Biology Notes regarding Cells and Related topics :: Biology Study Tests

1. The ability of ice to float because of the expansion of water as it solidifies is an important factor in the fitness of the environment. If ice sank, then eventually all ponds, lakes, and even oceans would freeze solid, making life as we know it impossible on earth. During the summer, only the upper few inches of the ocean would thaw. Instead, when a deep body of water cools, the floating ice insulates the liquid water below, preventing it from freezing and allowing life to exist under the frozen surface. 2. Carbon atoms are the most versatile building blocks of molecules. A covalent bonding capacity of four contributes to carbon’s ability to form diverse molecules. Carbon can bond to a variety of atoms, including oxygen, hydrogen, nitrogen, and sulfur. Carbon atoms can also bond to other carbons, forming the carbon skeletons of organic compounds. 3. Most macromolecules are polymers. Carbohydrates, lipids proteins, and nucleic acids are the four major classes of organic compounds in cells. Some of these compounds are very large and are called macromolecules. Most macromolecules are polymers, chains of identical or similar building blocks called monomers. Monomers form larger molecules by condensation reactions in which water molecules are released, dehydration. Polymers can disassemble by the reverse process, hydrolysis. 4. Monosaccharides are the simplest carbohydrates. They are used directly for fuel, converted to other types of organic molecules, or used as monomers for polymers. Disaccharides consist of two monosaccharides connected by a glycosidic linkage. Fats are constructed by joining a glycerol molecule to three fatty acids by dehydration reactions. Saturated fatty acids have the maximum number of hydrogen atoms. Unsaturated fatty acids have one or more double bonds between their carbons. The primary structure of a protein is its unique sequence of amino acids. Secondary structure is the folding or coiling of the polypeptide into repeating configurations, such as the a helix and the pleated sheet, which result from hydrogen bonding between parts of the polypeptide backbone. Tertiary structure is the overall three-dimensional shape of a polypeptide and results from interactions between amino acid side chains. Proteins made of more than one polypeptide chain have a quaternary level of structur e. The structure and function of a protein are sensitive to physical and chemical conditions. Protein shape is ultimately determined by its primary structure, but in the cell chaperone proteins may help the folding process. Each nucleotide monomer consists of a pentose covalently bonded to a phosphate group and to one of four different nitrogenous bases.