pH and Buffers Flashcards
(39 cards)
What difference is in Ka for strong bases and acids?
if Ka is less than one then the acid is “weak”
is the Ka is greater that 10, it is “strong”
Examples of physiological bases.
HCO3- , HPO4 2- , H2PO4- and
proteins-
Characteristic of a physiological base.
comparatively strong bases because they have a relatively strong affinity for H+ ions forming weak acids (relatively slight dissociation)
Ampholytes?
Substances which can function both as acids and bases are called ampholytes.
pH formula?
pH = -log [H+]
What is the normal plasma pH?
7.35 - 7.45
What effect do pH imbalances have on the nervous system?
H+ imbalances cause K+ imbalances because transporter proteins in kidneys move H+ and K+ in an antiport fashion
In acidosis: neurons become less excitable and CNS depression can result
In alkalosis: hyperexcitable
Definition of a buffer?
Solutions that resist change in pH upon the addition of small volumes of acid or base
Buffers are the mixtures of weak acids and their salts of strong bases (and vice versa)
What does the Henderson-Hasselbalch equation describe?
The quantitative relationship between
– pH,
– the buffering action of a weak acid and its conjugate base and
– the pKa value of weak acid is given by the
What are the applications of the Henderson- Haselbalch equation?
- Calculation of concentrations of constituents of buffers
- Determination of the proportions of conjugate pairs that exist at a given pH
- Determination of pH of buffers
- Calculation of the effective concentration of the permeable form of the drug at its site of absorption
- Predicting about renal clearance of a drug
Calculation of the pI for more complex amino acids?
the pI is the average of the pKa values that represent the boundaries of the zwitterionic form of the molecule.
If additional acidic or basic groups are present as side-chain functions, the pI is the average of the pKa s of the two most similar acids.
Calculation of the pI for more complex amino acids?
the pI is the average of the pKa values that represent the boundaries of the zwitterionic form of the molecule.
If additional acidic or basic groups are present as side-chain functions, the pI is the average of the pKa s of the two most similar acids.
What is a “Physiological buffer”?
Examples?
A system that controls the output of acids, bases or CO2
* urinary system buffers the greatest quantity, which takes several hours
* respiratory system buffers within minutes, limited quantity
What are “Chemical Buffer systems”?
– restore normal pH in fractions of a second
– bicarbonate, phosphate and protein systems bind H+ and transport H+ to an exit (kidney/lung)
What are the two types of Buffer systems?
- Physiological buffer
- Chemical Buffer system.
What is a “Buffering Capacity”?
The efficiency of a buffer in maintaining a constant pH on the addition of small amounts of acid or base is called as its buffering capacity.
What is Buffering Capacity determined by?
– the pH of the solution; Buffers work best within 1 pH unit of their pKa (± 1).
– the concentration of the buffer, the stronger the buffer, the greater its buffering capacity.
– Ratio of acid to conjugate base.
What are the three most important buffers in the body?
- Urine
- Blood
- ICF
What does a urine buffer involve?
Phosphate and Ammonia Buffers
What do the blood buffers involve?
Bicarbonate, Protein and
Haemoglobin (in RBC) buffers
What are the pH buffers in the ICF?
Proteins and Phosphates
What are the three types of physiological buffers in the body? and how fast do they act?
1) Chemical Buffers
* React very rapidly (less than a second) 2) Respiratory Regulation
* Reacts rapidly (seconds to minutes)
3) Renal Regulation
* Reacts slowly (minutes to hours)
What are the 3 Major Buffer Systems in the blood?
- Protein Buffer systems.
- Carbonic acid-bicarbonate buffer system.
- Phosphate buffer system.
In which space of the body does the carbonic acid-bicarbonate buffer system act?
ECF
