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Lecture 2

BIO270H1 Lecture Notes - Lecture 2: Thermal Energy, Osmotic Pressure, Ionic Bonding

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Chris Garside

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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
1st law: Law of conservation of energy: energy can be converted from one
form but total amount of energy is constant
2nd 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
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

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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
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
o Inhibit freezing point
o Vapour pressure
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
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