Amino acids - Defination, Function, Benifits

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

Apart from proline, all of the 20 aminoacids found in proteins have a common structure in which a carbon atom is linked to a carboxyl group, a primary amino group, and a side chain (R) which is different in each amino acid. Amino acids are dipolar ions (zwitterions) in aqueous solution. They behave as both acids and bases, amphoteric. The side chains differ in size, shape, charge and chemical reactivity, and are responsible for the differences in the properties of different proteins.

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:

Non-Essential Amino Acids

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

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.

Preparation Tips

• 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 Amino Acids in Exams

Types Of Questions Asked in Exams

Amino Acids NEET MCQs

Q1. Which one of the following amino acids is least likely to be in the core of a protein?

1. Phenylalanine

2. Valine

3. Isoleucine

4. Arginine

Correct answer: 1) Phenylalanine

Explanation:

An amino acid that is charged and hydrophilic, found to be on the exterior of proteins, is arginine. This allows it to interact with the aqueous environment. Amino acids such as phenylalanine, valine, and isoleucine are hydrophobic and often buried inside the protein core. Hence they contribute to structural stability by avoiding water. The proper arrangement of these different combinations of amino acids is important for maintaining the three-dimensional shape and function of the protein.

Hence the correct answer is Option (4) Arginine.

Q2. In the following question, a statement of assertion (A) is followed by a statement of reason (R)

Assertion: Covalent, peptide bonds that connect the amino acids maintain the primary structure of a protein
Reason: Bonding helps in the stability of protein structure.

1. Both Assertion & Reason are true and the reason is the correct explanation of the assertion.

2. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion.

3. Assertion is a true statement but the Reason is false.

4. Both Assertion and Reason are false statements.

Correct answer: 1) Both Assertion & Reason are true and the reason is the correct explanation of the assertion.

Explanation:

The assertion and the reason are also true because the reason has explained the correct explanation of the assertion. Peptide bonds with covalency bind amino acids together in a protein to produce its primary structure. This series of amino acids is important in maintaining the final stability and activity of the protein. The power of these covalent bonds helps the protein retain its stability to fold into its active three-dimensional structure. Hence, peptide bond formation is important not only for the development of the primary structure but also for contributing to the stability of the whole protein structure.

Hence the correct answer is Option 1) Both Assertion & Reason are true and the reason is the correct explanation of the assertion.

Q3. Primary protein is a linear chain of amino acids with

1. N- terminal at both ends

2. C- terminal at both ends

3. N- terminal at right end and C- terminal at left end

4. N- terminal at left end and C- terminal at right end

Correct answer: 4) N- terminal at left end and C- terminal at right end

Explanation:

In a protein, the sequence of amino acids forms a chain, and this chain has two distinct ends. The N-terminal amino acid refers to the first amino acid in the sequence, which has a free amino group (-NH2). The C-terminal amino acid is the last amino acid in the sequence, characterized by a free carboxyl group (-COOH). The terms N-terminal and C-terminal are used to describe the orientation of the protein chain, with the N-terminal being the starting point and the C-terminal being the endpoint. This directionality is important in understanding protein synthesis and function.

Hence, the correct answer is option 4) N- terminal at the left end and C- terminal at the right end.

Also Read:

• MCQs on Types of Structure of Proteins

• Applications of Enzymes

• Beriberi

FAQs on Amino Acids

What do you mean by amino acids?

Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid contains an amino group (-NH₂), a carboxyl group (-COOH), and a variable side chain (R group) attached to the central carbon. The R group determines the chemical nature of each amino acid. They play vital roles in protein structure, enzyme activity, hormone production, and metabolic pathways. Without amino acids, protein synthesis and life processes would not be possible.

How many amino acids are used in protein synthesis?

There are 20 standard amino acids that participate in the synthesis of proteins in all living organisms. These amino acids are encoded by the genetic code (codons) in DNA and mRNA. Some are essential amino acids i.e., obtained from diet) while others are non-essential i.e., synthesized in the body). They join together through peptide bonds to form long chains, which fold into functional proteins.

Which foods are rich in amino acids?

Foods rich in amino acids are those containing high-quality proteins. Animal-based sources like eggs, chicken, fish, meat, and milk provide all essential amino acids and are considered complete proteins. Plant-based sources include legumes, beans, soy, lentils, and nuts, though some may lack one or more essential amino acids. Thus, a varied diet ensures proper intake of all amino acids required for body functions.

What are essential amino acids?

The essential amino acids cannot be synthesized by the body and must be obtained through diet. These amino acids are crucial for growth, tissue repair, enzyme production, and overall metabolism. Their deficiency can lead to growth retardation, muscle wasting, and other health issues.

• Phenylalanine

• Valine

• Threonine

• Tryptophan

• Isoleucine

• Methionine

• Histidine

• Leucine

• Lysine

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