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
