Chapter 1

Chapter 1 - BISC 220 1 Chapter 1 BISC 220, Professor...

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Unformatted text preview: BISC 220 1 Chapter 1 BISC 220, Professor William McClure 2/13/2010 Reductionism o Solve little problems to attack a big one Emergent properties o What comes from two items Unifying concepts o Evolution and systematic o Biological organisms are chemical systems o Similar chemistry of all living organisms o Energetics (energy key to understanding a biological system) Chemistry of biological systems o We work in hydrophilic media o Organic chemistry refers specifically to molecules using carbon o Valence Carbon has four bonds, nitrogen has three, oxygen has two, hydrogen has one Trace elements are required by an organism but only in minute quantities o Many trace elements, like iron (Fe), are required by all organisms CH 4 has all four hybrid orbitals shared and has hydrogen nuclei at the corners of the tetrahedron o Hydrocarbon Electronegativity o Attraction of an atom for the electrons of a covalent bond o The ability of an atom to attract electrons o Strongly electronegative atoms attempt to pull the shared electrons toward themselves o Polarization, electrons will be more around the electronegative atom (e.g. OH) BISC 220 2 Polarity o Accumulation of negative charge Weak chemical bonds o Brief bonds between molecules are critical e.g. signal molecules from one neuron use weak bonds to bind briefly to receptor molecules on the surface of a receiving neuron o Weak interactions include ionic bonds, hydrogen bonds, and van der Waals Binding of two receptor proteins is weak forces o Must complement each other geometrically (selective binding) Hydrogen bonds o When hydrogen bonds to another highly electronegative atom BISC 220 3 Chapter 3 1/15/2010 Water o Physical properties: polarity, hydrogen bonds Surface tension (cohesion) Thermodynamics Head of vaporization Specific heat (calorie) Ice floats Solvent; concentration Thermodynamics o Energy Potential energy (concentration, structure) Kinetic energy o Heat o Temperature o Calories (one gram raised one degree) o Specific heat o Relation to reactions Hydrogen Bonds o Slightly negative regions of one molecule attracted to positive regions of nearby molecules (hydrogen bond) o Each water molecule can form H-bonds with up to four molecules When water reaches 0 o C, water becomes locked into a crystalline lattice with each molecule bonded to the maximum of four partners; ice is less dense than water Water is an effective solvent because it forms hydrogen bonds with charged and polar covalent molecules readily Hydrophilic substances BISC 220 4 o Dominated by ionic or polar bonds o Includes many large molecules that can be hydrated Hydrophobic substances o Dominated by non-ionic and non-polar covalent bonds o No H-bonds o Major ingredients of cell membranes Dissociation of Water o Reversible reaction o Very few molecules actually undergo this reaction o 2H 2 O H 3 O + + OH- o H 2 O H +...
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Chapter 1 - BISC 220 1 Chapter 1 BISC 220, Professor...

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