Bio 101 Final Essays - 1. A. Chemical work at the cellular...

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1. A. Chemical work at the cellular level a. Creating (electro)chemical gradients i. Specific example: Oxidative Phosphorylation (during cellular respiration) 1. Electron Transport Chain a. “falling electron”, -∆G b. Electron passed from one carrier to another, carriers alternate between oxidized and reduced states c. Each carrier has increasingly high affinity for electron (electronegativity) d. Complexes I, II, III, and IV accept and then donate electrons, pumping out a hydrogen ion simultaneously e. Source for energy: flow of electrons causes -∆G f. How energy source is being used to accomplish work : Total energy release from electron flow is controlled in steps, this energy is used to create an hydrogen ion gradient 2. Chemiosmosis a. Hydrogen ions diffuse through ATP synthase down their concentration gradient b. This energy is used to synthesize ATP c. Source for energy: hydrogen ion gradient d. How energy source is being used to accomplish work : hydrogen ion gradient is coupled with ATP synthase for ATP production B. Mechanical work at the cellular level a. Muscle Contraction i. ATP hydrolysis puts myosin head in high energy configuration ii. Myosin head will bind to actin (thin filament) if binding site is exposed - Forms cross-bridge iii. ADP and phosphate are released, Myosin head flips back to low energy state and pulls thin filament iv. ATP binding cross-bridge dissociation b. Source for energy : ATP c. How source is being used to accomplish work : ATP binds to myosin and causes a conformational change 2. Four properties of water and the role they play in biology Four emergent properties of water contribute to Earth’s fitness for life. Cohesion : Hydrogen bonding keeps water molecules close to each other, and this cohesion helps pull water upward in the microscopic vessels of plants. Hydrogen bonding is also responsible for water’s surface tension Moderation of Temperature : Hydrogen bonding gives water a high specific heat. Heat is absorbed when hydrogen bonds break and is released when hydrogen bonds form, helping minimizing temperature fluctuations to within limits that permit life. Insulation of Bodies of water by floating ice : Ice is less dense than liquid water because its more organized hydrogen bonding causes expansion into a crystal formation. The lower density causes ice to float, which allows life to exist under the frozen surfaces of lakes and polar seas.
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The Solvent of Life : Water is an unusually versatile solvent because its polar molecules are attracted to charged and polar substances. Ions or polar substances surrounded by water molecules dissolve and are called solutes. 3. Diffusion and its role in bulk flow and osmosis Diffusion is the tendency for molecules of any substance to spread out evenly into the available space. Each molecule moves randomly, yet diffusion of a population of molecules may be directional. Any substance will diffuse down its concentration gradient. It is a spontaneous process. The diffusion of a substance across a biological membrane is called
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Bio 101 Final Essays - 1. A. Chemical work at the cellular...

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