WEEK 1: Acid – Base Balance Flashcards
State the importance of acid-base balance.
- Necessary to sustain life
- The pH determines
*Properties of proteins: enzyme activity
part of the cell structure
*Permeability of membranes: distribution of electrolytes
State the Consequences of fluctuations in pH.
*Changes in excitability of nerve and muscle cells
*Marked influence on enzyme activity
*Changes influence K+ levels in body
What is the normal pH kept at?
State the pH levels not compatible to life.
pH is kept between 7.35 and 7.45.
pH levels <7.0 or> 7.8 are not compatible with life.
The free hydrogen ion (H+) concentration in body fluids is regulated exquisitely around _____________.
H+flux through the body greatly exceeds this magnitude.
In a 70-kg human being at a basal state, normal metabolic and dietary acid production rate is about 50 to 70 mmoles/d and respiratory volatile acid production at the basal state is around 15,000 mmoles/d, with peak production at maximal exercise reaching 200 mmoles/min.
The flux of H+through the organism over 24 hours is __orders of magnitude greater than the total pool of free H+in total body water (<2μmoles).
The free hydrogen ion (H+) concentration in body fluids is regulated exquisitely around 40 nmol/L (pH 7.40)
H+flux through the body greatly exceeds this magnitude.
In a 70-kg human being at a basal state, normal metabolic and dietary acid production rate is about 50 to 70 mmoles/d and respiratory volatile acid production at the basal state is around 15,000 mmoles/d, with peak production at maximal exercise reaching 200 mmoles/min.
The flux of H+through the organism over 24 hours is 8 orders of magnitude greater than the total pool of free H+in total body water (<2μmoles).
What is an electrolyte?
An electrolyte is a substance which develops an electrical charge in the presence of water.
-Cation
-Anion
What is an acid?
Electrolyte that forms a hydrogen cation and any anion in the presence of water.
Sources of H+ in the body.
*Carbonic acid formation
*Inorganic acids produced during breakdown of nutrients (e.g., HCl, nitric acid)
*Organic acids resulting from intermediary metabolism (e.g., lactic acid, acetic acid)
Define a strong and weak acid with examples.
- Weak acid
partially ionizes in water.
H2CO3, lactic acid, citric acid, ketones, aminoacids, fatty acids, uric acid - Strong acid
Totally ionizes in water.
HCl, sufuric, nitric, phosphoric,
What is a base?
A substance that can accept hydrogen ions.
Define weak and strong base with examples.
- Weak base
do not bind well with hydrogen.
HCO3- - Strong base
binds well with hydrogen.
OH-
What is pH?
Designation used to express the concentration of H+
On a typical Western diet, approximately 15,000 mmol of carbon dioxide and 50 to 100 mEq of nonvolatile acid (mostly sulfuric acid derived from the metabolism of sulfur-containing amino acids) are produced each day.
State two important sulfur-containing amino acids found in proteins.
Two important sulfur-containing amino acids found in proteins are methionine and cysteine.
State the different mechanisms in the body that maintain acid-base balance.
What exerts a pivotal role in the excretion of nonvolatile acid and base loads?
Acid-base balance is accomplished by concerted efforts of
1. extracellular and intracellular buffers,
2. highly efficient ventilatory responses,
3. metabolic functions of the liver, and
4. renal ammoniagenic and solute transport mechanisms.
For excretion of nonvolatile acid and base loads, the kidney assumes the pivotal role.
State the range of pH.
State the neutral pH.
State the physiologic pH.
Ranges from 0 - 14
Neutral pH (7) (physiological 7.4)
Physiological pH (7.4)
Define acidosis and alkalosis.
Acidosis refers to a pH less than 7.35.
Alkalosis refers to a pH greater than 7.45.
Which blood is used to determine acid-base status?
NB! Arterial blood is used to determine acid-base status. Normal arterial pH=7.4
What are volatile acids?
Can be eliminated as CO2 gas.
State the only physiological volatile acid.
What are the others?
Carbonic acid is the only physiological.
Others (Acetic acid formic acid, succinic acid, butyric acid and propionic acid)
State the 2 elements that carbonic acid dissociates into.
Which part of the body are volatile acids eliminated?
Carbonic acid dissociates to CO2 and H20.
Volatile acids are eliminated through the lungs.
What is a non-volatile acid?
An acid that cannot be eliminated as CO2 gas.
State examples of non-volatile acids.
Example
*Lactic acid
*Ketoacids
-Acetoacetate
-3hydroxybutyrate
-acetone
What is a buffer?
A buffer is an aqueous solution made of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.
Its pH changes very little when a small amount of strong acid or base is added.
It is used to prevent any change in the pH of a solution.
State the 3 functions of buffers.
*Control pH
*Converts a strong acid into a weak one
*Converts a strong base into a weak one
What is the Henderson-Hasselbalch equation?
The Henderson-Hasselbalch equation is a mathematical expression that describes the relationship between the pH of a solution, the pKa (acid dissociation constant) of a weak acid, and the concentrations of the weak acid and its conjugate base. The equation is as follows:
pH=pKa+log([A-] / [HA])
pH is the negative logarithm (base 10) of the hydrogen ion concentration in a solution.
pKa is the negative logarithm (base 10) of the acid dissociation constant (Ka) of the weak acid.
[A^-] is the concentration of the conjugate base of the weak acid.
[HA] is the concentration of the weak acid.
State the most important buffer which operates both in the lung and the kidney.
Bicarbonate buffer
State the components which make the bicarbonate buffer.
Consists of:
*H2CO3 and HCO3-
CO2 is excreted or retained as needed.
HCO3 is excreted or retained as needed.
Describe how the Protein Buffer System work.
Proteins carry a negative charge.
They can combine with H+.
Hemoglobin is an example of the protein buffering system.
Describe how it works.
- As tissues metabolize, they produce carbon dioxide (CO2) as a byproduct. Carbon dioxide can combine with water to form carbonic acid (H2CO3) through the action of an enzyme called carbonic anhydrase.
2.The carbonic acid (H2CO3) formed rapidly dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+).
- Hemoglobin plays a crucial role in buffering the increased hydrogen ions (H+) generated during this process. Hemoglobin can bind to hydrogen ions.
The reaction with hemoglobin looks like this:
HHb (deoxyhemoglobin) + H+⇌H2O + Hb (oxygenated hemoglobin)
When hemoglobin binds to hydrogen ions, it prevents the accumulation of excessive protons in the blood, helping to resist changes in pH.
- In the lungs, where oxygen levels are higher, hemoglobin releases the bound hydrogen ions, and the bicarbonate ion is converted back to carbon dioxide.
The overall reaction in the lungs is the reverse of the initial reaction:
HCO3- + H+ ⇌ H2CO3 → CO2 + H2O
Describe how the Phosphate buffer system works.
It involves the presence of dihydrogen phosphate (H2PO4-) and hydrogen phosphate (HPO4^2-) ions, which act as weak acids and bases, respectively.
Dibasic phosphate HPO4-2 filtered freely at glomerulus, 75% is reabsorbed.
- HPO4-2 combines with H + to form monobasic phosphate H2PO4-
- Bicarbonate is reabsorbed as needed
Describe the role of the liver in acid-base balance.
Detoxification of ammonia (NH3) in the liver is done via two ways (ammonia is produced during deamination of amino acids.
- Urea Synthesis:
The liver plays a role in the synthesis of urea through the urea cycle. Urea is a nitrogenous waste product formed from the breakdown of proteins and amino acids. The removal of nitrogen in the form of urea helps eliminate excess acids from the body, contributing to acid-base balance.
- Synthesis of Glutamine:
The liver can also detoxify ammonia by incorporating it into the amino acid glutamine.
Glutamine synthesis involves the combination of ammonia with glutamate in a reaction catalyzed by the enzyme glutamine synthetase.
The resulting glutamine is a relatively non-toxic form of ammonia.
Glutamine can be transported to other tissues, such as the kidneys, where it releases ammonia to be used in various metabolic processes or excreted.
Describe how the Renal buffer system works.
Kidneys regulate pH via 3 ways.
- Reabsorption of filtered HCO3-
- Generating consumed HCO3-by secreting protons(renal acidification)
- formation of titrable acid of
H2PO4- / HPO4–2 - Excretion of ammonia in Urine (as ammonium)
Describe the kidney role in ABB.
*Third line of defense
*Kidneys require hours to days to compensate for changes in body-fluid pH
Control pH of body fluids by adjusting
H+ excretion
HCO3- excretion (during alkalosis)
Ammonia (NH3) secretion (during acidosis)
Describe the Cellular Shifts in Buffer System during acidosis and alkalosis.
Acidosis
*Potassium leaves the cell
*Hydrogen ion enters the cell
Alkalosis
*Hydrogen leaves the cell
*Potassium enters the cell
State the time taken by the following to regulate pH.
1. Buffering system
2. Respiratory system
3. Renal system
- Buffering system
within seconds - Respiratory system
20-30 minutes - Renal system
several days