pH + buffers Flashcards
what is the formula to measure pH
pH= -log [H+]
what is the range of human blood plasma
pH =7.35 – 7.45
what is acidosis and when does it occur
blood pH below 7.3
what is alkalosis + when does it occur
blood pH greater than 7.5
why does pH blood need to be maintained
affects solubility of substrates
affects 3D structures + proteins
affects activity of biological system
what are 6 symptoms of acidosis
nausea shortness of breath headache increase heart rate arrhythmia confusion
what is acid definition
compound that donate proton + gains negative charge
what is alkali definition
compound that gains protons + gains positive charge
what is the average pH of human blood
pH 7.4 - slight basic
what are the 2 main sources of acid found in human body
metabolic
respiratory
what is the main acid from respiratory + describe the equation
CO2 dissolved in water –> carbonic acid
CO2 + H2O H2CO3 H+ + HCO3 -
what are the main acids that are made by metabolic
organic acid (lactic + uric)
inorganic (sulphuric)
keto acids
how are organic + inorganic acids made
metabolism of amino acids contain sulphur + phosphorus
sulphuric acid
how is lactic acid produced
anaerobic glycolysis
what can happen if there is too much kept acids
cause ketoacidosis in diabetes
not produce enough insulin
what is a buffer definition
chemical compound that help stabilise pH of solution removing or adding protons
how can a buffer be formed + give example of one
weak acid + its conjugate base
acetic acid + sodium acetate
name 4 different buffers
haemoglobin
proteins
phosphate
bicarbonate
haemoglobin - name the acid, conjugate base + site where found
HHb
Hb
interior of RBC
proteins - name the acid, conjugate base + site where found
Hprot
Prot
intracellular fluid
bicarbonate - name the acid, conjugate base + site where found
C02 –> H2CO3
HCO3-
blood plasma
Phosphate - name the acid, conjugate base + site where found
H2PO4-
HPO4-
intracellular fluid
what is definition of buffer capacity
amount of cid or base that can be added to a vol of buffer before its pH changes significantly
how is the buffer capacity measured
Experimentally by titration
what is definition of dissociation constant
specific type of eqbm constant that measures the dissociation of a object to separate/ split reversibly into smaller components
what is the eqn of dissociation + formula for dissociation constant
HA H+ + A-
Kd = [H+][A-]
[HA]
what is the Henderson hasselbach equation
pH= pKa + log [A-]/[HA] HA = conc weak acid A- = conc weak base
what does the pKa equal in hasselbach equation
pH when 50% of the HA (acid) is ionised
what is the hardest tissue in the body + its mineral content
enamel
96% mineral content
what is the problem with enamel having a high mineral content +
prone to demineralisation
causing dental caries
how is caries formed by enamel
sugars coat surface of tooth + cavity bacteria process + digest sugar --> produce lactic acid + plaque reduces pH below critical point enamel dissolved causes caries
what is scientific name of enamel
crystalline calcium phosphate
hydroxyapatite
what is the critical pH for the tooth
pH 5.2-5.5
what does the critical pH mean
fluid surrounding tooth become increasingly acidic
point reached below critical point
tooth mineral dissolves
stops being saturated with Ca2+ and phosphate
why is saliva important in the mouth
acts as buffer
causing normal resting pH of mouth not to fall under pH 6.3
what are the 3 buffers in saliva
phosphate
proteins
bicarbonate
how is protein as a buffer in saliva
not very effective –> charged groups form peptide bonds
how is phosphate as a buffer in saliva
good buffer but not concentrated enough in saliva to be effective
how is bicarbonate as a buffer in saliva
major buffer in saliva
what is the equation of the buffer in saliva with bicarbonate
HCO3- + H+ H2CO3 CO2 + H2O
what happens to the buffer equation in saliva when acid is produced by bacteria
equation shifts RIGHT
acid neutralised by bicarbonate
CO2 lost to atmosphere
what is carbonic acid one in mouth
1.3 mmol/L
how would you use hasselbach eqn to find the pH in the mouth
pH = pKa +(bicarbonate flow rate/ carbonic acid conc)
what is the pK for bicarbonate
6.1
