Slide 1Molecules of Life:Atoms  Molecules  Biomolecules (Unique to living world!)MOLECULES OF LIFE:Chapter 2: The Chemical basis of Life – WATER AND CARBONKey ConceptsBasic Atomic StructureElements – The Building Blocks of Chemical EvolutionSlide 9Chemical BondingCovalent BondsSlide 12Ions and Ionic Bonds (ionic Interactions):The Electron-Sharing ContinuumSlide 15Slide 16Interactions within/between Bio molecules:How Many Bonds Can an Atom Have?Representing MoleculesWhy Is Water Such an Efficient Solvent?Water and Hydrogen BondsCorrelation of Water’s Structure and PropertiesSlide 24Slide 25Properties of Water and pH:Slide 27Acid–Base Reactions and pHThe pH Scale and Buffers© 2011 Pearson Education, Inc.Substances Found in a Living cell:Organization and function of the cell:Chapter 2: Chemical basis of life: water and Carbon© 2011 Pearson Education, Inc.Molecules of Life:What Are the Chemical Elements That Make Up Living Organisms?•Atoms  Molecules  Bio molecules (C compounds)Proteins: Building blocks of proteins are the amino acids (C, H, O, N) example: enzymes catalyzing biochemical reactions, antibodies protecting against diseases… Nucleic acids: RNA, DNA (C, H,O, P, N) Storing/ transferring genetic information Carbohydrates: Monosaccharides & derivatives (C, H, O) Cn(H2O)n example: Starch, cellulose…(phosphorylated / sulphated sugars)lipids: Fatty acids, Cholesterol (C,H,O) membrane components (phosphorylated lipids)© 2011 Pearson Education, Inc.Atoms  Molecules  Biomolecules (Unique to living world!)•Proteins•Nucleic acids•Carbohydrates (sugars)•Lipids© 2011 Pearson Education, Inc.MOLECULES OF LIFE:• Living organisms contains C, H, O, N (~96% of all matter found in organisms).•Other important atoms: S, and P•All matter composed of atoms•Atoms  Molecules  Bio molecules•Simple molecules are the units for building complex structures.•Biomolecules are carbon compounds. (The cellular components of living organisms are made out of C compounds)•Life on earth is based on Carbon chemistry© 2011 Pearson Education, Inc. Chapter 2: The Chemical basis of Life – WATER AND CARBON•2.1 Atoms, ions, molecules  the building blocks…What Are the Chemical Elements That Make Up Living Organisms?How Do Atoms Bond to Form Molecules?How Do Atoms Change Partners in Chemical Reactions?•2.2 What Properties of Water Make It So Important in Biology?•2.3 Chemical reactions, chemical energy•2.4 The importance of Carbon, Functional groups© 2011 Pearson Education, Inc.Key ConceptsMolecules form when atoms bond to each other. Chemical bonds are based on electron sharing. The degree of electron sharing varies depending on the type of bond formed.Of all small molecules, water is the most important for life. Water is highly polar and readily forms hydrogen bonds, making it an extremely efficient solvent.© 2011 Pearson Education, Inc.Basic Atomic Structure•Atoms are composed of:–Protons – positively charged particles–Neutrons – neutral particles–Electrons – negatively charged particles•Protons and neutrons are located in the nucleus.•Electrons are found in orbitals surrounding the nucleus.© 2011 Pearson Education, Inc. Elements – The Building Blocks of Chemical Evolution •Every different atom has a characteristic number of protons in the nucleus, called the atomic number.•Atoms with the same atomic number have the same chemical properties and belong to the same element.•The mass number is the number of protons + neutrons of the most common isotope.•Forms of an element with different numbers of neutrons are isotopes.© 2011 Pearson Education, Inc.The electrons in the outermost shell are called valence electrons.Elements commonly found in organisms have at least one unpaired valence electron. The number of unpaired electrons in an atom is its valence.© 2011 Pearson Education, Inc.Chemical Bonding•Unfilled electron orbitals allow formation of chemical bonds, and atoms are most stable when each electron orbital is filled. –Covalent bond: Each atom’s unpaired valence electrons are shared by both nuclei to fill their orbitals.–Substances held together by covalent bonds are called molecules. Biological molecules are put together with covalent bonds and are very stable.© 2011 Pearson Education, Inc.Covalent Bonds•Electrons are not always shared equally. •Electronegativity: O > N >C = H  (δ–) and (δ+) charges•Differences in electronegativity dictate how electrons are distributed in covalent bonds.Polar bonds producePartial charges on Atoms.© 2011 Pearson Education, Inc.Electronegativity: Attractive force that an atomic nucleus of one atom exerts on electrons of another. O > N >C = H© 2011 Pearson Education, Inc.Ions and Ionic Bonds (ionic Interactions):•An atom or molecule that carries a charge is called an ion.–Cation: An atom that loses an electron and becomes positively charged.–Anion: An atom that gains an electron and becomes negatively charged.•The resulting attraction between oppositely charged ions is an ionic bond (interaction). [Ionic bond: Electrons are transferred from one atom to another.]© 2011 Pearson Education, Inc.The Electron-Sharing Continuum•The degree to which electrons are shared in chemical bonds forms a continuum, from equal sharing in nonpolar covalent bonds, to unequal sharing in polar covalent bonds, to the transfer of electrons in ionic bonds.© 2011 Pearson Education, Inc.Equal sharing Unequal sharingComplete gain or loss of electronsPolar or non-polar??Benzene C6H6R-OH© 2011 Pearson Education, Inc.Covalent Bonds vs Non-Covalent Interactions:© 2011 Pearson Education, Inc.Interactions within/between Bio molecules:•Bio molecules are made up of simple monomer units held together by covalent interactions. •However, non covalent interactions, although transient, are also important in studying structure/ function of bio molecules. These interactions stabilizes 3D structures. •Non-covalent bonds are weak and a single bond is usually not sufficient to hold 2 molecules together. •However, DNA, RNA, and Proteins have numerous functional groups ( -OH, -NH2 etc….) that participate in non covalent interactions.© 2011 Pearson Education, Inc.How Many Bonds Can an Atom Have?•The number of unpaired electrons determines the number of bonds an atom can make.•Atoms with more than one unpaired electron can form multiple single bonds or double