PHIS 206 Lecture Notes - Lecture 22: Ph, Conjugate Acid, Diarrhea
2 May 2018
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Lecture 22: Acid-Base Balance
Acid Makers
• As a by-product of our metabolism, we create acid, in the form of phosphoric acid, lactic
acid, citric acid, and other organic acids.
• We manufacture amino acids to build proteins.
• The stomach makes hydrochloric acid to aid in the digestion of food.
• We make acid all the time → not a good thing
The Problem of Acid
• All of these acids present a problem. Free hydrogen ion (what defines an acid) can wreak
havoc on the proteins of the body.
• Proteins work because of how they are shaped. If the pH of their environment is altered,
even a small amount, the shape and function of proteins can be compromised. Works
both ways though
→ too little acid is also a problem.
• Body is pH sensitive→ specifically enzymes
• 7.35-7.45
• Changes in pH denatures proteins
pH Scale
• pH
o Odd measurement
o Compresses a large range using a logarithm
o Backwards → a lower pH means more free hydrogen ion and a stronger acid
• Free hydrogen ions = acids
Strong versus Weak Acids
• Strong/Weak Acids can be described by how much the hydrogen ion dissociates (pH
quantifies this)
• Weak Acids exist in both their acid form and their base (conjugate base) form, and never
fully dissociate.
• Weak acids help buffer the strong acids
• Buffer = temper how much acid changes pH
• Buffering capacity in our body→ we need to have an ability to buffer the acids we make
Weak Acids
• Weak acids remain partially in their acidic form, and partially in their basic (alkaline)
form
• The base form of these weak acids can serve the body a purpose → they can help
”absorb” strong acids → ”buffering”
Blood pH
• Neutral pH in chemistry does not equal Normal pH in physiology
• Compatible range for life 7.35-7.45
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Document Summary
The problem of acid: all of these acids present a problem. Free hydrogen ion (what defines an acid) can wreak havoc on the proteins of the body: proteins work because of how they are shaped. If the ph of their environment is altered, even a small amount, the shape and function of proteins can be compromised. Weak acids: weak acids remain partially in their acidic form, and partially in their basic (alkaline) form, the base form of these weak acids can serve the body a purpose they can help. Blood ph: neutral ph in chemistry does not equal normal ph in physiology, compatible range for life 7. 35-7. 45, can"t remain outside of that range long without consequences, proteins designed to live between 7. 35 to 7. 45. Buffering: main blood buffer is bicarbonate (base form is hco3 , hco3 serves to soak up much of the acid we make, the one with less h+ is the base/buffer.
