Eleven Standard >> Biomolecules | Part - 1

Bio molecules : Protein

Biomolecules are the organic molecules that are essential for the structure, function, and regulation of living organisms. They are the building blocks of life and play crucial roles in various biological processes. Biomolecules comprise proteins, fats, carbohydrates, nucleic acids, and enzymes.

Protein:

Proteins are complex biomolecules composed of amino acids. They are essential for the structure, function, and regulation of cells and tissues in living organisms.

1. Amino Acids:

   • Proteins are formed by the assembly of amino acids, which serve as the fundamental constituents or elemental units of protein structures.
   • They consist of an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable side chain denoted as "R."
   • There are 20 standard amino acids commonly found in proteins, each with a distinct chemical structure and side chain properties.

2. Structure:

   • Primary Structure: The primary structure of a protein pertains to the sequential arrangement of amino acids in the polypeptide chain. It is determined by the DNA sequence in the gene encoding the protein.
   • Secondary Structure: Secondary structure refers to local folding patterns within the protein chain, such as alpha helices and beta sheets. These structures are stabilized by hydrogen bonding between the peptide bonds.
   • Tertiary Structure: Tertiary structure refers to the overall three-dimensional arrangement of the protein. It results from interactions between amino acid side chains (R-groups) and the surrounding environment.
   • Quaternary Structure: Some proteins consist of multiple polypeptide chains, and their arrangement forms the quaternary structure.

3. Functions:

   • Enzymes: Enzymes are protein catalysts that accelerate biochemical reactions in living organisms.
   • Structural Proteins: Proteins like collagen and keratin provide support and structure to tissues, such as skin, tendons, and hair.
   • Transport Proteins: Proteins like hemoglobin and membrane transporters facilitate the movement of molecules, such as oxygen, across cell membranes and within the bloodstream.
   • Hormones: Hormonal proteins, like insulin, act as chemical messengers, regulating various physiological processes in the body.
   • Antibodies: Antibodies are proteins of the immune system that recognize and neutralize foreign substances (antigens).

Carbohydrates:

Carbohydrates are organic compounds comprising carbon, hydrogen, and oxygen atoms. The ratio of hydrogen to oxygen is 2:1, similar to that in water (\(H_{2}O\)). Carbohydrates are categorized according to the quantity of sugar units they contain.

1. Monosaccharides:

   • Monosaccharides represent the most basic structure of carbohydrates, comprising only one unit of sugar.
   • Common monosaccharides include glucose, fructose, and galactose.
   • They are typically classified based on the number of carbon atoms they contain, such as trioses (3 carbon atoms), pentoses (5 carbon atoms), and hexoses (6 carbon atoms).
   • Monosaccharides serve as a source of energy and are the building blocks for larger carbohydrates.

2. Disaccharides:

   • Disaccharides are formed when two monosaccharide units join together through a glycosidic bond.
   • Common disaccharides include sucrose, lactose, and maltose.
   • Sucrose (glucose + fructose) is found in sugar cane and sugar beets and is commonly used as table sugar.
   • Lactose (glucose + galactose) is the sugar present in milk and dairy products.
   • Maltose (glucose + glucose) is a product of starch digestion and is found in germinating grains.

3. Polysaccharides:

   • Polysaccharides are intricate carbohydrates that consist of numerous monosaccharide units bonded together.
   • Starch: Starch is a type of polysaccharide primarily present in plants, serving as a storage form for carbohydrates. It consists of glucose units linked together in the form of amylose (unbranched) and amylopectin (branched). Starch acts as a reservoir of energy in plants, storing carbohydrates for future use.
   • Glycogen: Glycogen is the storage polysaccharide in animals and humans. It is highly branched and serves as a short-term energy store, mainly in the liver and muscles.
   • Cellulose: Cellulose is a structural polysaccharide found in the cell walls of plants. It consists of glucose units arranged in a linear chain, linked by beta-1,4-glycosidic bonds. Cellulose provides rigidity and strength to plant cells and is a major component of dietary fiber.

4. Functions of Carbohydrates:

   • Energy Source: Carbohydrates are a primary source of energy for organisms. They are broken down during cellular respiration to release energy in the form of ATP.
   • Structural Support: Carbohydrates like cellulose provide structural support to plant cells and contribute to the rigidity of cell walls.
   • Energy Storage: Plants store energy in the form of starch, while animals store energy in the form of glycogen.
   • Recognition and Signaling: Carbohydrates on cell surfaces play a role in cell recognition, immune response, and cellular signaling.