Lactate vs Lactic Acid
Lactic acid and lactate are conjugate acid and base of each other. Chemically, their difference is in having and not having hydrogen. Lactic acid is a weak acid, but it is stronger than acetic acid.
Lactic acid is a carboxylic acid. Lactic acid was first isolated and identified by a Swedish chemist, Carl Wilhelm Scheele in 1780. It is also known as milk acid because it is produced from milk.
Lactic acid has the chemical formula of C3H6O3. It has the following structure. There is a hydroxyl group attached to the next carbon atom after the carboxyl group. Therefore, lactic acid is an alpha hydroxyl acid. The carbon atom in which the hydroxyl group is attached is chiral. Therefore, lactic acid has two optical isomers. They are L-(+)-lactic acid or (S)-lactic acid, and the other is its mirror image D-(−)-lactic acid or (R)-lactic acid.
Because of the presence of the hydroxyl group and a carboxylic group in the same molecule and their close proximity, intra-molecular hydrogen bonding can be seen in lactic acid. This makes lactic acid a good proton donor (than acetic acid). In other words, because of the intra-molecular hydrogen bonding, carboxylic group is unable to attract its proton strongly; thus it tends to remove easily.
The molar mass of lactic acid is 90.08 g mol−1. Since it is a small organic molecule with polar groups, it is miscible with water and is hydroscopic. It is miscible with ethanol too. Lactic acid is produced under anaerobic conditions in animals. This process is known as fermentation. It is produced from pyruate via the enzyme lactate dehydrogenase. Usually, fermentation doesn’t take place in cells, but during exercise lactic acid can be produced in large amounts. Lactic acid can also be produced from lactic acid bacteria. This is how it is produced industrially. Lactic acid is used in the pharmaceutical industry for foods and for detergents.
Lactate is the anion produced from lactic acid. When lactic acid is dissolved in water, it tends to dissociate, and produces a lactate ion and a proton. It is -1 charged ion. The pka of lactic acid is 3.86. Under physiological conditions, the pH is higher than the pKa of lactic acid. So the majority of lactic acid in the body is dissociated and present in the form of lactate. Therefore, lactate is the conjugate base of lactic acid. Lactate has the formula of CH3CH(OH)COO−.
Lactate is important in brain metabolism. During exercises, lactate is produced in muscles.
Lactic Acid vs Lactate
- Lactate is produced from the deprotonation of lactic acid.
- Lactic acid has the ability to give a proton and lactate cannot.
- In solutions (cellular fluid), lactate form is dominant.
- Lactate is an anion; therefore has a -1 charge. Lactic acid doesn’t have a charge.
- Lactate is the conjugate base of lactic acid.
- Lactic acid has an intra-molecular hydrogen bond whereas lactate doesn’t have.
- Lactic acid can pass through the lipid membranes whereas lactate cannot.