Importance of Water in Biology

Water Molecule

• Water is a polar molecule due to uneven distribution of charge within the molecule, with hydrogen atoms being more positive than the oxygen atom.
• It has a high heat specific capacity, requiring a lot of energy to warm it up, which minimizes temperature fluctuations in living things.
• Water has a relatively large latent heat of vaporization, providing a cooling effect with little water loss during evaporation.
• Strong cohesion between molecules enables effective transport of water in tube-like transport cells.
• Maximum density of water is at 4°C, making ice less dense and causing it to float on top of water, creating an insulating layer.

Monomers and Polymers

• Monomers are small units that are components of larger molecules, such as monosaccharides, amino acids, and nucleotides.
• Polymers are molecules made from monomers joined together by chemical bonds.
• Condensation reactions join monomers by eliminating a water molecule, while hydrolysis is the opposite, breaking a chemical bond between two molecules by adding water.

Carbohydrates

• Carbohydrates consist only of carbon, hydrogen, and oxygen and are long chains of sugar units called saccharides.
• There are three types of saccharides: monosaccharides, disaccharides, and polysaccharides.
• Monosaccharides, such as glucose, can join together to form disaccharides and polysaccharides by glycosidic bonds.

Monosaccharides

• Glucose is a monosaccharide containing six carbon atoms, and is the main substrate for respiration.
• It has two isomers: alpha and beta glucose.

Disaccharides

• Maltose is a disaccharide formed by condensation of two glucose molecules.
• Sucrose is a disaccharide formed by condensation of glucose and fructose.
• Lactose is a disaccharide formed by condensation of glucose and galactose.

Polysaccharides

• Polysaccharides are formed from many glucose units joined together.
• Glycogen is the main energy storage molecule in animals, formed from many alpha glucose molecules joined together by 1, 4 and 1, 6 glycosidic bonds.
• Starch stores energy in plants, and is a mixture of amylose and amylopectin.
• Amylose is an unbranched chain of glucose molecules joined by 1, 4 glycosidic bonds, making it a compact molecule.
• Amylopectin is branched, made up of glucose molecules joined by 1, 4 and 1, 6 glycosidic bonds, allowing for rapid digestion by enzymes.

Learn about the significance of water in biological systems, including its role as a polar molecule, metabolite, and solvent in metabolic reactions. Explore how water facilitates the formation and breaking of chemical bonds.