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MOLECULES OF LIFE CH 4 and 5 I. Carbon is the building block of the molecules of life A. Chemistry of Carbon Forms 4 covalent bonds Bonds can be single double or triple Forms bonds with sulfur, carbon, nitrogen, oxygen, phosphorus, hydrogen Forms rings chains and branches Result: HUGE variety of molecules formed from carbon backbone B. Macromolecules Large molecules many of which are polymers Polymer: a macromolecules made of repeating units called monomers Macromolecules are made by dehydration reactions: linking of monomers together with the removal of water Macromolecules are broken down by hydrolysis reactions: breakdown of a macromolecule with the addition of water The 4 macromolecules that make up all living things are: o Proteins o Carbohydrates o Lipids o Nucleic acids II. Carbohydrates A. Monosaccharides 1. structure A single sugar ex: glucose Most monosaccharides exist as a ring 2. isomers Molecules with same structural formula but different arrangement of atoms Ex: glucose, fructose, and galactose 3. function Quick energy source Immediately enters into cellular respiration for production of ATP B. Disaccharides 1. Structure 2 monosaccharides linked via dehydration reactions EX: sucrose, lactose 2. Function Energy http://www2.nl.edu/jste/biochem.htm C. Polysaccharides Long chain of GLUCOSE molecules linked via dehydration reactions 2 groups of polysaccharides Storage: starch and glycogen Structural: cellulose chitin 1. Storage polysaccharides a. function store glucose for later use b. structure Glycogen o Stores glucose in animals o Many glucose molecules linked via α1-4 linkages o Is highly branched o The α1-4 linkage is important in its function Starch o Stores glucose in plants o Many glucoses linked by α1-4 linkages o Not that branched 2. structural polysachharides a. cellulose forms cell wall in plants many glucoses linked via β14 linkages not branched b. chitin forms exoskeleton in arthropods and cell wall in fungi III. Lipids Diverse group of hydrophobic molecules B. Triglycerides (fats and oils) 1. structure One glycerol + 3 fatty acids linked via dehydration reactions http://www2.nl.edu/jste/biochem.htm 2. Fatty Acid Long chain of C and H with a carboxyl group Usually 14 to 20 Cs Fatty acids can be o Saturated: no carbon to carbon double bonds. Solid at room temp o Monounsaturated: 1 carbon to carbon double bond. Liquid at room temp o Polyunsaturated: more than 1 carbon to carbon double bond. Liquid at room temp 3. Function Long term energy storage Seeds use stored triglycerides as energy during germination Insulation in mammals C. Phospholipids 1. Structure One glycerol + 2 fatty acids + 1 phosphate head 2. Property Amphiphathic: polar charged phosphate head and nonpolar uncharged fatty acid tails 3. Function: Make up phospholipid bilayer found in all biological membranes D. Waxes Function as protective barrier E. Steroids Function as chemical messengers IV. Proteins Large polymer made of repeating monomers called amino acids A. Functions of Proteins Enzymes: catalyze cell’s reactions Defense: antibodies destroy foreign invaders Transport: move molecules around body and into and out of cells Support and structure: long fibrous proteins in hair nails skin Movement: contractile proteins in cells Regulation: proteins involved in maintaining homeostasis B. Amino Acids 1. general structure 2. Groups of amino acids: based on the characteristics of R group Nonpolar amino acids o R group is hydrophobic o Includes aromatic amino acids o Involved in hydrophobic interactions Polar uncharged amino acids o Involved in hydrogen bonding Polar charged amino acids o Basic R groups have NH2 o Acidic ones have COOH o Involved in ionic interactions Special function amino acids Nonpolar Glycine (Gly or G) Alanine (Ala or A) Leucine (Leu or L) Valine (Val or V) Isoleucine (Ile or I) Proline (Pro or P) Methionine (Met or M) Phenylalanine (Phe or F) Trypotphan (Trp or W) Polar Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Tyrosine (Tyr or Y) Asparagine (Asn or N) Glutamine (Gln or Q) Electrically charged Acidic Aspartic acid (Asp or D) Basic Glutamic acid (Glu or E) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) The R groups in the amino acids determine the type of interactions they will form with other amino acids in the protein chain. This determines how the protein folds into its 3D shape. The shape of the protein determines its function. Different proteins assume different functions because they fold into different shapes How a protein folds into its shape is determined by the order of amino acids in the chain 3. Linking of amino acids Linked together via dehydration reactions http://www2.nl.edu/jste/biochem.htm C. Protein Structure Protein function is dependent on its shape Alter the shape = alter the function As protein is being synthesized, it begins to fold into its correct shape Proteins fold as a result of the interactions between amino acid R groups http://www.ncbi.nlm.nih.gov/sites/entrez ?db=structure 1. General rules on protein folding Nonpolar amino acids tend to cluster in the interior of protein away from water Polar amino acids tend to be on the surface 2. There are 4 levels of protein structure a. primary structure number and order of amino acids in the protein chain primary structure is determined by______________ all proteins have a different primary structure b. secondary structure Hydrogen bonding among amino acids that are relatively close together. 2 forms: α helix and β sheet c. Tertiary structure Interaction among the R groups of amino acids farther apart in the chain o Nonpolar amino acids will interact via hydrophobic interactions o Polar uncharged amino acids will form hydrogen bonds with each other o Charged amino acids will form ionic bonds with each other o Disulfide bonds between cysteines The driving force for tertiary structure is the hydrophobic interactions. As the nonpolar amino acids interact with each other, it brings the other amino acids close enuf to form hydrogen bonds and ionic bonds and disulfide bonds d. Quaternary structure 2 or more polypeptide chains associated together to form a functional protein Special proteins called chaperonins help proteins fold into their secondary and tertiary structures All proteins have primary and secondary structure Most proteins have tertiary structure Some proteins have quaternary structure http://parasolwww.cs.tamu.edu/groups/amatogroup /research/folding/proteinA.php 3. Protein unfolding Denaturation: unfolding of a protein as a result of changes in pH and temp V. Nucleic Acids The information molecules Contain and express all of the hereditary info A. Structure Long chains of nucleotides linked via dehydration reactions B. Nucleotides Made of a: 5 carbon sugar Phosphate group One of 4 bases C. Function DNA: stores hereditary info RNA: expresses it