Transcript L01_2002
Bio 366: Biological Chemistry 2 Lecture 1: Course Introduction and Review of Carbohydrate Structure Instructor: Dr. Caro-Beth Stewart Teaching Assistant: None Course URLs: http://www.albany.edu/faculty/cs812/bio366/bio366_2002.html or http://www.albany.edu/biology/courses/index.html Look at the online syllabus regularly for reading list updates and any changes to the course schedule! These notes will be posted online after the class. Last year’s notes are available through the link to the 2001 web site. Examples of exams from previous years are also available on the 2001 web site for ABio366. Please note, however, that the format for the exams this year will be quite different. Required (or at least strongly recommended!) readings will be posted on the 2002 web site, and PDF of selected journal articles will also be made available to you. Notice that students will be required to give classroom presentations to the class during the last three class sessions. These presentations will cover recent, important advances in a biochemical topic of the student’s choice. More information about this will be given throughout the term. Do not panic! Students from previous years (nearly) unanimously claim that the experience is both highly educational and fun. Review of Metabolism (various places in text) & Carbohydrate structure (mostly from Chapter 8) METABOLISM--the biosynthesis (anabolism) and degradation (catabolism) of complex metabolites. We'll focus on metabolism of "food" in humans over the next few weeks: 1. Carbohydrates (sugars) 2. Lipids (fats) 3. Amino acids (proteins) 4. Nucleic acids (DNA and RNA—not used for major nutritional purposes in humans, but are metabolized for energy purposes by some animals such as ruminants) Fig. 13.2 OVERVIEW OF CATABOLISM: Glycolysis, TCA (citric acid) cycle, Oxidative-phosphorylation Sugars, proteins & fats all feed into these cycles. CARBOHYDRATE metabolism • GLYCOGEN metabolism. To understand this material, you must first learn (review) some basic SUGAR structures (especially GLUCOSE). Most of this material comes from Chapter 8 of Voet, Voet and Pratt (VVP). You're expected to know: • Carbohydrate and sugar nomenclature, especially pertaining to GLUCOSE monomers and polysaccharides. • The numbering system of glucose (and, later, ribose) • The reducing end of sugars • Storage polysaccharide structures (a-amylose and amylopectin) • The structural polysaccharides, cellulose and chitin. • The peptidoglycan wall of bacteria Carbohydrates or saccharides are the most abundant biological molecules, and are composed of (see figures in Chapter 8 for structures): Simple sugars: monosaccharides have single unit disaccharides have two units sucrose = "sugar" legally! You must know the numbering system of glucose (see next slide, Fig. 8-4), as it helps make sense of the bond names. a-D-glucopyranose D-glucose (linear form) ß-D-glucopyranose (pyranose = sugar with a six-membered ring) •GLUCOSE is a major metabolic fuel source in living organisms which is degraded via glycolysis to produce ATP. •Higher organisms protect themselves from potential fuel shortages by storing glucose by polymerizing it into high molecular mass GLUCANS, or glucose polysaccharides — complex carbohydrates with monosaccharides held together by "glycosidic" bonds (the bond connecting the anomeric carbon to the acetyl oxygen) between neighboring units. •Enzymes that hydrolyze glycosidic bonds are referred to as glycosidases. In PLANTS: The major glucose storage substance is STARCH, which is a mixture of... a-amylose, an a(14)-linked glucan, usually several thousand glucose units long amylopectin, & like amylose, but has a(16) branches every 24-30 residues on average; up to 106 glucose units/molecule These are stored in the cytoplasm of plant cells. Fig. 8-10: a-Amylose a-Amylose is a regularly repeating polymer that form a left-handed helix. Compare a-amylose: To cellulose: The major structural component of plant cell walls. Is a linear polymer of up to 15,000 D-glucose residues. WHAT’S THE DIFFERENCE? a-amylose: Compare Figure 8-10 (aamylose structure)…. a(1 4) linkage Cellulose: to Figure 8-9 (cellulose structure) to see the structural consequences of these different linkages b(1 4) linkage In ANIMALS: The storage glycan of animals is GLYCOGEN, which differs from amylopectin only in that the branches occur every 8-12 residues. Glycogen occurs in granules of about 100-400 Å diameter in cytoplasm of cells that use it most. For example: • Muscle has a maximum of 1-2% of its weight in glycogen. • Liver has a maximum of 10% by weight. Combined, this is about a 12 hour energy supply for the body (about 1 day). ["Carbohydrate loading" fills these glygogen stores.] Fig. 8-11: a beautiful micrograph of a liver cell showing stored glycogen: Glycogen granules also contain the enzymes that catalyze glycogen synthesis and degradation, as well as some regulatory enzymes. Chitin is the major structural component of the exoskeletons of crustaceans, insects, and spiders. It is also present in the cell walls of most fungi and many algae. PEPTIDOGLYCAN is the major structural component of the cell walls of gram-positive bacteria. It is digested by the enzyme LYSOZYME, causing the cells to ‘lyse’ (break open).