Amino Acids

Introduction

Amino Acids

Amino acids are the building blocks of proteins, and they play a fundamental role in the structure and function of living organisms.

Proteins

Proteins are essential biomolecules that carry out a wide range of functions in cells, tissues, and organisms. They are involved in processes such as enzyme catalysis, cell structure, immune response, and transport of molecules.

Formation of Polypeptides

Peptide Bonds

Amino acids are linked together by peptide bonds to form polypeptides. A peptide bond is a covalent bond formed between the amino group of one amino acid and the carboxyl group of another.

Polypeptide Definition

A polypeptide is a chain of amino acids connected by peptide bonds. Polypeptides can vary in length, with some consisting of just a few amino acids, while others can be hundreds or thousands of amino acids long.

Three-Dimensional Structure of Proteins

Protein Folding

Polypeptide chains fold into specific three-dimensional shapes to form functional proteins. The folding of a protein is critical for its function.

Interactions Between Amino Acids

The three-dimensional structure of proteins is maintained by various interactions between individual amino acids within the polypeptide chain. These interactions include hydrogen bonds, disulfide bonds, ionic bonds, and hydrophobic interactions.

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Amino Acids - Linked by Peptide Bonds to Form Polypeptides

Diversity of Protein Shapes and Functions

1. Variety of Shapes

Proteins exhibit a vast diversity of shapes, and this structural diversity determines their specific functions in the cell.

2. Functional Roles

Examples of protein functions include enzymes that catalyse chemical reactions, antibodies that aid in immune responses, structural proteins that provide support and shape to cells and tissues, and transport proteins that facilitate the movement of molecules across membranes.

3. Haemoglobin Example

Haemoglobin, a protein found in red blood cells, has a quaternary structure that allows it to bind and transport oxygen throughout the body. Its unique shape and iron-containing heme groups enable it to carry out this crucial function.

Gene Expression and Phenotype

1. Gene Expression

Gene expression is the process by which genetic information encoded in DNA is used to produce proteins. It involves the transcription of DNA into mRNA (messenger RNA) and the translation of mRNA into proteins.

2. Phenotype Determination

The phenotype of an organism is determined by the proteins produced as a result of gene expression. These proteins carry out various functions that collectively determine an individual's traits, characteristics, and overall physiology.

3. Environmental Factors

While genes play a significant role in determining phenotype, environmental factors can also influence it. Environmental factors such as diet, exposure to toxins, and temperature can affect protein expression and, consequently, an organism's phenotype.

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Amino Acids - Linked by Peptide Bonds to Form Polypeptides

Example: Eye Color Determination

1. Genetics of Eye Colour

Eye colour in humans is determined by multiple genes, with variations in the OCA2 and HERC2 genes playing significant roles.

2. Protein Expression

The proteins produced by these genes are involved in the production and distribution of melanin, the pigment responsible for eye colour. The specific combination of alleles and the resulting protein expression determine an individual's eye colour.

3. Environmental Influence

While genetics is a primary determinant of eye colour, environmental factors such as exposure to UV radiation can influence the intensity of eye colour by affecting melanin production.

Summary

In summary, amino acids are the building blocks of proteins, and they are linked together by peptide bonds to form polypeptides. The three-dimensional structure of proteins is crucial for their function and is maintained by various interactions between individual amino acids. Proteins have diverse shapes that determine their specific functions in cells and organisms, including roles in enzymatic reactions, immune responses, structural support, and molecular transport. Phenotype, the observable traits of an organism, is determined by the proteins produced as a result of gene expression, with environmental factors also playing a role in influencing phenotype. Understanding the relationship between amino acids, polypeptides, and protein function is fundamental to the study of biology and genetics.