Biomolecules | Part - 1

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 include proteins, lipids, carbohydrates, nucleic acids, and enzymes.

Protein:

Proteins are complex biomolecules composed of amino acids. They're essential for the structure, function, and regulation of cells and apkins 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 (\(-NH_{2}\)), 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 unique chemical structure and side chain properties.

2. Structure:

   • Primary Structure refers to the specific sequence of amino acids in a protein's 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 refers to the complete three-dimensional folding pattern of a protein, determining its overall shape and function. 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 natural substances consisting of carbon, hydrogen, and oxygen elements. 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 categorized based on the number of carbon atoms they have, 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:

   • Two monosaccharide molecules combine via a glycosidic bond to form a disaccharide.
   • 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, made of glucose and galactose, is the sugar found in milk and other dairy products.
   • Maltose (glucose + glucose) is a product of starch digestion and is found in germinating grains.

3. Polysaccharides:

   • Polysaccharides are complex carbohydrates made up of many monosaccharide units linked together.
   • Starch: Starch is a type of polysaccharide primarily present in plants, serving as a storage form for carbohydrates. It is made up of glucose units connected as amylose (which is unbranched) and amylopectin (which is branched). Starch acts as a reservoir of energy in plants, storing carbohydrates for future use.
   • Glycogen: It is made up of glucose units connected as amylose (which is unbranched) and amylopectin (which is branched). 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:

   • Carbohydrates serve as a main energy source for living organisms. They are broken down in cellular respiration to produce energy stored as 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.