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# BIOLOGICAL MOLECULES ## WATER * **Makeup:** Makes up about 80% of a cell's contents. * **Function:** Good solvent; useful substances can be dissolved; good transport medium for substances like glucose; important in regulating temperature (high specific heat capacity and high latent heat of evapo...

# BIOLOGICAL MOLECULES ## WATER * **Makeup:** Makes up about 80% of a cell's contents. * **Function:** Good solvent; useful substances can be dissolved; good transport medium for substances like glucose; important in regulating temperature (high specific heat capacity and high latent heat of evaporation). * **Properties:** * High specific heat capacity: The energy needed to raise the temperature of 1 gram of a substance by 1°C. * High latent heat of evaporation: A lot of energy is needed to break the bonds between water molecules. This means that a lot of energy is used when water evaporates, which has a cooling effect. * **Cohesion and Adhesion:** The attraction between water molecules and other water molecules. Both of these forces help water flow and transport substances. * **Lower Density when Solid:** When water freezes, bonds are made that push molecules further apart in a lattice shape. This creates an insulating layer that allows organisms to survive underneath the ice. * **Solvent:** Water is polar; its slightly positive side surrounds negative ions and its slightly negative side surrounds positive ions, completely dissolving them. ## CARBOHYDRATES * **Function:** Needed for energy storage and support. * **Makeup:** Carbohydrates are made up of carbon, hydrogen, and oxygen. Monosaccharides (with 6 carbons, hexose sugars), are the monomers. Glucose is a hexose sugar in two forms: alpha and beta. Ribose is a component of RNA nucleotides. * **Polysaccharides:** Monosaccharides are joined together by glycosidic bonds. * **Starch:** Main energy storage material in plants. It's insoluble and is a mixture of two polysaccharides of alpha-glucose: * **Amylose:** Long, unbranched chain, 1,4-glycosidic bond, coiled structure, compact, good for storage. * **Amylopectin:** Long, branched chain, side branches allow enzymes to break down the glycosidic bonds. * **Glycogen:** Main energy storage material in animals. Similar to amylopectin, but more branched, so branches can be accessed quickly for energy release. * **Cellulose:** In cell walls in plants, long, unbranched chains, beta glucose chains held together by hydrogen bonds. Provides structural support for cells. ## LIPIDS * **Makeup:** Made up of carbon, hydrogen, and oxygen. A molecule of glycerol and three fatty acids with an ester bond between them. * **Triglycerides:** Used as energy storage molecules. The long hydrocarbon tails of the fatty acids contain a lot of chemical energy. * **Phospholipids:** Similar to triglycerides, except a fatty acid molecule is replaced by a phosphate group. The phosphate group is hydrophilic (water-loving), whereas the fatty acid tail is hydrophobic (water-fearing). They make up the phospholipid bilayer. * **Cholesterol:** The molecules help strengthen the cell membrane by fitting in between the phospholipids. They work to make the membrane less fluid and more rigid. ## PROTEINS * **Makeup:** Polymers; monomers are amino acids. Dipeptide = 2 amino acids; Polypeptide = more than 2 amino acids. Amino acids have the same general structure, containing carbon, oxygen, hydrogen, and nitrogen. * **Peptide Formation:** Peptides hold amino acids together. * **Primary Structure:** The sequence of amino acids in a polypeptide chain. Each protein has a unique sequence of amino acids; changing one amino acid may change the primary structure of the protein. * **Secondary Structure:** Alpha helix and beta-pleated sheet. Hydrogen bonds form between amino groups and carboxyl groups, causing the polypeptide chain to coil and fold. * **Tertiary Structure:** The coiling and folding of the secondary structure is further coiled and folded. Hydrogen bonds, weak attractions between positively charged and negatively charged groups, hydrophobic/hydrophilic interactions, and disulfide bonds between cysteine molecules are involved. * **Quaternary Structure:** Some proteins are made of more than one polypeptide chain. The quaternary structure is the way the proteins are assembled. * **Globular Proteins:** Round and compact; soluble and easily transported. Examples: Amylase, insulin, and Hemoglobin. * **Fibrous Proteins:** Tough and ladder-shaped; insoluble and fairly unreactive. Examples: Collagen, Keratin, and Elastin. _(Note: The image includes some chemical structures, which are difficult to fully represent in markdown format.)_