Cell bio- acid-base balance Flashcards
metabolic processes in the body result in the production of what?
large amounts of acids
Where are acids produced by the metabolisms transported to, how are they transported and how it it accomplished?
transported to the lungs and kidneys
via ECF and blood without changing plasma pH
accomplished by the buffering capacity of blood and respiration and renal regulatory mechanisms
define acid
proton donor
define base
proton acceptor
define strong acid and weak acid, and what are examples?
strong dissociates very quickly in solution and release large amount of H (HCl, HNO3, H2SO4)
weak partially dissociate in aq sol (H2CO3)
define strong base and weak base and what are examples?
strong reacts vey quickly with H, removing it from sol (OH)
weak doesn’t fully ionize in an aq sol (HCO3)
what is the concept of acidity?
in aq sol, protons are normally bound by electrostatic interaction to H2O= H3O
what does the acidity of a solution refer to?
the chemical activity of its constituent H ions
what is the concentration of H ions compared to electrolytes in body fluids?
a million times less
why must [H] of body fluids be kept constant, and what can it affect?
they are highly reactive
affects enzyme function and cellular structure
What equation defines pH?
-log10[H]
what does [H] determine?
the pH of the body fluids
what is the normal extracellular fluid [H] and what is the pH of blood?
40 nEq/L
7.4
define pH
a numeric scale used to specify the acidity or basicity of an aq sol
what is the relationship between pH and [H]?
inverse relationship
the greater the H, the lower the pH
define acidemia
decrease in ECF pH below normal limits, [H] increases above normal limits
define acidosis
the pathophysiologic processes that cause net accumulation of acid in the body
define alkalemia
the increase in ECF pH above normal limits, [H] is below normal limits
define alkalosis
the pathophysologic processes that cause net accumulation of alkali in the body
t/f: an animal can have alkalosis without alkalemia?
true
what is the graphical relationship between pH and [H], a change in one pH unit changes [H] by what?
they vary exponentially of one another
factor of ten
what is the law of mass action?
the velocity of a reaction is proportional to the product of concentrations of the reactants
what three things does the law of mass action describe?
- explains and predicts behavior of solutions in dynamic equilibrium
- for the acid, there are two opposing reations (HA -> H+ A & H+A -> HA)
- the velocity of the 1st and 2nr rxns (v1=k1[HA] & v2=k2[H][A])
what does the law of mass action describe at equilibrium?
the rates of the two opposing reactions counterbalance one another and the two velocities are equal
k1[HA]=k2[H][A]
what is Ka?
dissociation constant
the concentration of the acid relative to its dissociated ions
what are two equations that equal Ka?
k1/k2
[H][A]/[HA]
what is the equation for law of mass action when the concept if pH is applied to the H and Ka?
pH= pKa + log ([A]/[HA])
what is the henderson-hasselbalch equation used to calculate, and what is the equation?
the pH of a solution based on the base and acid concentrations
pH=pKa + log(base/acid)
define buffer
a compound that can accept of donate protons and minimize a change in pH when an acid or base is added
what does a buffer solution consist of? (2)
a weak acid and its conjugate base
what is considered the first line of defense to prevent major changes in pH?
blood buffers
what is the isohydric principle, and what does it allow?
multiple buffers in the same solution are always in equilibrium
if one system is known, changes in other systems can be predicted
how the the ionic composition of fluids maintained and why?
within marrow limits
important for optimal functioning of the cells
serious deviations of pH disrupt cell metabolism
what are the 3 systems that help regulate [H] and pH in body fluids and what is their function?
chemical buffer systems (manage the imbalance)
lungs & kidneys (try to correct the pH by adjustments in ventilation or changes in renal function)- bicarbonate buffer system and phosphate buffer system
how to blood buffers act as the first life of defense to prevent major changes in pH?
thay don;t add or remove H, but keep them in control until the balance is restored
what are the 2 proteins used in a buffer system?
hemoglobin
plasma protein
what are proteins used as buffers for?
intracellular acid-base balance
why to RBC have a significant and rapid impact on ECF?
hemoglobin
H and HCO3 move slowly across other protein membranes, causing a delay for the max ability of intracelluar proteins to buffer extracellular acid-base abnormalities
what do proteins have that allow them to be buffers and what are two examples?
a large number of acidic and basic groups
imidazole ring of histidine residues
amino-terminal groups
what do proteins couple with to contribute to the total body acid-base balance?
phosphate buffer
what is the most important blood buffer and what system is it with?
hemoglobin
bicarbonate buffer system
what are the two mechanisms by which H bind to hemoglobin?
via basic carboxym groups (RCOOH)
via imidazole groups of histidine (bond with ion of the heme group)
what molecule is continuously formed by the intracellular metabolism and what are three forms that it is transported in the blood as?
CO2
dissolved CO2, carbonic acid, bicarbonate ions
what buffer system is the most important of the ECF, what does it consist of (2), how are its components regulated and by what organs?
Bicarbonate buffer system
weat acid (carbonic acid) and conjugate base (bicarbonate ion)
independently regulated= open system
CO2 by lungs and bicarbonate by kidneys
how is carbonic acid and bicarbonate formed? are their reactions reversible or irreversible and what is it called?
carbonic acid= reaction between CO2 and H20
bicarbonate= dissociation of H2CO3 in H + HCO3
reversible reaction
hydration reaction
what enzyme catalyzes the hydration reaction and where is it abundant (3)?
carbonic anhydrase
within RBC
in walls of the lung alveoli
in epithelial cells of the renal tubules
what is the concentration of phosphates compared to bicarbonate buffer?
low concentration
where are phosphates used as buffers (2) and what is it made up of?
intracellular and tubular filtrate of the kidneys weak acid (monosodium phosphate) and conjugate base (disodium phosphate)
what is formed when phosphates react with a strong acid/base?
strong acid: a weaker acid and a salt
strong base: a weaker base and water
what is the second line of defense to acid-base balance and how quickly does it occur?
respiratory system
acts within minutes
what is the capacity to buffer in the respiratory system compared to the chemical buffer system and what is the role of lungs?
twice the capacity
lungs control the [CO2] in the ECF
what is the effect of pH on alveolar ventilation and how does the respiratory system respond to an abnormal pH?
ventilation inc 4-5 times when pH dec to 7.0
ventilation dec when pH is over 7.4
respiratory system tries to compensate an abnormal pH
How do Pco2, H and Po2 affect alveolar ventilation?
inc Pco2 & H, dec Po2 = inc ventilation
dec Pco2 & H, inc Po2= dec ventilation
what is the effect of alveolar ventilation on pH and what can be the primary cause for an abnormal blood pH?
a double inc in ventilation inc ECF pH to 7.63
a 1/4 dec in ventilation dec ECF pH to 6.95
respiratory disease
what is the third line of defense for acid-base balance, how does it compare to the other regulators and how quickly does it respond?
kidneys
most powerful regulator
hours to days
how do the kidneys act to balance pH and how does it achieve real loss of base or acid?
act through the excretion of basic or acid urine
HCO3 is continuously filtered to the tubules and new ones are formed, high amounts of H are secreted in the tubular lumen and excreted with other buffers (phosphate and ammonium)
real loss= changes in the amount of HCO3 filtered or H secreted
what is the role of the kidneys, how does it perform its role and where?
regulate the [H] in ECF
secretion of H (85% proximal tubules, 10% distal tubules, 5% collecting ducts)
reabsorption of filtered HCO3
production of new HCO3
what two organs keep pH within tolerable limits and when are these mechanisms inadequate?
lungs & kidneys
severe disease
what are 4 possible primary acid-base disturbances?
metabolic acidosis & alkalosis
respiratory acidosis & alkalosis
define acidosis
the pathophysiological processes that result in an abnormal low pH
define alkalosis
the pathophysological processes that result in an abnormal high pH
what is the pH range for arterial blood and what may the values vary based on (3)?
7.35-7.45
vary depending on sea level, lab and assay
what are the metabolic and respiratory components?
metabolic= HCO3 respiratory= Pco2
what are the three causes of metabolic acidosis?
gain of acids
loss of bicarbonate
compensatory mechanism for respiratory alkalosis
what are 4 methods of gain of acids causing metabolic acidosis?
ketones (beta-hydroxybutrate)
lactate (hypoperfusion)
intoxication with exogenous compounds (ethylene glycol, aspirin)
renal failure (build up of phophates and sulfates)
what are 3 methods of loss of bicarbonate causing metabolic acidosis?
renal tubular acidosis diarrhea rumen acidosis (large animals)
what are 3 causes of metabolic alkalosis?
excessive elimination of hydrogen
intake of a base
compensatory mechanism for respiratory acidosis
what are 4 methods of excessive elimination of hydrogen causing metabolic alkalosis?
persistent vomiting (loss of HCl) hypokalemia (tenal tubule cells secrete inappropriate amounts of H into urine) torsion and dilation of abomasum (ruminants)
what are 2 methods for intake of a base causing metabolic alkalosis?
injection of bicarbonate solution
ingestion or injection
when does respiratory acidosis occur and what are 3 causes?
when the CO2 production exceeds the CO2 loss by the lungs
depression of respiratory centers in the central nervous system
abnormality of the chest wall or respiratory muscles
obstructions to gas movement or diffusion within the lungs
compensatory mechanism for metabolic alkalosis
what is an example of depression of respiratory centers in the CNS causing respiratory acidosis?
analgesic/anesthetic drugs
what are 2 examples of abnormality of the chest wall of respiratory muscles causing respiratory acidosis
cervical lesions
neuromuscular disorders
what are 3 examples of obstructions to gas movement of diffusion within the lung causing respiratory acidosis?
decreased alveolar ventilation
impediment of diffusion between alveoli and capillary blood
primary pulmonary diseases
when does respiratory alkalosis occur and what are 2 causes?
when the loss of CO2 exceeds the rate of production
hyperventilation
compensatory mechanism for metabolic acidosis
what are 3 examples that cause hyperventilation, which causes respiratory alkalosis?
any cause of hypoxemia
congestive heart failure, hypotension, anemia
