8204985
Description
Flashcards by Louise Mason, updated more than 1 year ago
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Created by Louise Mason
about 7 years ago
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| Question | Answer |
| What is pH? | a measure of Hydrogen ion concentration in solution |
| In pure water, what is the ratio of Hydrogen ions to Hydroxide ions? | 1:1 |
| What is involved in protein denaturation? | adding or removing hydrogen ions from proteins, causing conformational change and denaturing the protein |
| What effect can a low pH have on the central nervous system? | a low pH has a depressive effect on the CNS |
| What is the usual range of pH for extracellular fluid? | 7.36-7.44 |
| What is the usual range of pH for intracellular fluid? | 7.10-7.20 |
| Is the pH of body fluids always closely associated with the pH of plasma? | no, can largely deviate from each other like in gastric juice and pancreatic juice |
| What kind of scale is the pH scale and what does this mean about small pH changes? | logarithmic scale, so a small increase in pH can equal a large change in ionic concentrations |
| What is the first line of defense against H+ concentration changes and how quickly does it react? | body's buffer systems, reacting almost immediately |
| What is the second line of defence against H+ concentration changes and how quickly does it react? | the lungs, reacting rapidly but not as immediately as buffer systems |
| What is the third line of defence against H+ concentration changes and how quickly does it react? | the kidneys, reaction time can take up to several hours |
| What are the lungs unable to do regarding H+ changes that the buffers and kidneys can do? | remove excess acids or bases |
| What does the Law of Mass action state? | the rate of a reaction is proportional to the product of the concentrations of the reactants |
| What is a weak acid or alkali? | one that only partially dissociates in solution |
| What is formed when an alkali accepts a proton? | a conjugate acid |
| In what blood vessels is H+ concentration highest? | in venous blood |
| H+ concentration rises as blood flows through which vessels? | peripheral capillaries |
| What is the relationship between pH and H+? | negative logarithm: pH = -log10[H+] |
| What are volatile acids? | an acid that can be easily removed when an animal breathes |
| How are volatile acids derived? | from CO2, as H+ can be made from H2CO3 (potential acid) |
| What are non-volatile acids? | acids that cannot be eliminated by the lungs |
| In an animals, where do non-volatile acids derive from? | produced during metabolism (lactic acid) and are then rapidly metabolised to H20 and CO2 |
| Problems with which system can affect CO2 levels in the body? | respiratory system |
| The influence of dietary feed on acid-base balance depends on what ratio? | the ratio between the content of dietary bases and the components that metabolise into non-volatile acids |
| In carnivores, is there a net acid or net base production? | net acid (net acid producers) |
| When organic anions are metabolised, what is produced? | HCO3- |
| What happens to excess HC03- that is produced from anion metabolism? | excess bicarbonate is excreted in the kidneys |
| Why do some herbivores/omnivores have alkaline urine? | the dietary bases are higher than the production of non-volatile acids and so they produce more excess HCO3-, which is excreted in the urine |
| Why do carnivores have the highest acid production? | there is a higher concentration of dietary proteins and as these are oxidised, they produce non-volatile acids |
| What does a a buffer do? | a buffer minimises the change in pH when an acid or base is added |
| What is a base? | a proton acceptor |
| What is an acid? | a proton donor |
| What are amphoteric buffers? | a buffer with both basic and acidic characteristics and can accept or donate protons |
| What equation can be used to predict changes in pH? | Henderson-Hasselbalch equation : pH= pK + log[base] [acid] |
| Buffers work best when there is what kind of difference between pH and pK? | small difference, pH and pK should ideally be close together |
| When pH=pK, how does H+ changes affect pH? | any H+ changes will have a minimal effect on pH |
| Out of all the body buffering systems, which one maintains around half the body's buffering capacity? | intracellular buffers inc. proteins and inorganic/organic phosphates |
| Which buffering systems are involved in long term acidosis? | Carbonate in bone and Ion exchange in bone |
| What is meant by a closed buffer system? | a system where the sum of the two components of the buffer pair is constant |
| What is meant by an open buffer system? | a system where the concentrations of both components of the buffer pair are subject to regulation |
| Why is the bicarbonate buffer system so important in the body? | two elements of the system can be regulated, as changes work across a 3 part equilibrium at both ends of the equations, making it flexible for acidosis and alkalosis |
| How do kidneys control the H+ concentration in ECF? | can produce acidic or alkaline urine to compensate for H+ balance changes, by varying H+ secretion and bicarbonate reabsorption) |
| How do the lungs control Carbon Dioxide levels in the body? | can vary respiratory rate to increase or decrease the pCO2 |
| What does the amount of HCO3- absorbed depend on? | the composition of the diet, with herbivores reabsorbing around 99% |
| Why do carnivores continuously produce HCO3-? | H+ is produced for metabolism and so bicarbonate is needed to buffer the acidic metabolism process |
| What percentage of bicarbonate is reabsorbed in the proximal tubule? | 85% |
| What percentage of bicarbonate is reabsorbed in the LoH? | 10% |
| As HCO3- can't cross the apical membrane in the tubules, how is is reabsorbed into the capillary lumen? | CO2 freely diffuses from the tubular lumen into the tubular cell, where it reacts to make bicarbonate which can then diffuse across the interstitium into the capillary |
| What is the ionic movement within bicarbonate secreting cells? | bicarbonate ions are secreted into the tubular lumen whilst Cl- is transported into the cell H+ moves into the capillary from the tubular cell |
| What ionic movement takes place in H+ secreting cells? | H+ is secreted into the tubular lumen in exchange for K+ ions bicarbonate and Cl- are transported into the capillary lumen |
| What are the two types of urinary buffers? | inorganic phosphate and ammonia/ammonium |
| Which is the most important urinary buffer? | ammonia/ammonium buffer as it can cope with large acid increases |
| Why is the phosphate buffer only useful with small changes in H+? | the concentration of phosphate in renal tubules is always low and so only limited H+ can be excreted in urine as bound to phosphate |
| How does the inorganic phosphate buffer exist in solution? | equilibrium between a weak base and a weak acid : Na2HPO4 (alkaline) and NaH2PO4 (acid) |
| How does NH3 produce NH4+? | crosses the membrane to 'mop up' H+ to convert into NH4+ |
| How does the ammonia/ammonium system also influence Na+ levels in the body? | contributes to Na+ levels in the body by allowing Na+/NH4+ exchange |
| What is acidosis? | acidosis occurs when the arterial pH falls below 7.35 |
| What is alkalosis? | alkalosis occurs when the pH of arterial blood rises above 7.45 |
| In acid-base disturbances, what is involved in Compensation? | rapid, short term pH regulation using buffers and the respiratory system |
| In acid-base disturbances, what is involved in Correction? | longer term effect to return bicarbonate and carbon dioxide levels to normal |
| How can respiratory acidosis/alkalosis occur? | when the lungs remove CO2 at a lower or higher rate |
| With respiratory acid-base disturbances, in what way do H+ and HCO3- concentrations change? | both H+ and bicarbonate concentrations are changed in the same direction - in acidosis, both ion concentrations increase |
| What system is involved in compensation of respiratory acid-base disturbances? | The kidneys are used to regulate ECF pH back to normal levels in compensation |
| In respiratory acidosis, what happens to kidney function? | as the pCO2 increases and pH decreases, there's an increased stimulation of urinary H+ excretion and increased bicarbonate production |
| How are metabolic acid-base disturbances defined? | metabolic acid-base disturbances arise when the H+ comes from another source other than CO2, like lactic acid |
| In metabolic acid-base disturbances, H+ and bicarbonate changes occur in which direction? | H+ and bicarbonate change in opposite directions |
| In metabolic acid-base disturbances, what system is involved in compensation and what type of compensation is it? | the lungs compensate by altering pCO2, however this is only partial or incomplete compensation |
| In metabolic acid-base disturbances, what system is needed for complete correction? | kidneys |
| What is the primary determinant of intracellular pH? | arterial pH |
| Do respiratory or metabolic changes have a greater effect on H+ secretion? | changes in arterial pH due to respiratory changes more readily affect H+ secretion |
| Why do respiratory changes have a more rapid effect on pH changes than metabolic changes? | CO2 crosses cell membranes more easily than H+ and bicarbonate ions and so can more quickly change the pH levels |
| In acid-base balance, what are the two main functions of H+ excretion? | - facilitates bicarbonate reabsorption - facilitates bicarbonate formation |
| Following arterial H changes, what is the most important determinant of H+ renal excretion? | changes in K+ plasma concentration |
| Why does K+ plasma concentration have a large effect on H+ excretion rates? | K+ influences how H+ is transported across cell membranes, as they are often involved in carrier proteins or exchange mechanisms |
| Hyperkalemia will cause what type of acid-base disturbance? | metabolic acidosis - more K+ efflux will lead to a greater rate of H+ influx, so more H+ will be excreted into the urine |
| Hypokalemia causes what type of acid-base disturbance? | metabolic alkalosis |
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