The chemical building blocks of life Carbon: The framework of biological molecules- Biological molecules consist primarily of Carbon atoms bound to carbon atoms Carbon bound to other molecules Molecules consisting only of carbon and hydrogen are called hydrocarbons Hydrocarbons store energy-good fuels Gasoline is rich in hydrocarbons Carbon can form up to four covalent bonds Carbon can be bound to functional groups with specific properties What is meant by Organic? Chemical vs. structural formulas Easy way to express the particular atoms that makeup an element Uses chemical symbol and number of atoms Propane-C 3 H 8 Butane-C 4 H 10 Graphical representation to show how atoms are arranged. Shows chemical bonding Propane Butane Primary functional chemical groups Biological Molecules Isomers are molecules with the same chemical formula Structural isomers-differ in carbon structure Example: glucose and fructose Stereoisomer-differ in how the groups attached to the carbon skeleton are arranged (have same carbon skeleton) Subcategory: Enantiomers: mirror-images of each other A molecule that has mirror-image versions is called a chiral molecule When carbon is bound to 4 different molecules, symmetry exists Polarized light has single plane, chiral molecules rotate this plane either to the left or to the right Call 2 chiral forms: D for dextrorotatory & L for levorotatory In living systems, only single enantiomer (D-sugars & L-amino acids Chiral molecules 1
Four biological macromolecules Carbohydrates Nucleic Acids Biological Molecules Biological molecules are typically large molecules constructed from smaller subunits Monomer: single subunit (mono=1; -mer=unit) Polymer: many units (poly=many;-mer=unit) Nature of a polymer is determined by the monomers used to build the polymer 1.) Dehydration reactions: formation of large molecules by the removal of water Example: monomers are joined to form polymers 2.) Hydrolysis reactions: breakdown of large molecules by the addition of water Example: polymers are broken down to monomers Making and breaking macromolecules Energy Currency Adenosine triphosphate (ATP) stores and releases energy during cell processes, enabling organisms to function. Carbohydrates Molecules with a 1:2:1 ratio of C, H, O Empirical formula: (CH 2 O) n Examples: sugars, starch, glucose C-H covalent bonds=energy Carbs are good energy storage molecules Monosaccharides Mono =single; saccharum = sugar Simplest of the carbohydrates Can contain as few as 3 carbon atoms Normally have 6 Empirical formula: C 6 H 12 O 6 or (CH 2 O) 6 very important in energy storage -fructose is a structural isomer of glucose -galactose is a stereoisomer of glucose 6-carbon sugars can exist in a straight-chain form, but in water, they form rings 2
Monosaccharides Example: glucose Important in energy storage 7 C-H bonds 2 forms (α & β) Depends on orientation of carbonyl group Fructose is a structural isomer of glucose Galactose is a stereoisomer of glucose Structure of the glucose molecule Isomers and Stereoisomers di- 2 Disaccharides 2 monosaccharides linked together by dehydration synthesis Used for sugar transport or energy storage Examples: sucrose (sugarcane), lactose (milk sugar), maltose (storage) Polysaccharides Poly = many Long chains of sugars Used for energy storage Plants use starch; animals use glycogen Used for structural support Plants use cellulose; animals use chitin Examples: Starches Amylose: simplest starch Amylopectin: branched, complex starch Glycogen Polymers of Glucose 3
Polymers of glucose Polymers of glucose Cellulose Chitin Cellulose Chitin Polymer of β-glucose Main component of plant cell walls Cows digest cellulose by means of bacteria and protists inside their digestive tracts Found in arthropods and many fungi Modified form of cellulose where N-acetyl group replaces a hydroxyl in each glucose unit Forms hard exoskeleton of insects and crustaceans 2 types Nucleic Acids DNA (deoxyribonucleic acid) RNA (ribonucleic acid) Functions: specialized for the storage, transmission, and use of genetic information Nucleic Acids Nucleic acids are polymers of nucleotides Nucleotides: sugar+ phosphate+ nitrogenous base Sugar= deoxyribose in DNA or ribose in RNA Nitrogenous bases include: Purines: adenine and guanine Pyrimidines: thymine, cytosine, uracil Structure of a nucleotide Made up of 3 elements Five-carbon sugar (ribose or deoxyribose) Organic nitrogenous base Phosphate group *Sugar numbers are given as primes to distinguish between numbering on rings of bases Structure of Nucleic Acids & Nitrogen-containing bases 4
DNA Nucleotides connected by phosphodiester bonds Double helix: 2 polynucleotide strands connected by hydrogen bonds Polynucleotide strands are complementary Genetic information is carried in the sequence of nucleotides The structure of DNA RNA Contains ribose instead of deoxyribose Contains uracil instead of thymine Single polynucleotide strand Functions: Read the genetic information in DNA Direct the synthesis of proteins DNA vs. RNA Other Nucleotides ATP: adenosine triphosphate Primary energy currency of the cell NAD+ and FAD Electron carriers for many cellular reactions Seven functions 1. enzyme catalysts 2. defense 3. transport 4. support 5. motion 6. regulation 7. storage 5
Figure 3.16 Enzymatic proteins Defensive proteins Function: Selective acceleration of chemical reactions Function: Protection against disease Example: Digestive enzymes catalyze the hydrolysis of bonds in food Example: Antibodies inactivate and help destroy viruses and bacteria. molecules. Antibodies Enzyme Virus Bacterium Storage proteins Transport proteins Function: Storage of amino acids Function: Transport of substances Examples: Casein, the protein of milk, is the major source of amino Examples: Hemoglobin, the iron-containing protein of vertebrate acids for baby mammals. Plants have storage proteins in their seeds. blood, transports oxygen from the lungs to other parts of the body. Ovalbumin is the protein of egg white, used as an amino acid source Other proteins transport molecules across cell membranes. for the developing embryo. Transport protein How Enzymes Work Ovalbumin Amino acids for embryo Cell membrane Hormonal proteins Receptor proteins Function: Coordination of an organism s activities Function: Response of cell to chemical stimuli Example: Insulin, a hormone secreted by the pancreas, causes other Example: Receptors built into the membrane of a nerve cell detect tissues to take up glucose, thus regulating blood sugar signaling molecules released by other nerve cells. concentration. High blood sugar Insulin secreted Normal blood sugar Signaling molecules Receptor protein Contractile and motor proteins Structural proteins Function: Movement Function: Support Examples: Motor proteins are responsible for the undulations of cilia Examples: Keratin is the protein of hair, horns, feathers, and other skin and flagella. Actin and myosin proteins are responsible for the appendages. Insects and spiders use silk fibers to make their cocoons contraction of muscles. and webs, respectively. Collagen and elastin proteins provide a fibrous framework in animal connective tissues. Actin Myosin Collagen Muscle tissue 30 m Connective tissue 60 m are polymers of amino acids Amino acids Amino group (-NH 2 ) & carboxyl group (-COOH) 20 different Joined together by dehydration synthesis Amino acids are held together by peptide bonds 33 Peptide Bond Amino Acid Structure Central carbon atom surrounded by Amino group Carboxyl group Single Hydrogen Variable R-group 6
The structure of the R group dictates the chemical properties of the amino acid. Amino acids can be classified as Nonpolar Polar Charged Aromatic Special function The shape of a protein determines its function. Primary structure-sequence of amino acids Secondary structure-interaction of groups in the peptide backbone α-helix β-sheet Tertiary structure-folded shape of the polypeptide chain Protein folding is aided by chaperone proteins. Quaternary structure-interactions between multiple polypeptide subunits Motifs are common elements of secondary structure seen in many polypeptides. Domains are functional regions of a polypeptide. Denaturation is a change in the shape of a protein, usually causing loss of function May involve complete unfolding Caused by changes in the protein s environment ph Temperature Salt Concentration 7
are a group of molecules that are insoluble in water. Triglycerides (fats) are composed of 1 glycerol + 3 fatty acids A high proportion of nonpolar C-H bonds causes the molecule to be hydrophobic Two main categories: Fats (triglycerides) Phospholipids Fatty acids are long hydrocarbon chains which may be Saturated Unsaturated Polyunsaturated Triglycerides are An excellent molecule for energy storage Store 2X as much energy as carbohydrates Animal fats are usually saturated fats and solid at room temperature lard Plant fats are usually unsaturated fats and liquid at room temperature Vegetable, canola, olive, peanut oils Phospholipids are composed of 1 glycerol 2 fatty acids A phosphate group Phospholipids contain polar heads and nonpolar tails 8
Phospholipids spontaneously form micelles or lipid bilayers These structures cluster the hydrophobic regions of the phospholipid toward the inside and leave the hydrophilic regions exposed to the water environment. Lipid bilayers are the basis of biological membranes. Cell membranes Figure 3.UN06a Wax-1 fatty acid joined to alchol Steroid- 4 fused carbon rings Figure 3.UN06b 9