Amino acids - Defination, Function, Benifits

Edited By Irshad Anwar | Updated on Jul 02, 2025 05:18 PM IST

Amino acids are among the basic components of biomolecules, which play a significant role in the biochemical processes of life. These organic compounds, as they are considered to be the building blocks of proteins, play an essential physiological role in such functions as enzymatic activity, hormone production, and tissue repair. Amino acids can be classified into two major types: essential amino acids and non-essential amino acids, which the body can synthesize. Understanding the importance of amino acids is important for students who are to appear for entrance examinations like NEET, AIIMS, and other paramedical courses because this is a major topic in Biology from the Class 11 CBSE syllabus for biomolecules.

This Story also Contains

What Are Amino Acids?
Types Of Amino Acids
Classification Of Amino Acids
How Many Amino Acids Are There?
Food Sources Of Amino Acids
Functions Of Amino Acids
Tips, Tricks, And Strategies To Prepare For Amino Acids
Weightage Of Questions From Amino Acids In Different Exams
Types Of Questions Asked On Amino Acids In Different Exams
Recommended Video On Amino Acids

Also Read:

What Are Amino Acids?

Amino acids are organic compounds containing carbon, hydrogen, nitrogen, oxygen, and sometimes sulfur. They have an amino group (-NH₂), a carboxyl group (-COOH), and a unique side chain, or R group, that determines the unique characteristics of each amino acid.

Structure Of Amino Acids

Each amino acid has the following general structure:

Amino group: -NH₂
Carboxyl group: -COOH
Hydrogen atom: -H
R group: Variable side chain that defines the amino acid

Types Of Amino Acids

Amino acids can be divided on the basis of the requirement of human health and chemical characteristics. The primary classification is as follows:

Essential Amino Acids

There are several amino acids that the human body cannot produce and must obtain from the diet. This is listed in the essential amino acids list:

Essential Amino Acids
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine

Non-Essential Amino Acids

Non-essential amino acids can be synthesized by the body. Some common examples are:

Non-Essential Amino Acids
Alanine
Asparagine
Aspartic acid
Glutamic acid
Serine
Tyrosine

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Semi-Essential Amino Acids

These amino acids are generally non-essential but may become essential under certain circumstances, such as illness or stress. Examples include:

Arginine
Cysteine
Glutamine
Glycine
Proline
Tyrosine

Classification Of Amino Acids

Amino acids can also be classified based on their chemical properties that influence their function in proteins and metabolism.

Basic Amino Acids

These are amino acids whose side chains consist of basic (alkaline) groups. They include;

Lysine
Arginine
Histidine

Acidic Amino Acids

These are the amino acids whose side chains contain acidic groups. They include:

Aspartic acid
Glutamic acid

Aromatic Amino Acids

These are amino acids that possess an aromatic ring in their side chains. They include:

Phenylalanine
Tyrosine
Tryptophan

How Many Amino Acids Are There?

20 standard amino acids coded by the genetic code and used in protein synthesis exist. The particular sequence of these then goes to form proteins into their appropriate shapes and functions.

Food Sources Of Amino Acids

Amino acids can be obtained from a variety of foods. Foods that are rich in amino acids are;

Animal products: Chicken
Fish: Salmon and tuna
Milk products: Milk, cheese, yoghurt
Legumes and Lentils: Good source of amino acids
Nut and seed products: Almonds, pumpkin
Eggs: Source of complete amino acids

Functions Of Amino Acids

Amino acids perform some key functions:

They are used as the building blocks for proteins.
They act as precursors to hormones.
They participate in enzyme activity.
Some of the amino acids are involved in the formation of neurotransmitters.

Tips, Tricks, And Strategies To Prepare For Amino Acids

Study Aids: Draw diagrams or tables showing the functions and sources of essential and nonessential amino acids.
Mnemonics: To remember what the essential amino acids are, use "PVT TIM HLL": Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Leucine, Lysine.
Multimedia: View videos or animations showing the structures of amino acids and the function that the different kinds serve in protein synthesis.
Real-Life Example: Connect the amino acids to common foods. For example, for essential amino acids, connect it to meat and for non-essential ones to beans.
Flashcards: Use flashcards to memorize the key terms and characteristics of different amino acids.

Weightage Of Questions From Amino Acids In Different Exams

Exam Type	Weightage of Amino Acids
CBSE	5-7%
NEET	2-3%
Nursing Entrance Exams	3-5%
Paramedical Entrance Exams	2-4%

Types Of Questions Asked On Amino Acids In Different Exams

Exam Type	Types of Questions
CBSE Board Exams	Definitions and differences between essential and non-essential amino acids Examples of food sources rich in amino acids Short answers on the structure and functions of amino acids
NEET	MCQs on the role and classification of amino acids Assertion and reason questions related to amino acid metabolism Long answer questions on protein synthesis and dietary needs
Nursing Entrance Exams	True/False questions on amino acid functions Scenario-based questions on dietary recommendations for patients
Paramedical Entrance Exams	Questions on the impact of amino acid deficiency on health Case studies on amino acid supplementation and management of related conditions.

Also Read:

Biological Functions Of Proteins	Biomolecules mcqs
Applications Of Enzymes	Factors Affecting Enzyme Activity
Water: Structure, Molecule, Facts	Metabolites: Definition, Examples, Types

Recommended Video On Amino Acids

Frequently Asked Questions (FAQs)

1. What are amino acids?

The building components of proteins are amino acids. You need 20 of these molecules for your body to function properly because they are the building blocks of protein that are required by all living organisms.

2. What foods contain a lot of amino acids?

These five foods are some of the top providers of dietary amino acids:

Quinoa is currently one of the cereals with the highest nutritious content available. Eggs contain all nine essential amino acids, which are also contained in turkeys, cottage cheese, mushrooms, salmon, lentils, and beans.

3. Which foods are high in amino acids?

These five foods are some of the top providers of dietary amino acids:

Quinoa. Quinoa is currently one of the cereals with the highest nutritious content available. Eggs contain all nine essential amino acids, which are also contained in turkey, cottage cheese, mushrooms, salmon, lentils, and beans.

4. What results in an amino acid deficit?

Reasons for Potential Amino Acid Deficiency:

Protein breakdown in the digestive system is insufficient.

Anomalies in the body's biochemical processes that are inherited. a bad diet stress.

5. Does amino aid in weight loss?

As you gain muscle, your metabolism speeds up and you start burning more calories because muscle tissue consumes more energy than fat tissue does. So, if taking an amino acid supplement will help you gain more muscle, it may also help you lose weight. Supplementing with BCAAs, or branched-chain amino acids, may be the answer in this situation.

6. What Are the 20 Amino Acids?

The 20 amino acids are the standard building blocks of proteins and include both essential and non-essential amino acids

Essential Amino Acids:

Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine

Non essential Amino Acids:

Alanine
Arginine
Asparagine
Aspartic acid
Cysteine
Glutamic acid
Glutamine
Glycine
Proline
Serine
Tyrosine

7. What Are the 5 Main Amino Acids?

The five main amino acids include:

Leucine
Lysine
Methionine
Threonine
Valine

8. What Are Essential Amino Acids?

Essential amino acids are those that the body cannot synthesize and must be obtained through diet.

9. What Are Non-Essential Amino Acids?

Non-essential amino acids are those that the body can produce on its own, even if they are not consumed in the diet.

10. What is the difference between essential and non-essential amino acids?

Essential amino acids cannot be produced by the body and must be obtained from food, while non-essential amino acids can be synthesized by the body from other compounds. However, some non-essential amino acids may become conditionally essential in certain situations, such as illness or stress.

11. What is the significance of amino acid chirality?

Most amino acids exist in two forms that are mirror images of each other, called L-form and D-form (chiral molecules). In nature, almost all amino acids used in proteins are L-form. This chirality is crucial for the proper folding and function of proteins.

12. What is the significance of branched-chain amino acids (BCAAs)?

Branched-chain amino acids (leucine, isoleucine, and valine) are particularly important for muscle metabolism. They can be oxidized in muscle tissue for energy and play a crucial role in promoting muscle protein synthesis. BCAAs are often used as supplements by athletes to support muscle growth and recovery.

13. How do amino acids contribute to the production of creatine?

Creatine, an important compound for energy metabolism in muscles, is synthesized from three amino acids: glycine, arginine, and methionine. The liver and kidneys are the primary sites of creatine synthesis. Understanding this process has led to the development of creatine supplements popular among athletes.

14. What is the role of amino acids in maintaining acid-base balance in the blood?

Amino acids contribute to acid-base balance through their amphoteric nature (ability to act as both acids and bases). They can accept or donate protons, helping to buffer changes in blood pH. Additionally, the metabolism of sulfur-containing amino acids can produce acid, while the metabolism of other amino acids can produce bases.

15. What is the significance of amino acid transporters in the body?

Amino acid transporters are proteins that facilitate the movement of amino acids across cell membranes. They are crucial for nutrient absorption in the intestines, reabsorption in the kidneys, and the distribution of amino acids to various tissues. Defects in these transporters can lead to various metabolic disorders.

16. How do amino acids contribute to the immune system?

Amino acids are crucial for the immune system. They are needed to produce antibodies, cytokines, and other immune molecules. Some amino acids, like glutamine, also serve as fuel for immune cells. A deficiency in certain amino acids can impair immune function.

17. How do amino acids affect sleep patterns?

Certain amino acids influence sleep patterns. Tryptophan, for instance, is a precursor to serotonin and melatonin, both of which are involved in regulating sleep-wake cycles. Glycine has been shown to improve sleep quality by lowering core body temperature and reducing the time it takes to fall asleep.

18. How do amino acids interact with vitamins and minerals in the body?

Amino acids often work in conjunction with vitamins and minerals. For example, iron requires histidine for proper absorption, while zinc interacts with histidine and cysteine in various enzymes. Some amino acids, like methionine, are involved in the metabolism of B vitamins. Understanding these interactions is crucial for comprehending overall nutrient metabolism.

19. What is the role of amino acids in the production of nitric oxide?

The amino acid arginine is the precursor for nitric oxide (NO) production in the body. NO is a crucial signaling molecule that plays roles in vasodilation, neurotransmission, and immune function. Understanding this connection has led to the use of arginine supplements for various health purposes, particularly cardiovascular health.

20. How do amino acids form proteins?

Amino acids join together through peptide bonds to form long chains called polypeptides. These polypeptides then fold and interact with other polypeptides to create the three-dimensional structure of proteins. The sequence and number of amino acids determine the protein's structure and function.

21. How do amino acids contribute to the body's pH balance?

Amino acids can act as buffers in the body, helping to maintain a stable pH. They can accept or donate hydrogen ions (protons) through their amino and carboxyl groups, which allows them to neutralize small changes in pH and keep the body's acid-base balance within a narrow range.

22. What is the role of amino acids in neurotransmitter production?

Several amino acids serve as precursors for neurotransmitters, which are chemical messengers in the nervous system. For example, tryptophan is used to produce serotonin, tyrosine is used to make dopamine and norepinephrine, and glutamate itself acts as a neurotransmitter.

23. How do amino acids contribute to energy production in the body?

When carbohydrates are not available, amino acids can be broken down and used for energy production through a process called gluconeogenesis. The amino group is removed (deamination), and the remaining carbon skeleton can enter the citric acid cycle to produce ATP.

24. What is the significance of the R group in amino acids?

The R group, or side chain, gives each amino acid its unique properties. It determines whether the amino acid is polar or nonpolar, acidic or basic, and influences its role in protein structure and function. The R group is what distinguishes one amino acid from another.

25. How many essential amino acids are there, and why are they called "essential"?

There are 9 essential amino acids in humans. They are called "essential" because the human body cannot synthesize them, so they must be obtained through diet. These are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

26. How do amino acids affect muscle growth and repair?

Amino acids, particularly branched-chain amino acids (BCAAs), are essential for muscle protein synthesis. They provide the raw materials needed to build new muscle tissue and repair damaged muscle fibers after exercise. This is why protein intake is crucial for athletes and bodybuilders.

27. What is the connection between amino acids and kidney function?

The kidneys play a crucial role in amino acid metabolism. They filter amino acids from the blood and reabsorb them to prevent loss through urine. Certain amino acids, like arginine, are important for kidney function. However, in kidney disease, the metabolism of some amino acids can be impaired, leading to their accumulation in the blood.

28. How do amino acids contribute to the body's thermal regulation?

Amino acids play a role in thermal regulation through various mechanisms. Some amino acids, like glycine, can lower core body temperature. Additionally, the metabolism of amino acids generates heat, contributing to the body's overall thermal balance. Protein-rich meals can increase thermogenesis, temporarily boosting metabolic rate.

29. How do amino acids contribute to the production of melanin?

Melanin, the pigment responsible for skin, hair, and eye color, is synthesized from the amino acid tyrosine. The enzyme tyrosinase converts tyrosine to dopaquinone, which then undergoes further reactions to produce melanin. Variations in this process contribute to differences in pigmentation among individuals.

30. What is the role of amino acids in maintaining gut health?

Amino acids are crucial for gut health. They are needed to produce the proteins that form the gut lining and the enzymes that aid in digestion. Some amino acids, like glutamine, serve as a primary fuel source for intestinal cells. Additionally, certain amino acids can influence the composition of the gut microbiome.

31. How do amino acids contribute to the body's response to exercise?

Amino acids play multiple roles in exercise response. They are used to repair and build muscle tissue after exercise. During prolonged exercise, they can be used as an energy source. Some amino acids, like beta-alanine, can enhance exercise performance by buffering lactic acid buildup. Post-exercise, amino acids are crucial for recovery and adaptation.

32. What is the significance of amino acid racemization in aging and disease?

Amino acid racemization is the conversion of L-amino acids to their D-form counterparts. This process occurs slowly over time and is considered a marker of protein aging. Accumulation of D-amino acids in tissues has been associated with various age-related conditions and diseases, such as cataracts and Alzheimer's disease.

33. What is the role of amino acids in neurodegenerative diseases?

Amino acids play complex roles in neurodegenerative diseases. Some amino acids, like glutamate, can be neurotoxic in excess. Others, like glycine and D-serine, are important for proper neurotransmission. Imbalances in amino acid metabolism have been implicated in diseases like Alzheimer's, Parkinson's, and Huntington's disease.

34. What is the relationship between amino acids and the genetic code?

The genetic code specifies the sequence of amino acids in proteins. Each group of three nucleotides (codon) in mRNA corresponds to a specific amino acid. This code is universal across almost all living organisms, demonstrating the fundamental importance of amino acids in life.

35. How do amino acids contribute to collagen formation?

Collagen, the most abundant protein in the human body, requires specific amino acids for its formation. Glycine, proline, and hydroxyproline are particularly important. These amino acids allow collagen to form its characteristic triple-helix structure, crucial for its strength and flexibility.

36. What is the role of amino acids in hormone production?

Many hormones are proteins or peptides made from amino acids. For example, insulin is a protein hormone made of amino acids. Additionally, some amino acids serve as precursors for non-protein hormones, such as tyrosine for thyroid hormones.

37. How do amino acids contribute to hair, skin, and nail health?

Amino acids are essential for the production of keratin, the primary protein in hair, skin, and nails. Specific amino acids like cysteine, lysine, and methionine are particularly important for keratin synthesis and can affect the strength and appearance of these tissues.

38. What is the connection between amino acids and mood regulation?

Certain amino acids are precursors to neurotransmitters that affect mood. For example, tryptophan is needed to produce serotonin, often called the "feel-good" neurotransmitter. Tyrosine is used to make dopamine, which affects motivation and pleasure. Imbalances in these amino acids can potentially impact mood disorders.

39. How do amino acids contribute to wound healing?

Amino acids play a crucial role in wound healing. They are necessary for the synthesis of new proteins needed in tissue repair, such as collagen. Arginine and glutamine, in particular, have been shown to enhance wound healing by promoting collagen deposition and improving immune function.

40. What is the significance of amino acid sequence in proteins?

The sequence of amino acids in a protein, known as its primary structure, determines how the protein will fold into its three-dimensional shape. This shape, in turn, determines the protein's function. Even a single change in the amino acid sequence can dramatically alter a protein's structure and function, potentially leading to diseases.

41. How do amino acids contribute to the aging process?

Amino acids play complex roles in aging. On one hand, they are essential for maintaining and repairing tissues throughout life. On the other hand, the accumulation of damaged proteins (made of amino acids) is a hallmark of aging. Some amino acids, like glycine and N-acetylcysteine, have been studied for their potential anti-aging properties due to their antioxidant effects.

42. How do amino acids contribute to bone health?

Amino acids are essential for bone health in several ways. They are needed to produce collagen, which forms the organic matrix of bone. Some amino acids, like lysine, enhance calcium absorption. Additionally, amino acids contribute to the synthesis of hormones and growth factors that regulate bone metabolism.

43. What is the connection between amino acids and appetite regulation?

Amino acids play a role in appetite regulation through various mechanisms. Some amino acids stimulate the release of hormones that affect hunger and satiety. For example, leucine can stimulate the release of leptin, a hormone that suppresses appetite. Additionally, the brain monitors amino acid levels to regulate food intake.

44. What are amino acids and why are they important?

Amino acids are organic compounds that serve as the building blocks of proteins. They are crucial for life because they form the structural components of cells, catalyze biochemical reactions as enzymes, and play vital roles in metabolism, growth, and repair of body tissues.

45. What is the general structure of an amino acid?

The general structure of an amino acid consists of a central carbon atom (alpha carbon) bonded to four groups: an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (H), and a unique side chain (R group) that determines the specific properties of each amino acid.

46. How do amino acids act as antioxidants in the body?

Some amino acids, such as cysteine, methionine, and taurine, have antioxidant properties. They can neutralize harmful free radicals in the body, protecting cells from oxidative stress and damage. This antioxidant action contributes to overall health and may help prevent chronic diseases.

47. What is the role of amino acids in liver function?

The liver uses amino acids for various functions, including protein synthesis, glucose production, and detoxification. For example, the liver uses amino acids to produce albumin, an important blood protein. It also uses amino acids in the urea cycle to remove toxic ammonia from the body.

48. What is the role of amino acids in DNA synthesis?

While amino acids are not directly used in DNA synthesis, they play supportive roles. For example, glycine, aspartate, and glutamine contribute to the synthesis of purines, which are components of DNA. Additionally, the amino acid metabolism is linked to the production of energy and reducing agents needed for DNA synthesis.

49. How do amino acids contribute to the body's detoxification processes?

Amino acids play crucial roles in detoxification. For example, glycine and glutamine are used in Phase II liver detoxification to conjugate and neutralize toxins. Cysteine is a component of glutathione, one of the body's most important antioxidants and detoxifying agents.

50. What is the role of amino acids in maintaining fluid balance in the body?

Amino acids contribute to fluid balance through their role in protein synthesis. Proteins, particularly albumin, help maintain oncotic pressure in blood vessels, which is crucial for proper fluid distribution between blood and tissues. Some amino acids also act as osmolytes, helping to regulate cell volume.

51. How do amino acids contribute to cardiovascular health?

Amino acids impact cardiovascular health in several ways. Arginine, for example, is a precursor to nitric oxide, which helps dilate blood vessels and improve blood flow. Taurine has been shown to lower blood pressure and reduce cholesterol levels. Additionally, amino acids are needed to produce heart muscle proteins and enzymes involved in heart function.

52. What is the role of amino acids in the stress response?

Amino acids are crucial in the body's response to stress. They are needed to produce stress hormones like adrenaline and cortisol. Additionally, certain amino acids like tyrosine can help mitigate the effects of stress by supporting the production of neurotransmitters that regulate mood and cognitive function under stress.

53. How do amino acids contribute to the body's circadian rhythms?

Amino acids play a role in circadian rhythms through various mechanisms. The metabolism of certain amino acids, like tryptophan, is involved in the production of melatonin, a key hormone in regulating sleep-wake cycles. Additionally, the availability of amino acids can influence the expression of clock genes that control circadian rhythms.

54. How do amino acids contribute to the body's response to altitude and hypoxia?

Certain amino acids play important roles in the body's adaptation to high altitude and low oxygen conditions. For example, branched-chain amino acids (BCAAs) may help maintain muscle mass at high altitudes. Arginine can enhance nitric oxide production, potentially improving blood flow and oxygen delivery in hypoxic conditions.

55. What is the significance of amino acid catabolism in glucose homeostasis?

Amino acid catabolism can contribute to glucose homeostasis through gluconeogenesis, the production of glucose from non-carbohydrate sources. This process is particularly important during fasting or low-carbohydrate diets. However, excessive protein breakdown for glucose production can lead to muscle wasting in prolonged starvation or uncontrolled diabetes.

56. How do amino acids contribute to the production of bile acids?

Amino acids, particularly glycine and taurine, are used to conjugate bile acids in the liver. This conjugation makes bile acids more water-soluble, enhancing their ability to emulsify fats in the small intestine. Understanding this process is important for comprehending lipid digestion and absorption.

57. How do amino acids contribute to the body's response to radiation exposure?

Certain amino acids have radioprotective properties. For example, cysteine and its derivatives can scavenge free radicals produced by radiation, potentially