5.1: Macromolecules are Polymers, Built from Monomers ● All life’s organic compounds, except lipids, are chain-like molecules called polymers ○ A polymer is a long molecule consisting of many identical or similar building blocks linked by covalent bonds ■ These building blocks are known as monomers ● Synthesis and Breakdown of polymers ○ These processes are basically the same in all cases of polymer ○ Enzymes facilitate these processes ○ Monomers are connected with the loss of a water molecule (dehydration) and broken down with the addition of a water molecule (hydrolysis) ■ In dehydration, one monomer provides the OH and one provides the H ■ In hydrolysis, the hydroxyl group attaches to one monomer, while hydrogen attaches to the other ■ ● Diversity of polymers ○ All polymers built from the same 40-50 monomers, but the way they are arranged leads to an immense diversity ■ Despite this diversity, molecular structure and function can still be grouped by class ● Carbohydrates ● Proteins ● Lipids ● Nucleic acids 5.2: Carbohydrates ● Monosaccharides (sugars) generally have molecular formulas that are some multiple of the unit CH2O. ○ Glucose is one of the most important Monosaccharides in the chemistry of life ● Sugars can either be aldose or ketose, depending on the location of the carbonyl group ● Size of the carbon skeleton and the spatial arrangements of their parts around asymmetric carbons are both factors of sugar diversity ○ ● Monosaccharides, particularly glucose, are major nutrients for cells ○ Necessary for cellular respiration ○ Their carbon skeletons also serve as raw material for the synthesis of other types of small organic molecules ● A disaccharide consists of two monosaccharides joined by glycosidic linkage (a type of dehydration reaction) ○ Examples of this: ● Polysaccharides ○ Macromolecules, polymers with a few hundred to a few thousand monosaccharides joined by glycosidic linkage ■ They serve as storage material, hydrolyzed as needed to provide sugar for cells ● Plants store starch as energy ● Mammals can also hydrolyze plant starch ● Animals store a polysaccharide called glycogen, a polymer of glucose ■ Polysaccharides also serve as building material for structures that protect the cell or entire organism ● Organisms build strong materials from structural polysaccharides ○ One example is cellulose ○ Cellulose, like starch, is a polymer of glucose, but they have different glycosidic links, due to the different ring structures glucose has ○ 5.3: Lipids ● Lipids are: ○ Generally not big enough to be considered macromolecules, and do not consist of true polymers ○ Hydrophobic (or just very poor at mixing w water) ● Fats ○ Composition ■ Although they are not polymers, they are assembled by dehydration reactions ■ Constructed from glycerol and fatty acids ■ Long carbon skeleton (usually 16-18 carbons) and a hydrocarbon chain ■ Because of these hydrocarbons, fats are hydrophobic ■ While making a fat, three fatty acid molecules are joined to glycerol by an ester linkage ○ Unsaturated vs Saturated ■ Saturated fats have saturated hydrocarbon chains (as many hydrogens per carbon and all single bonds) ● Animal fats ■ Unsaturated fats have carbon chains with one or more double bonds ● Unsaturated fats with trans double bonds are known as trans fats ○ Function ■ Mainly for energy storage ■ Twice as much energy as starches ■ Also, serve as protection for mammals organs ● Phospholipids ‘ ○ Only two fatty acids bonded to the glycerol, instead of three ○ The third hydroxyl group of glycerol is joined to a phosphate group ○ Phosphate end of the lipid is hydrophilic, while the hydrocarbon tail is hydrophobic ■ When added to water they separate into two separate layers known as bilayers, in order to shield the hydrophobic parts from the water ■ This also happens at the surface of the cell ● Steroids ○ Lipids with a Carbon skeleton of four fused rings ○ Differences between steroids depended on the chemical group attached to the ring 5.4: Proteins ● Amino Acid Monomers ○ Organic molecules with an amino group and a carboxyl group ○ Asymmetrical carbon at the center ○ The hydrogen atom and R group side chain make up rest of the molecule ■ This side chain determines the chemical and physical properties of the amino acid ■ Nonpolar and polar groups of amino acids based on the side chain ■ Basic and acidic amino acids based on positive (basic) or negative (acidic) charges ■ All basic and acidic amino acids are hydrophilic ● Amino Acid Polymers (polypeptides) ○ Two amino acids bonded together make a peptide ○ Multiple peptides make a polypeptide ○ The repeating sequence of amino groups bonded to adjacent carboxyl groups is called the peptide backbone ○ Sidechains determine the type of molecule ● Protein Structure and Function ○ The specific activities of proteins are determined by their three-dimensional architect ○ Polypepdides=piece of yarn while proteins=every single thing you can knit that yarn into ○ Polypeptides are folded and twisted into multiple shapes and arrangements ■ Global and fiber-like proteins ○ Four levels of protein structure ■ All proteins share three superimposed levels of structure ● Primary ○ The sequence of amino acids ● Secondary ○ Coils and folds of amino acid chains in the result of hydrogen bonding/interactions of the backbone ■ Helix ■ Pleated sheet ● Tertiary ○ The overall shape of the structure in the result of the interactions between the side chains ■ Quaternary structure is the fourth level ● When two or more polypeptides make up one protein, and aggregation between these subunits results ○ What determines the protein structure? ■ Environment ● Ph ● Salt concentration ● Temperature ● All of these can cause weak chemical bonds to be destroyed ○ This causes the protein to become unraveled, otherwise known as denaturation ○ Denaturing can occur when proteins are transferred from an aqueous environment to nonpolar substance ○ Other denaturation can happen when ionic and hydrogen bonds are disrupted or excessive heat ● Chaperonins: proteins that assist the folding of other proteins ● Misfolding of proteins can cause serious problems and diseases 5.4: Nucleic Acid ● Two types of nucleic acid that allow for living organisms to reproduce their complex components to the next generations ○ Deoxyribonucleic acid ■ Provides directions for its own replication ■ Directs RNA synthesis, and through RNA, directs protein synthesis ■ Genetic material that organisms inherit from their parents ■ Encoded in the DNA is the information that programs all the cells activities (molecular hardware of the cell) ○ Ribonucleic acid ■ Messenger Directs productions of polypeptides ■ Is directed by DNA ○ DNA → RNA → protein ■ Protein is synthesized in the part of the cell known ribosomes ● The region in between the nucleus and the plasma membrane ● DNA resides in the nucleus ● mRNA sends messages from the nucleus to the cytoplasm ● Components of Nucleic Acids ○
