Acid Base Biochemistry Flashcards
(24 cards)
When can death occur?
Major deviation from the normal pH is fatal. Death is likely at pH below 6.9 or above 7.9.
What are the normal pH values?
Normal arterial pH is 7.35-7.45 with a H+ concentration of 35-45 nmol/ l.
When does acidosis occur?
Acidosis occurs when the pH is lower than 7.35 so when pH is 6.9-7.35.
When does alkalosis occur?
Alkalosis occurs when the pH is above 7.45 so when pH is 7.45-7.8
What are acids?
Acids are compounds that form H+ in solution. They are proton donors.
What are bases?
Bases are compounds that bind H+ in solution. They are proton acceptors.
What characterises strong acids or bases?
They dissociate completely in solution.
What characterises weak acids?
They are only partially ionised in solution.
For any weak acid or base,what determines the pH of the solution? What equation shows this?
For any weak acid or base in solution, the pH of the solution is determined by the ratio of dissociated base to undissociated acid. This is shown by the Henderson-hasselbach equation.
pH = pK + log [A-]/[HA]
What are buffers?
Buffers are weak acids or bases that act as a sponge for H+ by accepting H+ when there is more of it and by releasing H+ when there is less of it. Buffers have a buffering capacity- the range within which they are most effective. Once this is reached, the buffer will no longer be able to maintain pH.
Name and describe three physiological buffers.
Three physiological buffers are bicarbonate, proteins and phosphate. Components of the bicarbonate buffer system can be regulated by excretion of co2 by three lungs and excretion of bicarbonate by kidneys.
Proteins carry a net negative charge at physiological pH which means that they can absorb H+. H+ has the highest concentration of H+ in the blood.
The phosphate buffer is important in urine. It’s concentration is too low in the blood to be an effective buffer there.
Why is pH important?
H+ are reactive and readily combine with exposed negative charges on proteins, which can alter the tertiary structure and therefore function of proteins. Extreme amounts of H+ can even denature proteins.
As proteins, enzymes have an optimal pH between 7.35- 7.45
How is acid base balance maintained?
Maintaining pH within limits is vital. Acids produced by the body are dealt with in a two step process. H+ are first buffered by physiological buffers. Then, acid products are eliminated via lungs and kidneys.
what are the sources of acid?
ingestion of acid has little effect on pH. The majority of acid is produced by metabolism and divided into one of two major sources: metabolic acids exreted via the kidneys and CO2 excreted via the lungs.
How much acid is made in the body and from what?
about 50-100mmoles/ day of acid is made in the body from metabolism; this includes ketone bodies, lactic acid from anaerobic respiration, phosphoric acid from phosphate and sulphuric acid from oxidation of sulphur containing amino acids.
How is carbonic acid produced? What enzyme catalyses this?
CO2 is produced by respiration which reacts with water in a reaction catalysed by carbonic anhydrase to form carbonic acid.
H2O + CO2 H2CO3
How are bicarbonate and hydrogen ions formed from carbonic acid?
carbonic acid spontaneously dissociates to form H+ and bicarbonate.
H2CO3 H+ + HCO3-
How much CO2 is generated by the average person?
about 13 moles
What is the H+ produced by respiration buffered by?
H+ produced by respiration is buffered by bicarbonate ions and haemoglobin.
In red blood cells, the body takes up CO2 and converts it into H+ and HCO3-. The lungs take up the HCO3- and H+ and convert it into CO2.
In the kidney, HCO3- is reabsorb in the proximal tubule.
How is acid handled?
Acid is first buffered by proteins such as haemoglobin and albumin and by bicarbonate ions made by the kidney. It is then expired via the lungs as CO2.
What is characteristic of respiratory regulation of acid base balance?
respiratory regulation of acid bade balance is high capacity and fast acting.
Changes in CO2 and pH affect what?
rate and depth of respiration
Increased pH will do what to the rate and depth of breathing?
It will reduce the rate and depth of breathing –> less CO2 expired = decreased in pH
Increased CO2 will do what to the rate and depth of breathing?
Increased CO2 will increase rate and depth of breathing –> increase in expiration of CO2 –> pH is increased
