buffer systems
2 chemicals that undergo a reversible chemical reaction that can either remove H+ or add H+ in order to keep the pH steady
4 types of buffer systems
- the [H2CO4]:[HCO3] buffer system
- the protein buffer system
- haemoglobin buffer system
- phosphate buffer system
unbuffered solution
all the added H+ remain free and contribute to the acidity of the solution
buffered solution
bicarbonate ions bind with some of the added H+ and remove them from the solution so they do not contribute to the acidity of the solution
what are the 2 reasons why the H2CO3 : HCO3- buffer solutions are highly effective
1) both H2CO3 and HCO3- are highly present in ECF meaning the system has high buffere capacity
2) both H2CO3 and HCO3- are highly regulated in the body to keep conc. stable
what regulates HCO3- conc. in the body
kidneys
what regulates H2CO3 conc. in the body
respiratory system by regulating CO2
Buffer reaction equation
CO2+H20 <-> H2CO3 <-> (HCO3-) + (H+)
Henderson Hasselbalch equation
pH= pKa + log[HCO3-/H2CO3]
or
pH= pKa + log[HCO3-/CO2]
what are proteins like as buffers? and why?
excellent buffers because they are composed of amino acids
what happens if the pH of intracellular fluid rises?
in alkaline medium, amino acids acts as acids and release H+
what happens if the pH of intracellular fluid falls?
in acidic medium, AA act as bases and absorb H+
Haemoglobin buffer system: CO2 in plasma
as CO2 leaves tissues and enters blood, most of it forms H2CO3 in the RBCs
- with help from enzyme called carbonic anhydrase
Haemoglobin buffer system: O2 in plasma
Most of this H+ will immediately bind to haemoglobin and no longer add to acidity of fluids
- frees up oxygen bound to haemoglobin so it is released into tissues
Haemoglobin buffer system: H2CO3 in plasma
some of it will immediately dissociate into HCO3- and H+
phostphate buffer system
uses an acid phosphate salt that can donate H+ when [H+] falls (or opp. when conc. increases)
- the conc of the acid buffer salt is low in EFC so doesn’t play major role
phosphate buffer system equation
Na2HPO4 + H+ <-> NaH2PO4 + Na+
important role of phosphate buffer system
to buffer pH in urine
Carbonic acid: bicarbonate buffer system main role
primary ECF buffer against non-carbonic acid changes
Haemoglobin buffer system main role
primary buffer against carbonic acid changes
protein buffer system main role
primary ICF buffer
- also buffers ECF
what are chemical buffers known as? and why?
first line of defence because they are fast
can buffer systems face constant addition of H+ to body fluids?
NO
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Module 4: Section 136
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Module 4: Section 228
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Module 5: Section 115
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Module 5: Section 223
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Module 6: Section 146
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Module 6: Section 351
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Module 6: Section 629
