Biology

Molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. A biomolecule is any molecule that is produced by a living organism, including large macromolecules such as proteins, polysaccharides, lipids, and nucleic acids, as well as small molecules such as primary metabolites, secondary metabolites, and natural products. These large biological molecules are called "macromolecules". The four kinds are: carbohydrates, lipids, proteins, and nucleic acids. These are the main molecules: 1. Carbohydrates: Carbohydrates are organic compounds made of carbon, hydrogen, and oxygen atoms. Carbs are made of monosaccharaides (single sugars) linked together. Their function is to provide a key source of energy for cells. An example is starch, made of many linked glucose molecules. 2. Lipids: Lipids are nonpolar molecules that are not soluble in water. They include fats, phospholipids, steroids, and waxes. Lipids' functions are to provide energy and serve an important part in the structure and functioning of cell membranes. Some examples of lipids: butter (saturated fat), cholesterol (steroid), earwax (wax). 3. Proteins: Proteins are chains of amino acids. Proteins have a wide variety of functions. They can be enzymes, to promote chemical reactions; they can have important structural functions like collagen does in your skin. They can also help structure your ligaments, tendons, bones, hair, and muscles. They are found in fibers that help your blood clot. Proteins called antibodies help your body defend against infection. Other proteins in muscles allow them to contract (making body movement possible). Yet another type of protein called hemoglobin carries oxygen to cells throughout the body. 4. Nucleic acids: Nucleic acids are long chains of smaller molecules called nucleotides. Nucleic acids mainly serve the purpose of providing the organism with its genetic blueprint and coding. They basically tell you who you are. DNA and RNA are two types of nucleic acids In terms of chemical bond formation and cleavage, they are opposites of each other. For example, a dehydration reaction between two groups involves the formation of a chemical bond between the groups and the release of a water molecule. Almost always one H comes from one molecule and a hydroxyl OH group comes from the other. A hydrolysis reaction occurs when a water molecule reacts with the bond in such way that bond is broken and the individual atoms which make up the water molecule are distributed to the two products. Hydrolysis = hydro (water) lysis (splitting). So you are splitting/breaking a chemical bond by the addition of water (H2O). More correctly, it is by the introduction of the elements that make up water (hydrogen and oxygen). The reactions are more complicated than just adding water to a compound, but by the end of a hydrolysis reaction, there will be 2 more hydrogen’s and 1 more oxygen shared between the products, than there were before the reaction occurred. An ester is hydrolysed into an alcohol and a carboxylic acid. Condensation is the opposite. It is when 2H and 1O are LOST from a compound or compounds during the reaction. Most often this occurs when 2 reactants form 1 product - the bond between them being formed by the concerted loss of H2O Example - an alcohol + a carboxylic acid -> ester + H2O