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The Chemical Basis of Life

The Chemical Basis of Life. BASIC CHEMISTRY. ATOMIC STRUCTURE NUCLEUS PROTONS – ATOMIC MASS = 1 NEUTRONS – ATOMIC MASS = 1 ELECTRONS NOT ENOUGH MASS FOR US TO CONSIDER. Atomic Structure. (-). (+). Chemical Elements.

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The Chemical Basis of Life

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  1. The Chemical Basis of Life

  2. BASIC CHEMISTRY • ATOMIC STRUCTURE • NUCLEUS • PROTONS – ATOMIC MASS = 1 • NEUTRONS – ATOMIC MASS = 1 • ELECTRONS • NOT ENOUGH MASS FOR US TO CONSIDER.

  3. Atomic Structure (-) (+)

  4. Chemical Elements • All matter on Earth is composed of combinations of chemical elements. • Elements cannot be broken down by chemical processes into simpler substances. • There are over 90 naturally-occurring chemical elements. • The most common chemical elements in living things are: • S, P, O, N, C, H

  5. Periodic Table

  6. MOLECULES and COMPOUNDS • MADE OF MORE THAN ONE KIND OF ATOM HELD TOGETHER BY A CHEMICAL BOND. • FAMILIAR ONES INCLUDE WATER, SUGAR, FAT, PROTEIN, CARBOHYDRATE, SALT.

  7. WHY DO SOME ATOMS COMBINE TO FORM COMPOUNDS AND MOLECULES? • An Atom’s ability to combine with other atoms relies on its number of electrons in its outer shell (energy level): the outer shell needs to be full for the atom to become stable (stable atoms do not combine with other atoms). • For our purposes, the first shell contains 2 electrons, and each successive shell contains up to 8 electrons.

  8. Electron Energy Levels: First energy level holds up to 2 electrons Second energy level holds up to 8 electrons Third energy level holds up to 8 electrons

  9. Stable atoms: • Some atoms already have a full outer energy level. • These atoms do not react with other atoms to form molecules. • These include the inert or noble gases: helium, argon, neon, krypton, xenon, and radon.

  10. If an atom is not stable: • It will combine with other atoms • Some will give up or gain electrons. • These form ionic bonds • Each member is an ion • The opposite electrical charges attract each other • Some will share electrons between them. • The force holding them together is called a covalent bond.

  11. Ionic Bonds NaCl = salt

  12. POLAR MOLECULES • BECAUSE OF THE WAY SOME MOLECULES COMBINE, THEY CONTAIN DIFFERENT ELECTRICAL CHARGES AT OPPOSITE ENDS. • THIS CREATES ATTRACTION TO OPPOSITE CHARGES ON OTHER MOLECULES

  13. Polar Molecules Positive end

  14. HYDROGEN BONDS • HOLD TOGETHER MOLECULES THAT CONTAIN HYDROGEN. • IMPORTANT IN WATER MOLECULES AND MANY MOLECULES IN LIVING ORGANISMS. • WEAKER THAN IONIC OR COVALENT BONDS. • THESE HOLD DNA TOGETHER

  15. CHEMICAL REACTION • ONE OR MORE SUBSTANCES IS CHANGED INTO NEW SUBSTANCES BY BREAKING OR FORMING CHEMICAL BONDS. • EX: • 6CO2 + 6H20  C6H12O6 + 6O2 • WHAT IS THE ABOVE EQUATION AND WHAT DOES IT MEAN?

  16. ALL CHEMICAL REACTIONS INVOLVE ENERGY • WHEN BONDS FORM, ENERGY IS STORED • WHEN BONDS BREAK, ENERGY IS RELEASED ATP = energy carrier of a cell

  17. ORGANIC COMPOUNDS • COMPOUNDS THAT CONTAIN CARBON, HYDROGEN AND OXYGEN IN DEFINITE PROPORTIONS. • USUALLY ASSOCIATED WITH LIVING THINGS

  18. CARBOHYDRATES • BUILDING BLOCKS = SIMPLE SUGARS (MONOSACCHARIDES). • MONOSACCHARIDES INCLUDE • GLUCOSE • FRUCTOSE ISOMERS • GALACTOSE ALL THREE HAVE THE SAME MOLECULAR FORMULA, BUT DIFFERENT STRUCTURE: C6H1206 THESE MOLECULES ARE THE MOST COMMON SOURCE OF ENERGY FOR LIVING THINGS.

  19. Isomers – can you tell the difference? glucose C6H12O6

  20. MORE COMPLEX CARBS • DISACCHARIDES • MADE UP OF TWO MONOSACCHARIDES CHEMICALLY COMBINED. • GLUCOSE + GLUCOSE = MALTOSE • GLUCOSE + GALACTOSE = LACTOSE • THIS IS MILK SUGAR • GLUCOSE + FRUCTOSE = SUCROSE • THIS IS TABLE SUGAR • These molecules store energy for later use

  21. THE MOST COMPLEX CARBS • STARCH – MADE UP OF MANY GLUCOSE UNITS COMBINED. • PLANT LONG-TERM FOOD STORAGE • GLYCOGEN – MADE OF MANY GLUCOSE UNITS COMBINED • ANIMAL STORAGE IN LIVER AND MUSCLES • CELLULOSE – MADE OF MANY GLUCOSE UNITS COMBINED. • PLANT CELL WALLS; FIBER • CHITIN – PROTECTIVE COVERINGS IN INSECTS AND OTHER ARTHROPODS; ALSO IN FUNGUS CELL WALLS

  22. DEHYDRATION SYNTHESIS • In order for two molecules to join together, each molecule must break off atoms to provide a bonding place. • Most organic molecules do this by losing a hydrogen atom from one molecule and a hydroxyl group from the other. • These two join to form water, and allow the molecules to make a bond.

  23. Dehydration Synthesis C6H12O6 + C6H12O6 C12H22O11+ H2O disaccharide

  24. Hydrolysis • In order to break down a large molecule to make smaller molecules, a molecule of water has to be added. • This fills in the spots where the bond broke – one molecule gets a hydrogen atom, the other gets the hydroxyl group.

  25. Hydrolysis ADD WATER TO A POLYSACCHARIDE AND FORM MANY MONOSACCHARIDES

  26. Dehydration Synthesis and Hydrolysis store and release energy • Dehydration synthesis stores energy by forming bonds. • As in the formation of polysaccharides from monosacharides • Hydrolysis releases energy by breaking bonds.

  27. Lipids: fats, oils, waxes, phospholipids, steroids • Used for longer-term storage of energy • Fats – in animals • Oils – in plants • Waxes – water repellent (In your ears, beeswax, coat plant leaves), waterproof bird feathers. • Steroids – in animal cell membranes and some hormones. • Phospholipids – make up parts of cell membranes

  28. A common fat = Triglyceride • Composed of one glycerol and three fatty acids, joined together by dehydration synthesis: 3 F A T T Y A C I D S G L Y C E R O L

  29. Saturated and unsaturated fats: • Saturated fats have no C=C bonds within the fatty acids • These are considered unhealthy – they clog up the coronary (heart) arteries. • These are solid at room temperature. • From animals. • Unsaturated fats have at least one C=C bond in one of its fatty acids • These are considered healthier. • Plant oils are usually unsaturated. • Liquid at room temperature.

  30. PROTEINS • Important for movement, structure, regulation, transport, nutrition, and defense. • Composed of building blocks called amino acids • Humans cannot make these from scratch – we must eat foods with proteins, then use the amino acids to make our own proteins.

  31. Amino Acids • There are 20 different aa’s • They are combined in various numbers and orders to produce a great number of different proteins. • Each aa has an amino group, an acid group (carboxyl), and a variable group (there are 20 different variable groups). • Amino acids attach to each other by dehydration synthesis forming a peptide bond between the amino group of one aa and the acid group of the other aa. • Change the number or arrangement of the aa’s and the protein ischanged.

  32. Amino acids Acid group Three different R groups: Amino group

  33. Dipeptide – two aa’s joined by a peptide bond.

  34. Polypeptide

  35. Enzymes – Special Proteins • Change the rate of chemical reactions without being used up themselves (biological catalyst). • Can be used over and over. • Action is very specific – each enzyme will only work on one particular substance (the substrate).

  36. LOCK AND KEY MODEL INDUCED FIT MODEL HOW DOES AN ENZYME WORK?

  37. Nucleic Acids • Molecules of heredity. • DNA – deoxyribonucleic acid • makes up chromosomes (GENES) • Contains the genetic code • Determines the organism’s traits • Contains the code for making proteins Which control the cell’s activities • RNA– ribonucleic acid • Helps DNA make proteins

  38. Metabolism • All the chemical reactions that take place in the organism • These reactions need to be balanced to keep the organism alive • The balance is called homeostasis

  39. Water and Solutions • H2O • Forms solutions easily – all life’s chemical reactions take place in solutions. • Solution – two or more substances are mixed together that they cannot be distinguished. • Ex- sugar + water or salt + water • Sugar or salt is the solute • Water is the solvent

  40. Salt + Water Solution:

  41. Acids and Bases • Form when an ionic compound is mixed with water to form a solution. • Acid – releases H+ (hydrogen) ions (like HCl = hydrochloric acid) • Base – releases OH- (hydroxide) ions (like NaOH = sodium hydroxide)

  42. pH scale • Standard measurement of the H+ ions in a solution • Ranges from 0 – 14 • 7 is neutral • Water has an equal number of H+ and OH- ions, so there is no excess of either ion.

  43. pH scale • Acids are less than 7 • Bases are more than 7 • The further away from 7, the stronger the acid or base • Most chemical reactions in humans take place between 6+8 • However, stomach acid is 2-3 • Enzymes are pH specific

  44. the end

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