weber uiuc edu 27 August 2007 MCB150 Lecture 03 Lecture 03 27 August 2007 Announcements Post lecture questions are due by noon tomorrow All three bookstores now have the course texts Three pre lecture questions are being posted tomorrow o This begins the 3 5 pre post lecture question split The study tips class will likely be this Thursday from 7 9 PM o This will be confirmed during Wednesday s lecture o They need someone to summarize what is covered in the class Tour of the Cells Organelles membranes etc The purpose of a cell is to provide compartmentalization of the chemical reactions chemicals and products necessary for life to function We need to understand what the components of a cell are how they work what are the pieces etc Macromolecules There are four major types of macromolecules that make up a cell o Proteins the workhorses of the cell o Nucleic Acids DNA RNA the genome o Carbohydrates Polysaccharides sugars o Lipids Fats These are the things we will be investigating all semester How does the cell make these Composition Study the chemical composition table illustration 70 of the composition is water Note the relationships of the various macromolecules and their ratios These are more easily seen in the pie charts where water is the most abundant chemical in a cell followed by proteins etc Macromolecules make up the bulk of the remainder of the cell proteins nucleic acids etc Macromolecules Made of monomers smaller identical subunits The building blocks of macromolecules Proteins are made of amino acids The amino acids are the monomers Nucleic acids are made of nucleotides Carbohydrates Polysaccharides are made of monosaccharides Lipids are made of fatty acids Condensation Hydrolysis The process of adding monomers is a condensation reaction Page 1 of 6 weber uiuc edu 27 August 2007 MCB150 Lecture 03 o H2O is condensed via a reaction between hydrogen on one monomer and a hydroxyl OH on another o This is also referred to as a dehydration synthesis reaction All macromolecule formation reactions are condensation reactions o Not accurate to say all condensation reactions are macromolecule formations These are reversible hydrolysis reactions o To retrieve the monomers from the larger molecule H2O is consumed in a hydrolysis reaction hydro water lysis split o That is one molecule of H2O is consumed split into a proton H and a hydroxyl group OH with each being added to separate monomers o This is how you recycle monomers Condensation and hydrolysis how to build and tear down Polysaccharides Make from monosaccharides through condensation reactions Polysaccharides can be used for o Energy storage carbohydrates are an energy source o Structural support cells have structural molecules made from monosaccharides cellulose for instance o Recognition identification often a function of the carbohydrates found on the outside of the cell Carbohydrates are often important on the surfaces of cells Carbohydrates can refer to poly or monosaccharides o If it is relevant to the situation he will distinguish between them General formula o CH2O n o Generally speaking these are repeating units of hydrogen and hydroxyl units attached to a carbon o At the beginning of Chapter 3 Sadava we need to be comfortable with the structures that are mentioned there Chemistry Conventions Conventions of naming and numbering o With ring structures the molecule is represented as a 3D structure using thick lines protruding from the page and thin lines receding into the page Medium lines are in the plane of the page or are parallel to the page o In chemical diagrams when not told specifically then the atom is a carbon atom Otherwise the atom is specified using the elemental name such as O for oxygen When outside of a ring the carbon is identified specifically as are situations when there may be ambiguity o Hydrogens are not drawn in in a form of shorthand In organic chem we were taught that hydrogens aren t drawn at all but in this class it appears that hydrogens are represented by lines Page 2 of 6 weber uiuc edu 27 August 2007 MCB150 Lecture 03 There are chemicals that are not typically found in biological situations o Chemistry is about possibilities while biology is about reality Monosaccharides Most monosaccharides we encounter will contain 3 5 or 6 carbon atoms There are others that are created by chemical processes but these typically are not found in biological systems There are plenty of exceptions but we will rarely deal with these in class Glucose a six carbon monosaccharide o C6H12O6 o It has a linear chain formula with carbon 1 starting with the aldehyde group If it has an aldehyde at the 1 carbon position it is an aldose sugar o If there isn t an aldehyde on the end but a ketone at the 2 carbon it is called a ketose sugar We won t talk much about the ketose sugars Classification of monosaccharides o Aldose versus ketose Also by the number of carbons present glucose is a hexose sugar Glucose Glucose will form a circular ring structure naturally It is possible to find both though 99 of the glucose is in the ring form How does it get that way o It folds over on itself and rearranges the atoms o It is not a condensation reaction The atoms are preserved simply rearranged It is random chance when the resulting hydroxyl from the aldehyde group is above or below the ring o This is biologically relevant so it must be named o If the hydrogen is above the ring the hydroxyl underneath the ring then it is an glucose o If the hydrogen is below the ring the hydroxyl is superior to the ring then it is a glucose Glycerol A triose because it only has three carbons o Three carbons three hydroxyl groups and the rest are hydrogens Can convert into glyceraldehyde by turning it into a carbohydrate by changing the end into an aldehyde group This molecule is too small to circularize it is in straight chain form o All other sugars are circular Page 3 of 6 weber uiuc edu 27 August 2007 MCB150 Lecture 03 Ribose A pentose sugar a sugar with five carbons This is a very biologically relevant molecule C5H10O5 Isomers C6H12O6 for example This does not necessarily mean glucose Different conformations different structures are called isomers o It may simply be the position of the hydroxyl group Think of structures in 3D o Do not think of them as flat on the page o A shift from one side to another can change the conformation enough to make the molecule s reactivity Be able to count the carbons to be able to name them as hexose 6 carbons