Module 12 Flashcards
Define an acid
Any molecule that will release hydrogen ions when put in a solution
Define a base
Any molecule that will accept a hydrogen ion
Define a hydrogen atom
A single proton (positive charge) and a single election (negative charge) resulting in an electrically neutral element
Define a hydrogen ion
A hydrogen atom that has lost its electron, leaving only the positively charged proton, sometimes called just a proton
Describe the pH scale
A way of quantifying the concentration of H+ in any solution
Goes from 0 to 14 with 7 being neutral
Below 7 is acidic, above 7 is basic or alkaline
Describe how pH is calculated
It is a negative logarithm (base 10) of the H+ concentration
Define the normal pH of body fluids
Between 7.35 and 7.45, with an average of 7.4
Arterial blood has a pH of 7.45 while venous blood has a pH of 7.35
Define acidosis
Body fluids when the pH is below 7.4
When there is either too much acid (H+) in the body or too little bicarbonate (HCO3-)
Two types: respiratory or metabolic
Define alkalosis
Body fluids when the pH is above 7.4
When there is either too much bicarbonate (HCO3-) or too little acid (H+)
Two types: respiratory or metabolic
Describe the pH of body fluids that are lethal
Below 6.8 or above 7.8 for long periods of time
Define a volatile acid
An acid that comes from the interaction of CO2 and water forming carbonic acid, no net increase in free H+ because the reaction is reversible and CO2 is removed at the lungs
Define a nonvolatile acid
Any acid that cannot be removed by the lungs
Examples: sulphuric acid, phosphoric acid, lactic acid, hydrochloric acid, and other organic acids produced by metabolic breakdown
List three mechanisms the body uses to regulate free H+ concentrations
Buffers, the respiratory system, and the kidneys
Define a buffer
Any molecule that can reversibly bind or release free H+
Describe how buffers work
Reacts almost immediately to sudden, brief changes in free H+, do not remove H+ from the body or alter pH, just bind up free H+ to stabilize pH until balance can be re-established
General reaction: X + H+ XH
Minimize the pH change until free H+ can be removed by the lungs or kidneys
List examples of intracellular buffers
Buffers inside RBCs, like phosphates and intracellular proteins like hemoglobin
Give an example of an extracellular buffer
Bicarbonate ions, the most powerful extracellular buffer, normally works in the blood
Describe how the respiratory system maintains body fluid pH
CO2 is potentially a very large source of free H+ when reacting with water and forming carbonic acid, and the respiratory system removes CO2 from the body
CO2 levels are regulated in the blood using central and peripheral chemoreceptors, and when CO2 levels rise, both receptors detect it and increase ventilation to cause more CO2 removal from the body
This keeps CO2 levels in the body relatively constant, thus keeping the blood pH relatively constant
List 3 ways the kidney regulates pH
Excreting H+ from nonvolatile acids
Attempting to reabsorb all bicarbonate ions
Creating new bicarbonate ions
Describe how the kidney excretes H+
In the proximal tubule using the Na+/H+ exchanger (secondary active transport)
In the late distal tubule and collecting duct by a H+/ATP pump (active transport)
Describe how the kidney reabsorbs bicarbonate ions
In the proximal tubule, cannot be directly reabsorbed, are converted to CO2 to be reabsorbed into tubule cells, then combines with water to form carbonic acid and dissociates into bicarbonate and H+
Bicarbonate leaves tubule cells by diffusion and are reabsorbed, H+ is secreted into lumen by Na+/H+ exchanger
For every bicarbonate ions reabsorbed, one H+ must be secreted
Describe respiratory acidosis, its causes, and what mechanism maintains body pH
Caused by decreased ventilation and increased PCO2
Can occur if respiratory centers in brain stem are damaged, or from lung damage, result is decreased ability to remove CO2 from blood
Buffers in blood and kidney excretion will counteract it
Describe respiratory aklalosis, its causes, and what mechanism maintains body pH
Caused by increased ventilation and decreased PCO2
Stress or emotionally induced hyperventilation (too much CO2 being removed from blood) or high altitudes (low O2 levels in air cause low PO2 levels in blood, stimulating hyperventilation) can cause this
Kidneys will excrete bicarbonate ions
Describe metabolic acidosis and its causes
Many factors, but generally a decrease in extracellular bicarbonate ions (does not involve blood CO2 levels)
Causes include kidney failure (can’t excrete acids or can’t reabsorb bicarbonate), forming excess metabolic acids in the body, ingesting acids (like aspirin and methyl alcohol), or loss of bicarbonate in diarrhea (MOST COMMON)
Describe metabolic alkalosis and its causes
Caused by either a buildup of bicarbonate ions or loss of H+, most commonly loss of HCl from the stomach when vomiting, but also from ingesting alkaline drugs like sodium bicarbonate for treating ulcers
