Why Is Leucine Essential in Biochemistry and Nutrition?
Leucine is a type of amino acids which is received through the hydrolysis of most common proteins. The first amino acids that were discovered in the wool and muscle fibre, leucine amino acids, were discovered in large proportions in haemoglobin, the oxygen-carrying red pigment blood cells. This substance is among the several so-called amino acids for fowls, rats, and human beings who cannot synthesize it but obtain it from dietary sources. On the other hand, this leucine amino acid in microorganisms and plants is synthesized from pyruvic acid, a product breakdown from carbohydrates. When the hydrolysis of dietary proteins takes place, it forms a white crystalline form of amino acid with a chemical formula C6H13NO2.
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State About Leucine and Isoleucine
The 20 naturally existing amino acids in the human body contain leucine and isoleucine. Structurally, both these amino acids are very much alike, but there are slight differences observed in their physiological properties. Leucine isoleucine, both the amino acids, are aliphatic and non-polar, with four carbon chains arising from the basic amino acid structure. The skeletal structure of leucine isoleucine looks very much similar. These two contain the same carboxyl and amino functional groups with the same size, but their side chain layout is distinct. These are a perfect example of structural isomers, where the carbon atoms occupy different positions.
Solved Questions and Answers
I. Explain the Three Branched-Chain Amino Acids with Reference to Leucine Isoleucine Valine?
Ans. The branched-chain amino acids consist of a group of three essentials known as the leucine isoleucine valine. These three amino acids are often grouped together because they have a chain that branches off to one side. These three branched-chain amino acids constitute 35% of human muscle protein and 40% of preformed amino acids needed by mammals in a combined quantity. In plants, the synthesis of BCCA takes place in every location within the plastids of the cells and are determined by the presence of mRNAs encoding enzymes in the metabolic pathways. The BCCAs contribute to both metabolic and physiological functions. The metabolic functions include protein synthesis and turnover, metabolism of glucose, and signalling of the pathways. For the physiological part, these contribute to brain function and the immune system.
II. How Acetyl Leucine is Used in the Treatment Process?
Ans. Acetyl leucine is a type of modified amino acids. With the advance in medical sciences, this amino acid has been found effective in the treatment procedure of several diseases. The standard treatment procedures include vertigo, dizziness, and cerebellar ataxia. A company called IntraBio is looking for possible ways to include this amino acid in the cure of several neurological disorders. Some clinical trials using acetyl leucine are on-process for treatments like three orphan, fatal, and neurodegenerative disorders. It is also considered for some commonly inherited and acquired neurological diseases such as migraine, restless leg syndrome, lewy body dementia, amyotrophic lateral sclerosis, and multiple sclerosis.
III. What is the Role of Leucine Protein Supplements in the Body?
Ans. Today, many dietary supplements are based on the leucine protein that is found to degenerate the muscle tissues and improve the synthesis of muscle proteins. This synthesis of muscle protein is responsible for the building of the tissues in the body. Hence, diets need to be optimized with leucine proteins which can further boost muscle growth and repair. This mainly depends on how much leucine your protein contains. There are many healthy sources of leucine obtained from food like whey protein, soy protein, pea protein, soybeans, beef, hemp, and fish sources.
IV. Role of Leucine in the Human Body?
Ans: The general function of the leucine in the human body is to regulate the muscle structure. It mainly contributes to protein synthesis and protein breakdown, especially in the muscle tissue recovering the damage from physical trauma. Some other functions involve increasing the level of insulin in the blood. It is vital for regulating the blood sugar level involving gluconeogenesis in the liver. This helps the muscle and body to heal.
Did You Know?
Having leucine amino acids in the diets can improve the conditions of ones detected with pre-diabetes or metabolic syndrome. This improved insulin sensitivity and the overall metabolism of substances like sugar and fat.
FAQs on Leucine: Structure, Properties & Importance
1. What is leucine and why is it important for the human body?
Leucine is an essential amino acid, which means the body cannot produce it on its own and it must be obtained through diet. It is one of the three branched-chain amino acids (BCAAs). Its primary importance lies in its role as a fundamental building block for proteins, crucial for muscle growth, tissue repair, and regulating metabolic functions like blood sugar levels.
2. What is the chemical structure of leucine?
From a chemical standpoint, leucine (symbol: Leu or L) is an α-amino acid. Its structure consists of a central α-carbon atom bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a distinctive side chain. The side chain for leucine is an isobutyl group, which makes it a non-polar, hydrophobic amino acid.
3. What are the main functions of leucine in the body?
Leucine performs several vital functions within the body, which are critical for both athletic performance and general health. Its main roles include:
- Muscle Protein Synthesis: It acts as a powerful trigger for building new muscle proteins, essential for recovery and growth after exercise.
- Energy Production: During periods of fasting or intense physical activity, leucine can be used as an energy source.
- Blood Sugar Regulation: It helps maintain stable blood sugar levels by aiding in the production of glucose and insulin.
- Growth Hormone Production: Leucine contributes to the synthesis of growth hormones.
4. Which foods are the best sources of leucine?
Leucine is found in a wide variety of protein-rich foods. Good sources include:
- Animal-Based: Meat (beef, chicken, pork), fish (tuna, salmon), eggs, and dairy products like milk, cheese, and whey protein.
- Plant-Based: Soybeans (tofu, tempeh), lentils, chickpeas, quinoa, oats, nuts (almonds), and seeds (pumpkin seeds).
5. How is leucine classified as an amino acid according to the CBSE syllabus?
In the context of the CBSE Class 12 Chemistry syllabus (Chapter: Biomolecules), leucine is classified in two main ways:
- Essential Amino Acid: It is categorised as essential because the human body cannot synthesise it, making its inclusion in our diet necessary.
- Neutral and Non-polar Amino Acid: Based on its side chain (isobutyl group), which is aliphatic and has no charge, leucine is classified as a neutral and non-polar amino acid.
6. Why is leucine considered a 'branched-chain amino acid' (BCAA)?
Leucine is classified as a branched-chain amino acid (BCAA) due to the specific structure of its aliphatic side chain. Unlike amino acids with straight side chains, the carbon atoms in leucine's isobutyl side chain form a branched, non-linear structure. The other two BCAAs, isoleucine and valine, also share this characteristic of having a branched side chain.
7. How does leucine differ from its isomer, isoleucine?
Leucine and isoleucine are structural isomers, meaning they share the same chemical formula (C₆H₁₃NO₂) but have a different arrangement of atoms. The key difference lies in the structure of their side chains. In leucine, the branch is on the gamma-carbon (third carbon from the α-carbon), whereas in isoleucine, the branch is on the beta-carbon (second carbon). This subtle structural difference affects how they are metabolised and used by the body.
8. What is the specific role of leucine in triggering muscle protein synthesis?
Leucine plays a unique role beyond just being a building block for protein. It acts as a critical signalling molecule that activates a key pathway in the body known as the mTOR (mammalian target of rapamycin) pathway. The mTOR pathway is the primary regulator of cell growth and protein synthesis. By activating mTOR, leucine essentially 'switches on' the cellular machinery responsible for building new muscle tissue, making it particularly effective for muscle repair and growth after exercise.
