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Unformatted text preview: Lecture 1 : 3/29/10 Building Blocks of Life INTRODUCTION TO CELLS The cell is life’s fundamental unit o Smallest form of life Eukaryotic cell Prokaryotic cell All life forms are made from one or more cells o Mitosis Scientific study of cells o Discovery science: describe observations o Hypothesis-based science: propose and test explanations o Better understanding of nature o Biotechnology applications ATOMS & BONDS Element: cannot be broken down into other substances o 25/92 natural elements are essential for life o 4 elements make up 96% of living matter Carbon Nitrogen Oxygen Hydrogen o Elements combine to form chemical bonds and compounds Atom: Smallest unit of matter that retains the properties of an element o Protons o Neutrons o Electrons Valence: bonding capacity, determined by the unpaired valence elections in outermost shell Covalent bond: sharing of electrons between elements • Single • Double • Polar • Nonpolar Ionic bond: transfer of electrons between atoms Hydrogen bond: H shared between polar molecules • F, O, N • Partial +/- charges between polar molecules o Molecule: Elements held together by covalent bonds o Compound: fixed ratio of 2 or more elements o Van Der Waals: Slight interactions between nonpolar covalent molecules WATER Most important molecule for life on Earth Life began in water and evolved here for 3 billion years before spreading to land Our cells are 70-95% water, we can only survive for 1 week without water Water is polar molecule attracted to itself. This is the critical factor for all of water’s most important properties Properties of Water: o Cohesion: Water molecules stay close together due to hydrogen bonding o High specific heat: A great deal of energy is required to break H-bonds to release/vaporize individual molecules o Evaporative cooling: water molecules with highest energy leave water reservoir as vapor, lowering the T of remaining liquid o Ice floats: Solid water is 1-% less dense than liquid form. This unusual feature results in crystal-like matrix of water molecules in ice. Insulates water underneath o Excellent solvent: dissolves polar and nonpolar substances and salts ACIDS & BASES Dissociation of water results in ions Pure water has equal concentrations: [H+] =[OH-] Pure water is NEUTRAL or ph=7 pH Scale o measures level of acidity o pH = -log[H+] o Acid: Increases [H+] or reduces pH o Base: Reduces [H+] or increases pH BUFFERS Compound that prevents sudden change in pH Critical for most cells to maintain pH 6-8 Lecture 2 : 3/31/10 Macromolecules I REVIEW Water has a covalent bond : sharing electrons o It is a molecule CHEMISTRY OF CARBON (C) Whereas water is the universal medium for life, C makes up the majority of the cell’s structures The C in our bodies ultimately derives from the action of plants. Plants harness the power of sunlight to convert CO 2 into Carbon-based macromolecules...
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This note was uploaded on 03/05/2012 for the course BILD 1 taught by Professor Boulanger during the Spring '08 term at UCSD.
- Spring '08