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Organisms must exchange ____ and ____ aka ______ gases. This is done via ______ along their concentration gradients. Gas exchange systems are made up of ______ and the ______ that ______ and ______ them.
- CO2 & O2
- respiratory gases
- ventilate & perfuse
- partial pressure: the concentration of a gas in a mixture
- barometric pressure: is the pressure exerted by the weight of air in the atmosphere of Earth (or that of another planet)
Fick's law of diffusion applies to all _____ _____ systems.
What is Q?
What is D?
What is A?
gas exchange systems
- Q: rate of diffusion
- D: the diffusion coefficient (a charac. of the diffusing substance, the medium (like water vs air) and temp.)
- A: the area where diffusion occurs
What are P1 & P2?
What is L?
What does (P1-P2)/L signify?
- P1 & P2: partial pressures of the gas at two locations
- L: the path length between the locations
- (P1-P2)/L: a partial pressure gradient
The _____ rate of diffusion of oxygen in water limits the ____ & _____ of species without internal systems for ____ ____. These species have evolved to have ______ surface areas, or _____ ______, or ________ _______ systems
- size and shape
- gas exchange
- central cavities
- specialized respiratory systems
_______ is easier to obtain from the air than from water
State 3 reasons why this is so.
- O2 content of air is higher than that of water
- O2 diffuses much faster through air
- Air and water must be moved by the animal over its gas exchange surfaces—requires more energy to move water than air
Respiratory gas exchange is a two-way process explain.
CO2 diffuses out of the body as O2 diffuses in
The concen. gradient of CO2 from air breathers to the environment is always ______. CO2 is _____ soluble in water and is easy for aquatic animals to _____.
Some respiratory systems have adaptations to maximize the exchange of O2 and CO2. Name 4 such adaptations
- Increased surface area (A)
- Maximized partial pressure gradients (P1-P2)
- Minimized diffusion path length (L)
- Minimize the diffusion that takes place in an aqueous medium (D)
Name 4 ways Surface area is increased
- External gills—also minimize the diffusion path length (L) of O2 and CO2 in water
- Internal gills—protected from predators and damage
- Lungs—internal cavities for respiratory gas exchange with air
- Tracheae—air-filled tubes in insects
Air enters the human lungs through the ____ ____ or the ______ ______, both of which join in the _______.
- oral cavity
- nasal passage
Below the pharynx, the ______ (at the beginning is the voice box or _____)leads to the _____
The trachea branches into two _____, then into _______, and then into _______ (the site of gas exchange)
Capillaries surround and lie between the ______, here the _____ path between _____ & ____ is less than two micrometers.
- blood & air
________ from smoking destroys alveoli
Respiratory gases are transported in the _____. Blood plasma carries _____ O2, however the blood contains molecules that _____ _____ to O2. O2 is picked up where its partial pressure is _____ and released where its partial pressure is ______.
- binds reversibly
Hemoglobin is protein with four ______ ______ and is an O2 ______
- polypeptide subunits
In hemoglobin, each polypeptide surrounds a _____ _____ that can bind a molecule of _____. One hemoglobin can bind up to ____ _____
- heme group
- four oxygens
The relationship between PO2 and O2 is that binds is ______. Low PO2 means one ______ binds O2.
one subunit binds and changes shape, making it easier for the next one to bind—the affinity for O2 is increased.
When _____ subunits are bound, a larger increase in PO2 is needed.
Myoglobin is a single ______ _____ in
muscles and can bind ___ molecule of O2. It has a ______ affinity for O2, binds it at low PO2 values when ______ molecules would release their O2
- polypeptide molecule
Myoglobin provides a reserve for high _______ demand for O2
The affinity of hemoglobin for O2 varies. Three
- Hemoglobin composition
- pH—in the Bohr effect, blood circulating through active tissues has a lower pH and H+ ions bind to the hemoglobin molecule in place of O2
- 2,3-bisphosphoglyceric acid (BPG)—also lowers the affinity for O2 (byproduct of glycolysis)
CO2 is transported ____ from the tissues after diffusing into the blood. In the blood plasma, CO2 is slowly converted into ______ ___. In endothelial cells and red blood cells ______ _______ speeds up the conversion.
- bicarbonate ions (HCO3-)
- carbonic anyhydrase
The conversion of CO2 to bicarbonate (2)
- keeps PCO2 low
- facilitates diffusion away from the tissues.
Some CO2 binds to _______ molecules. In the lungs the conversion reaction is _______, CO2 diffuses from the _____ into the _____ and is ______
Breathing is controlled in the _____ specifically the _____. In ______ and _______, the breathing rate is more sensitive to changes in PCO2 than to PO2. The PCO2 of blood is the _____ ______ ______ for breathing.
- humans and mammals
- primary metabolic feedback