BIOL 2420 Lecture Notes - Lecture 10: Intracellular Ph, Respiratory Failure, Alkalosis
26 Apr 2018
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Unit 8 – Lecture 10
Acid-Base Balance
- Acid-base balance = pH homeostasis
o Essential function of the body
o pH measured in H+ concentration
▪ normal H+ concentration of arterial plasma is 0.00004mEq/L
• minute compared with the concentrations of other ions
- pH 7 = neutral
- above pH 7 = alkaline/basic
- below pH 7 = acidic
- normal pH of the body is 7.40 – slightly alkaline
pH changes Can Denature Proteins
- normal pH range of plasma: 7.38-7.42
- plasma values are used clinically as an indicator of ECF and whole body pH
o extracellular pH usually reflects intracellular pH
- ody fluids outside the ody’s iteral eviroet suh as those i the lue of the
gastrointestinal tract or kidney tubule
o can have a pH greatly exceeding the normal range
o acidic secretions in the stomach can create a gastric pH as low as 1
o pH of urine varies between 4.5 and 8.5 – depedig o the ody’s eed to
excrete H+ or HCO3-
- concentration of H+ in the body is closely regulated
o intracellular proteins (enzymes) and membrane channels are sensitive to pH
because the function of these proteins depends on their three-dimensional shape
o changes in H+ concentration alter their tertiary structure of proteins by
interacting with hydrogen bonds in the molecules = disruption of the 3-
dimensional structures and activities
- abnormal pH may significantly affect the activity of the nervous system
o too low = acidosis = neurons become less excitable, and CNS depression results
▪ patients become confused and disoriented, then slip into a coma
▪ if depression of the CNS continues then the respiratory center ceases to
function = death
▪ kidneys excrete H+ and reabsorb K+ using an H+-K+-ATPase
o too high = alkalosis = neurons become hyperexcitable, firing action potentials at
the slightest signal
▪ shows up first as sensory changes
• numbness or tingling
▪ followed by muscle twitching
▪ severe alkalosis
• muscle twitches turn into prolonged/sustained contractions
(tetanus) leading to respiratory paralysis
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Document Summary
Acid-base balance = ph homeostasis: essential function of the body, ph measured in h+ concentration, normal h+ concentration of arterial plasma is 0. 00004meq/l, minute compared with the concentrations of other ions. Normal ph of the body is 7. 40 slightly alkaline ph changes can denature proteins. Plasma values are used clinically as an indicator of ecf and whole body ph: extracellular ph usually reflects intracellular ph. Acids and bases in the body come from many sources. Hydrogen ions come from both food and internal metabolism. Maintaining mass balance requires that acid intake and production be balanced by acid excretion: hydrogen balance in the body is summarized in the following figure. Many metabolic intermediates and foods are organic acids that ionize and contribute h+ to body fluids: amino acids fatty acids intermediates in the cta cycle lactate produced by anaerobic metabolism. Metabolic production of organic acids each day generates a significant amount of h+ that must be excreted to maintain mass balance.
