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The MCAT-BIO
PHYSIOLOGICAL BUFFERS & GAS EXCHANGE
| Question | Answer |
|---|---|
| What is physiological pH? | 7.4 |
| respiratory acidosis | retention of CO2 |
| respiratory alkalosis | loss of CO2 |
| metabolic acidosis | loss of HCO3 |
| metabolic alkalosis | loss of H3O |
| How does blood compensate for reduced uptake of oxygen? | increase heart rate and make more blood cx |
| What kind of rxn is the binding / releasing of oxygen from Fe? | redox |
| What does myoglobin do? Does it have quaternary structure? | -transfers oxygen from hemoglobin to muscle cell -no |
| How many oxygens can myoglobin bind to? | one |
| Does myoglobin exhibit cooperativity and Bohr effect? | NO |
| How is CO2 carried through blood? | 1. physical solution (plasma) 2. bicarbonate ion (RBC) 3. combined with hemo (carbamino cpds) |
| How to form bicarbonate? | CO2 enters RBC - meets carbonic anhydrase - combines with water to form carbonic acid - bicarbonate |
| Does gas exchange require ATP? | NO --> passive process |
| Pulmonary arteries turns into pulmonary ______ in the lungs. | capillaries |
| How can respiratory system adjust to high altitudes? | 1. breathe rapidly 2. make more RBC 3. develop more blood vessels 4. alter binding of hemo and oxygen |
| polycythemia | making more RBC |
| What is the oxygen pressure that enters lungs vs. pressure in alveoli? | 40 mmHg vs. 105 mmHg |
| Do we breathe out bicarbonate? | NO! Reverse rxn occurs in alevoli to produce CO2 |
| To balance electrostatic forces, what moves out of cx when bicarbonate is formed? | chloride |
| What is a buffer? | acid/base sponge that soaks up excess H+ or OH- |
| How does kidney fit into balance of carbon dioxide in blood? | increase / decrease amt of bicarbonate ion secreted into nephron |
| What is the shape of the O2-dissociation curve? | sigmoidal |
| What does the O2-dissociation curve depend on? | CO2 pressure, pH, temp, and 2,3-DPG |
| Why is the shape of the O2-dissociation curve sigmoidal? | positive cooperativity in hemo |
| What does a right shift mean? | at the same pressure of oxygen, less oxygen will be bound to Hb --> lower hemo's affinity for oxygen |
| What causes a right shift? | -increase in partial pressure of CO2 -decrease in pH -increase in temp -2,3-DPG (CADET) |
| What does a left shift mean? | at the same pressure of oxygen, more oxygen will be bound to Hb |
| What causes a left shift? | carbon monoxide and fetal hemoglobin |
| Does oxygen or carbon monoxide have greater affinity for Hb? | Carbon monoxide! --> 200 times stronger |
| torpor | energy conservation by having decreased arousal |
| aestivate vs. hibernate | torpor during warm months vs. cold months |
| Haldane Effect | oxygen-saturated Hb has reduced affinity for CO2 -facilitates transfer of CO2 from blood to lungs, tissues to blood |
| When hemo is attached to O2, is it reduced or oxidized? | reduced |
| How does reduced hemo (hemo with O2) act as a blood buffer? | accepts protons |
| Bohr Effect | increasing conc. of protons and CO2 will reduce hemo's affinity for O2 |
| How does bicarbonate in RBC turn back into CO2 in lungs? | In lungs, binding of O2 to Hb causes release of protons which combine with HCO3 |
| How does Hb know to get rid of oxygen? | -CO2 formation (aerobic) -lactic acid formation (anaerobic) --> greater effect |
| Under acidic conditions, how does Hb release O2? | protons bind to Hb and causes release of O2 |
| How does oxygen curve look for myoglobin? | linear --> no cooperativity and one subunit |
| What does fetal curve look like? | shifted left and up -at same pressure of O2, more O2 will be bound to Hb |
| What brain structure is involved in respiration? | medullar |
| What receptors monitor breathing rate? | chemoreceptors for oxygen and CO2 |
| What happens to breathing rate when acidosis? | body increases breathing rate to expel CO2 and raise pH |
| Carbonic Acid / Bicarbonate Buffer Eqn | CO2 + H2O --> H2CO3 --> H+ + HCO3- |
| Why is bicarbonate impt for maintaining homeostasis? | -excess protons can combine with bicarbonate and turn into CO2 to be expelled (maintains pH) -forms acid in stomach -neutralizes pH of chyme leaving stomach and entering small intestine |
| What is the predominate form CO2 is carried through the body as? | bicarbonate |
| Where is carbonic anhydrase located? | inside RBC |
| When bicarbonate from plasma enters RBC, what leaves? | chloride |
| Does pH decrease / increase when bicarbonate leaves? | decreases |
| Haldane effect: High O2 vs. low O2 | -high O2: enhanced unloading of CO2 -low O2: promote loading of CO2 onto hemo |
| Haldane Effect vs. Bohr Effect | -haldane: describes how O2 determines hemo's affinity for CO2 -Bohr: describes how CO2/H affect hemo for O2 |
| In lungs, high oxygen levels, does hemo affinity for CO2 decrease / increase? | decrease |
| Where does phosphoric acid come from? | nucleic acid and phosphopx breakdown |
| Can px act as buffers? | YES --> can absorb excess H+ (esp. amino and carboxyl groups) |
| Phosphate Buffer Eqn | H3PO4 -> H+ + H2PO4 -> H+ + HPO4 -> H+ + PO4 (H2PO4 / HPO4 is the main buffering region) |
| Why is fetal circulation complicated? | non-functional lungs and liver |
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