Acid-Base Flashcards
(40 cards)
What is the pH of blood?
7.35-7.45
If you blood hydrogen ion conc is >45nmol/L you are….
Acidaemic
If you blood hydrogen ion conc is <35nmol/L you are….
Alkalaemic
Describe some H+ ion turnovers from metabolic processes
Incomplete oxidation of energy substrates generates acid e.g. lactic acid
- Further metabolism of these intermediates consumes it e.g. gluconeogensis from lactate
What is a temporary imbalance of rate H+?
Accumulation of lactic acid during anaerobic exercise
- Dealt with using hyperventilation
How much CO2 is produced every 24hr?
A. 150mol
B. 1500000000000nm
C. 15000mmol
D. 190mol
C
In health what controls excretion of hydrogen matching rate of formation?
Pulmonary ventilation
What is a buffer system?
Consist of weak acid and conjugate base
- Addition of H+ to buffer some will combine with conjugate base and convert it to the undissociated acid
What is pKa and what does the value tell you?
Represent the negative log of the ionisation constant of an acid
- Acids pKa <7
- Base pKa >7
At what pH will the buffer be the most effective at
Where pKa = pH
What are some natural buffer systems?
Blood
- bicarbonate
- haemoglobin
- plasma proteins
Bone
Urine
- phosphate
- ammonium
Describe bicarbonate as a buffer system.
The most important buffer in the body.
- The action of bicarbonate as a buffer is unique because it forms H2CO3, which can be broken down into H2O and CO2.
- Both H2O and CO2 can be reabsorbed excreted or used in separate pathways.
- Bicarbonate is lost once it served as a buffer, but can be regenerated using a resorption in the kidneys. The uptake is possible by excreting H+ and using carbonic anhydrase to uptake it as water and carbon dioxide
HCO3 is conjugate base
What does the blood pH depend on?
Ratio of HCO3:CO2
20:1
Haemoglobin as a buffer system
- Most powerful in deoxygenated state and the proportion in this state increases during the passage of blood through capillary beds because oxygen is lost to tissues
Haemoglobin has a high capacity for binding to H+
CO2 can diffuse into the RBC for appropriate gas exchange, but it can be utilised to release HCO3 into plasma with pick up Cl- (chloride shift)
How are plasma proteins acting as buffering systems?
Based on their amino acid composition, which contains both weakly acidic and basic groups.
How much of the non-bicarbonate buffering of plasma does the protein account for?
A. 50%
B. 65%
C. 75%
D. 95%
D
Which protein is the most predominant buffer in plasma?
Albumin - behaves as a weak acid due to high conc of negatively charged AA
How does increased H+ affect bones?
Stimulates the bone resorption
How does renal processes aid in acid base balance?
Excess H+ is excreted in urine since the body is a net producer of acid. Achieved by:
- Reabsorb bicarbonate
- Excrete H+ against a steep gradient
How is urine acidified?
By active secretion of H+ by intercalated cells of the distal tubular cells and proximal collecting duct cells
- Significant acid excretion is achieved by H+ being buffered by phosphate titrating
Monohydrogen and dihydrogen phosphate are what?
Buffer pair at pKa 6.8
True or false. The acid secretion in the GI tract is the main contributor to net acid production.
False. Acid and bicarbonate secretion is normally in balance, meaning it does not contribute to net H+ excretion
What regulates respiratory rate?
Blood CO2
- Rate of CO2 elimination is equal to production
What type of analysis sample is most appropriate for investigating gases?
Heparin blood sample from radial artery - measured in blood gas analyster
