Lecture 2 Chemistry 2 PDF

The Chemistry of Life Chapter 2 Elements, atoms, bonds, ions, molecules, chemical reactions, buffers Objectives Describe the types of chemical bonds Explain how properties of water enable life Explain what characterizes acids, bases, and buffers and how...

The Chemistry of Life Chapter 2 Elements, atoms, bonds, ions, molecules, chemical reactions, buffers Objectives Describe the types of chemical bonds Explain how properties of water enable life Explain what characterizes acids, bases, and buffers and how they function Chemical Elements 91 naturally-occurring 24 have physiological roles 6 = 98.5% body weight O, C, H, N, Ca, Ph Remaining are lesser and trace elements. Chemical Elements Top 4: Carbon, Hydrogen, Nitrogen, & Oxygen 96% of an organism’s mass 99% of the atoms Radically different from that of the Hydrogen = ~63% Earth’s of the atoms in the crust human body, but 10% of the mass. Oxygen = 65% of the mass, but 24% of the atoms in a human body. Minerals Inorganic lack Carbon & C-H bonds Ca, P, Cl, Mg, K, Na, and S Extracted from soil by plants Enzyme structure & function Electrolytes Mineral salts needed for muscle and nerve function Ca2+, Mg2+, K+, Na+, Cl-  Ionic bonds An ion is an atom or molecule that has gained or lost one or more electrons Cations – have a net positive charge (+) Ionic bonds Anions electrostatic – have a net negative charge (−) between cations and attractions anions Na+ + Cl-  NaCl Ionic compounds are called salts Example NaCl, KCl, CaCl2  Water & Ionic bonds Ionic bonds are weak in water  ionize in water  hydration spheres Electrolytes Chemical reactivity Osmotic effects Electrical effects Covalent Bonds Covalent bonds: Sharing of electrons Molecules Filling outer electron shell  more stable Single to triple covalent bonds Based on # shared e- pairs Covalent Bonds Nonpolar covalent bond: atoms have similar e- affinity Polar covalent bond: atoms have dissimilar e- affinity  partial charges High: O & N Low: C & H  Types of Covalent Bonds Single bond allows rotation Carbon- Carbon allows for single covalent changes in bond chape Double bond shorter & Carbon- stronger Carbon more rigid double covalent Hydrogen Bonds Attraction between slightly (+) H and (–) O or N charges Individually Weak E.g., water, DNA, proteins Hydrogen Bonds? Stop and Think Which type(s) of chemical bonds create molecules? What is the strongest of all chemical bond types? What types of bonds within and between atoms of water? Water and Mixtures Mixture Blended but not chemically combined Each substance maintains its own chemical properties Body fluids H2O (50%-75% body weight) Age, sex, fat content, etc. Water Polar covalent bonds Properties  ability to support life Universal solvent Dissolve hydrophilic substances/molecules Important for metabolism Hydrolysis & dehydration reactions Adhesion Can cling to membranes Reduces friction around organs Solution Solute Particles mixed within solvent Can be gas, solid, liquid Particles under 1 nm Do not scatter light Pass through most membranes Will not separate on standing E.g., Sugar in water Colloids Mixtures of protein and water Can convert to gel state Particles 1-100 nm Scatter light, usually cloudy Particles can’t pass through membrane Particles remain permanently mixed when standing E.g., albumin in blood Suspension and Emulsion Suspension Particles >100 nm Can’t pass through membranes Cloudy – opaque Separates on standing E.g., RBCs in blood Emulsion Liquid suspended in another liquid E.g., fat in breast milk Acids, Bases, pH Acid Donates proton (H+ ions in water) Base Proton acceptor Can release OH- pH Molarity of H+ (log scale) 7.0 = neutral (H+ = OH-) < 7.0 = acidic (H+ > OH-) + - 1:1 ratio: H+ to OH- Tolerate only small changes in pH Buffers help to maintain a constant pH An acid-base buffer system can shift to generate or release H+ to adjust for changes in pH Contain a weak acid and its corresponding base Carbonic acid is a buffer that contributes to pH stability in human blood: Water – Break or Build Hydrolysis Uses water to break bonds (“water” & “unbind”) Dehydration synthesis H 2O Removes water to form bonds (opposite of hydrate [adding water])  Carbon’s Bonding Behavior Each carbon atom can form covalent bonds with up to four atoms Organic Compounds contain carbon bound to hydrogen and possibly other elements Met  Chemical Groups Chemical groups: Atoms or clusters of atoms that are covalently bonded to carbon backbone Give organic compounds their different properties Each type of functional group exhibits the same properties in all molecules in which it occurs Chemica l group Examples of Chemical Groups Examples of Chemical Groups Four Main Families of Small Organic Molecules Synthesized in Cells.  Cellular Macromolecules Macromolecules are abundant 24 % What makes their wide-ranging functions possible? approximate composition by mass  Sugars - Carbohydrates Sugars are made up of Carbon, Hydrogen & Oxygen (CH2O)n Carbohydrate functions: Energy sources Structural materials Glucose, C6H12O6 Signaling & recognition  Monosaccharides Monosaccharides are the simplest carbohydrates (simple sugars) Consist of only one sugar molecule Subunits of chains Examples: Glucose Galactose C6H12O6 Mannose  Disaccharides Disaccharides: short chain of 2 monosaccharides Formed by condensation reactions forming glycosidic bonds Examples: Sucrose Lactose Sucrose Polysaccharides: “Complex Carbs” Polysaccharides are polymers of many glucose units Long term energy storage  Lipids Lipids are nonpolar hydrocarbons (C, H, and O) Hydrophobic - don’t dissolve in water Greasy to the touch Lipid functions: Major sources of energy Structural materials Used in cell membranes Cell communication (hormones)  Fatty Acids - Amphipathic Palmitic acid Very Hydrophilic reactive carboxylic acid head Not very Hydrophobic reactive hydrocarbon tail  Fatty Acid Saturation Triglyceri de Predominantly Phospholipids Form Cell Membranes Amphipathic : Amino Acids free a.a. in cell @ pH 7  20 Amin o NONPOLAR SIDE CHAINS Acids  Protein Synthesis - Directionality Protein: A chain of amino acids Structurally & functionally diverse macromolecules 20 differing amino acids (vary by the R group) R group: Charged/uncharged, hydrophilic/hydrophobic Amino acids are linked by Peptide bonds Covalent bond Links carboxyl group (-COO-) of one amino acid with amino group (–NH3+) of the next  Nucleotides Nucleotides are the Subunits of DNA and RNA Functions: Energy carriers ATP Building blocks for nucleic acids DNA and RNA Phosphate group Coenzymes Sugar (5 carbon ring) Chemical messengers Base (Nitrogen containing)  Adenosine Triphosphate (ATP) Adenosine Triphosphate (ATP) energizes many molecules by phosphate-group transfers  Covalent & Noncovalent Bonds Both are Needed for Macromolecule Assembly ~ 90 macromolecules  Office Form Cholesterol belongs in which class of macromolecules? Properties of organic molecules able to pass thru a cell membrane lacking in transporters? The hydrogens of a fatty acid tail participates in which type of bonding? Next topic Cell Biology