Module 12: Acid/Base homeostasis Flashcards
why is pH of the body important? What can H+ ions alter?
many chemical reactions in the body are very sensitive to the presence of H+
- H+ ions can alter the shape of proteins that act as enzymes to speed up chemical reactions
- any change in H+ concentration will affect activity of almost every cell
Difference between hydrogen atom/ion
hydrogen atom:
- has a single proton which is positively charged and a single electron which is negatively charged
- neutral element
hydrogen ion (H+):
- a hydrogen atom that lost its electron, leaves only the positively charged proton
What are acids and bases?
an acid:
- any molecule that will release hydrogen ions when put in a solution, ex. HCL -> H+ + Cl-
- the more free H+ the more acidic a solution is
a base:
- any molecule that will accept a hydrogen ion, ex. HCO3- + H+ -> H2CO3
- bases lower the concentration of free H+ solution by combing with H+
- with less free H+, the acidity of a solution will decrease and become more basic/alkaline
Explain how the pH scale works, what classifies acidic/basic/neutral?
The pH scale is a way of quantifying the concentration of H+ in any solution
- the more free H+ the lower the pH, the less free H+ the higher the pH
- the pH scale goes from 0-14
pH > 7 = basic
pH = 7 = neutral
pH < 7 = acidic
What is the normal pH range & average of the body? What is the pH of arterial/venous blood? What are acidosis and alkalosis?
The normal pH of the body is between 7.35-7.45 and has an average of 7.4, slightly alkaline/basic.
- arterial blood has a pH of 7.45
- venous blood has a pH of 7.35
acidosis is when the pH of body fluids is below 7.4 (<)
alkalosis is when the ph of body fluids is above 7.4 (>)
Explain the volatile acid, source of acid in the body (carbonic acid)
when cells in the body make ATP, CO2 is produced as a byproduct.
- In RBC’s this CO2 with the help of carbonic anhydrase combines with H2O to produce carbonic acid (H2CO3)
- H2CO3 will disassociate into free hydrogen ions (H+) and bicarbonate ions (HCO3-)
- in the lungs, reaction will reverse carbonic acid (H2CO3) will reform, disassociate into H2O and CO2. The CO2 will be exhaled
overall there is no net increase of free H+ in the plasma
explain the nonvolatile acid process, source of acid in the body
the metabolic breakdown of various proteins will produce a number of acids such as: sulphuric, phosphoric, lactic acid, etc.
- the stomach is a large source of hydrochloric acid (HCl)
- these acids cannot be removed by the lungs
- these acids are a significant source of free H+ ions and are constantly produced in the body
Explain the regulation of hydrogen ion concentration (3 ways)
- buffers
- act immediately to sudden changes in free H+, body’s first line of defence
- they do not directly remove H+ from the body or alter the pH
- they bind up free H+, stabilizing pH until balance can be reestablished by respiratory system or kidneys - respiratory system
- regulates H+ concentration from volatile acids within seconds to minutes - kidneys
- respond slowly, over period of hours/days
- powerful control over H+ produced by nonvolatile acids
What do buffers do? Where can they be found, what types are found?
any molecule that can REVERSIBLY bind or release free H+
- they bind free H+ and therefore reduce the amount of free H+ in a solution, stabilize pH
- they DO NOT prevent pH from changing, only minimize the changes until free H+ can be removed by the lungs or kidneys
- ex. of buffers are bicarbonate ions or hemoglobin
free H+ can bind with buffers in the intracellular and extracellular fluid:
- intracellular buffers include: phosphates and intracellular proteins, like hemoglobin inside RBC’s
- extracellular buffers include: bicarbonate ion (HCO3-)
How does the respiratory system regulate pH? Describe the process of detection of the gas (CO2)
CO2 is a very large source of free H+ as it combines to form a volatile acid (carbonic acid, H2CO3)
- respiratory systems job is to remove CO2, maintaining pH
regulation of CO2 in the blood involves detection of this gas by the central and peripheral chemoreceptors
- when CO2 increases both chemoreceptors detect this change and cause an increase in ventilation
- this causes more CO2 to be removed at the lungs, returning blood CO2 levels to normal
Kidneys role in pH regulation and how they do it (3 ways), where/how are HCO3- reabsorbed and H+ secreted?
nonvolatile acids are produced all the time, the kidneys must remove them to maintain a constant pH of 7.4, to do so they do three things:
- excrete H+ that come from nonvolatile acids
- attempts to reabsorb all bicarbonate ions that are filtered at the glomerulus (HCO3-)
- create new bicarbonate ions (HCO3-)
- 90% of bicarbonate ions are reabsorbed in the proximal tubule
- H+ are secreted into the filtrate in the proximal tubule by the Na+/H+ exchanger
- H+ are secreted in the distal tubule and collecting duct by the H+-ATP pump
explain the reabsorption of bicarbonate ions (HCO3-) and secretion of H+ in the proximal tubule
- bicarbonate ions (HCO3-) which are filtered at the glomerulus CANNOT be directly reabsorbed by tubule cells. they must be converted to CO2 which is then reabsorbed.
- once in tubule cells, carbonic anhydrase combines CO2 and H2O to produce HCO3- and H+
- bicarbonate ions (HCO3-) will leave by simple diffusion and reabsorbed back into circulation
- remaining H+ in the cell are secreted into the lumen by Na+/H+ exchanger
Reabsorption of bicarbonate ions (HCO3-) and secretion of H+ in the late distal tubule and collecting ducts
H+are secreted by active transport using the ATP powered hydrogen pump
- its on the luminal side of the tubule cells and secretes one H+ for every ATP molecule consumed
- responsible for very little H+ reabsorption
- H+ secreted comes from the carbonic acid reaction producing HCO3- and H+
- HCO3- is reabsorbed
- BUT, the CO2 for the reaction DOES NOT come from the filtrate, it comes from the cell itself or the interstitial fluid
When can acidosis and alkalosis occur, relating to H+ and HCO3-? Describe two types of acidosis and alkalosis
acidosis can occur when there is too much acid (H+) or too little bicarbonate (HCO3-)
alkalosis can occur when there is too little acid (H+) or too much bicarbonate (HCO3-)
2 types of acidosis:
- respiratory acidosis
- metabolic acidosis
2 types of alkalosis:
- respiratory alkalosis
- metabolic alkalosis
Explain what causes both respiratory acidosis and alkalosis, what causes it in the body, and how it is counteracted/compensated
Respiratory acidosis is caused by decreased ventilation and increased PCO2:
- caused if the respiratory centers in the brainstem are damaged or from lung damage resulting in decreased ability to remove CO2 from the blood
- counteracted by buffers in the blood and by excretion of excess H+ by the kidney
Respiratory alkalosis is caused by an increase in ventilation and decreased PCO2:
- caused by hyperventilation, results in increased removal of CO2 from the blood causing a decrease in PCO2
- high altitudes have low oxygen levels in the air causing lower PO2 levels in blood, stimulating hyperventilation
- compensated by the excretion of bicarbonate from the kidney
explain what causes both metabolic acidosis and alkalosis, and what causes it in the body
Metabolic acidosis is caused by numerous factors that result in decrease of extracellular bicarbonate ions (HCO3-)
causes include:
- kidney failure resulting in inability to excrete acids in the urine or reabsorb bicarbonate
- formation of metabolic acids in the body
- ingestion of acids
- loss of bicarbonate in diarrhea (most common cause)
Metabolic alkalosis is caused by either buildup of bicarbonate ions (HCO3-) or loss of H+ from the body:
causes include:
- loss of HCl from the stomach by vomiting
- ingestion of alkaline drugs
