Hb used for O2 storage and transport in divers, have very high concentration

Question 25

How is most CO2 carried in the blood?

Answer 25

As HCO3- with H+ being carried on Hb

Question 26

What is the equation for metabolic rate?

Answer 26

MO2 = Q x (CaO2 - CvO2)