NSCI 314LIFE IN THE COSMOS4 - The Biochemistry of Life on EarthDr. Karen KolehmainenDepartment of Physics CSUSBhttp://physics.csusb.edu/~karen/BASIC FACTS ABOUT LIFE ON EARTHLIVING ORGANISMS ON EARTH ARE MADE OF CELLS. EXCEPTION: VIRUSESA CELL IS TINY DROP OF WATER AND VARIOUS ORGANIC MOLECULES, SURROUNDED BY A MEMBRANE. SOME CELLS CONTAIN CERTAIN STRUCTURES, TO BE DISCUSSED LATER. SOME ORGANISMS (e.g., BACTERIA) ARE SINGLE-CELLED, AND OTHER ORGANISMS (i.e., HUMANS) ARE MULTICELLULAR. A CELL CAN DIVIDE, RESULTING IN TWO CELLS.BASIC FACTS ABOUT LIFE ON EARTHORGANIC MOLECULE: A MOLECULE COMPOSED OF CARBON AND HYDROGEN ATOMS (AND OFTEN OTHER ELEMENTS ALSO) EXAMPLES: CH4 C2H5O2NMONOMER: A SIMPLE ORGANIC MOLECULE SUCH AS AN AMINO ACID, SIMPLE SUGAR, FATTY ACID, OR GENETIC BASEPOLYMER: A LARGE ORGANIC MOLECULE COMPOSED OF A CHAIN OF REPEATING MONOMERSORGANIC MOLECULESCARBON ATOMS OCCUPY CENTRAL POSITIONS IN MOST MONOMERS. WHEN THE MONOMERS COMBINE TO FORM POLYMERS, THE CARBON ATOMS FORM THE CENTRAL STRUCTURE OF THE CHAIN, WITH ATOMS OF OTHER ELEMENTS STUCK TO THE SIDES. H H H | | | C – C – C | | | H H HLIFE ON EARTH IS CARBON-BASED.EXAMPLES OF POLYMERSCARBOHYDRATES: STARCHES, CELLULOSE, SUCROSE.MONOMERS: SIMPLE SUGARS, GLUCOSELIPIDS: FATS, CHOLESTEROL, HORMONES, CELLULAR MEMBRANES.MONOMERS: FATTY ACIDSNUCLEIC ACIDS: DEOXYRIBONUCLEIC ACID (DNA) & RIBONUCLEIC ACID (RNA).MONOMERS: GENETIC BASESPROTEINS: STRUCTURAL PROTEINS FOR BONE, ORGANS, TISSUE, AND MEMBRANES; ENZYMES, CHEMICAL SENSORS AND TRANSPORTERS.MONOMERS: AMINO ACIDSLET’S EXAMINE PROTEINS AND NUCLEIC ACIDS IN MORE DETAIL.STRUCTURE OF PROTEINSA PROTEIN IS A LONG POLYMER MADE OF MONOMERS CALLED AMINO ACIDS.EACH PROTEIN IS COMPOSED OF A CHAIN OF HUNDREDS OF AMINO ACIDS.PROTEINS USED IN LIFE ON EARTH ARE FORMED FROM ONLY DIFFERENT 20 TYPES OF AMINO ACIDS. ADDITIONAL TYPES OF AMINO ACIDS EXIST AND COULD BE USED BY LIFE ELSEWHERE.PROTEIN STRUCTUREEXAMPLE:AA1—AA3—AA3—AA1—AA17—AA11—AA11—AA11 — AA2—AA9—AA9—AA9—AA9—AA9—AA10—AA15 — AA8—AA5—AA5—AA1—AA16—AA12—AA4—AA20 — AA19—AA7—AA3—AA5—…. CONTINUING ON FOR HUNDREDS MORE OF AMINO ACIDS.PROTEIN STRUCTURECHANGING EVEN ONE OF THE AMINO ACIDS OUT OF THE HUNDREDS IN THE CHAIN CHANGES THE PROTEIN.AA1—AA3—AA3—AA1—AA17—AA11—AA11—AA11 — AA2—AA9—AA9—AA9—AA9—AA9—AA10—AA15 — AA8—AA5—AA6—AA1—AA16—AA12—AA4—AA20 — AA19—AA7—AA3—AA5—…. CONTINUING ON FOR HUNDREDS MORE OF AMINO ACIDS.THIS IS NOW A DIFFERENT PROTEIN FROM THE ONE ON THE PREVIOUS SLIDE.NUMBER OF POSSIBLE PROTEINS EXAMPLE: IMAGINE A PROTEIN THAT CONSISTS OF A CHAIN OF 200 AMINO ACIDS.20200 = 10260 DIFFERENT PROTEINS ARE POSSIBLE.(NUMBER OF POSSIBLE ORDERINGS OF A CHAIN OF 200 AMINO ACIDS OF 20 DIFFERENT TYPES)IN COMPARISON, THE TOTAL NUMBER OF PROTONS, NEUTRONS, AND ELECTRONS IN THE ENTIRE UNIVERSE IS ESTIMATED TO BE LESS THAN 1090.ANOTHER PROTEIN OF A DIFFERENT LENGTH WOULD HAVE A SIMILARLY LARGE NUMBER OF POSSIBLE COMBINATIONS.EXAMPLE: A SEQUENCE OF 312 AMINO ACIDS WOULD RESULT IN 20312 = 10406 DIFFERENT POSSIBLE PROTEINS.CONSEQUENCE:EVEN IF EXTRATERRESTRIAL LIFE USES THE SAME 20 AMINO ACIDS AS LIFE ON EARTH …IT IS VERY UNLIKELY THAT ANY OF THE PROTEINS WILL BE THE SAME AS THOSE USED BY LIFE ON EARTH.THIS MAKES IT UNLIKELY THAT WE COULD EAT EACH OTHER'S FOOD, BE INFECTED BY EACH OTHER'S DISEASES, ETC.AMINO ACIDSAMINO ACIDS ARE THE MONOMERS THAT MAKE UP PROTEINS.AMINO ACIDS ARE FOUND:IN ALL TERRESTRIAL FORMS OF LIFE.IN METEORITES (ROCKS THAT FALL TO EARTH FROM SPACE).IN INTERSTELLAR CLOUDS OR NEBULAE.NOTE: AMINO ACIDS CAN BE PRODUCED BY NON-BIOLOGICAL CHEMICAL REACTIONS. THEREFORE, THE PRESENCE OF AMINO ACIDS DOESN’T NECESSARILY INDICATE THE PRESENCE OF LIFE.HANDEDNESS OF AMINO ACIDSEACH AMINO ACID CAN HAVE TWO “ISOMERS” OR MOLECULAR VERSIONS:L (LEVO- OR LEFT-HANDED) D (DEXTRO- OR RIGHT-HANDED)THE TWO ISOMERS ARE MOLECULAR MIRROR IMAGES OF EACH OTHER.HANDEDNESS OF AMINO ACIDSAMINO ACIDS FROM NON-BIOLOGICAL SOURCES (INCLUDING THOSE IN METEORITES AND INTERSTELLAR CLOUDS) ARE 50% LEFT- HANDED AND 50% RIGHT-HANDED.AMINO ACIDS IN TERRESTRIAL LIVING ORGANISMS ARE ALL LEFT-HANDED.EXTRATERRESTRIAL LIFE COULD USE EITHER LEFT-HANDED AMINO ACIDS OR RIGHT-HANDED AMINO ACIDS (OR POSSIBLY BOTH, ALTHOUGH NOT LIKELY).The 20 Amino Acids Found in Living OrganismsAMINO ACID* CHEMICAL FORMULA NUMBER OF ATOMS L-ALANINEL-ARGININEL-ASPARAGINEL-ASPARTIC ACIDL-CYSTEINEL-GLUTAMIC ACIDL-GLUTAMINEGLYCINEL-HISTIDINEL-ISOLEUCINE13271715141820102022C3H7O2NC6H15O2N4C4H8O3N2C4H6O4NC3H7O2NSC5H8O4NC5H10O3N2C2H5O2NC6H9O2N3C6H13O2NThe 20 Amino Acids Found in Living OrganismsAMINO ACID* CHEMICAL FORMULA NUMBER OF ATOMS L-LEUCINEL-LYSINEL-METHIONINEL-PHENYLALANINEL-PROLINEL-SERINEL-THREONINEL-TRYPTOPHANL-TYROSINEL-VALINE22252023171417272419C6H13O2NC6H15O2N2C5H11O2NSC9H11O2NC5H9O2NC3H7O3NC4H9O3NC11H12O2N2C9H11O3NC5H11O2N*For those amino acids that have both a left-handed (L) and a right-handed (D) form, we have indicated that only the left-handed member of these stereoisomer pairs appears in living organisms. Only glycine, the simplest of the amino acids, has no L and D forms, and thus requires no L or D designation.ROLE OF DNAPROVIDES A “BLUEPRINT” OR “RECIPE” FOR MAKING PROTEINS–CARRIES INFORMATION ABOUT THE SEQUENCE OF AMINO ACIDS IN A PARTICULAR PROTEINFOUND IN EVERY CELL IN A LIVING ORGANISM–IN “HIGHER” ORGANISMS, THE DNA IS SEPARATED INTO LARGE PIECES CALLED CHROMOSOMES (e.g., 46 IN HUMANS)CAN REPLICATE ITSELF – WHEN A CELL DIVIDES INTO TWO, AN IDENTICAL COPY OF THE ORIGINAL DNA (i.e., A COPY OF EACH CHROMOSOME) GOES INTO EACH CELL1 2 3 4 5 67 8 9 10 11 1213 14 15 16 17 18 19 20 21 22 X YA NUCLEIC ACID IS A POLYMER CHAIN CONSISTING OF PAIRS OF GENETIC BASES (PLUS SOME SUGARS AND PHOSPHATES). THE BONDING OF GENETIC BASES IS VERY SPECIFIC – EACH TYPE OF BASE BONDS ONLY WITH ONE OTHER TYPE OF BASE, AS SHOWN BY THE DASHED LINES.DNA (DEOXYRIBONUCLEIC ACID)Adenine (A)---------Thymine (T)Guanine
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