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Lactic Acid is a chemical byproduct of anaerobic respiration. Present in blood and gut, it is also referred to as lactate. Lactic Acid is produced by some bacteria in yoghurt. It is deposited in human blood through the muscles and red blood cells.
- It is a chiral molecule with two optical isomers - L-lactic acid and D-lactic acid.
- Lactic acid is an alpha-hydroxy acid due to the presence of a carboxyl group next to a hydroxyl group.
- The acid is produced when milk or lactose undergoes fermentation.
- They are also found in dairy products such as yoghurt and cottage cheese.
- Lactic acid was isolated from milk in 1780 by Carl Wilhelm Scheele, a Swedish chemist.
| Table of Content |
Key Terms: Fermentation, Lactic Acid, Bacteria, Muscles, Respiration, Anaerobic respiration, hydroxyl group
What is Lactic Acid?
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Lactic acid is an organic acid with the chemical formula C3H6O3. It is soluble in water
- It is a chiral molecule as it has two optical isomers - Levo and Dextro.
- L-lactic acid is commonly found in living organisms and is important for different biochemical processes.
- It is produced by the muscles in case of intense activity.
- Lactic acid appears to be colourless in a liquid state and in a solid state it becomes white.
- Calcium can be derived from the soluble salt of lactic acid such as calcium lactate.
- The pH of 1 mM of lactic acid is around 3.51.
- The molar mass of lactic acid is 90.08 g/mol.
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Structure of Lactic Acid
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The lactic acid formula can also be written in an extended way as CH3CH(OH)CO2H.
- Since a single carbon includes a hydroxyl group (-OH) and carboxylic group (-COOH), the molecule is known as alpha-hydroxy acid.
- The central carbon of lactic acid is chiral and the other two substituent groups it includes are hydrogen atoms on a methyl group (-CH3).
- This results in two different structures which are L-lactic acid (+) and D-lactic acid (-).
- The structural representation of C3H6O3 or lactic acid is as follows –
Structural Representation of Lactic Acid
Properties of Lactic Acid
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The main characteristics of lactic acid are as follows -
- When it is in a liquid state, lactic acid is colourless.
- It turns into a white powder in a solid state.
- The molar mass or molecular weight of the acid is 90.08 g/mol.
- It is soluble both in water and ethanol.
- Lactic acid is corrosive to metals and tissues.
Thus, overuse of lactic acid can lead to severe side effects.
| Properties of Lactic Acid | |
|---|---|
| Name of the Acid | Lactic Acid |
| Chemical Formula | C3H6O3 |
| Molar Mass | 90.08 g/mol |
| pH | 3.51 |
| Melting Point | 53° C |
| Boiling Point | 122° C |
Uses of Lactic Acid
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Human body produces lactic acid on its own. However, due to its wide range of applications, there is a significant requirement for industrially produced lactic acid. It is formed as a result of fermentation by the involvement of nutrients such as amino acids, vitamins, glucose, peptides, and salt. Lactic acid is used to form the following products –
- Healthcare and personal products
- Dairy products such as yoghurt.
- Food preservatives
- Cleaning and dishwashing products
- Paint additives
- Leather Tanning and Textile dyeing
- Pharmaceuticals
- Plastics
Lactic acid also helps in the coagulation of protein in milk. It plays an important role to treat traumatic brain injuries. Lactate also signals the release of norepinephrine in the brain.
Lactic acid has three main functions in the body including:
- Energy: Lactic acid fuel cells in the body when they work harder than usual in case of intense exercises.
- Generating glucose: After the acid is created in other tissues, the liver and kidneys filter it out from the blood. The organs break it down to convert it into glucose that the body can use for energy.
- Molecular Signalling: Lactic acid in the blood is a signal molecule throughout your body. Think of it like a set of flags or markers a construction crew puts down before they begin working in an area. Lactic acid attracts cells in your immune system to heal wounds and fight infections.
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Things to Remember
- Lactic acid acts as a fuel for the cells in the body at times of intense exercise.
- It is formed when the body breaks down glucose and other carbohydrates for energy.
- Muscle cells and red blood cells are mostly known to produce lactic acid.
- The organs and tissues producing lactic acid in the body are Muscles, Red blood cells, brain, skin, and Gastrointestinal tract.
- Lactic acid, also known as lactate, is a product of pyruvate metabolism in anaerobic conditions.
Sample Questions
Ques 1: Name the foods that are high in Lactic Acid. (3 marks)
Ans: The foods that are high in Lactic Acid are as follows:
- Soy Products like Soy milk and Tofu
- Pickled Meat (Salami) and Pickled Vegetables (sauerkraut and kimchi)
- Legumes: Beans and Peas
- Chees
- Bread and Beer
Ques 2: What is the natural source of Lactic Acid? (1 mark)
Ans: The natural sources of lactic acid are Sour milk or curd.
Ques 3: What are the uses of Lactic Acid? (3 marks)
Ans: Lactic Acid is used in many ways, such as:
- It is used in the making of plastics.
- Used in leather tanning and dyeing of the textiles.
- In healing of the traumatic injuries of the brain, lactate plays a vital role.
Ques 4: What is the chemical formula of Lactic Acid and write its IUPAC name? (1 mark)
Ans: C3H6O3 is the chemical formula of Lactic Acid and its IUPAC name is 2-Hydroxypropanoic acid.
Ques 5: What are the boiling and melting points of the Lactic Acid? (2 marks)
Ans: The boiling and melting points of lactic acid are:
Boiling Point: 122°C
Melting Point: 16.8°C
Ques 6: Write a few benefits of Lactic Acid. (3 marks)
Ans: a. The nutritional value of the food is improved.
- The serum of the cholesterol levels is controlled
- The digestion of the lactose is improved
- Intestinal infections and some types of cancer is controlled by lactic acid.
Ques 7: List the two types of Lactic Acids. (2 marks)
Ans: The two types of Lactic Acids are:
- L- Lactate
- D- Lactate
Ques 8: Briefly explain the lactic acid fermentation. (2 marks)
Ans: A method to convert carbohydrates and glucose into energy and lactate is known as Lactic acid fermentation. This process takes place in insufficient oxygen. Glucose or other six-carbon sugars are transformed into cellular energy and the metabolite lactate, which is lactic acid in solution, during lactic acid fermentation. It's a process that occurs in certain bacteria and animal cells, such as muscle cells, that's anaerobic.
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