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Lecture 2

Lecture 2.docx

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University of Toronto St. George
Chris Garside

Lecture 2 Cellular processes & physiological system  Physiological processes are based on cellular function  Cellular function obey laws of physics and chemistry  Work with other cells: organ homeostasis Thermodynamics  1 law: Law of conservation of energy: energy can be converted from one form but total amount of energy is constant nd  2 law: Entropy: the universe is becoming more chaotic  Life must continuously extract energy from the environment to maintain itself, whereas the rest of the universe degrades even faster than it would on its own Energy  Ability to do work (force x distance)  Energetics: energy transfer between system  Potential: trapped energy  Kinetic: energy of movement Categories of energy  Radiant energies: transmitted from one object to another as waves/particles; solar energy  Mechanical energy: movement of objects  Electrical energy: movement of charged particles  Thermal energy: movement of molecules  Chemical energy: within chemical bonds  Interconvertible: all rely on five types of energy Found webs transfer energy  Plants: herbivores: carnivores Electrochemical Gradients  Gradient: difference between 2 points  Diffusion: tendency of random dispersal of molecules  Gradients are a form of energy storage: potential energy  Gradients: chemical, electrical and both Chemical reactions and thermal energy  Thermal energy: movement of molecules  Enthalpy: average thermal energy of a collection of molecules  Delta G is negative: exergonic  Delta G is positive: endogonic  Thermal energy increase, increase rate of chemical reaction Chemical bonds  Covalent bond (strong bond): sharing electrons  Non-covalent bond (weak bond): organize into 3-D shapes Covalent bonds  Functional groups: combinations of atoms and bonds Bond energy: amount of energy needed to break a bond Non-covalent bonds  Van der Waals forces o Transient dipole: asymmetry of electron distribution (short distances) o Lizard to walk on glass  Hydrogen bonds o Oxygen and water o Charge distribution  Ionic bonds o Anion: (-) too many electrons o Cation (+) few electrons o Ionic bond joining of anion and cation o Ex. Salts, acids and bases  Hydrophobic bonds o Molecules with mutual version to water Temperature sensitivity of weak bonds  High temperature denatures bonds Water  Cells are composed of water  Liquid water network of interconnected water molecules  Surface Tension: the force due to water attraction Boiling and Freezing  High temp. less hydrogen bonds per water molecules  Low temp. more hydrogen bonds per molecules Density of water is affected by temperature  Ice is less dense floats on water  Deep water 4 degrees Celsius  High of vaporization: energy required to transform a given quantity to change from liquid to gas Solvent and Solutes  Solvent: most abundant molecules in water  Solute: molecules in a liquid  Solution: solvent and solute  Hydration shell: solutes surround water molecules Solutes affect properties of water  Reduce o Inhibit freezing point o Vapour pressure  Increase o Boiling point o Less SA for molecules to exit o Osmotic pressure Solutes create osmotic pressure  Osmosis: diffusion of water  Osmosis pressure: force associated with the diffusion of water  Osmolarity: the ability to cross a membrane  Semipermeable membrane: allows some molecules to cross Osmotic Pressure  Hyperosmotic: higher osmolarity: cell shrinks  Hyposmotic: lower osmolarity: cell burst  Isosmotic: same osmolarity Tonicity  Tonicity: affect of a solution on cell volume  Cell shrinks in hypertonic solution o Water leaves through osmosis  Cell swells in hypotonic o Water enters the cell by osmosis  Isotonic solution o No movement of water  Rate of diffusion o dQs/dt = Ds x A x (dc/dX) o dQs/dt = Rate of diffussion o Ds = diffusion coefficient o A = diffusion area o (dc/dX) = size of concentration gradient Biochemistry  Metabolic pathways o Catalyzed by enzymes o Synthetic (anabolic) and degradative (catabolic) o Metabolism: sum of metabolic pathways  Enzymes o Active have 3 properties o 1. Active at low temperature o 2. Increase rate of reactions but are themselves not altered o 3. Do not change the nature of the products o Most proteins and cofactors o Enzymes lower the activation energy o Not specific  Environment effect enzyme activity o Weak bonds alter 3-D o Ionization state of amino acid within the active site o Changes in structural change
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