Explain, step by step, the mechanisms for ATP production and pH regulation in a bluefin tuna during their annual migration and during foraging.
-Migration: red muscle sustains cruising swimming (Obtains ATP from aerobic metabolism, Highly efficient, moderate speeds, Mitochondrial sink = little intracellular acidification)
Foraging: white muscle sustains powerful swimming (anaerobic, high intensity fast burst swimming, Obtains ATP from core glycolysis => LDH, Acidification: high buffering capacity, intra- and extra-cellular pH regulation)
What are the different mechanisms for intracellular and extracellular A/B balance?
- intracellular buffering: histidine and histidine-related compounds, phosphates
extracellular: proteins dissolved in the blood plasma of vertebrate animals (the most important is albumin) or proteins dissolved in the hemolymph of invertebrate animals (hemocyanin is most important) act as buffers, CO2/HCO3-buffer system
What are the most important intracellular and extracellular buffer systems?
- CO2/HCO3- buffer system is most important extracellular
- histidines are most important intracellular
Explain step by step the processes involved in O2 and CO2 uptake, transport, and excretion.
In tissues:
-CO2 from tissues diffuses into RBC
-~10% of the CO2 binds to hemoglobin (Hb)
-CA hydrates CO2 into H+ and HCO3-
-H+ binds to Hb (so pH is buffered)
-HCO3-is exported out of the RBC into plasma
At respiratory surface:
-CO2 from RBC and plasma diffuses into air or water
-CO2 unbinds from Hb => also diffuses out
-H+ unbinds from Hb
-HCO3-is imported from plasma into RBC
-CA dehydrates H+ and HCO3- into CO2 => diffuses out
- process also facilitates O2 uptake at gills / lungs
- Bohr Effect: Increased O2 affinity at high pH and low CO2
How do gases move throughout the circulatory system?
-diffuse into blood and RBCs, then are transported by convection and diffuse out again
What happens in RBCs at the gills and at the tissues? How are H+ and CO2 linked to hemoglobin O2 binding and unbinding, and to O2 uptake and delivery?
- RBC takes up CO2 from tissues(converts to other forms to be able to transport more), so lower oxygen affinity and oxygen in RBC is offloaded
- RBC excretes this CO2 and its associated forms in the lungs, making it once again favorable for O2 to bind to the hemoglobin
- Bohr Effect: Increased O2 affinity at high pH and low CO2, so changes to [H+] and [CO2] cause oxygen to bind or unbind to hemoglobin and then bind/unbind at their place of delivery in those differing conditions
What is the function of Carbonic Anhydrase in RBCs?
- speeds up the conversion between CO2 + H20 HCO3- + H+
- would take 2-3 minutes naturally, occurs in 1 second in the presence of CA
- can increase the speed by 1 million fold
What are the A/B regulatory organs in air-breathing animals? And in water-breathing animals?
- Air Breathers: lungs and kidney
- Water Breathers: gills and skin
How does CO2 and O2 solubility in water affect A/B regulation in water breathing animals? Why water breathing animals cannot regulate blood pH via changes in gill ventilatory rate?
- CO2 and O2 are similarly soluble in air, so changing ventilation speed can change the concentration of CO2 while not depriving the organism of O2
- in water, CO2 is far more soluble than O2
- Gills are normally ventilated at a high rate to extract as much O2 as possible
- If there is too much CO2 in the blood, fish cannot ventilate any faster to try blow off the excess CO2
- If there is too little CO2 in the blood, fish cannot ventilate slower, because they wouldn’t be able to take up enough O2
What are the different types of A/B stress?
- Metabolic Acidosis: reduced pH due to increased metabolic acid (H+) production (e.g. anaerobic metabolism)
- Metabolic Alkalosis: elevated pH, most times due to increased metabolic HCO3- (e.g. “post-feeding alkaline tide”)
- Respiratory Acidosis: reduced pH due to elevated CO2 levels (which increases [H+])
- Respiratory Alkalosis: elevated pH due to lower CO2 levels (which decreases [H+])
Give three examples of acid-base regulatory epithelia. Describe how they counteract blood acidosis and alkalosis
- kidney, gill, skin
- during blood acidosis, acid-secreting cells are activated, they excrete more H+ in the environment and absorb more HCO3- into the blood
- during blood alkalosis, base-secreting cells are activated, they excrete more HCO3- in the environment and absorb more H+ into the blood
