Term
| What is a substance called that can donate a hydrogen ion? |
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Definition
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Term
| What is a substance called that can accept a hydrogen ion (proton)? |
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Definition
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Term
| What is the formula for Keq? |
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Definition
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Term
| What is the equation for pH? |
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Definition
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Term
| What is the definition of a buffer? |
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Definition
| A substance that can donate or accept a H+ in solution thereby mitigating a change in pH. |
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Term
| What are the two parts of a buffer pair? |
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Definition
1. A weak acid
2. the conjugate base of that acid |
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Term
| What is the Henderson-Hasselbalch Equation? |
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Definition
| pH = pKa + log ([A-]/[HA]) |
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Term
| The ______ the pKa, the stronger the acid. |
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Definition
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Term
| T/F: The ability of a buffer to prevent changes in pH is highest when the pH is much higher than the pKa of the buffer. |
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Definition
| False. Ability of the buffer is highest when the pH and pKa are near to each other. |
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Term
| Buffers are most effective when pH is within what range of pK? |
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Definition
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Term
| If blood has a pH of 7.4 appropriate buffers should have pKs in what range? |
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Definition
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Term
| T/F: The higher the concentration of the buffer, the higher the buffer capacity. |
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Definition
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Term
| T/F: Changes in pH cannot affect the electrical charge on proteins and other molecules in the body. |
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Definition
| False. Changes in pH can affect the electrical charge by protonating anionic sites. |
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Term
| What are the effects of altering protein structure? |
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Definition
1. Decrease enzyme activity
2. Alterations in structural proteins
3. Dysfunction of transmembrane channels and pumps. |
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Term
| What are the effects of raised blood pH on albumin? |
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Definition
| When blood pH rises, additional anionic sites on albumin are exposed which bind C2+ and lower the free concentration of C2+. |
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Term
1. What is the range of extracellular fluid pH for survival?
2. What is the range of extracellular fluid pH for health? |
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Definition
1. 6.8 to 7.8
2. 7.35 to 7.45 (narrow range) |
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Term
| What are the 3 non-bicarbonate physiological buffers in the body in order of importance? |
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Definition
1. Hemoglobin (80% of non-bicarb buffering)
2. Plasma Proteins (20%)
3. Phosphate (2nd Proton Dissociation) |
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Term
| What is the major buffering element in hemoglobin? |
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Definition
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Term
| Which plasma protein has the highest concentration and highest buffering capacity? |
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Definition
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Term
| What is the acid and base in the Bicarbonate-CO2 Buffer? |
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Definition
CO2 - Acid
Bicarbonate, HCO3- - Base |
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Term
| What is the enzyme that catalyzes the formation of carbonic acid from carbon dioxide? |
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Definition
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Term
| In health, what are the normal bicarbonate and carbon dioxide concentrations? |
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Definition
Bicarbonate - 24 mM
Carbon Dioxide - 1.2 mM (PCO2 - 40 mmHg) |
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Term
| What is the solubility of carbon dioxide? |
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Definition
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Term
| What is the Henderson Equation? |
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Definition
| [H+] in nanomolar (10-9 M) = (24 PCO2) / [HCO3-] |
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Term
| Why is the bicarbonate-CO2 buffer system particularly important in acid-base physiology? |
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Definition
1. Total concentration of the buffer pair is high
2. Even though the pK is 6.1, the buffer is effective because it is an "open" system (open to the environment with ready gas exchange). |
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Term
| How does PCO2 increase in the gas phase in the body? |
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Definition
| With decreased ventilation, or hypoventilation, PCO2 will increase. |
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Term
| How does the kidney compensate for respiratory acidosis? |
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Definition
| Increases excretion of acid and adds bicarbonate to the blood. |
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Term
| How does pulmonary respiration compensate during metabolic alkalosis? |
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Definition
| Respiration would decrease in order to decrease (more acidic) the pH of the body. |
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Term
| An increase in alveolar ventilation results in an ________ in [CO2] while a decrease results in an ___________ in [CO2]. |
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Definition
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Term
| What are the relatively important buffers extracellularly and intracellularly? |
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Definition
| bicarbonate and plasma proteins, respectively |
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Term
| What is the Isohydric Principle? |
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Definition
- All buffers in a homogenous solution are in equilibrium with the same [H+]
- Any change in [H+] will be redistributed among all buffers in the body
- all buffers have the appropriate ratio of acid and base given their pK |
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Term
| Why is the bicarbonate-CO2 buffer most used to establish acid-base status? |
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Definition
1. Its components can be readily determined by measurements on arterial blood
2. It is the most important extracellular buffer
3. It is tightly linked to the physiologic mechanisms involved in maintaining acid-base status |
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Term
| What is the major source of acid in the body? |
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Definition
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Term
1. What is an example of volatile acid?
2. What is an example of fixed acid? |
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Definition
1. CO2
2. H2SO4, HCl, H3PO4, nucleic acids |
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Term
| What is the key to maintaining a balance of PCO2, [HCO3-], and pH? |
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Definition
| As long as the CO2 that is formed during metabolic respiration is expired from the lung as fast as it is created, the physiological levels will not change. |
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Term
| T/F: There is a net acid reduction in the body per day due to comsuming metabolic reactions |
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Definition
| False. There is a net creation of about 1mEq H+/kg body weight/day |
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Term
| What do non-volatile acids use as a buffer? |
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Definition
| Bicarbonate, which results in Na+ salts that need to be excreted by the kidney. |
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Term
| T/F: During stool base loss, every molecule of base (HCO3-) lost in the stool results in H+ being retained in the extracellular fluid. |
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Definition
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Term
| T/F: Dietary intake is a significant source of acid. |
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Definition
| False. Dietary intake does not play much of a role in acid concentrations in the body |
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Term
| What must the kidney's do in order to maintain acid-base balance? |
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Definition
| Kidneys must excrete an amount of acid equal to the net acid load which is approximately equal to the non-volatile acid production. |
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Term
| What controls the reabsorbtion of HCO3- in the nephrons? |
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Definition
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Term
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Definition
| It is the amount of H+ that is excreted combined with urinary buffers such as phosphate, creatinine, and other bases. |
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Term
| T/F: Each NH4+ excreted in the urine results in the return of HCO3- to the extracellular fluid. |
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Definition
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Term
| What is the formula for Net Acid Excretion (NAE)? |
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Definition
NAE = (Titratable Acid Excretion) + (NH4+ Excretion) - (HCO3- lost in urine)*
* HCO3- lost in urine is normally extremely small |
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Term
| Where is most of the Bicarbonate reabsorbed in the nephron? |
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Definition
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Term
| How does H+ secretion lead to HCO3- reabsorption? |
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Definition
| H+ in the tubular fluid reacts with HCO3- to form H2CO3 which is acted on by carbonic anhydrase to form CO2 and H2O. CO2 moves into the cell and is acted again upon by Carbonic Anhydrase to form H+ and HCO3-. This HCO3- exits the basolateral membrane via Na+ - HCO3- symporter. |
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Term
| Under what conditions do intercalated cells in the collecting ducts increase secretion of HCO3-? |
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Definition
| Under conditions of Alkalosis |
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Term
| What is the primary factor that regulates H+ secretion and thus HCO3- reabsorption? |
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Definition
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Term
| Acidosis _______ H+ secretion while alkalosis ________ it. |
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Definition
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Term
| What are the two sources of new bicarbonate in the kidneys that are needed to compensate for lost bicarbonate that buffers non-volatile acid? |
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Definition
1. Formation of Titratable Acid
2. Ammonium Production (For every NH4+ excreted in the urine, a "new" HCO3- is returned to the systemic circulation. |
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Term
| When the acid-base disturbance is results from a primary change in [HCO3-], it is a _________ disorder,; when ther is a primary change in blood PCO2 it is a __________ disorder. |
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Definition
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Term
| What is consumed when non-volatile acid is added to the body? |
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Definition
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Term
| [HCO3-] increases ~1 meq/L for each 10 mmHG ______ in PCO2. |
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Definition
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Term
| [HCO3-] decreases ~2 meq/L for each 10 mmHG ______ in PCO2. |
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Definition
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Term
| What determines the PCO2 levels? |
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Definition
Ventilatory Rate
Increased ventilation will decrease PCO2 and a decreased ventilation will increase PCO2. |
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Term
What is the primary event with Respiratory Acidosis?
What is the compensatory event? |
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Definition
Increased PCO2
Increased plasma [HCO3-] |
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Term
| What are the causes of Respiratory Acidosis? |
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Definition
Results from decreased gas exchange across the alveoli because of inadequate ventilation or impared gas diffusion.
- Obstructive or Restrictive lung disorders
- CNS depression affecting respiratory center
- Neuromuscular disorders affecting respiratory muscles |
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Term
What is the primary event in Respiratory Alkalosis?
What is the compensatory event? |
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Definition
Decreased PCO2
Decrease in plasma [HCO3-] |
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Term
| What are some causes of Respiratory Alkalosis? |
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Definition
- Hyperventilation
- Normal people at altitude |
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Term
What is the primary event in Metabolic Acidosis?
What is the compensatory event? |
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Definition
Decreased plasma [HCO3-]
Decrease in PCO2 due to hyperventilation |
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Term
| If the predicted PCO2 value is much higher than predicted, then metabolic acidosis is coupled with _______________. |
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Definition
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Term
| If predicted value of PCO2 is much lower than predicted, then metabolic acidosis is coupled with _______________. |
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Definition
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Term
| What are the causes of metabolic acidosis? |
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Definition
- Increase in H+ from endogenous sources (lactic acidosis, ketoacidosis)
- An increase in H+ from exogenous sources (ingestion of methanol, ethylene glycol, salicylates)
- Decreased H+ excretion from kidney
- Loss of bicarbonate from GI tract |
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Term
| What is the normal range for the Anion Gap? |
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Definition
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Term
| An increase in the Anion Gap indicates the presence of what disorder? |
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Definition
| Metabolic Acidosis. This is because bicarbonate is being used up to eliminate excess H+ without a concomitant decrease in cations. |
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Term
| Can one have metabolic acidosis without an increased anion gap? |
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Definition
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Term
| What is a common cause of metabolic acidosis that is not associated with an increased anion gap? |
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Definition
| Diarrhea. Bicarbonate that is lost in the feces is balanced by the increased Cl- absorption. |
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Term
What is the primary event in Metabolic Alkalosis?
What is the compensatory event? |
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Definition
Increased plasma [HCO3-]
Increase in PCO2 |
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Term
| What are the common causes of metabolic alkalosis? |
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Definition
Vomiting - Loss of gastic HCl
Antacids - used by patients with renal dysfunction that cannot readily remove HCO3-
Diuretics |
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Term
| Why is it difficult for the kidney to compensate for metabolic alkalosis due to excessive vomiting? |
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Definition
| Since urine pH is low, it leads to increased bicarbonate reabsorption. Cause of vomiting must be eliminated and plasma volume must be brought up to normal levels. |
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