Lecture 2 - Macromolecules (1).pdf

Macromolecules Lecture 2 BIOL2020 Prof. Nicanor González Lipids are high molecular weight molecules soluble in nonpolar solvents. Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Polysaccharides are long polymer chains of sugars Nu...

Macromolecules Lecture 2 BIOL2020 Prof. Nicanor González Lipids are high molecular weight molecules soluble in nonpolar solvents. Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Polysaccharides are long polymer chains of sugars Nucleic acids: DNA and RNA Lipids are an heterogeneous structure group which are broadly defined as hydrophobic a fatty acid is a carboxylic acid with an aliphatic chain (no rings), which is either saturated or unsaturated. Triacylglycerols are made up of one Glycerol molecule and 3 fatty acids Phospholipids have a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, Steroids and terpenes have aromatic rings Phospholipids are the main components of cell membranes Amphipathic = having both hydrophilic and hydrophobic parts. cell membranes consist of two layers of oppositely oriented phospholipid molecules, with their heads exposed to the liquid on both sides, and with the tails directed into the membrane. Outside the cell Inside the cell Polysaccharides (sugars) are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic bonds. Disaccharides are two monosaccharides joined by a glycosidic bond. Polysaccharides are storage or structural molecules Cellulose is a structural polysaccharide of the cell wall of green plants Unbranched chains of B-D-glucose Chitin is a long-chain polymer of N-acetylglucosamine and the main component of insect exoskeleton Proteins include a diversity of structures, resulting in a wide range of functions. ● Protein shape matters ● Everything in a cell is mediated by proteins An amino acid is an organic molecule with both an amino group and a carboxyl group ● ● Side chain is variable All amino acids have amino and Carboxyl groups Proteins are made up of 20 amino acids, which have different physical and chemical properties Proteins are made up of 20 amino acids, which have different physical and chemical properties Polypeptides are Amino Acid Polymers ● The covalent bond between amino acids is called a peptide bond. Proteins have Four Levels of Protein Structure The primary structure is the sequence of amino acids The secondary structure are the regions stabilized by hydrogen bonds between the polypeptide backbone. Alpha helices and beta-strands are the main secondary structures Tertiary structure is the overall shape of a polypeptide resulting from interactions between the various amino acids Quaternary structure is the overall structure that results from the aggregation of more than one polypeptide subunits. explore 5 min the structure https://www.rcsb.org/3d-view/1C7D/1 Nucleic acids are macromolecules that exist as polymers called polynucleotides. The monomers are called nucleotides. A nucleotide, in general, is composed of three parts: a nitrogenous base, a five carbon sugar, and one phosphate group There are two families of nitrogenous bases: pyrimidines and purines. DNA Deoxyribonucleic acid is composed of Cytosine, Thymine, Adenine , and Guanine. RNA is made of Cytosine, Uracil, Adenine , and Guanine DNA is composed of two polynucleotide chains that coil around each other to form a double helix. The nucleotides are joined to one another in a chain by phosphodiester bonds 5’ end of the chain has a phosphate group. The 3’ end has a sugar Through the processes of transcription and translation, information from genes is used to make proteins. Transcription: RNA polymerase uses DNA as a template to produce a pre-mRNA (transcript) Translation: A ribosome builds the protein molecule (polypeptide) from a mature mRNA. A single amino acid substitution in hemoglobin causes sickle-cell disease. hydrophilic; acid Discuss for 5 min: Considering the chemical characteristics of the amino acids valine and glutamic acid, propose a possible explanation for the dramatic effect on protein function that occurs when valine is substituted for glutamic acid. hydrophobic Summary Macromolecules ● Proteins and amino acids ● Lipids make membranes ● Nucleic acids DNA and RNA carry information ● Carbohydrates storage and structural Proteins are encoded in DNA DNA→mRNA →Protein